ssc-360 use of fiber reinforced plastics in the marine industry

2/- -SSC-360USE OFFIBER REINFORCED PLASTICSIN THE MARINE INDUSTRYThis tiurnent has been approvedfor public release snd sale; itsdistribution is unlimitedSHIP STRUCTURE1990COMMITTEE

SHIP STRUCTURECOMMITTEETHE SHIP STRUCTURE COMMllTEE is constituted to prosecutea researchprogramto improvethe hull structure ofships and other marine structures by an extension of knowledge pertaining to design, materials and methods of construction,RADM J. D. Sipes, USCG, (Chairman)Chief, Office of Marine Safety, Securifyand Environmental ProtectionU. S, Coast GuardMr. Alexander MalakhotiDirector, Structural IntegritySubgroup (SEA 55MNaval Sea Systems CommandDr. Donald LiuSenior Vice PresidentAmerican Bureau of ShippingMr. H. T. HailerAssociate Administrator for Shipbuildingand Ship OperationsMaritime AdministrationMr. Thomas W. AllenEngineering Officer (N7)Military Sealift CommandCDR Michael K. Parmelee, USCG,Secretary, Ship Structure CommitteeU. S, Coast GuardCONTRACTING OFFICER TECHNICAL REPRESENTATIVESMr. William J. SiekierkaSEA55Y3Naval Sea Systems CommandMr. Greg D. WoodsSEA55Y3Naval Sea Systems CommandSHIP STRUCTURESUBCOMMllTEETHE SHIP STRUCTURE SUBCOMMl~EE acts for Ihe Ship Structure Committee on technical matters by providingtechnical coordinating for the determination of goals and objectives of the program, and by evaluating and Interpretingthe results in terms of structural design, construction and operation.U, S, COAST GUARDDr. John S, Spencer (Chairman)CAPT T. E. ThompsonCAPT Donald S. JensenCDR Mark E, NellMILITARY SEALIFT COMMANDMr. Glenn M. AsheMr. Michael W, ToumaMr, Albert J, AftermeyerMr. Jeffery E, BeachNAVAL SEA SYSTEMSCOMMANDAMERICANBUREAU OF SHIPPINGMr. Roberl A, SielskiMr, Charles L. NullMr. W. Thomas PackardMr. Allen H. EngleMr. John F, ConIonMr. Stephen G. ArntsonMr. William M. HanzalekMr. Philip G, RynnMARITIME ADMINISTRATE ONMr. Frederick SeiboldMr. Norman O. HammerMr, Chao H. LinDr. Walter M. MacleanSHIP STRUCTURE SUBCOMMllTEE LIAISON MEMBERSU,s. cn AST GUARIT ACADEMYLT Bruce MustainU. S. MERCHANT MARINE ACADEMYDr. C, B, KimU. S, NAVALACADEMYDr. Ramswar BhattacharyyaSTATF UNIVERSITY OF NEW YORKMARITIME COLLEGEDr. W. R. PotterWELDING RESEARCH COUNCILDr. Martin PragerNATIONAI ACA 13EMY OF SCIENCFSMARINE BOARDMr. Alexander B, StavovyNATIONAL ACADEMY OF SCIENCESCOMMllTEF ON MARINE STRLfCTUjSMr. Stanley G, StiansenSOCIETY OF NAVAL ARCHITECTS ANDMARINE ENGINEERS-HYITRODYNAMICSCOM Ml~EEDr. William SandbergAMERICANMr. Alexander D. WilsonIRON AND STEEL INSTITUTE

MemberAgencies:Address Correspondenceto:United States Coast GuamlNaval Sea Systems CommandMaritimeAdministrationAmerican Bureau of Sh@pingMilitatySealift CommandShipStructureCommitteeAn InteragencyAdvisoty CommitteeDedicatedto the Improvementof MarineStructuresSeptember 6, 1990Secretary,Ship StructureCommitteeU.S.CoastGuard(G-MTH)2100 Sscond Street S.W.Washington,D.C. 20593-0001PH: (202)267-0003FAX (202)267-0025SSC-360SR-1328USE OF FIBER REINFORCED PLASTICSIN MARINE STRUCTURESFiber reinforced plastics ( FRP ) have been used extensively in therecreational boating industry for more than 30 years. We are nowbeginning to see applications for more widespread uses of FRP inlarger marine structures. Many traditional naval architects anddesign engineers are not familiar with the processes used in thefabrication of FRP structures nor with the terminology associatedwith these processes. Although fundamental design considerationsfor FRP and steel structures are quite similar, the design ofstructural details varies drastically and must not be overlooked.This report is the most comprehensive study to date on the stateof the marine composites industry and should for many years serveas an excellent reference and source book for designers andbuilders of FRP structures. Over 200 manufacturers providedinformation concerning current building practices and materialuses. Numerous charts, illustrations, and graphs are includedand help to explain many of the concepts in the report.Rear ~ Admir -tGuard . .Chairman, Ship Structure Committee,.,/.(”” “’-,,4” !;s~{,,,/,{ u’-’’’’” ,,!,. ‘)

METRIC CONVERSIONFACTORSApproxlmma Comr.mlonsto M.tric MecturacApproximateConversionsSymbolWhm YOU Know Multiply bV To FindSymbolwhen YOU Know MultiplvLENGinftVddLENGTH9.6m0.91.6AREA9quaro inchn 6.6tquora f-tquuo~ardsquw~ mhtmO.mOaEcantlmoturcwrtimotutnntortkilormtwt~usrm cmtirrwtutcqums motwstquuo rmmrttquwo kilornotorsIucwmmmcmm#mIxr#dkrtdhnmill imotmsmm imomrtmttorsnwtorskilomotors0.040.43.31.10.6‘ AREAquart tantimmtws 0.16tqmrt nwt4r8 1.2quaro k ilomotort 0.4hocwrat {10.000 m$ ] 2.6ttoT&fiozcptqtgalU@3MAS(woi@tt)Oulwm 26 wtmtpourrdn 0.45 kil~~* tons 0.9 tonnmMx10 lb]fluid ou-CupopinttquwtsgdlontCUMCIoatcubk v-VOLUME616300.240.470.86&0.76miililitorcmill ilhcamillilitomIiwrsIitorcIitmtIitoracubic mmorswbic nwtmc32————=—-TEMPERATURE(exact] Oc Cdsiuc 9/% hh——Fnhrantuit 6/9 kltw C41durranpumm tubtractina ttrnpwturo321—-~kgtml1Iims~3Wum 0.036kilofpmt 2.2,torrrrw l?CK)Okg) 1.1VOLUmill illtms 0.03iimrs 2.?liwr8 1.06lit ●rt 0.26cubic maters 36cubic matorc 1.3TEMPERATUwmpwatur- MM 32w 32-40 0 40t 1 I II I r ,-40 –20 I xOco

INTRODUCTIONTechnicalReport Documentotiotr Page1. Report No. 2, Govemmcni Accocxion No. 3. Rocipiont’t Catalog No,SSC 3601 Ii, Titlt and subtitle I 5. R-port DatoMARINECOMPOSITES June, 1990Investigationof FiberglassReinforcedPlastics6. PorforminB Orgoni ~atien Codsin Marine Structures?. Authotf,)Eric Greene8. P.rlorming Organization R*por+ No.SR 13289. Pderrni.H 0r9~izotion Nqmo ad Addresz 10. Work Unit tSo. (TRAIS)Eric Greene Associates,Inc.1SCushingAvenueAnnapolis,Maryland 2140312. Sponsoring Agency Namoand Addf*s~11. Contract m Gront No.DTCG23439-C-2001511 Typomf Repor! and PcriQd C*vorodFinal ReportShip StructureCommitteeU. S. Coast Guard2100 SeeondStreet 14. Spo”roring Agofic~ CQd-Washington,DC 20593-001G-M15. Supol,montory N~*O_16. Ab=tructThe use of FiberglassReinforcedPlastic (FRP)has increased recentlyin marine structureswith aminimum of engineeringanalysisand design evolution Althoughfiberglasshas ben used formany years in small recreationaland high-performanceboats, a range of new compositematerialsare now being utilized for various applications. The objectiveof this documentis to examhmtheuse of FRP and other compositematerials in m’arinecmwruction, determineimportantconsiderationsin past desigq review developmentsin related industries;prediet areas for fituremarine applications;and recommendfuture researchneeds.Reference informationfor this project included investigationsof previousresearchers,materialsmanufacturers’data and marine industry survey results. The publicationis orgarsiz?dinto thefollowingchapters:. Applications. Materials● Design. Pmformance● Fabrication. Testig● Referenee17. Kw Ward, I 18. DISWI butkn StdtomontFi&r@assReinforcedPlastic (FRP)Composites,Hull Structure,ReinforcementMaterial,Resin, SandwichConstructionThis documentis availableto the public throughthe National TechnicalInformationSenice,Sprin@eld, VA 22161 and the Marine TechnicalInformationFacilitv,National MaritimeResearchI Center, Kings Poin~jNY 10024-169919. $gcurity Clossif. (of this mpmd M. $ocurity Clg@f. (of thl ~ pogo) 21. Nm of Pmwva 22. PriceUnclassified Unclassified 284.Fwm DOT F 1700.7 (B-T21 Reproduction of completod pago authorizedi.,-..,,,.., .”., ~ -.. .(‘\,,, ]%,? ,.,u“’”

MarineCompositesThe use of Fiberglass Reinforced Plastic (I?RP) has increased recently in marine structures witha minimum of engineetig analysis and design evolution. Although fiberglass has been usedfor many years in small recreational and high-performance boats, a range of new compositematerials are now being utilized for various applications. The objective of this document is toexamine the use of FRP and other composite materials in marine construction; determineimportant considerations in past desigq review &velopments in related industries; predict areasfor future marine applications; and recommend future research needs.This publication has been developed for use by designers and builders in the HIP marineindustry. Most of the materials and applications were drawn from current practice in the UnitedStates. All data is presented in English units, although an extensive set of conversion tables isincluded in Chapter Seven.The FRP marine industry in this country is market driven with very little structure.Consequently, little formal engineering guidance is available. This document attempts tosummarize the works of investigators over the past thirty years who have studied both thetheoretical and experimental performance of FRP in a marine environmentAn industry survey was performed as part of this project to provide input regarding the buildingpractices and materials in use today. The responses from over 200 manufacturers are includedin the report in graphic form.Although formulas are presented to give the reader some insight into the vsriables thatinfluence the behavior of a composite structure, current state-of-the-art does not satisfactorilypredict the exact strength of laminates found in marine construction. The behavior of sandwichpanels under extreme dynamic load is only recently being understood. In addition, a databaseof tested physical properties for the myriad of materials presented and possible orientations hasyet to be established. This sort of comprehensive test program is needed by the industry tosupport the rule-based design guidance developed by classillcation organizations.ii,/,,----...,L“ k /,’

INTRODUCTION● “Chapter One APPLICATIONSRecreational Marine lndustryi iii... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..1Racing Powerboats, .,, ,,, . . . . . . . . ,,, , . . . . . . . . ...1Racing Milboats i.. .,, ... . . . ..ii#. ., . . . . . . . . . . ...1Sunfish . . ..i. .,tt# . . . . . . . . ..tt #..... . . . . . . ..ti ...2Boston Whaler ., . . . . . . . ..i ii t..... . . . . . ..iiti . . ...2Block island @,, . . . . . . . . . . . . . . . . . . . ii. i . . . . . . . ...3Laser International . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...3;4$4*mm.mm.mm,**, ,.. mmmm. mmmmm . . ..mmm. . . . . . ...*..Bertr6rn ~::~::~: ~:::::::::::::’.::: ~:~~:::::::~~~;42G$x!%l%?gYacht’’::::::::::::::::::::::::::Canoes and Kayaks . . . . . . .. i....... . . . . . . . . . . ...15Evolution of Recreational Boat Construction Techniques ., ,1....1 5Single-Skin Construction ii, ,,i . . .. ii . . . . . . . . . . . ...16Sandwich Construction .i, ,,i . . ..i. . . . . . . . . . . . . . . ..Resin Development ,, . . . ..r . . . . . . . . ,. ..,,,, . . . . . .Unidirectional and Stitched Fabric Reinforcement , ., ,6Advanced Fabrication Techniques , . i . i i i t t i . . . . ...6Alternate Reinforcement Materials . . . . . . . . . . . . i i i , ,7Commercial Marine lndust~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,.,,,,,,8fishinglndust ~. . . . . ..ii . . . . . ..i. . . . . . . . . . . . . . . . . . . .. *4.....8AMTMatine, ,, i . .,, ,, . . . . . . . . . . . . . . . . . . . . . . . . ...8Delta Mafine, iii, ,,, ... ,.. .ii iii . . . . . . . . . . . . . ...8Lequerq, ... ,,. .iiii, ,.ii. iii iii. , . . . . . . . . . . . ...8Young Brothers . . . . . . . . .,, ,,... . . . . . . . . ,,, ,,,,, ,s 9Lifeboats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...9Watercraft America,,,,,,,,...,,. . . . . . . . . . . . . . ...9Schat-Matine Safe~ . . . ..i . . . . . . . . ..i . . . . . . . . . ...10Utii~Vessels ii. ..it, tii. .ilt. .i. lt ... . . . ..s . . . ..l . . . . . . ...10Boston Whaler i i i . . . . . . . . . . . . . . . . . . ., . . . . . . . . ...10LeComte, ,i. i . . . .. i . . . . . . . . . . . . . ,,, , . . . . . . . ...10Tetiron Mafine SySems . . . . . . .. ii.. ., . . . . . . . . . ...11Passenger Ferries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...11Blount Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...11Karlskronavarvet, AB , ., .,, . . . . . . . . . . . . . . . . . . . ...11ArRide Crafi. , . . . . ..i . . . . . . . . ..i. ., . . . . . . . . . ...12Italcrafl i,. ... ii, .iiii . . . . ..i. ii.. ... s . . . . . . . ...12Commercial Ship Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . ...12Commercial Deep Sea Submersibles . .,, , . . . . . . . . . . . . . . . . . ...13Navigational Aids ... ,**... . . . . . . . . . . . . . . . . . . ,“, ,..1.. ..,,*, 13O~hore Engineering .i. hi, . . . . . . . . . .,, . . . . . . . . . . . . . . . . . . ...14Piling Forms and Jackets, ,,i, ,i, i. ,,, ,, .,...,,,,,14...111

Marine CompositesMilitarv. Amlication . . so fComDosites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ,15Navy . . . . . . . . . . . . . . . . ...*.., . . . . . . . . . ,,, ,. .,,, . . . . . . . . . ,,, 15Submarines, ,., ,., ,,, iiii, ,,, . ..i . . . . . . . . . . . . ...15Patrol Boats, , .,, ,,, . . . . . . . . . . . . . . , . . . . . . . . . . ...16Mine Counter Measure Vessels , ..,,......,,..,..,16Components ...,,,,.,.......,..,,. . . . . ... . . . ...18Army . . . . . .,, ,,,.. . . . . . . . . ,s, ,,..s .s . . . . . . ,,, .ss.. . . . . . . . . 19Transportation Industw ,,,,,,, ,,,,,,, ,,,,,, ,., ,,,,, .s . . . . . . .,, ,,,,. . . . .21Automotive Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,.21MOBIK . . . ..ii. ... ,iiii. ... , ii.,.,,.. . . . . . . . . ...21Ford, ,, ...,,,.. .,, ,,,*.. . . . . . . . . . ,,, ,,,,,, . . . . .22General Motors, ,.. .iii, , . . .. iii.. . . . . . . . . . . . ...23Ch~sler .,, .,, .,, ,,, .ii i ii,,.,... ,, . . . . . . . . . . ...23Leahptings .,,,,,.,,,.......,.,,,. . . . . . . . . . . . ...24Frames, ,,, ,, ... ,,,,,* . . . . . . . . . ,., !!,... . . . . . . .24Safety Devices ... ,,,,.. . . . . . . . . . .,, ,,,,,, . . . . . .24Manufacturing Technologies ,, ., ., , . . . . . . i i , i i i , ,25Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...26Cargo Handling ..i i i i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...27lndustfial Useof FRP, , . . . . . . . . . . . . . . , . . . ..i . . . ..i. i . . . . . . . . ..i. i.iiitti28Piping Systems .,, iii,,,,,...,,,,. . . . . . . . . . . . . . . . . . . . . . . . ...28Pipe Construction ..i . . . . . .. iii... , . . . . . . . . . . . ...28Piping Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...28Enineering Considerations . . . . . . . . . . . . . . . . . . . ...28FRPPiping Appications Y . ..i . . .. i.. , ., . . . . . . . . . . . . . . . . . . . . ...30Oillndust~ .i. ,,. ... iii, . . . .. iii. ,, . . . . . . . . . . ...30Coal Mine . . . . . . . . . . . . . . ..tt iii... . . . . . . . . . . ...31Paper Mill iii. i,, ., . . . . . . .. i....... . . . . . . . . . . ...31Power Production . . ..t . . ..i. .i . . . . . . . . . . . . . . . ...31Tanks, ,,, ,,, ,i, iii, ,,, ,,, ,,, i,,. . . . . . . . . . . . . . . . . . . . . . . . ...32Confiruction, . . . . ..ti. t . . . . .. i... . . . . . . . . . . . ...32Application “,. . . ...1 .,, ,,,,!, ,,, ,, . . . . . . . . . . . . .32Air Handling Equipment ,, . . . . . . . . . . . . . . ,,, ,,,,. ,,, ,,,.. . . . .32Commercial Ladders . i . . . . .,, ,,,1,. . . . . . . . . . . . . . . . . . . . . . . . .33Aerial Towers, ,,, i. i,,,,,...,,,, . . . . . . . . . . . . . . . . . . . . . . . . ...33Aerospace Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...34Business and Commercial, . ..i. i,. . . . . . . . . . . . . . 1. . . . . . . . . ...35Lear Fan21~. i,, ,,itt . . . . . . . . ..i. .,, ,,, ,. . . ...35Beech Starship .,, ,,, .,,.,,,......,........,.,,,35Boeing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...35Airbus, ,,, ,,, i,, i i i,, ,,, . . . . . . . , . . . . . . . . . . . . ...35Milita~ .,, , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...35Advanced Tactical Fighter (ATF) . . . . , . . . i i . i . . . . , ,35Advanced Technolo y Bomber (B-2) , . . . i i , , , , . ...36Second Generation # rltish Harrier ‘JumpJet” (AV-8B) . .,, , . .,, , . . . . . . . . . . . . . . . . . . . . . . . ...36Navy Fi hter Aircrafl (F-18A) . . . . . . . . . . ..i. .t . . . ...37Osprey Yilt-Rotor (V-22) , . . . . . . . . . . . . . . . . . . . . . . ...37Helico~ters, ,.. iii, ,,, ,,. ..i. ii,. ,,, ,,, ..,,.....,,,,,..,,,,37Rotors i.iii. , . . . . ..i . . . . .. i..... . . . . . . . . . . . . ...37Structure and Components . . . . . . . . . . . . . . . . . . . ...37Experimental, ,,. ii, ,,, ,.. .,i. ,i. . , .,, ,,, ,,, , . . . . . . . . . . . ...38Voyager ,Daedalus,,, . . . . ,,,,,,, ,,,,.,. .,,,,ss ,,,,... . . . 38,,, ..,,. ,,, ,,,,, ,, . . . . . . ,,, ,,,,, . . . . . .38iv;

INTRODUCTIONChader Two MATERIAI=SComposite Materials . . . . .. i....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..41Reinforcement Materials . .,, ,,, ,.. . . . . . . . . . . . . . . . . . . . . . . . ...41Fiberglas, .ii, ,,, ,, i,, ,, . . . . . . . . . ,,, ,, ...,....,41Polymer Fibers . . . . . . ..ii. .. t...... . . . . . . . . . . . ...41Carbon Fibers tt, t, . . . . . . . . . . .. iit ,, . . . . . . . . . ...43Reinforceme;’~g$ruction. .iiii. i i,i, , . . . . ..i . . . . . . . ..ti. .fijKnits, ,, :::::::::::::;::::::::::::: :::: :;:: ::: ..46Omnidirectional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...46Unidirectional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...46Resins i . . . . . . . . . . . . . . . . . . ..i. i.i ., . . . . . . 1. . . . . . . . . . . . . . ...47Polyester ii, , . . . . . . . . . . . ..ii. i.. r. . . . . . . . . . . . ...47;~~~Etier, ,,, , . .,, . . . . . . . . . . . . . . . . . . . . . . . . . . ...48., *,...,, . . . . . .48Thermoplast’ic~:::: :::: :::: :::: :::i ,, . . . . . . . . . ...48Core Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...49Balsa i,, ., . . . . . . . . .. i i i . . ..*...... ., . . . . . . . . ...49Thermoses Foams ..i. i.iii, ,i #,... . .,........,,,49Syntactic Foams, ..ii. ii, i.. t...... ., . . . . . . . . ...50Cross Linked PVC Foams t,. tt . . . . . . . .,........,,,50Unear PVC Foam, ., . . ..ii. .ii. i. . .,, ,,, , . . . . ...51tii;:~mmb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51,,, ,,,,, ,* ...,,. . . . ,,, ,!,,$! t# i...... .52FRP Planking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52Core Fabfics . . . . . . . . . . . ..ii. ..tt* ,,, ., . . . . . . ...52Pl~ood, ,,, . . . . . . . . . . . .. i i........ 1.,........153Cost Considerations i i i,, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...53Laminate Property Assumptions . . . . . i , , t t i #. . . . . i .54Reinforcement Description i.. .i . . . . ,, . . . . . . . . . ...54Test Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..$~Fiber Weight Percentage ,. !,..... . . . . . . . . . ,.CCIIFiber Volume Percenta ett i,,..... . . . . . . . . . . . ...55Dty Fiber and Uncured B esin Density. . . . . i i ., . . . ...55Cured Laminate Density .. i i,....... . . . . . . . . . . ...55D~Hber Thickness, . . . . . . . . . ... . . . .ii, iiitit . . . ...55Fiber Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...56Resin Weihtii i,tt, ,.. .,iii. iii. i.. . .,, , . . . . ...56Laminate % eihtiii ..iitt. t . . . . . . . . . . . . . ..itt ,,56Reinforcemen7Cost Data *t, i....... . . . . ..i. ttiii56Total Material Cost . . . . . . . . ..i. ..i . . . . . . . . . . . . ...56Labor Cost, , . . . . . . . . . . . . ..ii. tt*. i , . . . . . . . . . ...56Total and Relative Ply Cost . . . . . . ...*. . . . . . . . . . ...56Strength Data . ..i. iii, i . . . . . . .. i... . . . . . . . . . ...56Single Skin Strength Criteria Thickness Comparison . ..56Single Skin Stiffness Criteria Thickness Com~arison i i .57Sandwich Construction Tension Criteria ThicknessCom~afison ..iii. .F . . . . . . .. F.. i.i . . . 1. . . . . . . ...57Sand’with Construction Compression CriteriaThickness Comparison ii,.....,.. . . . . . . . . . . . . . . .Sandwich Construction Stiffness Criteria ThicknessComparison ..i. i.4t* . . . . ..1. .i ii. . 1. . . . . . . . . . .Cost Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5859Reinforcement Description ...,.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii. 60]entEngineering Properties ,,, ,,,.. . ...,,,, . . . . . . . . . . . . . . . . . . .6858

INTRODUCTIONSandwich Panel Flexural Stiffness ,,, i....., . . . . . . . . . . ,,, ,,, ,, 110Design of Details i.. ,ii. hi,,,,,,.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..114Secondary Bondin!?.l, l,t* . . ..l14Deck dge Connection: : : : : : : : ;:::::... . . . . . ...115Centerline Joints .t . . . . . . . . . ..t. .t ,, . . . . . . . . . ...118Keel Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . ...119Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...121Stiffeners $ii . . ..i . . . . . . . ..iqtt i... . . . . . . . . . ...1122Engine Beds . . ..i. .t. ii . . . . . . . . . .. ii . .,.,,,,,.,126Hardware .i. i.i, t, . . . . . . . . . . . . . . . .,..,,.......126Thickness Transition . ..ii. .i . . .. iii , .,......,....129Hatches and Portlights . . . . . . ..iii. .i ,,, ,,, ,. . ...129Through-Hulls . . . . . . . . . . ..i. ..ii. i. *i . . . . . . . ..i.l29;~$$gr$tiachment .i i i t . . . . . . . . . . . . . . . . . . . . ...130... ,,,,,, . . . . . . . . . ., . . . ..!1 tli*iI... . . 130Chapter Four PERFORMANCEFatigue, ,,, ,,ti . . . . . . . . . . . . . . ..t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133Composite Fatiue Theory . . . ..i. i... . .,.,,,.,,,,,,,,......136Fatigue Test Daa. ? ..i. .i . . . ..ii iii .,, ,, . . . . . . . . . . . . . . . . ...137impact . . . ..i . . . . ..ll ti c. . . . . . . . . . . . . . . . . ...1.......................139impact Desin Considerations, .tt. . . . . . . . . . . . . . . . . . . . . ..ttt]~~Theoretical 8 envelopments ,, CII**. . . . . . . . . . . . . . . . . ,, ,11*.. .Delamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...111..143Water Absorption ... .i. ... .. i,,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...146Blisters . . . . . . . .. i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,,,,.,......149Case -Histories . . . . . . . . . . . . . . .. iii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..154US Coast Guard 40 foot Patrol Boats . . . . . . . . . . . . . . . . . . . . . . ..1WSubmarine Fai~ater . . . . . . . . . . . . ..t. ,,, . . . . . . . . . . . . . . . . . ..l~Gel Coat Cr;;;$~i, ii, t . . . . . . . . .. ii i . . ..i. .ii. ti.l~. .i. ..l~.,, . . . . . . . . . . . . . . . . . . . . . iii,,, 156Type n::::: :::: :,, tt . . . . . . . . . .. ii.. . .,,,,,,...157Type Ill ... .,1,, . . . . . . . . . . . . . . . . ... .,,** . . . 157Core Separation in Sandwich Construction . . . . . . . . . . . . i . . . ...157Failures in Secondary Bonds ..i it i,. . . . . . . . . . . . . . . . . . . . . . ...158Ultraviolet Exposure ,, **..,, . ...,,.. . ,., ,..., ,, s...., . . . . . . 158Temperature Effects . i i .,, ,,, ,,, . . . . ....,......,t,........:~~~Repair . i . .‘Major ~ng~&S~nbarn~ge’::::::~:~ :::ll; :::1:~~: ~~~~11111i161Major Dama e in Sandwich Construction ., . . . . . i . i i , , , . . . ...1628 oreDebonding ... .,...1 . . . . . . . . . . . . . . . . . . . . . 163Small Non-Penetrating Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...163Blisters i . . . . . ..i. i . . . . . . . . . . . . . . . ,,. , . . . . . . . ..i . . ..i . . . . ..laChader Five FABRICATIONManufacturing Processes . . ..i i i i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..l M$ old Buildin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..ii. .l~. ..l~v Ius, ,,, . . . . ..i .,, ,,11.s . . . . . . . . . .,, ,,,,,, ,,, 166Mods Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...166Single Skin Construction l o. . . . . . . . . . ..r, l.t. l . . . ..ili. .il. ..lMCored Construction from Female Molds . . . . . . . . . . . t . . . . . . ...167Cored Construction over Male Plugs . . . . . . . . . . . . . . . . . . . . . ...167vii

Marine CompositesEquipment, ,,, .iiii, i,,,,,,,,,,, ,,, ,,, ,,, ,,, ,,, ,,, .,..,,,69&?%@ &%%%;”&ns’ :::::::::::::::::Impregnator ,,, ,s .,,,- ,,, - .!, ,,,,, ,,, ,,,,, ,,,,,,Health Considerations,,,,,,,,.,,, ,,, ,,, ,,, ,,, ,,, ..,,,,,,,,Future Trends,,,,,,,,,,,,.,.,,,,,, ,,, ,,, .,,,.....,,,,,,,,,Open Mold Resin Transfer Moldin (RTM) , , , , , , , , , ,Thermoplastic-Ther noset Hybrid 9recess .,, ,,,,,,,Post Curing,,, ,Hand Lay-Up,,,,,,.,,,::::: ,,, . :::::::::::::::::::::::::Spray-Up . . . . . . . . . . . . . . . . . . ,,, , .,, ,,, ,.. .,, ,,, ,,, ,,, ,s, ,Compression Molding .i i,,,, ,,, , ,,, ,,, ,,, ,,, ,,, ,,, ,, .,,,,filamen t~nding, ,iii, ii.,, ,,, , ,,, ,,, ..,.,.,,,,,,,,.,,,,Pultrusion iii, i,..,,,,,,,,,,,, s,,Vacuum Ba Molding, ,,, , . . . . . ..l l....::::::: :::l:;lll:::Autoclave 8 oldini,, ,,,,, ,,, ,,,,, ,,,,, ,,, ,,,,,Resin Transfer Moling:::::::: 3ii,. ,,, ,,, ,,, ,,, ,,, ,,, ,,, ,,, ,Quali~Assurance t, . . . . . . . . . . . . . . , ..,,....,,,..,,,,........,,,,,,,, ,Materials ,, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,,, ,,, ,,, ,,, ,Reinforcement Material, ,,, ,.. .i iii i i,,,,,,.,,,,Resin, ,,i, ,,, ,,, ,,, hi,,.,,,,,,, ,,, ,,, ,, .,.,,,,Core Material, ,,, ,,, ,,, ,,, ,., ,,, , ,,, ,,, ,,, ,,, ,In-Process Quality Control, ,,, ,. ..,, ,,, . . . . . . . . . . . . . . . . . . . . .Cha@er Six TESTINGMechanical Testin . .,.,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,, ,,, ,,, , .,,,,,,197ASTM ? RPM;;; f; Tests,,,,,,,,,,,,,,,,,, , .,,,,,,,,,.,,,,,,197,,, ,,,,, ,, ., .,.,,, ,,, ,,,,, ,,, ,,,,, ,.,,,, 197Rbe~and Fabtic, ,,, ,i, hi...,,,, ,,, ,,, .,,,,,,,198Core Materials, ,. i.,,,,,,,,,,,,,,, ,,, ,,, ,,, ,,, ,199Solid FRP Laminates,,,,,,,,,.,,,,. ,,, ,,, ,,, ,,, ,201FRPSandwich Laminates,,.,,,,,,, ,,, ,,, ,,, ,,, ,,204ASTM FRPStructure Tests,,,,,,,,, ,,, ,,, ,,, ,,, ,, ,205SACMAFRP Material Tests, ,,, ,, i,,, ,,, ,,, ,,, ,,, ,,, ,,, ,,, ,, ,205Sandwich Panel Testing,,,,,,,,,,,, ,,, ..,,,,,,,,,,,,,,,,,,,208Background, ,,, ,,, ,,, ,,, . . . . . . . . . ,,, , .,,,,,,,,208Pressure Table Design ,,, ,,iii, ,,, ,,, ,,, ,,, ,,, ,,208Test Results, ,,, ,,, iii, ,,, hi,,,,,,, ,,, ,,, ,,, ,,, ,208Material Testing Conclusions , , , , , , , , , i , , , , , , , , , , ,209Accelerated Testing, ,,. hi,,,,,,,, ,,, ,,, ,,, ,,, ,,211Rre Testing, ,., ,,, ,,, ,,, ,, iii.,,, ,,, ,,, ,,, ,,, ,,, .,,,,.,,,,,,,,,,, ,,, ,212Small Scale Tests iiiii, ,,, ,i, i,, ,.i . . . . . . . . . . . . . . . . . . . . . ...212O gen-Tem erature Limitin Index (LOI)Tes Y - ASTM d’2863 (Modifie8 ,212N.BS. Smoke Chamber-ASTM E~2’ :::::::::::::,213Cone Calorimeter -ASTM P190, ... .ii ,,, ,,, .,,,,214Radiant Panel -ASTM E162 , . . . . . . . . . . . . . . . . . ...214Intermediate Scale Tests hi..,,,,,,, ,,, ,,, , ..,,,,,,,,,,,,,,,215DTRCBurn Through Test, , iii....,,, ,,, ,,, , ..,,..215US, No Quarter Scale Room Fire Test , , , , , i , , , , ,216One MeYer Furnace Test - ASTM E 119 (Modified) , , ,216Large Scale Tests, ,,, ,,i iii,,,,,,, ,,, ,,, , .,,,,,,,,,,,,,,,,216Corner Tests i iii,,,,,,,,,....,.,,, ,,, ,,, ,,, ,,, ,216Room Tests.,,,,,,.,,.,,,,,,,,,,,, ., .,,,,,,,,,,216Summary of Proposed MIL-STD-2202 (SH) Requirements , , , , , , , ,216777778;:81828384858687889090929494...mu

Marine CompositesReview of SOLAS Requirements for Structural Materials in Fires ..219Nondestructive Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,, . . . . . . ...11224Radiogra~hy Techniques . ...,..... ., ..,,,,,,........,,,...224Ultrasonic inspection . . ..ttl t..... . . . . . . . . ..1 . . ..$ 111......224Acoustic Emission, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..225Thermography ... ,,*,,. . . . . ,,, ,0.s.. . . . . . . . . . . . . . . . . . . I*. 225SevenREFERENCERules and Re ulations1?S. CoastAmericanConversion Factors . iGlossary . . . . . . . . . . . .:~e~ter References .. . . . . . . . . . . . . .,,, ,,... . . . . . . . . . . . . . . . . I! *..... .W...c.c *. ...,,. 227Guard, itt, . . ..i. .i, it, tl. ..t. .t, ,i . . . . . . ..rt 11227Subchapter C - Uninspected Vessels i. i i.. , t t t t t. 227Subchapter H - Passenger Vessels . . i i i i . i t . i . . ...228Subchapter I - Cargo and Miscellaneous Vessels .. ,229Subcha ter T ~Small Passenger Vessels . . . . . . . . . . ,229Bureau oShippmg ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2wRules for Buildin and Classing ReinforcedPlastic Vesels178 v . . . . . . . ..t. ttt t... . . . . . . ..ttt230Guide for Buildin and Classing OffshoreRacing Yachts, 186 8 . . . . . . ..i . . .. t... . . . . . . . . ...231Proposed Guide for Building and Classin High SpeedCraft (Commercial, Patrol and Utility Cra I ) . . . . . . ...232Proposed Guide for High S eed andDisplacement Motor Yachft........ . ...,,,,.....233Classification . . . . ..t. t.. t . . . . . . ..t ,, . . . . . . . . ...233Hull Cetification, ii, . . . . . ..it. .tt i . . . . . . . . ..ttt235Plan Approval i . . . . . . .. i i i........ i....tttt235.235. . . . . . . . . ..!!.*. . . ...0.. .. !*.... . . . . . . . . ,~~...., 236,,...1. . ...!.. . . . . . . . l.w..t. . . . . . . . ,.,,,,~ ~,,,,, 2429L7,, . . . . . . ...!*! . . . . . . . 1 . . . . . . . . . . . . . ,1,,,,, ,J.,, , Ltif... ,,,.. . . . . . . . . I I*..,.. . . ...!!! s, ...,,, ,,,,,,~~ 268ix

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Ch@er OneAPPLICATIONS● ✍-O*O ● - ,Over30 years of FRP boat building experience stands behind today’s pleasure boats. Complexconfigurations and the advantages of seamless hulls were the driving factors in the developmentof FRP boats. FRP materials have gained unilateral acceptance in pleasure craft because oflight weight, vibration damping, corrosion resistance, impact resistance, low construction costsand ease of fabrication, maintenance and repair.Fiberglass construction has been the mainstay of the recreational boating industry since the mid1960’s. Mer about 20 years of development work, manufacturers seized the opportunity tomass produce easily maintained hulls with a minimum number of assembled parts. Much ofthe early FRP structural design work relied on trial and error, which may have also led to thehigh attrition rate of stat-up builders. Current leading edge manufacturing technologies aredriven by racing vessels, both power and sail.Racing PowerboatsThe structural components of a powerboat called the Aramid Arrow arc! an aramid prepreg and ~honeycomb sandwich composite. The boat weighs 3300 pounds, consumes 11 gallons of fuelper hour at 32 lmots, and has a top cruising speed of 42 knots. [1-1]The winner of the 1984 “Round Britain Powerboat Race” was White Iveco, which averaged ashigh as 69 knots on one leg of the race. The hull is constructed in a sandwich configurationwith glass mathramid over 0.8 inch Contourkore@ (bottom), 0.4 inch Contourkore@ (sides), and0.5 inch core (deck). The 36 foot hull and deck structure weighs 4600 pounds. [1-2]Racing boats employ advanced and hybrid composites for a higher performance craft and driversafety. FothergiU Compositm Inc., Bennington, VT, has designed, tested and manufactured asafety cell cockpit for the racing boat driver. The safety cell is constructed of carbon andaramid fibers with smrnid honeycomb core. This structure can withstand a 100 foot drop testwithout significant damage. During the Sacramento Grand Prix, three drivers in safety cellequipped boats survived injury from accidents. The performance advantage of advancedcomposites was clearly demonstrated in 1978 in the Offshore Racing circuit, where boatsconstructed using aramid fiber reinforcement won 8 of the 10 races, including the U.S. and theWorld Championships. [1-3]Racing SailboatsOver the past ten years, the American Bureau of Shipping (ABS) has reviewed over 400different design plans for racing yachts. Designers used the “ABS Gui& for Building andClassing Offshore Racing Yachts” [1-4] for scantling development. Some of these vessels havesuccessfully endured very heavy weather for long periods in events such as the ThitbreadRound the World Race” and the “Sydney Hobart Race.”The 77 foot carbon-glass-foam sandwich ketch Great Britain 11,launched in 1973, won the1975-1976 “Financial Times Clipper Race” and set a record of 134.5 days for the 1977-1978“Whitbread Round the World Race.” British Oxygen, a 70 foot GRP ocean racing catamaranlaunched in 1974, won the “Round Britain Race” that year. Launched in 1978, the GreatBritain IV was a carbon-glass hybrid composite ocean racing trimaran which won its first event,the 1978 “Round Brith Race.” The Brittany Ferries GB, a 65 foot carbon-aramid-foam1

RecreationalMarineIndustryA4arineCompositessandwich composite trimaran, won the 1981 Two-Handed Transatlantic Race. The E~Aquitaine 11was a 60 foot catamaran and, at the time, the largest structure built in carbon fiber.The Fmnule TAG was the world’s largest racing catamaran when it was launched in September1983. The hulls are aramid-epoxy prepreg and measure 80x 42 feet, and the sailing weight is20,000 pounds. This is possibly the fastest sailing yacht in the world, having covered 524nautical miles in 24 hours and averaging 21.8 knots. One of tlm lightest racing hulls built wasthe 35 foot Sumner Wine, a contender for the British Admirals Cup, which weighed 580pounds just out of the mold. Her construction was Divinycell sandwich with unidirectionalcarbon fibers. A carbon fiber rudder was also used. The 60 foot carbon framed trimamnApricot won the 1985 “City of Plymouth Round Britain and Ireland Race,” the 1985 “TAGRound Europe Multihull Race,” and Class II of the 1986 “Transatlantic Race.” Apricot iscapable of 30 Imots under full sail. The Colt Cars GB H, built by Mitsubishi Marine as anentrant for the 1985-1986 “Whitbread Race,” was at the time the world’s largest monocoquecomposite yacht. The UBS Switzerland was the fist boat to cross the line at the end of the1985-1986 ‘TVhitbread Race,” The 80 foot, 4400 pound hull was constructed with aramidprepreg over aramid honeycomb core and additional aramid fabric resulting in a hull thicknessof 0.16 inches.The Spectrum 42 cruising catamaran incorporates the same structural t~chniques and materialsas the racing catamarans. The laminate is vsried throughout the boat to achieve optimalstrength and fiber orientation. Unidirectional, aramid and E-glass tri-axial fibers are used.Carbon fibers are used in the crossbeam and in areas where extra reinforcement is needed. Theboat’s initial production weight was estimated to be 30% lightm than any production multihullof equivalent size. [1-5]Several classes of boats were pioneers for various construction and production techniques andare presented here as illustrations of the industry’s evolutionary process.SunfishThe perennial sunfish has seined as the introduction to the sport for many sailors. Thesimplicity of the lanteen rig and the board-like hull make the craft ideal for beaching andcsrtopping. Alcort has produced over 250,000 of them since their inception in 1952. Thebasically two-piece construction incorporates a hard chine hull to provide inherent structuralstiffening.Boston WhalerBoston Whaler has manufactured a line of outboard runabouts since the early 1960’s. The 13foot tri-hull has been in production since 1960 with over 70,000 built. The greatest sellingfeature of all their boats is the unsinkable hull construction resulting from a thick foamsandwich construction. Hull and deck sections are sprayed-up with ortho-polyester resin to a33% glass content in massive steel molds before injected with an expanding urethane foam.The 1% to 2V2 inch core provides signif~cant strength to the hull, enabling the skins to be fairlythin and light. Another interesting component on the Whalers is the seat reinforcement, whichis made of fiberglass reinforced Zytel, a thermoplastic resin.

ChapterOneAPPLICATIONSBlock Island 40The Block Island 40 is a 40 foot yawl that was designed by William Txipp and built by theAmerican Boat Building Co. in the late 1950’s and early 1960’s. At the time of construction,the boat was the largest offshore sailboat built of fiberglass. Intended for transatlanticcrossings, a ve~ conservative approach was taken to scantling deterrnhation. To detmnine thedamage tolerance of a hull test section, a curved panel was repeatedly run over with thedesigner’s car. The mat/woven roving lay-up proved adequate for this trial as well as manyyears of in-service performance. At least one of these craft is currently enjoying a secondracing career thanks to some keel and rig modifications.Laser InternationalDoyle and Hadley-Coates applied amathematical model to the case of a Laser 14foot racing dinghy. The model successfullyanalyzed the causes of structural failure fromlaunching and beaching such boats in SaudiArabia. [1-6]Laser International invested $1.5 million inthe development and tooling of a new,bigger boat, the 28 foot Farr Design GroupLaser 28. The Laser 28 has a PVC foamcore deck with aramid fabric inner and outerskins. A dry sandwich mold is injected witha slow curing liquid resin through multipleentry ports, starting at the bottom of themold and working upward. [1-7]k\Figure 1-1 14 Foot Laser Sailboat[Laser International]Figure 1-2 International J/24 Sailboat[J /Boats]J/24The J/24 fractional rigged sloop has beenmanufactured since 1977 at the rate of about500 per year. The vessel has truly become auniversally accepted “one-design” classallowing sailors to race on a boat-for-boatbasis without regard for handicap allowances.Part of the fleet’s success is due to themanufacturer’s marketing skills and part isdue the boat’s all-around good performance.The hull construction is cored with“Contourkore” end-grain balsa. Tillotson-Pearson manufactures J/Boats along withFreedoms, Rampages and Aldens. Thecompany supports extensive R & D andquality control programs.3

RecreationalMarineIndustryMatine CompositesIMP .IMP is a 40 foot custom ocean racing sloop that represented the U.S. in the Adrairal’s Cup in1977 and 1979. Sheisprobably themost successful design of Ron Hollmd, with much of herpefiormance attributable to sophisticated construction techniques. The hull and deck are ofsandwich construction using a balsa core and unidirectional reinforcements in vinyl ester resin.Primary rig and keel loads are anchored to an aluminum box and tube frame system, which inturn is bonded to the hull. In this way, FRP hull standings are determined primarily to resisthydrodynamic forces. The resulting hybrid structure is extremely light and stiff. The one-offconstruction utilized a male mold, which has become the standard technique for custom racingboats.BertramBerttam Yachts has built cruiser and sport fishczman~ powerboats since‘1962. Their longevityin thebusiness is in pan attribumbleto sound construction and some innovative prwluction techniques. Allinterior joirmy and structumlelermms are laminated to a steel jig, which positions these elements forprecise attachmentto the hull. A combinationof ma~ woven roving, knitted m.infbmrmnts and carbonfibers are Uti dwing the hand kly-llp Of ktmtn craft.Westpoti ShipyardThe Westport Shipyad cbveloped theirvariible size mold concept when theyfound that a 70 foot by 20 fti mold wasconstantly being modikd to fabricatevessels of slightly dMerent dimensions.A single bow section is joined to a seriesof shapablepanels that raeasum up to 10feet by 48 fmt The panels are used todefine the developable sections of thehull. Since 1983, 40 to 50 hulls haveken prduced using this technique.Expensive individual hull tooling iseliminated thus making customconstructioncompetitive with aluminum.A layer of mat and four woven rovingscan lx layed-up wet with impregnatormachines.Christensen Motor YachtChristensen has been buildinga line ofsemi-custom motor yachts over 100 feetlong, as illustrated in Figm 1-3. Thehulls are foam cored using a vacuumassist process. All yachts are built toABS~Alffl~S classification andinspection.130’ Pilot House0a.&?Fi;H;>c,- ..-—107’ Flush Deck with Cockpit%!107’ Raised PilotHousefigure 1-3 Motor Yachts Greater than 100feet Produced by Christensen Motor Yacht Corporation[Christensen]4

ChapterOneAPPLICATIONSCanoes and KayaksCompetition canoes and kayaks employ advanced composites because of the better performancegained from lighter weight, increased stiffness and superior impact resistance. Aramid fiberreinforced composites have been very successful, and new fiber technologies usingpolyethylene fiber reinforcement are now being attempted. The boat that won the U.S. NationalKayak and Canoe Racing Marathon was constructed with a new high molecular weightpolyethylene fiber and was 40% lighter than the identical boat made of aramid fiber. [1-3]Pounds of Reinforcement (Mllllons)500400. . . . . . ..300. . . . . . . . . ..L . . . . . .200. . . . . . . . . . . . . . . . . . . . . . . . . . . . .100. . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . .:... . . . . . . . . .. . . . . . . . . . . .} . . . . . . . . . . .. . . . . . . . . . . . } . . . . . . . . . ..!...... . . . . . . . . . . . ..01900 1909 1986 1969 197a 1976 1978 1981 1984 1987I I I I I I I I 1 I I I I I I I I I IF@Jre 1-4 Annual Shipment of Reinforced Thermoset and Thermoplastic ResinComposites for the MarineIndustrywith Associated Construction Developments. [DataSource: SPI Composites Institute (1960-1973 Extrapolated from Overall Data and 1989is Estimated)]Evolution of Recreational Boat Construction TechniquesFrom the 1950’s to the 1980’s, advances in materials and fabrication techniques used in thepleasure craft industry have helped to reduce production costs and improve product quality.Although every boat builder employs unique production procedures that they feel areproprietary, general industry trends can be traced over time as illustrated in Figure 1-4.5

RecreationalMarineIndustryMarine CompositesSingle-Skin ConstructionEarly fiberglass boat building produced single-skin structures with stiffeners to maintainreasonable panel sizes. Smaller structures used isotropic chopped strand mat layed-up manuallyor with a chopper gun, As strength requirements increased, fiberglass cloth and woven rovingwere integrated into the laminate. An ortho-polyester resin, applied with rollers, was almostuniversally accepted as the matrix material of choice.Sandwich ConstructionIn the early 1970’s, designers realized that increasingly stiffer and lighter structures could berealized if a sandwich construction technique was used. By laminating an inner and outer skinabout a low density core, reinforcements are located at a greater distance from the panel’sneutral axis. These structures perform exceptionally well when subjected to bending loadsproduced by hydrodynamic forces, PVC foam and end-grain balsa have evolved as the primarycore materials.Resin DevelopmentGeneral purpose orrho-polyester laminating resins still prevail throughout the boating industrydue to its low cost and ease of use. However, boat builders of custom and higher-end crafthave used a variety of other resins that exhibit better performance characteristics. Epoxy resinshave long been known to have better strength properties than polyesters. Their high cost haslimited use to only the most specialized of applications. Iso-polyester resin has been shown toresist blistering better than ortho-polyester resin and some manufacturers have switched to thisentirely or for use as a barrier coat. Vinyl ester resin has performance properties somewherebetween polyester and epoxy, exceeding epoxy in some respects, and has recently beenexamined for its excellent blister resistance. Cost is greater than polyester but less than epoxy.Unidirectional and Stitched Fabric ReinforcementThe boating industry was not truly able to take advantage of the directional strength propertiesassociated with fiberglass until unidirectional and stitched fabric reinforcements becameavailable. Woven reinforcements, such as cloth or woven roving, have the disadvantage of“pre-buckling” the fibers, which greatly reduces in-plane strength properties. Unidirectionalreinforcements and stitched fabrics that are actually layers of unidirectional offer superiorcharacteristics in the direction coincident with the fiber axis. Pure unidirectional are veryeffective in longitudinal strength members such as stringers or along hull centerlines. The mostpopular of the knitted fabrics is the 45° by 45° knit which exhibits superior shear strength and isused to strengthen hulls torsionally and to tape-in secondtuy structure:Advanced Fabrication TechniquesSpray-up with chopper guns and hand lay-up with rollers are the standard productiontechniques that have endured for 30 years. In an effort to improve the quality of laminatedcomponents, some shops have adapted techniques to minimize voids and increase fiber ratios.One technique involves placing vacuum bags ‘with bleeder holes over the laminate during thecuring process. This has the effect of applying uniform pressure to the skin and drawing outany excess resin or entrapped air. Another technique used to achieve consistent laminatesinvolves using a mechanical impregnator which can produce 55% fiber ratios.6

ChapterOneAPPLICATIONSAlternate Reinforcement MateriaisThe field of composites gives the designer the freedom to use various different reinforcementmaterials to improve structural performance over fiberglass. Carbon and aramid fibers haveevolved as two high strength alternatives in the marine industry. Each material has its ownadvantages and disadvantages, which will be treated in a later chapter. Suffice it to say thatboth are significantly more expensive than fiberglass but have created another dimension ofoptions with regards to laminate design. Some low-cost reinforcement materials that haveemerged lately include polyester and polypropylene, These materials combine moderatestrength properties with high strain-to-failure characteristics.

ComercialMarineIndustryMarine CompositesThe use of fiberglass construction in the commercial marine industry has flourished over timefor a number of different reasons. Initially, long-term durability and favorable fabricationeconomics were the impetus for using FRP. More recently, improved vessel performancethrough weight reduction has encouraged its use. Since the early 1960’s, a key factor thatmakes FRP construction attractive is the reduction of labor costs when multiple vessels arefabricated from the same mold, Various sectors of the commercial market will be presented viaexamples of craft and their fabricators, Activity levels have traditionally been driven by theeconomic factors that influence the vessels’ use, rather than the overall success of the vesselsthemselves.Fishing IndustryAlthough the production of commercial vessels has tapered off drastically, there was muchinterest in FRP trawlers during the early 1970’s. These vessels that are still in service providetestimony to the reduced long-term maintenance claims which led to their construction. Forexample, the 55 foot POLLY ESTER has been in service in the North Sea since 1967. Shrimptrawlers were the first FRP fishing vessels built in this country with the R.C. BREiVT,launchedin 1968. Today, commercial fishing fleets are approximately 50% FRP construction. Otheraspects of FRP construction that appeal to this industry include increased hull life, reduction inhull weight and cleaner fish holds.AMT MarineAMT Marine in Quebec, Canada is probably today’s largest producer of FRP commercialfishing vessels in North America. They offer stock pot fishers, autoliners, seiners and sterntrawlers from 25 feet to 75 feet Over 100 craft have been built by the company in the 11 yearsof their existence, including 80910of all coastal and offshore fishing vessels registered inQuebec in recent years. AMT utilizes a variety of materials and manufacturing processes underthe direction of their R & D department to produce rugged utility and fishing craft.Delta MarineDelta Marine in Seattle has been designing and building fiberglass fishing, charter and patrolboats for over 20 years. A 70 foot motor yacht has been developed from the highly successfulBearing Sea Crabber. Yachts have been developed with 105 foot and 120 foot molds, whichcould easily produce fishing boats if there was a demand for such a vessel. The hulls can befitted with bulbous bows, which are claimed to increase fuel economy and reduce pitching.The bulb section is added to the solid FRP hull after it is pulled from the mold. Delta Marinefabricates sandwich construction decks utilizing balsa core.LequerqAnother FRP commercial fishboat builder in Seattle is Lequerq. They specialize in buildingseiners for Alaskan waters. The average size of the boats they build is 50 feet. At the peak ofthe industry, the yard was producing 15 boats a year for customers who sought lowermaintenance and better cosmetics of their vessels. Some customers stressed the need for fastvessels and as a result, semi-displacement hull types emerged that operated in excess of 20knots. To achieve this type of perforrmmce, Airex@ foam cored hulls with directional glass8

ChapterOneAPPLICATIONSreinforcements were engineered to produce hull laminate weights of approximately threepounds per square foot.Young BrothersYoung Brothers is typical of a number of FRP boatbuilders in Maine. Their lobster and deckdraggers range in size from 30 to 45 feet and follow what would be considered traditional hulllines with generous deadrise and full skegs to protect the props. Solid FRP construction isoffered more as a maintenanctt advantage than for its potential weight savings. Following thepath of many commercial builders, this yard offers the same hulls as yachts to offset the declinein the demand for commercial fishing vessels.LifeboatsThe first FRP lifeboats were built in Holland in 1958 when Airex foam core made its debut in a24 foot vessel. The service profile of these vessels make them ideally suited for FRPconstruction in that they are required to be ready for service after years of sitting idle in amarine environment. Additionally, the craft must be able to withstand the impact of beinglaunched and swinging into the host vessel. The ability to economically produce lightweighthull and canopy structures with highly visible gelcoat finishes is also an attribute of FRPconstruction.Watercraft AmericaWatercraft is a 40 year old British company that began operations in the U.S. in 1974. Thecompany manufactures 21, 24, 26 and 28 foot USCG approved, totally enclosed, survival craftsuitable for 23, 33, 44 and 58 men, respectively. Design support is provided by HamptonUniversity in England. The vessels are diesel propelled and include compressed air systemsand deck washes to dissipate external heat Figure 1-5 shows the general conilguration of thesevessels. The plumbing incorporates PVC piping to reduce weight and maintenance. Hull andcanopy construction utilizes a spray layup system with MIL- 1140 or C19663 gun roving. Resinis MIL-2-21607 or MIL7575C, Grade 1, Class 1,fme retardant with Polygardiso/mpg gelcoat finish.Each pass of the chopperAgun is manuallyconsolidated with a rollerand overlaps the previouspass by one third of itswidth. Quality controlmethods ensure hardness,thicknesses and weight ofthe Iinished laminate.The company hasdiversified into a line ofworkboats and SubchapterT passenger vessels toF@Ure 1-5 Typical Configuration of Watercraft EnclosedLiferaft pNatercraft]9

ComercialMarineIndustryMarine Compositesoffset the decline in the offshore oil business. Reliance Workboats of England and WaterCraftAmerica IrIc. have tearned up to build the Worlmuaster 1100 multipurpose boat. The 36 footboats can travel in excess of 50 mph and can be custom fitted for groups such as customs andlaw enforcement agencies, commercial or charter fishing operators, and scuba-diving operators.The boat was introduced in Britain in early 1989 and recently in America, [1-8]Schat-Marine SafetyA more diversified line of lifeboats meeting CFR 160.035 is offered by the $chat-hhrine SafetyCorporation. Although they claim that fiberglass construction is the mainstay of the lifeboatindustry, steel and aluminum hulls are offered in 27 different sizes ranging from 12 to 37 feetwith capacities from 4 to 145 persons. Molds for FRP hulls exist for the more popular sizes.These hulls are made of fiberglass and fm retardant resins which are by far the mostmaintenance free and feature built-in, foamed in place flotation.The company also manufacturers FRP rigid hull int3atable rescue boats (RIBs), fairwaters,ventilators, lifefloats and buoyancy apparatus.Utilitv VesselsBoats built for utility service are usually modifications of existing recreational or patrol boathulls. Laminate schedules may be increased or additional equipment added, depending uponthe type of service. Local and national law enforcement agencies including natural resourcemanagement organizations compromise the largest sector of utility boat users. Other missionprofdes, including pilotage, fue-fighting and launch service, have proven to be suitableapplications of FRP construction. To make production of a given hull form economicallyattractive, manufacturers will typically offer a number of different topside configurations foreach hull.Boston WhalerUsing similar construction methods outlined for their recreational craft, Boston Whaler typicallyadds some thickness to the skins of their commercial boats. Hulls 17 feet and under are oftri-hull conf@ration while the boats above 18 feet are a modi!5ed deep- ‘V’ with a deackiseangle of 18 degrees. The majority of boats configured for commercial service are for either theNavy, Coast Guard or Army Corps of Engineers. Their durability and proven record makethem in demand among local agencies.LeComte fLeComte Holland BV manufactures versatile FRP landing craft using vacuum-assisted injectionmolding. S-glass, carbon and amunid fibers are used with polyester resin. The entire hull ismolded in one piece using male and female molds via the resin transfer molding (RTM)process.LeComte introduced a new type of rigid hull, inflatable rescue boat. The deep-’V’ hull is madeby RTM with hybrid fibers, achieving a 25% weight savings over conventional methods. Boatspeeds are in excess of 25 knots. [1-9]10

ChapterOneAPPLICATIONSTextron Marine SystemsTextron Marine Systems has long been involved with the development of air cushion andsurface effect ships for the government. In 1988, the company implemented an R & D programto design and build a small air cushion vehicle with a minimal payload of 1200 pounds. Theresult is a line of vessels that range in size from 24 to 52 feet that are fabricated from shapedsolid foam block, which is covered with GRP skins. The volume of foam gives the addedvalue of vessel unsinkability. Shell Offshore Inc. has recently taken delivery of a 24 footversion for use near the mouth of the Mississippi River.configuration of the type of vessel delivered to Shell.Figure1-6shows a typical CargoA==”==---”’--’”------=-------------------A9IFigure 1-6 Cargo Configuration for Textron Marine’s Utility Air Cushion Vehicle -ModeI 1200 Textron Marine]PassengerFerriesBlount MarineBlount Marine has developed a proprietary construction process they call Hi-Tech@ thatinvolves the application of rigid polyurethane foam over an aluminum stiffening structure. Afleet of these vessels have been constructed for New York City commuter runs.Karlskronavarvet, ABKarlskronavamet, AB in Karlskrona, Sweden, is among several European shipyards that buildpassenger and automobile ferries. The Surface Effect Ship (SES), JET RIDER is a high speedpassenger ferry designed and fabricated by Karlskronavarvet in 1986 for service in Norway.The SES JET RHIER is an air cushioned vehicle structured entirely of GRP sandwich. TheSES conf@ration resembles a traditional catamaran except that the hulls are much narrower.The bow and stern are fitted with flexible seals that work in conjunction with the hulls to trapthe air cushion. Air flow for a surface effect ship is shown in Figure 1-7. The air cushion11

ComercialMarineIndustryMarine Compositescarries about 85% of the totalweight of the ship with theremaining 15% supported by thehulls. The design consists of alow density PVC cellular plasticcore matetial with closed, *non-water-absorbing cells, coveredwith a face material of glass fiberfigllre 1-7 Air Flow in a Surface Effect Shipreinforced polyester plastic. The[Hellbratt & Gullberg, The High Speed Passengercomplete hull, superstructure and Ferry SES JET RIDER]foundation for the main enginesand gears are also built of GRP sandwich. Ttis for fuel and water are made of hull-integratedsandwich panels. The sp=d under full load is 42 knots (full load includes 244 passengers andpayload totaling 27 metric tonnes). [1-10]Air Ride CraftDon Burg has patented a surface effect ship that utilizes a hi-hull configuration and hasdeveloped the concept for the passenger ferry marke~ Although the 109 foot version isconstructed of aluminum, the 84 and 87 foot counterparts are constructed from Airex-coredfiberglass to ABS spectilcations. The FRP vessels are constructed in Hong Kong by CheoyLee Shipyards, a pioneer in Far East FRP construction. To their credit is a 130 foot,twin-screw motor yacht that was constructed in 1976.ItalcraftItalcraft has developed a 70 foot aramid/GRP hull with variable geometry to achieve highspeeds. The prototype demonstrated a 50 knot speed potential with 40% fuel savings. Theconcept is being developed for a high-speed passenger ferry to accommodate 80 passengers andattain a cruising speed of 43 knots. [1-11]CommercialShip ConstructionIn 1971, the Ship Structure Corrunittee published a detailed report entitled “Feasibility Study ofGlass Reinforced Plastic Cargo Ship” prepared by Robert Scott and John Sommella of Gibbs &Cox. A 470 foot, dry/bulk cargo vessel was chosen for evaluation whereby engineering andeconomic factors were considered. It would be instructive to present some of the conclusionsof that study at this time.. The general conclusion was that the design and fabrication of a large GRPcargo ship was shown to be totally within the present state-of-the-art, butthe long-term durability of the structure was questionable.. The most favorable laminate studied was a woven-roving/unidirectionalcomposite, which proved 43% lighter than steel but had 20% of the stiffness.●GRP structures for large ships currently can’t meet present U.S. CoastGuard fire regulations and significant economic incentive would benecessary to pursue variants.12

ChapterOneAPPLICATIONSc Cost analyses indicate unfavorable required freight rates for GRP versussteel construction in all but a few of the sensitivity studies.●●Major structural elements such as deckhouses, hatch covers, king posts andbow modules appear to be very well suited for GRP construction.Commercial vessels of the 150-250 foot size appear to be more promisingthan the vessels studied and deserve further investigation.Thert are numerous non load-bearing applications of FRP materials in commercial ships whereeither corrosion resistance, weight or complex geometry justied the departure fromconventional materials. As an example, in the early 1980’s, Farrell Lines used FRP false stacksin their C1O vessels that weighed over 30 tons. Also, piping for ballast and other applicationsis commonly made from FRP tubing.CommercialDeeD Sea SubmersiblesFoam cored laminates are routinely being used as buoyancy materials in commercial submersibles,The Continental Shelf Institute of Norway has developed an unmanned submersible called theSNURRE, with an opemting depth of 1,500 fee~ that uses high crush point closed cell PVC foammaterial for buoyancy. From 1977 to 1984 the SNURRE operak.d successfully for over 2,000 hoursin the North Sca The Finch manned submersible, NAUTILE, recently visited the sea floor at thesite of the Titanic. The NAUTILE is a manned submersible with operating depths of 20,000 feetand uses high crush point foam for buoyancy and FRP materials for non-pressure skins and fakings.The oil industry is making use of a subrnmible named DAVID that not only utilizes foam forbuoyancy, but uses the foam in a sandwich configuration to act as the pressure vesseL The use ofcomposites in the DAVID’s hull allowed the enginem to design speckdid geometries that areneeded to make effective repairs in the offshcm envimnmen~ [1-3]Slingsby Engineering Limited designed and developed a third-generation remotely operatedvehicle, called SOLO, for a variety of inspection and maintenance functions in the offshoreindustry. SOLO carries a comprehensive array of sophisticated equipment and is designed tooperate at a depth of 5,000 feet under a hydrostatic pressure of 2 ksi. The pressure hull, chassisand fakings are constructed of glass fiber woven roving. [1-12]A prototype civilian submarine has been built in Italy for offshore work. “The design consists ofan unpressurized, aramid-epoxy outer hull and offers a better combination of low weight withimproved stiffness and impact toughness. The operational range at 12 knots has been extendedby two hours over the range of a glass hull. [1-13]NavigationalAidsSteel buoys in the North Sea are being progressively replaced with plastic buoys due toincreasing concern of darnage to vessels. Balrnoral Glassfibre produces a complete line ofbuoys and a light tower made of GRP that can withstand winds to 125 mph. Anchor mooringbuoys supplied to the Egyptian offshore oil industry are believed to be the largest GRP buoysever produced. These 13 foot diameter, 16.5 ton reserve buoyancy moorings are used to anchortankers of up to 330,600 ton capacity. [1-14]13

ComercialMarineIndustryMarine CompositesOffshoreEngineeringComposite materials are already being used in offshore hydrocarbon production because of theirlightness, resistance to corrosion and good mechanical properties. One proposed new use forcomposites is for submarine pipelines, with circumferential carbon fibers providing resistance toexternal pressure and longitudinal glass fibers providing lengthwise flexibility. [1-9]Another application for deep sea composites is driUing risers for use at great water depths.Composites would signillcantly reduce the dynamic stress and increase either the working depthor the safety of deep water chilling. Fifty foot lines made from carbon and glass fibers, with aburst pressure of 25 ksi, have been effectively subjected to three successive drilling sessions to10 ksi fkom the North Sea rig PHVTAGONE84. [1-9]Piling Forms and JacketsDowns Fiberglass, Inc. of Alexandria, VA has developed a line of forms and jackets for use inthe building and mwnration of bridge columns. The “tidal zone” of maritime structures isknown to endure the most severe erosion effects and traditionally is the initial area requiringrestoration. Common practice involves the use of a pourable epoxy to encapsulate this portionof decaying piles.The forms shown in Figure 1-8 are lightweight permanent forms with specially treated innersurfaces to enhance bonding characteristics. The basic jacket material- is E~glass mat andwoven roving in a polyester resin matrix.Conaate PileFonnforNewCoftskuotlonor Major Re@r—FormwithEw)ry Filler,,.0 L ..>A>~, ;’*,, .,“ “: +. :~,:;. ....’ r%,. -, .* ‘“:,,., ..: .-,.j ...;.,..*. - .: ....,●,7 ,’”- :.. .,’ 4 ‘“,,.; ;{, ..,..... ● .,~. :,..,;:. ,:... “t!!‘? ,. :.* d . .,,,: . .. ,,.. . .ii? .. ‘figure 1-8 Fiberglass Forms and Jackets for Waterline Corrosion Restoration[Dowries]14

ChapterOneAPPLICATIONSThe Department of Defense has sponsored composites research and &velopment projects tosupport military applications since World War It. Typically, research has been orientedtowards a particular system or platform without regard to integration within or amongst theDoD research entities. Advanced materials investigated by the Air Force and NASA areusually too cost prohibitive for consideration in mwine structures. For that reason, this sectionwill deal primarily with the past and current activities of the Navy and the Army.NawAccording to a study prepared for the U.S. Navy in 1988, the military has been employingcomposite materials effectively for many years and has an increasing number of projects andinvestigations underway to further explore the use of composites. [1-3] In 1946, the Navy lettwo contracts for development of 28 foot personnel boats of laminated plastic. WinnerManufacturing Company used a “bag molding” method while Marco Chemical employed an“injection method.” The Navy used the second method for some time with limited successuntil about 1950 when production contracts using hand layup were awarded. Between 1955and 1962, 32 Navy craft from 33 to 50 feet in length were manufactured by the “core mold”process, which proved not to be cost effective and was structurally unsatisfactory. [1-15]During the 1960’s, the Navy conducted a series of studies to consider the leasability of using an FRPhull for minesweepers. In 1969, Peterson Builders, Inc. of Sturgeon Bay, M completed a 34 footlong midship test section. A complete design methodology and process description was developedfor this exercise. Although the scale of tie effort was forrnkkible, questions regarding economicsand materials performance in production units went unanswered [1-16]SubmarinesOne military program which employs composite materials is the W?iT SW?. Its compositecomponents have proven reliable for over 10 years. Both the elevator and the rudders amconstructed of a syntactic foam core with fiberglass and polyester skins. The outer skin and hatches,the tail section and the ilxed lins on the WETSUB arealsomadeof composite materials. [1-3]The Navy’s ROV and mine huntirgheutralization programs have been using composits materialsfor structural, skin and buoyancy applications. Current ROVS employ composite skins and framesthat are constructed from metal molds using the vacuum bagging process. [1-3]Various submarine structures am made of composite materials, including the periscope fairings onnuclear submarines and the bow dome on combatant submarines. Additionally, the use ofilarnent-wound air flasks for the ballast tanks of the Tlident class submarines has been investigatedu nmanned, deep submersibles rely heavily on the use of composites for structural members and forbuoyancy. Syntactic foam is used for buoyancy and thick-walled composites are used for pressurehousing. One unmanned deep sea submersible, which has a depth rating of 20,000 fee~ isconstructed with graphite composite by the prepreg fabrication technique. [1-3]The propellers for the MK 46 torpedo m now being made of composite materials. Moldedcomposite propeller assemblies have replaced the original forged ah.uninurn propellers. Thecomposite propellers are compression molded of glass fiber reinforced polyester resim Advantages of15

MilitaryApplicationsof CompositesMarine Compositesthe new composite propellers include weight savings, chemical inertness wd better acousticm~” -*of tie me~ ~wnents ~y reduces detectability. Additionally, studieshave projected this replacement to have saved the pmgmm about $21 milliom [1-3]A submarine launched missile utilizes a capsule module that is constructed of compositematefials. The capsule design consists of a graphite, wet, filament-wound sandwichconstruction, metal honeycomb core and Kevlsx reinforcements. Another torpedo project hasinvestigated using a shell constructed of filament-wound carbon fiber composite in a sandwichconfiguration. The nose shell of the torpedo was constructed with syntactic foam core andprepreg skins of carbon and epoxy resin. Tesdng revealed a reduction in noise levels andweight as compared to the conventional aluminum nose shell. [1-3]Patrol BoatsThe Navy has a lot of inshore special warfare craft that are mainly operated by the NavalReserve Force. More than 500 riverine patrol boats were built between 1965 and 1973. These32 foot FRP hulls had ceramic armor and waterjet propulsion to allow shallow water operation.Production of GRP patrol craft for the Navy has not proven to be profitable for severalconcerns recently. Uniflite built 36 Special Warfare craft, reportedly of GRP/Kevlar@construction, to support SEAL operations in the esrly 1980’s and has since gone out ofbusiness. The Sea Viking was conceived as a 35 foot multi-mission patrol boat with provisionsfor missiles. The project suffered major design and fiscal problems, including an unacceptableweight increase in the lead ship, snd eventually its builder, RMI shipyard of San Diego, wentout of business.Mine Counter Measure VesselsThe U.S. Navy in l?Y 1984 had contracted with Bell Aerospace Textron (now Textron Marine)to design and construct the first of 14 minesweeper hunters (MSH). The hulls were GRPmonohulls utilizing surface effect ship technology. Tests showed that the design could notwithstand explosive charges snd subsequent redesign efforts failed.In 1986, a contract was issued to Intermmine USA to study possible adaptations of the LERICIclasscraft to carry U.S. systems. The LERZCIis 167 feet and is made with heavy single skin constructionthat varies from one to nine inches and uses no frames. hmmarin e is currently building the leadship in Savannah, GA and Avondale Shipyards has been chosen as the Navy’s second source forthis ProcurementThe Swedish and Italian Navies have been building minesweeping operations (MSO) ships withcomposite technology for many years. The Swedish Navy, in conjunction with the RoyalAustralian Navy snd the U. S. Navy, studied shock loadings during the development of theSwedish composite MSO. Shock loadings (mine explosion simulations) were performed onpanels to study candidate FRP materials and corfgurations such as:. Shapes of frame terminations. Frames with different heightkidth ratio●Epoxy frames16

ChapterOneAPPLICATIONS. Sprayed-up laminatess Corrugated laminatess Sandwich with different core densities and thicknesses. Different types of repairs●Weight brackets and penetrations on panels. Adhesion of fire protection coatings in shock●The effect of double curved surfaces. Reduced scale panel with bolted and unbolted framesThis extensive testing program demonstrated that a fmtmeless Glass Reinforced Plastic (GRP)sandwich design utilizing a rigid PVC foam core material was superior in shock loading and resultedin better craft and crew survivability. The Swedish shock testing program demonstrates that whenproperly designd composite materials can withstand and dampen large shock loads. [1-17] Table1-1 Summarizes the current use of FRP for mine countermeasure vessels.Table 1-1. Current FRP Mine Counter Measure Vessels [ISSC, 1988]WILTON United Kingdom 1 425 46 15Hunt United Kingdom VesperThornycrofl 11 13 725 60 16SANDOWN United Kirmdom 9S~iffened ASTER Belgium Beliard 5 10 544 51.5 15Single Skin ERIDAN France Lorient Dockyard 6 10 544 49.1 15ALKMAAR Netherlands Van derModified Indonesia Giessen-deNorde l%+%+1 IKIISHI Finland Oy FiskarsAB 7 20 15,2 111 IBAMO France GESMA MCM 5 900LANDSORT Sweden Karlskronavarvet 4 5 360 47.5 15FoamSandwich Bay Australia Barrington 2 6 170 30.9 10Stan Flex 300 Denmark DanyardAelbXg Als 7 16 300 54.0 30-ILERICI Italy 4 10 520 50 15LERIC/ Nigeria Intermarine,SpAUnstiffenedThick Skin KIMABALU Malaysia l=%%%I 1 IModified LER/C/ I South Korea Kang Nam 2 3 540 51 15,1 1 IOSPREY UnitedStates Intermarine,USA o 17 660 57,317

MilitaryApplicationsof CompositesMarine CompositesComponentsComposite ship stacks versus conventional steel ship stacks are under investigation for the U.S.surface fleet Non-structural ship components are being considered as candibtes for replacementwith composite parts. It is reported that two types of advanced non-structural bulkheads are inservice in U.S. Navy ships. One of these consists of aluminum honeycomb with aluminum facesheets, and the other consists of E-glass PRP skins over an amunid core material. [1-3]The OSPREY Class (MHC-51) rninehunter incorporates many FRP components including deckgratings, flwr plates and support structure. Additional applications for composite materials arebeing considered for follow-on vesselsThe David Taylor Research Center (DTRC) recently contracted for the construction of ashipboard composite foundation. An open design competition attracted proposals featuringhand layup, resin transfer molding, pukrusion and filament winding. A filament woundprototype proposed by Brunswick Defense won out, in part, because the long term productionaspects of the manufacturing process seerned favorable. The foundation has successfully passeda shock testDevelopment of composite propulsion shafts for naval vessels is being investigated to replacethe massive steel shafts that comptise up to 2% of the ship’s total weight. Composite shafts ofglass and carbon reinforcing fibers in an epoxy matrix are projected to weigh 75% less than thetraditional steel shafts and offer the advantages of corrosion resistance, low bearing loads,reduced magnetic signature, higher fatigue resistance, greater flexibility, excellent vibrationdamping and improved life-cycle cost. [1-3]Composite pressure vessels are being develops tested and manufactured for space and militaryuses. Composite pressure vessels were used in three propulsion systems and the environmentalcontrol and life support system for the Space Shuttle ORBITER. Johnson Space Centerestimated a cost savings of $10 million in fuel over the life-span of the ORBITER as comparedto all-metal vessels of the Apollo program type. Filament-wound pressure vessels constructedof graphite, fiberglass or Kevlsr@ with epoxy resins over a titanium liner have been used.Aramid composites are used in the Space Shuttle program to reinforce equipment storageboxes, pressure vessels, purge and vent lines, thus allowing for weight savings and increasedstiffness. [1-3]The U.S. Navy studied the benefits of hydrofoils in 1966. The USN experimental patrol crsfthydrofoil (PCH- 1) HIGHPOINT was evaluated for weight savings. The overall weight savingsover HY 80 steel were 44~0 for glass reinforced plastic, 36~0 for titanium alloy and 24% forHY 130 steel. In the mid 1970’s a hydrofoil control flap (Figure 1-9) and a hydrofoil boxbeam element applying advanced graphite-epoxy composites were evaluated by the Navy. [1-9]A recent program evaluated the use of advanced composites instead of steel in the stabilizingflaps of the Italian RHS 160 hydrofoil. Carbon fibers were the primary reinforcement, withglass added for galvanic corrosion resistance. [1-9]Composite blades of carbon-glass FRP skins over polyurethane foam core have been developedfor and used successfiilly by hovercraft. The FRP blade weighs about 28 pounds, as compared to40 pounds for its duraluminum counterpart, snd tested better in fatigue than the metal blade. [1-9]18

ChapterOneAPPLICATIONSMI intitdfia~m$ 10 21 24 27.--L--aoti (IOI & I?OI &II & & & {w UOI tm} w) IIc9)I‘~%8AMV titmhnn=spm/umk~WECm@lmtinCmpmkmi@W&y~ : ,t-, ;$F@.ltel-g U.S. Navy Patrol Craft Hydrofoil (PCH-l) Composite Flap [ASMEngineer’sGuide to Composite Materials]The skirts surrounding the air cushion on hovercraft are made with fiber reinforced elastomers.Design and fabrication of three types, bag and finger skirts, loop and segment skirts, andpericell skirts, have been evaluated and are reviewed in the reference. [1-9]ArrowSome pressure vessels constructed of fiberglass and epoxy resin have evi&nced burst pressuresof 50,000 psi. Kevlar@/epoxy structured pressure vessels had burst pressures of 57,000 psi, andgraphitdepoxy structures had burst pressures of 60,000 psi. These lightweigh~ high pressurecomposite vessels have the potential for use not only as air supplies in submersibles but also ascompressed-ti-energy storage systems. [1-3]Composites are being considered for structural, non-structural and ballistic applications inmilitary combat and logistical support vehicles. In addition to weight reduction, compositeswill improve maneuvering capability, corrosion resistance, deployability and vehicle survival.Applications akeady investigated or considered include composite covers for external storageboxes, internal ducts, electrical boxes (non-structural), composite brackets, seat components,and turret basket assembly (structural). Also under development are a com~osite.torsion tubewith steel splines to substitute for heavy steel bars, which are used for vehicle suspension.[1-18]The U.S.structures,Amny has investigated the use of composite materials for combat vehicle hullstowage equipment and other mission critical structural components. A feasibility19

MilitaryApplicationsof CompositesMarine Compositesstudy was performed by FMC Corporation, San Jose, CA un&r contract to the U.S. A-my TankAutomotive Command (TACOM), Warren, MI to determine the technical and economicfeasibilities of a composite lower weapon station basket for the M-2 Bradley Fighting Vehicle(BFV). Critical issues were encountered and resolved in regard to design, producibility,material testing and evaluations, crew survivability, and quality assurance and control. FMCCorporation is continuing their development and refinement of composite manufacturingprocesses to meet the needs of the future. Some projects include composite battery trays,ammunition boxes and other stowage components. The U.S. Army Materials TechnologyLaboratory is investigating major vehicle component applications such as hulls, turrets andramp doors. [1-19]TACOM recognizes the advantages of composite materials for combat and tactical militaryground vehicles and is investigating composites for various military vehicle applications.Composite vehicle bodies are being evaluated. One-piece graphite/epoxy driveshafts are beingtested on the High Mobility Multipurpose Wheeled Vehicle (HMMWV) to replace themulti-piece metal shaft. TACOM sponsored a contract with General Dynamics that identifiedcomponents in the Abrams Tank, which are currently fabricated from aluminum or steel butcould be made from composites. Non-ballistic components were considered, such as seats,fenders, storage box, air ducts, torsion bar covers and fire extinguisher brackets. Compositeroad wheels have been designed for the Abrams Tank with equivalent strength as their forgedaluminum counterparts but with the potential of reducing vehicle weight by 1,100 pounds; fieldtesting of these is required. Track pins and track shoes for ground vehicles have also beeninvestigated. The Ml 13A3 armored personnel carriers manufactured after June 1987 containKevlar span liners mounted inside the aluminum body to catch spill fragments as a result ofprojectile impact and prevent further damage to persomel or equipment. [1-20]Components for the Five Ton Truck were fabricated of composites and road tested. Thecomposite components include the frame (graphite reinforced epoxy), front and rear springs(continuous glass reinforced epoxy), the drive shaft (filament wound graphite reinforcedepoxy), wheels (compression molded glass reinforced epoxy), cargo bed (balsa core withfiberglass reinforced polyester and steel plate), seat slats (pultruded glass reinforced polyester),and hood/fender assembly (chopped glass reinforced polyester). The final report on this projectis available through DTIC. [1-20]The U.S. Army is also evaluating two proto~e, composite, 7,500 gallon, bulk fuel tankers andcomparing them to standard metal tankers. The composite tankers have a composite frame anda flame resistant foam core with glass reinforced resin skins. [1-20]In addition to the composite material evaluations cited here, composites are currently beingused in some military vehicles. The current HMMWV has a glass reinforced, polyester,hood/fender assembly, and some versions have a composite roof. Kevlar@ is used in someversions of the HMMWV, such as the ambulance, for the walls and roof. The CommercialUtility Cargo Vehicle has a composite cap. [1-20]20

.—ChapterOneAPPLICATIONSThe transportation industry represents the best opportunity for growth in structural compositesuse. As raanufacturing technologies mature, the cost and quality advantages of compositeconstruction will introduce more, smaller manufacturers into a marketplace that will beincreasingly responsive to change. [1-21] Current FM technology has long been utilized inthe recreational vehicle industry where limited production runs preclude expensive tooling andcomplex forms are common. Truck hoods and fairing assemblies have been prevalent since theenergy crisis in 1974.AutomotiveApplicationsThe automotive industry has been slowly incorporating composite and FIW materials into carsto enhance efficiency, reliability and customer appeal. In 1960, the average car containedapproximately 20 pounds of plastic material, while a car built in 1985 has on the average 245pounds of plastic. Plastic materials are replacing smel in body panels, grills, bumpers andstructural members. Besides traditional plastics, newer materials that are gaining acceptanceinclude reinforced urethane, high heat distortion thermoplastics, high glass loaded polyesters,structural foams, super tough nylons, high molecular weight polyethylene, high impactpolypropylene and polycarbonate blends. New processes are also accelerating the use ofplastics in automobiles. These new processing technologies include reaction injection moldingof urethane, compression molding, structural foam molding, blow molding, thermoplasticstamping, sheet molding, resin injection molding and resin transfer molding. [1-22]MOBIKThe NIOBIK company in Gerlingen, West Germany, is researching and developing advancedcomposite engineering concepts in the automotive industry. They believe that tomorrow’s carmust be economical and functional and more environmentally compatible. Composite IntensiveVehicles (CIVS) will weigh less and thus enable considerable savings in other areas. Lowerhorsepower engines, less assembly time and cost, longer lifespan and fewer repairs are amongthe benefits of composite intensive automobiles. In addition, these advanced composites willdampen noise and vibrations, allow for integration of parts, experience less corrosion, need lesstooling and equipment transformation, and am recyclable. Obstacles they face include presentlack of a high-speed manufacturing technology for advanced composites and new engineeringsolutions to overcome structural discontinuities. [1-23]The April 1989 issue of Plastics Technology magazine reports that MOBIK has developed ahigh speed method for making advanced composite preforms for use in structural automotivecomponents. The prefomns are made from woven glass fabric and polyetherimide (PEI)thermoplastic. The method enables vacuum forming of 3 by 3 foot preforms in less than 30seconds at about 20 psi. The method involves high speed fiber placement while the sheet isbeing thermoformed. MOBIK plans to produce prototype automotive preforms at a pilot plantscheduled to open this fall. Initial applications will also include preforms for aircraft interiorcabins.21

TransportationIndustryMarine CompositesFordComposite driveshafts are being used in the automotive industry, During the 1985 Society ofPlastics Industries (SPI) exhibit, Ford Motor Company won the transportation category with agraphite composite driveshtit for the 1985 Econoline van. The driveshaft was constructed of20% carbon fiber and 40% E-glass fiber in a vinyl ester resin system. The shaft is totallycorrosion resistant and weighs 61YOless than the steel shaft it replaces. [1-22] MerlinTechnologies and Celanese Corporation developed carbon/fiberglass composite driveshtits tha~in addition to weight savings, offer reduced complexity, warranty savings, lower maintenance,cost savings, and noise and vibration reduction as compared to their metal counterparts. [1-24]Another structural composite developmental program, initiated in 1981 by Ford MotorCompany, focused on designing a composite rear floor pan for a Ford Escort model. Finiteelement models predicted that the composite part would not be as stiff but its strength would bedouble that of the identical steel part. The composite floor pan was made using fiberglass/vinylester sheet (SMC) and directionally reinforced sheet (XMC) molding compounds. Stock Escortcomponents were used as fasteners. Ten steel components were consolidated into onecomposite molding, and a weight savings of 1570 was achieved. A variety of static anddynamic material property tests were performed on the prototype, and all the specimensperformed as had been predicted by the models. The structural integrity of the part wasdemonstrated, hence the feasibility of molding a large structural part using selective continuousreinforcements was shown. [1-25]A sheet molding compound (SMC) material is used to make the tailgate of the Ford Bronco IIand is also used in heavy truck cabs. [1-22]Ford utilizes a blow molded TPE air duct on its Escort automobiles. The front and rear bumperpanels of Hyundai’s Sonata are made from engineered blow molding (EBM). [1-26]A study completed by Ford in 1988 confms the feasibility of extensive plastics use as a meansof reducing production costs for low volume automobiles, such as electric powered cars.According to the study, plastics yield a parts reduction ratio of 5:1, tooling costs are 60% lowerthsn for steel stamping dies, adhesive bonding costs are 25-40% lower than welding, andstructural composites demonstrate outstanding durability and crashworthiness. Composite frontaxle crossmember parts have undergone extensive testing in Detroit and await a rationale forproduction, [1-27]The Ford Taurus and Mercury Sable cars utilize plastics extensively. Applications includeexterior, interior and under the hood components, including grills, instrument panels andoutside door handles, to roof trim panels and insulations, load floors, cooling fans and batterytrays. The polycarbonate/PBT wraparound front and rear bumpers are injection molded ofGeneral Electric’s Xenoy@material. [1-28]Other significant new plastic applications in Ford vehicles include the introduction of the highdensity polyethylene fuel tank in the 1986 Aerostar van. [1-28]A prototype graphite reinforced plastic vehicle was built in 1979 by Ford Motor Company.The project’s objective was to demonstrate concept feasibility and identify items critical to22

ChapterOneAPPLICATIONSproduction. The prototype car weighed 2,504 pounds, which was 1,246 pounds lighter than thesame car manufactured of steel. Automotive engineers are beginning to realize the advantagesof part integration, simplified production and reduced investment cost, in addition to weightsavings and better durability. [1-22]The Ford Motor Company in Redford, MI established engineering feasibility for the structuralapplication of an HSMC Radiator Support, the primary concern being weight savings. [1-29]The Ford Motor Company and Dow Chemical Company combined efforts to design, build andtest a structural composite crossmember/transverse leaf spring suspension module for a smallvan. Prototype parts were fabricated and evaluated in vehicle and laboratory tests, and resultswere encouraging. [1-30]General MotorsBuick uses Hoechst Celanese’s Riteflex@ BP 9086 polyester elastomer alloy for the bumperfascia on its 1989 LeSabre for its paintability, performance and processability. [1-26]The Pontiac Fiero has an all plastic skin mounted on an all steel space frame. The space frameprovides all the functional strengthening and stiffening and consists of a five-piece modulardesign, and the plastic body panels are for cosmetic appearance. The shifter trim plate for thePontiac Fiero k made of molded styrene maleic anhydride (SMA) and resists warping and. scratching, readily accepts paints and exceeds impact targets.Drive axle seals on the 1985 GM front wheel drive cars and trucks are made of Hytrel polyesterelastomer for improved maintenance, performance and life.Wheel covers for the Pontiac Grand AM are molded of Vydyne mineral reinforced nylon forhigh temperature and impact resistance. [1-28]GenCorp Automotive developed a low density sheet molding compound (SMC) that is claimedto be 30% lighter than standard SMC. The material has been introduced on theall-plastic-bodied GM 200 minivan and the 1989 Corvette. [1-26] The automotive exteriorpanels on the GM 200 APV minivan are plastic. The minivan has polyurea fenders and SMCskin for roofs, hoods and door panels. BMW also uses plastic exterior panels on its Z1 model.[1-31]ChryslerIn a joint program initiated in 1984 between the Shell Development Company, Houston, TXand the Chrysler Corporation, a composite version of the steel front crossmember for Chrysler’sT-1 15 minivan was designed, fabricated and tested. Chrysler completed in-vehicle provinggrounds testing in March 1987. The program increased confidence that composites made fromnon-exotic commercially available materials and fabrication processes can withstand severeservice in structural automotive applications. [1-32]Chrysler uses nearly 40 pounds of acrylonitrile-butadiene-styrene (A13S) in its single-piece,four-segment molded interior unit for the Dodge Caravan and Plymouth Voyager. [1-28]23

Trsnsportatlon IndustryA4arineCompositesLeafspringsResearch and testing has been performedby the University of Michigan on acomposite elliptic spring, which wasdesigned to replace steel coil springs usedin current automobiles. The compositespring consists of a number of hollowelliptic elements joined together, as shownin Figure 1-10. The elliptic springelements were manufactured by windingfiber reinforced epoxy tapes to variousthicknesses over a collapsible mandrel.The work performed indicates that FRPsprings have considerable potentisl as asubstitute for steel coil springs. Amongthe advantages of the composite designare a weight savings of almost 50Y0,easier repairability, and the potentialelimination of shock absorbers due to thehigh damping characteristics inherent infiber reinforced plastics. [1-33]Figure 1-10 Composite Elliptic Spring[ASA4 Engineers’Guideto CompositeA4aterW]Composite leaf springs for heavy trucks have been designed, manufactured and tested. In oneprogram, a fiberglass sheet molding compound and epoxy resin were used with a steel mainleaf in a compression-molding process. Mechanical testing of the finished parts demonstratedthat design requirements for the component can be met using composites while achieving aminimum of 40% weight reduction over steel leaf springs. [1-34]FramesGraphite and Kevlar fibers with epoxy resin were used to make a composite heavy truck framedeveloped by the Convair Division of General Dynamics. The composite frame weighs 62%less than steel and has the same strength and stiffness. The frame was tested for one year(18,640 miles) on a GMC truck without any problems. No stracturtd damage was evident, boltholes maintained their integrity, and there was no significant creep of the resin matrix. [1-35]A torsionally stiff, lightweight monocoque chassis was designed and fabricated in 1986 by theVehicle Research Institute at Western Washington University, Bellingham, WA. Called theVildng VIII, this high performance, low cost sports car utilizes composite materials throughoutand weighs only 1,420 pounds. Fiberglass, Kevlar@and carbon fiber were used with vinyl esterresin, epoxy adhesive and aluminum honeycomb core in vsrious sandwich configurations.Final detailed test results were not available in the literature, however, most of the performancegoals were met with the model. [1-36]Safety DevicesHoneycomb structures can absorb a lot of mechanical energy without residual rebound and areparticularly effective for cushioning air dropped supplies or instrument packages in missiles,24

ChapterOneAPPLICATIONSproviding earthquake damage restraints for above ground pipelines, or protecting people inrapid transit vehicles. A life-saving cushioning device called the Truck Mounted CrashCushion (TMCC) has been used by the California Department of Motor Transportation. TheTMCC has proven effective in preventing injury to, and saving the lives of, highway workersand motorists. The TMCC is mounted to slow moving or stopped transportation departmentmaintenance and construction vehicles. In case of an accident, after an initial threshold stress(that can be eh.ninated by prestressing the honeycomb core) at which compressive failurebegins, the core carries the crushing load at a controlled, nem linear rate until it k completelydissipated wkhout bouncing the impacting car or truck into a work crew or oncoming traffic.Manufacturing TechnologiesMany competitive, stampable reinforced thermoplastic sheet products have been used during thepast few years in the auto industry both in the U.S. and abroad. In 1988, Exxon AutomotiveIndustry Sector, Farmington Hills, MI, introduced its Taffen STC (structural thermoplasticcomposite) stampable and compression-moldable sheet This long-glass reinforcedpolypropylene sheet has already been used by European auto makers Peugeot, Audi, Vauxhall(GM) and Renault for instrument panel components, load floors, battery trays and otherstructwd parts. A spokesman for Exxon claims that the materkil is under evaluation for 40different programs at Ford, General Motors and Chrysler. [1-26]A North American automotive engineering company has been designing and testing blowmolded fuel tanks for cars. Hedwin Corporation, West Bloorniield, MI recently announced theapplication of an all-HDPE blow molded fuel tank forward of the drive shaft. The tank wasproduced for the 1989 Ford Thunderbird and Mercury Cougar, and Hedwin claims it is the fistin a U.S.-built car to be mounted forward of the drive shaft. Because of the tank’s location, thedesign had to allow the shaft to pass through the middle of the tank, making it necessary to goto an exceedingly complex shape. [1-26]At the Spring 1989 Society of Automotive Engineers International Congress & Exposition,significant developments in quality-enhancing polymer systems and materials technology weredemonstrated. General achievements include: [1-26]...●✎✎☛Breakthroughs in high-productivity reaction injection molding (RIM)formulations and the equipment to handle them.Success for thermoplastic elastomer (TPE) fasci~ with an uhra-softthermoplastic stymnic-based product soon to emerge.Upgraded engineering and sound-damping foams for interior automotiveand other specialty applications.More high-heat polyethylene terephthalate PET materials.A polyphenylene sulfide stionegrade for underhood use.Long-steel-fiber reinforced resins designed for EMI shielding.Impact-modikd polycarbonates, high-heat ABS grades, glass-reinforcedacrylic-styrene-acrylonitrile/polybutylene terephthalate (ASA/PBT) blends,and impact acrylics.25

TransportationIndustryA.M7eCompositesAlso at the Spring 1989 Exposition, Mobay Chemical Co. introduced a MM polyureaformulation that is claimed to offer dramatic productivity gains, excellent thermal stability, asurface finish as smooth as steel, and good abrasion, corrosion and wear resistance. Mobay isbuilding a facility at New Martinsville, WV to produce a patented amine-terminated polyether(ATPE) claimed to improve the quality of auto body panels and other components made withits polyurea systems. Mobay claims that its unreinforced STR-400 structural RIM (SKIM)system, which can be used for automotive applications such as bumper beams, trunk modules,truck boxes, spare-tire covers and roof caps, offers 50% greater notched Izod strength than itsearlier grade of SRIM. [1-26]Dow Chemical announced at the show its completion of the design and engineering of ultrahigh speed equipment to run the fast new RIM materials. [1-26]Proof of SRIM’s practicality was seen on a bumper beam on the 1989 Corvette on display atthe Dow exhibit. It is molded by Ardyne Inc., Grand Haven, MI, using Dow’s Spectrim MM310 system. The SRIM beam combines a directional and random glass preform with a matrixof thermosetting polycarbamate resin and saves 18~0 in weight and 14~0 in labor and materialcosts, according to Chevrolet. [1-26]Hercules announced two new SRIM systems at the Exposition. One, Grade 5000 is a SRIMsystem designed for glass reinforcement and intended for such uses as hoods, trunk lids, doorpanels, side fairings and fenders. The other, Grade 1537, is said to offer a higher heatdeflection temperature (185”F) and better impact, stiffness and strength properties and isintended primarily for bumper covers, side fairing extensions, roof panels and sun visors. It isclaimed to maintain ductility from -3~ to 150°F. [1-26]MaterialsThe following is a list of some promising materialautomotive applications:systems that have been introduced for. Porsche uses Du Pent’s Bexoly V thermoplastic polyester elastomer for theinjection molded front and rear fascias on its new Camera 4 model.c Shell Chemical is introducing new styrcnic-based fiton elastomers, whichare extremely soft with “excellent” compression set and moldability. Itsapplications in the transportation industry include window seals and weathergasketing, where softness, better than average heat resistance, and lowcompression set are important.●●A foam that debuted at the Spring 1989 Exposition is a cold curing flexiblePUR from Mobay, which is designed to reduce noise levels insideautomobiles. BMW now uses the foam system, called Bayfit SA, on all itsmodels.General Electric Plastics has designed and developed a one-piece, structuralthermoplastic, advanced instrument panel module, called AIM, forautomobiles. The one-piece design sharply reduces production time. [1-26]26

ChapterOneAPPLICATIONSCargo Handling. Glass reinforced thermoplastic polyesters such as PBT (polybutyleneterephtlwilate) are used extensively in the automotive industry for exteriorbody parts such as grilles, wheel covers and components for doors, windowsand mirrors. PBT is also in demand for underhood applications such asdistributor caps, rotors and ignition parts. Other uses include headlampparts, windshield wiper assemblies, and water pump and brake systemcomponents.. Du Pent’s Bexloy K 550 RPET has been accepted by Chrysler for use onfenders on some 1992 models. [1-37]. The Polimotor/Lola T-616 is the world’s first competition race car with aplastic engine. The four cylinder Polirnotor engine is ?4 plastic andcontains dynamic parts of injection molded polymer supplied by AmocoChemicals. The race car weighs 1500 pounds and has a carbon fiber chassisand body.. Torlon@is a high performance polyamideimide thermoplastic made byAmoco. Torlon@has a very low coefficient of thermal expansion, whichnearly matches that of steel and is stronger than many other types of hightemperature polymers in its price range. It can be injection molded toprecise detail with low unit cost. Torlon@thrust washers were incorporatedinto Cummins’ gear-driven diesel engines starting in 1982. [1-28]Shipping containers are now being constructed of FRP materials to achieve weight savings andto facilitate and simplify transshipment. Santa Fe Railway has developed an FRP container unitthat is modular, allowing containers to be easily transferred to/from trucks, trains and ships.The containers me constructed using fiberglass in a polyester matrix with a core of balsa wood.The units are aerodynamically designed to reduce wind drag. The containers can be stacked up‘ to six containers high when placed on a ship for transport. Aside from the substantial weightsavings achieved using these containers, the transported goods need not be transferred from oneform of container to another. This results in lower handling costs and reduces the risk of cargodamage. [1-38]Rail and truck tanks made from sandwich FRP utilizetraditional metallic cylindrical counterparts. Projects inadvantage of this technology.more effective volume than theirNorthern Europe are now taking27

IndustrialUse of FRPMarine CompositesThermoplastic IEsinswere frrst introduced in 1889 and have since developed in form and applicationwith a variety of industrial uses. Reinforced polyester resins werE first utilized in 1944 and shall bethe focus of this investigation of industrial thermoplastics. FRP’s advantages in this field include:lightweight structural applications, wide useful temperature range, chemical resistance, flexibility,thermal and electrical insulation, and favorable fatigue characteristics.Piping SystemsThe use of FRP for large diameter industrial piping is attractive because handling and corrosionconsiderations are greatly improved. Filament wound piping can be used at worldngtemperatures up to around 300T with a projected service life of 100 years, Interior surfacesare much smoother than steel or concrete, which reduces frictional losses. The major difficultywith FRP piping installation is associated with connection arrangements. Constructiontechniques and engineering considerations are presented below, along with specific applicationexamples.Pipe ConstructionThe cylindrical geometry of pipes make them extremely well suited for filament windingconstruction. In this process, individual lengths of fiberglass are wound on to a mandrel formin an engineered geometry. Resin is either applied at the time of winding or pre-impregnated(prepreg) into the fiberglass in a semi-cured state. High pressure pipes and tanks are fabricatedusing this technique.A more economical method of producing pipes is called centrifugal casting. In this process,chopped glass fibers are rrtixed with resin and applied to the inside of a rotating cylindricalmold. The reinforcement fibers end up in a random arrangement making the structure’sstrength properties isotropic. This process is used for large diameter pipe in low pressureapplications.Contact molding by hand or with automated spray equipment is also used to produce largediameter pipe. The designer has somewhat more flexibility over directional strength propertieswith this process. Different applications may be more sensitive to either hoop stresses orlongitudinal bending stresses. Figure 1-11 shows the typical construction sequence of acontact-molded pipe.Piping MaterialsFiberglass is by far the most widely used reinforcement material for reinforced pipingcomponents. The strength benefits of higher strength fibers do not justify the added cost forlarge structures. The type of resin system used does vary greatly, depending upon the givenapplication. Table 1-2 lists various resin characteristics.Engineering ConsiderationsThe general approach to FRP pipe construction involves a chemically resistant inner layer thatis surrounded by a high fiber content structural layer and finally a resin rich coating.Additional reinforcement is provided by ribbed stiffeners, which are either solid or hollow.28

ChapterOneAPPLICATIONS1. SMOOTH INNER SURACE [ RESIN RICH INTERIOR REINFORCED WITH SURFACINGVEIL , 90% RESIN / 10% QLASS)2. NEKT INTERIORLAYER( REINFORCEDWITH CHOPPEDSTRAND MAT, $!5. 30% GLASS)3. REMAININ13TNICKNESS( 70% RESIN/ 30% QLASS)4. EXTERIORSURFACE( REsIN RICH SURFACINGVEIL/ PROTECTSAOAINST WEATHERING*SPILLAGE , FUMES , ETC.)Figure 1-11 Cutaway View of Contact-Molded Pipe [Cheremisinoff, Fiberg/ass-ReinforcedPlastics Deskbook]Table 1-2. FRP Pipe Resin SystemsICheremisinoffl Fiberg/ass-Reinforced Plastics Deskbao~ResinIsophthalicFurmaratedbi-sphenolA-type polyesterFire-retardant polyesterVariousthermoset resinsHigh-qualityepoxyVinyl ester and proprieta~resin systemsAppllcatlonMild corrosives at moderate temperaturesand generaI acid wastesMildto severecorrosivefluids includingmany alkaliesand acidsMaximum chemical resistance to acids,alkalies and solventsHigh degree of chemical resistance tospecific chemicalsExtremely high resistance to strongcaustic solutionsExtremelyhigh resistanceto organicacids, oxidizing acids, alkalis and s~ecificsolvents operating in excess of 350 F~FRPFIJ$NGEThe joining of FRP pipe to other bmaterials, such as steel, can beEaccomplished using a simple flange toflange mate; with an encased concretesystem that utilizes thrust rings; or with ak,.,rubber expansion joint, as shown in FigureJOINT1-12. For straight FRP connections, an’0’ ring seal can be used. Figure 1-12 Typical Expansion JointTie-In [Cheremisinoff, Fiberg/ass-/?einforcedPlastics Deskbook]L 0, InRFR tYDANClnM /DIDSPnUMNCNT(VALVE, PUMP,ETC.)29

IndustrialUse of FRPMarineCompositesPractices or codes regarding safe FRP pipe design are established by the following organimions:*The American Society for Testing and Materials (ASTM). The American Society for Mechanical Engineers (ASME). The American Petroleum Institute (API)Table 1-3 presents average properties of FRP pipe manufactured by different methods. Table1-4 lists some recommended wall thicknesses for fdament wound and contact molded pipes atvarious internal pressures.FRP Piping ApplicationsOil IndustryApproximately 500,000 feet of FRP pipe is installed at a Halge-Union Texas project near Ringw@OK and is believed to be tbe single largest FRP pipe installation. FRP epoxy pipe was selectedbecause of its excellent corrosion resistance and low paaffiu buildup. The smoothness of the pipewalls and low thermal conductivity contribute to the inherent resistance to pamffm accumulation. Thematerials that tend to corrode metallic piping include crudes, natural gases, saltwater and corrosivesoils. At an offshore installation in the Arabian Gulf, FRP vinyl ester pip was selected because of itsexcellent mistance to saltwater and humidity. At this site, seawater is illtered through a series of 15foot diameter treks that are connected by 16 inch diameter piping using a multitude of FIW fittings.Table 1-3. Average Properties of Various FRP Pipe[Cheremisinoff, F]b@ass-Reinforced P/astfcs DeskbooKjPropertyModulusof Elasticit inAxial Tension@ 7+F, psiUltimate Axial TensileStrength @ 77° F, psiUltimate Hoop TensileStrength @ 77° F, psiModulus of Elasticity inBeam Flexure @ 77° F, psiCoefficient of ThermaJExpansion, inch/inch/ FHeat DeflectionTemperature @ 264 psi, ‘FTherqal ~onductivity,Btu/ft -hr- F/inchFilamentWound CentrifugallyCast ContactMoldedwith Epoxy or with E o or with g:: :sterPolyester Resins Polyes???er esln)’1.O-2.7X 106 1.3 -1,5X106 0,8- I.8X 1068,000-10,000 25,000 9,000-18,00024,000-50,000 35,000 9,000-10,0001-2X106 1.3 -1.5X106 1.0- I.2X 1068.5- 12.7x 106 13 X106 15 X106200-300 200-300 200-2501.3- 2.0 0.9 1.5Specific Gravity 1,8- 1.9 1.58 1.3- 1.7Corrosive Resistance E E NRE = excellent, will resist most corrosive chemicalsNR = not recommendedfor highly alkaline or solvent applications30

ChapterOneAPPLICATIONS.Coal MineCoal mines have successfully used FRP epoxy resin pipe, according to the Fiber GlassResources Corporation. The materiil is capable of handling freshwater, acid nine water andslurries more effectively than mild steel and considerably cheaper than stainless steel.Additionally, FRP is well suited for remote areas, fm protection lines, boreholes and roughterrain installations.Paper MillA paper mill in Wisconsin was experiencing a problem with large concentrations of sodiumhydroxide that was a byproduct of the deinking process. Type 316 stainless steel was replacedwith a corrosion resistant FRP using bell and spigot-joining methods to further reduceinstallation costs.Power ProductionCirculating water pipes of 96 inch diameter FRP were specially designed to meet theengineering challenges of the BIG CAJUN#2 fossil fuel power plant in New Roads, LA. Theinstability of the soil precluded the use of conventional thrust blocks to absorb axial loads. Bycustom lay-up of axial fiber, the pipe itself was made to handle these loads. Additionally,custom elbow joints were engineered to improve flow characteristics in tight turns.ITable 1-4. Recommended Pipe Wall Thickness in Inches[Cheremisinoff, Fiberg/ass-Reinforced Plastics Deskbook]Internal Pressure Ratina. Dsi-. .InsideDiam. 25 50 75 100 125 150Inche& Flkunent Contact Fllamemt COntaGt Filament contact Ftlament Con@t Filament contact Fllment ContactWound Molded Wound Molded Wound Molded Wound Molded Wound Molded Wound Mo[d~2 0.188 0.187 0.188 0,187 0.188 0,187 0.188 0.187 0.188 0.187 0.188 o.j871 1 1 I I I I I I I I4 I 0.188 I 0.187 [ 0.188 I 0.187 I 0.188 I 0.187 I 0.188 I 0.250 I 0.188 I 0,250 I o.I88 I 0.2501 1 1 I I I I I IG I 0.188 I 0.187 I 0.188 I 0.187 I 0.188 I 0.250 I 0.188 ] 0.250 I 0.188 I 0,312 I 0.188 I 0,3751 1 1 1 I I I I8 I 0.188 I 0.187 I 0.188 I 0.250 I 0.188 I 0,250 I 0.188 I 0,312 ] 0.188 I 0.375 I 0,188 I 0.4371 1 1 I I I I I10 I 0.188 I 0.187 I 0.188 I 0.250 I 0.188 I 0.312 I 0.188 I 0.375 I 0,188 I 0.437 ] 0.188 I 0.50012 0.188 0.187 0.188 0,250 0.188 0,375 0.188 0.437 0.188 0.500 0,214 om62518 0.188 0.250 0.188 0.375 0,188 0.500 0,214 0.625 0.268 0.750 0.321 0.93724 0.188 0.250 0.188 0.437 0.214 0.625 0.286 0.812 0.357 1,000 0.429 1.1201 1 I 1 I I I I I I I36 I 0.188 I 0.375 I 0.214 I 0.625 I 0.321 I 0.937 I 0.429 I 1.250 / 0.536 I 1,500 I 0.843 I 1.810~ 0.188 0.437 0.286 0.812 0.429 1.250 0.571 1.620 0.714 2.000 0,857 2.44060 0.188 0,500 0.357 1.000 0.536 1.500 0.714 2.000 om893 2.500 1.070 3.00072 0.214 0.625 0,429 1.250 0,643 1.810 0.857 2m440 1.070” 3.000 1.290 3.62096 0.286 0.812 0.571 1.620 0.857 2.440 1.140 3.250 1.430 4.000 1.710 4.81031

Industrial Use of FRP Wine CompositesTanksFRP storage tanks megting increased attention asoflati duemrecent ~velationstiattiekmetallic counterparts are corroding and rupturing in underground installations. The fact that itsactivity can go unnoticed for some time can lead to severe environmental rmcations.ConstructionRESIN-RICH LAYER TOUTERSURFACEA cross-sectional view of a typical (CHEMIWY RESISTANTMN’ ORORWNICFRP tank would closely resemble POLYESTERORVINYLESTERI J~VEIL $PRWEOthe pipe described in the previoussection with a barrier inner skinfollowed by the primary reinforcingelement. Figure 1-13 shows thetypical construction of an FRP tank.A general limit for design strainlevel is 0.001 ‘w~~~h according toIIASTM for filament wound tanks/lDESMFERENTIALand National Institute of Standardsand Technology (NIST) for contactRANDOMLY ORIENjEDCHOWED STRANDUiYERmolded tanks. Hoop tensile moduliirange from 2.0 x 106to 4.3 x 106forfilament winding and 1.0 x 106 to Figure 1-13 Cross-Sectional View of StandardVetiical Tank Wall Laminate [Cheremisinoff,1.2 x 106for contact molding.Fiberglass-Reinforced Plastics DeskbookjApplicationFRP is used for vertical tanks when the material to be stored creates a corrosion problem forconventional steel tanks. Designs vary primarily in the bottom sections to meet drainage andstrength requirements. Horizontal tanks are usually used for underground storage of fuel oils.Owens-Coming has fabricated 48,000 gallon tanks for this purpose that require no heatingprovision when buried below the frost line.Air HandlingEquipmentFRP blower fans offer protection against corrosive fumes and gases. The ease of moldabilityassociated with FIW fan blades enables the designer to specify an optimum shape. An overallreduction in component weight makes installation easier. In addition to axial fans, varioustypes of centrifugal fans are fabricated of FRP.Ductwork and stacks are also fabricated of FRP when corrosion resistance and installation easeare of pammount concern. Stacks are generally fabricated using hand lay-up techniquesemploying some type of fwe-retardant resin.32

ChaDterOneAPPLICATIONSCommercialLaddersThe Fiber Technology Corporation is an example of a company that has adapted an aluminumladder design for a customer to produce a non-conductive FRP replacemen~ The intricateangles and flares incorporated into the aluminum design precluded the use of a pultrusionprocess. Additionally, the design incorporated unique hinges to give the ladder addedversatility. All these features were maintained while the objective of producing a lighter,non-conductive alternative was achieved.Aerial TowersIn 1959, the Plastic Composites Corporation introduced an aerial man-lift device used byelectrical and telephone industries. The bucket, upper boom and lower boom insulator are tillfabricated of fiberglass. The towers, known today as “cherry pickers,” are currently cerdf~ed to69 kVA in accordance with ANSI standards and vefiled for structural integrity using acousticemission techniques.33

AerospaceCompositesMarineConmosifesThe use of composites intlm aerospace industry has increased dramatically since the 1970’s.Traditional materials for aircraft construction include aluminum, steel and titanium. Theprimary benefits that composite components can offer are reduced weight and assemblysimplification. The performance advantages associated with reducing the weight of aircraftstructural elements has been the major impetus for military aviation composites development.Although commercial carriers have increasingly been concerned with fuel economy, thepotential for reduced production and maintenance costs has proven to be a major factor in thepush towards composites. Composites are also being used increasingly as replacements formetal parts on older planes. Figure 1-14 shows current and projected expenditures foradvanced composite materials in the aerospace industry.4000I$ mllllonseooo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0lQa2 1087 1982 2000= Mllltary ~ Oommerolal @ Bualnee8~ Hellooptera ~ Mlaslee U SpaoQ ProgramaFigure 1-14 Advanced Composite Sales for the Aerospace Industry, [Source: P-023N Advanced Po/yrner Matrix Composites, Business Communication Company, Inc.]When comparing aerospace composites development to that of the marine industry, it isimportant to note the differences in economic and engineering philosophies. The research,design and testing resources available to the aerospace designer eclipse what is available to hiscounterpart in the marine industry by at least an order of magnitude. Aircraft developmentremains one of the last bastions of U.S. supremacy, which accounts for its broad economic baseof support. On the engineering side, perfomce benefits are much more significant foraircraft than ships. A comparison of overall vehicle weights provides a good illustration of thisconcept.34

ChapterOneAPPLICATIONSAlthough the two industries are so vastly different lessons can be learned from aircraftdevelopment programs that are applicable to marine structures. Material and processdevelopment, design methodologies, quaMcation programs and long-term performance aresome of the fields where the marine designer can adapt the experience that the aerospaceindustry has developed. New aircraft utilize what would be considered high performancecomposites in marine terms. These include carbon, boron and aramid fibers combined withepoxy resins. Such materials have replaced fiberglass reinforcements, which are still thebackbone of the maxine industry. However, structural integrity, producibility and performanceat elevated temperatures are some concerns common to both industries. Examples of specilicaerospace composites development programs are provided to illustrate the direction of thisindustry.Business and CommercialLear Fan 2100As one of the fust aircraft conceived and engineered as a “composites” craft, the Lear Fan usesapproximately 1880 pounds of carbon, glass and aramid fiber material. In addition tocomposite elements that are common to other aircraft, such as doors, control surfaces, fairingsand wing boxes, the Lear Fan has an all composite body and propeller blades.Beech StarshipThe Starship is the first all-composite airplane to receive FAA certification.3000 pounds of composites are used on each aircraft.ApproximatelyBoeingThe Boeing 757 and 767 employ about 3000 pounds each of composites for doors and con~olsurfaces. The 767 rudder at 36 feet is the largest commercial component in service. The737-300 uses approximately 1500 pounds of composites, which represents about 3% of theoverall structural weight. Composites are widely used in aircraft interiors to create luggagecompartments, sidewalls, floors, ceilings, galleys, cargo liners and bulkheads. Fiberglass withepoxy or phenolic resin utilizing honeycomb sandwich construction gives the designer freedomto create esthetically pleasing structures while meeting flammability and impact resistancerequirements.AirbusIn 1979, a pilot project was started to manufacture carbon fiber fin box assemblies for theA300/A310 aircraft. A highly mechanized production process was established to determine ifhigh material cost could be offset by increased manufacturing efficiency. Although materialcosts were 35% greater than a comparable aluminum structure, total manufacturing costs werelowered 65 to 85%. Robotic assemblies were developed to handle and process materials in anoptimal and repeatable fashion.MilitaryAdvanced Tacticai Fighter (ATF)Advanced composites enable the ATF to meet improved performance requirements such asreduced drag, low radm observability and increased resistance tQtemperatures generated at high35

Aerospace Composites /Wtine Compositesspeeds. The ATF will be approximately 50% composites by weight using DuPont’s Avimid Kpolyamide for the fit prototype. Figure 1-15 depicts a proposed wing composition asdeveloped by McDonnell Aircraft through their Composite Flight Wing Program.FaiupBoron~ GraphiteaniumAluminum~ FiberglassUnderstructure ..—---- / “\u—Figure 1-15 Composite Wing Composition for Advanced Tactical Fighter [Moors, f3esjgnConsiderations - Composite Fhght Wing Pfogwn]Advanced Technology Bomber (B-2)The B-2 derives much of its stealth qualities from the material properties of composites andtheir ability to be molded into complex shapes. Each B-2 contains an estimated 40,000 to50,000 pounds of advanced composite materials. According to Northrop, nearly 900 newmaterials and processes were developed for the plane.Second Generation British Harrier “Jump Jet” (AV-8B)This vertical take-off and landing (VTOL) airmail is very sensitive to overall weight. As aresult 26~o of the vehicle is fabricated of composite material. Much of the substructure iscomposite, including the entire wing. Bisrnaleimides (BMI’s) are used on the aircraft’sunderside and wing trailing edges to withstand the high temperatures generated during take-offand landing.36

Ch@er oneAPPLICATIONSNavy Fighter Aircraft (F-18A)The wing skins of the F-18A represented the fmt widespread use of graphite/epoxy in aproduction aircraft. The skins vary in tilckness up to one inch, serving as primary as well assecondary load carrying members. It is interesting to note that the graphite skins are separatedfrom the aluminum hrning with a fiberglass barrier to prevent galvanic corrosion. The carrierbased environment that Navy aircraft are subjected to has presented unique problems to theaerospace designer. Corrosion from salt water surroundings is exacerbated by the sulfuremission from the ship’s exhaust stacks.Osprey Tilt-Rotor (V-22)The tilt-rotor V-22 is also a weight sensitive craft that is currently being developed by Boeingand Bell Helicopter. Up to 40% of the airframe consists of composites, mostly AS-4 and IM-6graphite fibers in 3501-6 epoxy (both from Hercules). New uses of composites are beingexploited on this vehicle, such as shafting and thick, heavily loaded components.Consequently, higher design strain values are being utilized.HelicoptersRotorsComposite materials have been used for helicopter rotors for some time now and have gainedvirtually 100% acceptance as the material of choice. The use of fibrous composites offersimprovements in helicopter rotors due to improved aerodynamic geometry, improvedaerodynamic tuning, good damage tolerance and potenthd low cost. Anisotrophic strengthproperties are very desirable for the long, narrow foils. Additionally, a cored structure has theprovision to incorporate the required bakmce weight at the leading edge. The favorablestructural properties of the mostly fiberglass foils allow for increased lift and speed. Fatiguecharacteristics of the composite blade are considerably better than their aluminum counterpartswith the aluminum failing near 40,000 cycles and the composite blade exceeding 500,000cycles without ftiure. Vibratory strain in this same testing program was * 510 ~‘mh~~hforaluminum snd * 2400 ~‘i~tih for the composite.Sikorsky Aircraft of United Aircraft Corporation has proposed a Cross Beam Rotor @BR)m,which is a simpfied, lightweight system that makes extensive use of composites. The lowtorsional stiffness of a unidirectional composite spar allows pitch change motion to beaccommodated by elastic deformation, whereas sufficient bending stiffness prevents areoelasticinstability. Figure 1-16 shows a configuration for a twin besm composite blade used with thissystem.Structure and ComponentsThe extreme vibratory environment that helicopters operate in makes composites look attractivefor other elements. In an experimental program that Boeing undertook, 11,000 metal parts werereplaced by 1,500 composite ones, thus eliminating 90% of the vehicle’s fasteners.Producibility and maintenance considerations improved zilongwith overall structural reliability.37

AerospaceCom~ositesMarine CompositesTIFigure 1-16 Twin Beam Composite Blade for XBRTM Helicopter Rotor System[Salkind, New CO/?pOsiteHelicopter Rotor Concepts]ExperimentalVoyagerNearly 90% of the VOYAGER aircraft was madeof carbon fiber composites. Thestrength-to-weight ratio of this matmkil allowed the vehicle to carry stilcient fuel to circle theglobe without refueling. The plane’s designer and builder, Burt Rutan, is renowned forbuilding innovative tdrcraft using composites. He has also designed an Advanced TechnologyTactical Transport of composites and built the wing sail that was fitted to the 60 foot catamaranused in the last America’s Cup defense.DaedalusThe GOSSAMERCONDORand GOSSAMERALBATROSScaught people’s imagination by beingthe f~st two human-powered aircraft to capture prize money that was unclaimed for 18 years. Theseaircraft wem constructed of aluminum tubes and mylar wings supporkd by steel cable. Theaerodynamic drag of the cabling proved to be the factor limiting flight endurance. The lMEDALUSproject’s goal was to fly 72 miles from Crete to Santorini. By hand constructing graphite spars overaluminum mandrels, the vehicle’s drag was minimized and the overall aircraft structure wasreduced to 68 pounds, which mad; this endurance record possible. Figure 1-17 is acompilation of sketches showing various details of the Daedalus.38

ChapterOneAPPLICATIONSFigure 1-17 Engineer’s Representation of the DAEDALUS [Drella,Techno/ogy /3eview]39

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Chapter TwoMATERIALSReinforcementMaterialsFiberglassGlass fibers account forover 90% of the fibers used in reinforced plastics because they areinexpensive to produce and have relatively good strength to weight characteristics.Additionally, glass fibers exhibit good chemical resistance and processability. The excellenttensile strength of glass fibers, however, has been shown to deteriorate when loads are appliedfor long periods of time. [2-1] Continuous glass fibers are formed by extruding molten glass tofdament diameters between 5 and 25 micrometers. Table 2-1 depicts the designations of fiberdiameters commonly used in the FRP industry.Individualfilsmnts are coated with a sizingto mdm abrasionaud then combined into a strand of either102or 204 filamnts. The sizingacts as a couplingagent duringresin impregnation. Table 2-2 lists sometypicalglassfinishesand their compatiblemin systems. E-glass (lime aluminumbomsilicate)is the mostcurmnonreinforcermnt used in marine hninates lwause of its gmd strenglhpmpwties and mistanm towatm degmdation. S-glass (silicon dioxide, aluminum and magnesium oxides) exhibits about ane thinibter tensile slrength, and in genersl, demonstrates betkr fatigue resistance. Table 2-3 lists thecornposidonby weight far both E- and S-glass. The cost for this variety of glass filxr is about three tofour tkres that of Bglass. Table 24 containsdata on mw E-#ass and S-#ass fibers.Table 2-1. Glass Fiber Diameter Designations[Shell, @o# Resins for F]&erg/ass Reinforced Plastics]IDeslgnatlon MllsMicrometers(10+ meters)Ic 0.18 4.57ID 0.23 5.84I DE 0.25 6.35IE 0.28 7.11l+=%==Polymer FibersThe-most common aramid fiber is Kevlsr@developed by DuPont This is the predominant organicreinforcing fiber whose use dates to the eaily 1970’s as a ~placement for steel belting in tires. Theoutstanding features of sramids are low weigh~ high tensile sirength and modulus, impact andfatigue resistance, and weaveability. Compressive performance of sramids is relatively poor, as theyshow nonlinear ductile behavior at low strain values. Although the fibem are resistant to strongacids and bases, ultraviolet degradation can cause a problem as can water absorption with Kevlar@49. Ultra-high modulus Kevlar” 149 absorbs almost two thirds less water at a given relativehumidity. Aramids tend to be difficult to cut and wet-out during lamination.41

ComDosite Materials Marine CwnwsitesTable 2-2. Typical Glass Finishes [BGF, Shell and SP Systems]Designation Type of Flnlsh Resin System114 Methacrylato chromic chloride Epoxy161 Soft, clear with good wet-out PolyesterVolan@ Methacrylato chromic chloride Polyester or Epoxy504 Volan@finish with .03%-,06% chrome Polyester or Epoxy504A Volan@finish with .06%-.07% chrome Polyester or EpoxyA-100 Amino silane Epoxy538 A-1 100 amino silane plus glycerine Epoxy550 Modiiied Volanm Polyester558 Epoxy-functional silane Epoxy627 Silane replacement for Volan@ Polyesteror EpoxySP 550 Proprietary Polyester or EpoxyY-2967 Amino silane EpoxyY-408617 Epoxy-modified methoxy silane EpoxyZ-6040 Epoxy-modified methoxy silane EPOXYZ-6030 Methacrylate Silane PolyesterGaran Vinyl silane EPOXYNOL-24 Halosilane (in xylene) Epoxys-553 Proprietary EpoxyS-920 Proprietary Epoxys-735 Proprietary EpoxyTable 2-3. Glass Composition by Weight for E- and S-Glass [BGF]E-GlassS-GlassSilicone Dioxide 52 -56% 64- 66?40Calcium Oxide 16- 25% 0- .3%Aluminum Oxide 12-16?40 24- 26%Boron Oxide 5-lo% —Sodium Oxide & Potassium Oxide 0- 2?.40 0- .3%Magnesium Oxide o-5% 9-11?40Iron Oxide .05- .4% 0- .3”/’0Titanium Oxide 0-.870 —Fluorides 0 -1.0% —42

Chapter TwoMATERIALSAllied Corporation developed a high strength/modulus extended chain polyethylene fiber calledSpectra” that was introduced in 1985. Room temperature specific mechanical properties ofSpectra@ are slightly better than Kevlar@, although performance at elevated temperatures fallsoff. Chemical and wear resistance data is superior to the aramids. Data for both Kevlar@ andSpectra@ fibers is also contained in Table 2-4, The percent of manufacturers using variousreinforcement materials is represented in Figure 2-1.FiberTable 2-4. MechanicalProperties of Reinforcement FibersD&;:lJy Tensile Strength Tensile Modulus Ultlmate ~btpsl x 103 psl x 106 ElongationE-Glass .094 500 10.5 4.8?40 .80-1.20S-Glass .090 665 12.6 5.7% 4Aramid-Kevla# 49 .052 525 18 2.9!/. 16Spectra@ 900 .035 375 17 3.5% 22Polyester-COMPE@ ,049 150 1.4 22.0% 1.75Carlmn-PAN .062-.065 350-700 33”57 0.38-2 .0% 17-450Polyester and nylon thermoplastic fibershave recently been introduced to themarine industry as primary reinforcementsand in a hybrid ammgernent withfiberglass. Allied Corporation hasdeveloped a fiber called COMPET@,which is the product of applying a finishto PET fibers that enhances matrixadhesion properties. Hoechst-Celanesemanufactures a product called Treveria@,which is a heat mated polyestm fikr fabricdesigned as a “bulking” material aud as a gelcoat barrier to reduce ‘>rint-through.”Although polyester fibers hav~ fairly highstrengths,their sdffnessis considembly belowthat of glass. Other attractivefeahrresincludelow density, nmsonable cost, good impactand fatigue resistance, and potential forvibration damping and blister resistanm.Carbon FibersThe terms “carbon” and “graphite” fibersare typically used interchangeably, althoughgraphite technically refers to fibers that aregreater than 99% carbon composition versus93 to 95% for PAN-base fibers. Allcontinuous carbon fibers produced to dateThermoplasticFibergiaaaCarbon FiberFiberaKeviarHybridsOthero% 20% 40% 60% 60% 100%-Hull ~Dsck ~PartsF@llre 2-I Marine Industry ReinforcementMaterial IJse [EGA Survey]I43

Composite Materials Marine Compositesare made from organic precursors, which in addition to PAN (polyacrylonitrile), include rayonand pitches, with the latter two generally used for low modulus fibers.Carbon fibers offer the highest strength and stiffness of all the reinforcement fibers. The fibersare not subject to stress rupture or stress corrosion, as with glass and aramids. Hightemperature performance is particularly outstanding. The major drawback to the PAN-basefibers is their relative cost, which is a function of high precursor costs and an energy intensivemanufacturing process. Table 2-5 shows some comparative fiber performance data.ReinforcementConstructionReinforcement materials are combined with resin systems in a variety of forms to createstructural laminates. The percent of manufacturers using vmious reinforcement styles isrepresented in Figure 2-3. Table 2-5 provides deffitions for the various forms ofreinforcement materials. Some of the lower strength non-continous configurations are limitedto fiberglass due to processing and economic considerations.Table 2-5. De cription of Various Forms of Reinforcements[Shell, Epon8Resins for Fi&erg/ass Reinforced Plastics]Form Descrlptlon Prlnclpal ProcessesFilaments Fibers as initially drawn Processed further before useContinuous Strands ContinuousBasic filamentsbun Iesathered together inProcessed further before usetYarnsTwisted strands (treated withafter-finish)Processed further before useChoppedStrands Strands chopped 1/4to 2 inches Injectionmolding; matcheddieRovingsMilled FibersReinforcing MatsStrands bundled together like rope butnot twistedFilament winding; sheet molding;spray-up; pultrusionContinuous strands hammermilled into Compounding; casting; reinforcedshort lengths %2 to M inches long reaction injection molding (RRIM)Nonwoven random matting consistingof continuous or chopped strandsHand lay-up; resin transfer molding(RTM); centrifugal castingWoven Fabric Cloth woven from yarns Hand lay-up;prepregWoven RovingSpun RovingNonwovenFabricsStrands woven like fabric but coarser Hand or machine la -up; resinand heavier transfer molding (R#M)Continuous single strand looped onitself many times and held with a twistProcessed further before useSimilarto matting but made with Hand or machine la -up; resinunidirectional rovings in sheet form transfer molding (R+M)Surfacing Mats Random mat of monofilament Hand lay-up; die molding; pultrusionWovensWoven composite reinforcements generally fall into the category of cloth or woven roving. Thecloths are lighter in weigh~ typically from 6 to 10 ounces per square yard and require about 40 to 5044

Chapter TwoMATERIALSPlainweave ‘-Basket weaveTwillCrowfootsatin8 harness satin5 harness satinfigUre z-z Reinforcement Fabric Construction Variations [ASiW Engineered Materkals Handbooklplies to achieve a one inch thickness.Their use in marine construction is limitedto small parts and repairs. Particular weavepatterns include plah weave, which is themost highly interlace@basket weave, whichhaswarpandfdl yarns thatarepaird~andsatin weaves, which exhibit a minimum ofinterlacing. The satin weaves are producedin standard four-, five- m eight-harnessconfgumtions, which exhibit a correspondinginmase in resistance to shear distortion(easily draped). Figure 2-2 shows somecommercially available weave patterns.Woven roving minforcenxmts consist offlattened bundles of continuous shards in aplain weave pattern with slightly morematerial in the warp direction. This is themost common type of reinforcement used forlarge marine structures because it is availablein fairly heavy weights (24 ounces per squareyard is the most common), which enables arapid build up of tbiclmess. Also, directionals~ngth charactistics are possible with amaterial that is stall fairly drapable.Impact resistance is enhanced because thefibers are continuously woven.Chopped Strand MatWoven RovingUnldlrectlonalClothKnitted FabricOtherro% 20% 40% 60% 80% 100%= Hull ~Deck ~Part6Figure 2-3 Marine Industry ReinforcementStyle Use [EGASurvey]I45

Comnosite MaterialsMarine CompositesEnd ViewWoven RovingEnd ViewKnitted BiaxialFigure 2-4 Comparison of Conventional Woven Roving and a Knitted Biaxial FabricShowing Theoretical Kink Stress in Woven Roving [Composites Reinforcements, Inc.]KnitsKnitted reinforcement fabrics were first introduced by Knytex@ in 1975 to provide greaterstrength and stiffness per unit thickness as compared to woven rovings. A lmittedreinforcement is constructed using a combination of unidirectional reinforcements that arestitched together with a non-structural synthetic such as polyester. A layer of mat may also beincorporated into the construction. The process provides the advantage of having thereinforcing fiber lying flat versus the crimped orientation of woven roving fiber. Additionally,reinforcements can be oriented along any combination of axes. Superior glass to resin ratiosare also achieved, which makes overall laminate costs competitive with traditional materials.Figure 2-4 shows a comparison of woven roving and knitted construction.OmnidirectionalOmnidirectional reinforcements can be applied during hand lay-up as prefabricated mat or viathe spray-up process as chopped strand mat. Chopped strand mat consists of randomly orientedglass fiber strands that are held together with a soluble resinous binder. Continuous strand matis similar to chopped strand mat, except that the fiber is continuous and layed down in a swirlpattern. Both hand lay-up and spray-up produce plies wifi equal properties along the x and yaxes and good interlaminar shear strength. This is a very economical way to build upthickness, especially with complex molds. The ultimate mechanical properties are, of course,not on par with the continuous strand reinforcements.UnidirectionalPure unidirectional construction implies no structural reinforcement in the Ill direction. Ultrahigh strength/modulus material, such as carbon fiber, is sometimes used in this form due to its46

Chapter TwoMATERIALShigh cost snd specificity of application. Material widths are generally limited due to thedifficulty of handling and wet-out. Anchor Reinforcements has recently introduced a line ofunidirectional that are held together with a thermoplastic web binder that is compatible withthermoset resin systems. The company claims that the material is easier to handle and cut thantraditional pure unidirectional material. Typical applications for unidimctionals include -stemand centerline stiffening as well as the tops of stiffeners. Entire hulls are fabricated fromunidirectional reinforcements when an ultra high performance laminate is desired.PolyesterThe percent of manufacturers using various resin systems is represented in Figure 2-5. Polyesterresins are the simplest, most economical resin systems that are easiest to use and show goodchemical resistance. Almost one half million tons of this material is used annually in the UnitedStates. Unsaturated polyesters consist of unsaturated material, such as rnaleic anhydride or fumaricaci~ that is dissolved in a reactive monomer, such as stymne. Polyester resins have long beenconsidered the least toxic therrnoset to personnel, although recent scrutiny of styrene emissions inthe workplace has led to the development of alternate formulations (see Chapter Five). Mostpolyesters are air inhibited and will not cure when exposed to air. Typically, parafiln is added to theresin formulation, which has the effect ofsealing the surface during the cureprocess. However, the wax l?dm on thesurface presents a problem for secondarybonding or finishing and must bephysically removed Non-sir inhibited Ortho Polyesterresins do not present this problem and are,therefore, more widely accepted in themarine industry.The two basic polyester resins used in themarine industry are orthophthalic andisophthdic. The ortho resins were theOrigitld ~Up Of polyesters d@Oped andsre still in widespread use. They havesomewhat limited thermal stabili~, chemicalresistance, and processability characteristics.The iso resins generally have bettermechanical properties snd show betterchemical resistance. Their increasedresistance to water permeation has promptedmany builders to use this resin as a gel coator barrier coat in marhe laminates,Vinyl Ester1s0 PolyesterEpoxy0% 20% 40% 60% 80% 100%-Hull = Deck = PartsiThe rigidity of polyester resins can belessened by increasing the ratio ofsaturated to unsaturated acids. FlexibleFigure 2-5 Marine Industry Resin systemUse [EGA Survey]47

Chapter TwoMATERIALSmolding compounds that soften at high temperatures. Polyethylene, polystyrene, polypropylene,polyamides and nylon me examples of thermoplastics. Their use in the marine industry hasgenerally been limited to small boats and recreational items. Reinforced thermoplastic materialshave recently been investigated for the large scale production of structural components. Someattractive features include no exothenn upon cure, which has plagued ~ament winding of extremelythick sections with thermoses, and enhanced damage tolerance. Processability and smngthscompatible with ~inforcernent material m key areas currently under developmentTable 2-7. Comparative Data for Some Thermoset Resin Systems (castings)OrthophthalicAtlas P 2020BarcolTensile TensileResin Stren thUltlmateHardnesspsl x 7‘odu’u? Elongation ~l~t03 pslxloDicyclo entadiene (DCPD)Atlas 8t-6044IsophthalicCoRezyn 9595Vinyl EsterDerakane411 -45EpoxyGouegonGLR 12542 7.0 5.9 .91% .6654 11.2 9.1 .86?’0 .6746 10.3 5.65 2.09!0 .8535 11-12 4.9 5-6% 1.4484D* 7 4.2 4.0940 2.69*Hardness values for epoxies are traditionally given on the “Shore D scaleCore MaterialsBalsaThe percent of manufacturers using various core materials is represented in Figure 2-6. Endgrain balsa’s closed-cell structure consists of elongated, prismatic cells with a length (graindirection) that is approximately sixteen times the diameter (see Figure 2-7). In densitiesbetween 6 and 9 pounds ft3, the material exhibits excellent stiffness and bond strength. Balsawill typically absorb more resin than closed cell foaro during lamination and is also subject towater migration, although this has been shown to be limited to action parallel to the grain.Although the static strength of balsa panels will generally be higher than the PVC foams,impact energy absorption is lower. End-grtin balsa is available in sheet form for flat panelconstruction or in a scrim-backed block arrangement that conforms to complex curves. ChapterFive goes into further detail regarding the core selection process.Thermoset FoamsFoamed plastics such as cellular cellulose acetate (CCA), polystyrene, and polyurethane arevery light (about 2 lbs/ft3) and resist water, fungi and decay. These materials have very lowmechanical properties and polystyrene will be attacked by polyester resin. These foams willnot conform to complex curves. Use is generally limited to buoyancy rather than structuralapplications. Polyurethane is often foamed in-place when used as a buoyancy materkd.49

Composite Materials Marine CompositesBalsaLinear PVCFabricRigid PVCUrethaneOtheru% 20% 40% 60% 80% 100%Figure 2-7 Balsa Cell Geometrywith A = Average Cell Length = ,025”;B = Average Cell Diameter= ,00126”;C = Average Cell Wall Thickness =.00006” [Baltek Corporation]Syntactic FoamsSyntactic foams are made by mixing hollowFigure 2-6 Marine Industry Core microsphere of glass, epoxy and phenolicMaterial Use [EGA Survey]into fluid resin with additives and curingagents to form a moldable, curable,lightweight fluid mass. Omega Chemical has introduced a sprayable syntactic core materialcalled SprayCore ‘. The company claims that thicknesses of %“ can be achieved at densitiesbetween 30 and 43 lbs/ft3. The system is being marketed as a replacement for core fabrics withsuperior physical properties. Material cost for a square foot of %“ material is approximately$2.20.Cross Linked PVC FoamsPolyvinyl foam ems am manufacti by corabining a polyvinyl copolyrmr with stabilizm-s,plasticizers,cross-linking compounds and blowing agents. The mixture is heated under pressure to initiate thecross-linkingreaetion and then submerged in hot water tanks to expand to the desired density. Celldiametersmnge fi-om.0100 to .KK1inches (as compared to .0013 inches fur balsa). [2-2] The msdtingmaterial is thermoplastic,enabling the mattxial to conform to compound curves of a hulL PVC foamshave almost exclusively replaced urethane f- as a structuralcore matmial, exmpt in confqgmttionswhere the foam is “blown” in place. A number of manufactmrs nmket ems-linked PVC pruducts tothe marine indus~ in sheet form with densitiesranging fmm 2 to 12 pounds per # As with the balsaproducts,solid sheetsor ti backed block constructionconfigurationsare available.50

Chapter TwoMATERIALSLinear PVC FoamAimx@is cutmntly tbe only linear PVC foam coreproduced for the marine industry. Its uniquemechanical properties aIE a result of anon-connected molecular structure, which allowssignificant displacements before faihue. Incomparison to the cross lhbd (non-linear)PVCS,Aimx@ will exhibit less favorable staticproperties and better impact absorptioncapability. Individual cell diameters rangefrom .020 to .080 inches. [2-3] A detailedcomparison of core material performance willbe presented in the Section on MechanicalTesting of Composite Materials. Table 2-8shows some of the physical properties of thecore materials presented here.AXESHoneycombVarious types of manufactured honeycombFigure 2-8 Hexagonalcores are used extensively in the aerospace.HoneycombGeometry [MIL-STD-401 B]industry. Constituent materials includealurnin~ phenolic resin impregnatedfiberglass, polypropylene andaramid fiber phenolic treatedpaper. Densities range from 1to 6 lbs/f? and cell sires varyfrom % to % inches. [2-4]Physical properties vary in anear linear fashion with density,as dlustrated in Figure 2-9.Although the fabrication ofextremely lightweight panels ispossible with honeycomb cmes,applications in a marineenvironment are limited due tothe difficulty of bonding tocomplex face geometries andthe potential for sigdicantwater absorption. The Navy has1 I 1I112Ibm 14 61 81 10I 121had some corrosion problemsDrollywhen an aluminum honeycombcore was used for ASROC A Shear Modulus (Longitudinal) D UnstabilizedCompressionStrengthB Stabilized CompressionStrength E Shear Strength (Longitudinal)housings. Data on a Nomex@ C Shear Modulus (Transverse) F Shear Stren~th (Transverse)honeycomb product ispresented in Table 2-8. Figure 2-9 Core Strengths and Moduli for VariousCore Densities of Aramid Honeycomb [Ciba-Geigy]51

Composite Materials Marine CompositesPMI FoamRohm Tech, Inc. markets a polymrthacrylimide (PMI) foam for composite construction cakdRohacell@. The material requires minimum laminating pressures to develop good peel strength.The most attractive feature of this material is its ability to withstand curing temperatures inexcess of 35(YF. Table 2-8 summarizes the physical properties of a common grade ofRohacell@.FRP PlankingSeemann Fiberglass, Inc. developed a product called C-Flex@ in 1973 to help the amateursbuild a cost effective one-off hull. The planking consists of rigid fiberglass rods held togetherwith unsaturated strands of continuous fiberglass rovings and a light fiberglass cloth. Theself-supporting material will conform to compound curves. Typical application involves a setof male frames as a form. The planking has more rigidity than PVC foam sheets, whicheliminates the need for extensive longitudinal stringers on the male mold. A 14iinch variety ofC-Flex@weighs about l/2 pound dry and costs about $2.00 per square foot.Table 2-8. Comparative Data for Some Sandwich Core MaterialsMateriai ‘ensi Stren th Stren th Stren th Eiasticitibslf~ ‘e;:#e com~ive ‘~ ‘;:::jf #!!~ ~,I Balsa CK 7 1320 1187 315 370.0 17.4 2.35IIAirex@R62.80 5-6 200 125 170 9.2 2.9 5.37Divinycell@ H 100 6 450 290 217 17.4 6.5 6,10I Klegecell II R 100 6,23 479 319 233 11.5 7,0 5.83Core-CeiilMC70.75 5 210 184 130 9.6 3.7 3.47Rohacell@ 711G 4.7 398 213 185 13.1 4.3 7.54Nomex@HRH-78 6 N/A 1125 200 60.0 6.0 13.53Nidaplast H8PP 4.8 N/A 218 160 — — 2.35Core FabricsVarious natural and synthetic materials are used to manufacture products called core fabrics thatare designed to build up laminate thickness economically. One such product that is popular inthe marine industry is Firet Coremat, a spun-bound polyester produced by Lantor. HoechstCelanese has recently introduced a product called Trevira@, which is a continuous filamentpolyester. The continuous fibers seem to produce a fabric with superior mechanical properties.Ozite produces a core fabric called Compozitex m from inorganic vitreous fibers. Themanufacturer claims that a unique manufacturing process creates a mechanical fiber lock within thefabric. Although many manufacturers have had much success with such materials in the center ofthe laminate, the use of a non-structural thick ply near the lamhate surface to eliminate print-tbmughis a dangerous practice. The high modulus, low strength ply carIproduce pmnamre failures. Othermanufacturers have started to produce “bulldng” products that are primarily used to build upkun.inatethickness. Some physical properties of core fabric materials are presented in Table 2-9.52

Chapter TwoMATERIALSTable 2-9. Comparative Data for Some “Bulking” Materials(impregnated with polyester resin to manufacturers’ recommendation)Coremat@ 4mm .157 37-41 551 3191 580 130 .44Trevira@ Core 100 ,100 75 2700 17700 1800 443 .28Baltek@Mat T-2000 ,098 40-50 1364 — 1364 — .31I Tigercore TY-3 ,142 35 710 3000 1200 110 .44 II CompozitexTM 3mm .118 — — — — — .35PlywoodPlywood should also be mentioned as a structural core material, although fiberglass is generallyviewed as merely a sheathing when used in conjunction with plywood Exceptions to thischaracterization include local reinforcements in way of hardware installations, where plywoodreplaces a lighter density core to improve compression properties of the laminate. Plywood isalso sometimes used as a form for longitudinal, especially in way of engine mounts. Recentconcern over the continued propensity for wood to absorb moisture in a maritime environment,which can cause swelling and subsequent delamination, has precipitated a decline in the use ofwood in conjunction with FRP. The uneven surface of plywood makes it a poor bonding surface.Also, the low strength and low strain characteristics of plywood can lead to premature failures.The technique of laminating numerous thin plies of wood developed by the Gougeon Brothersand known as wood epoxy saturation teehnique (WEST@ System) eliminates many of theshortcomings involved with using wood in composite structures.Cost ConsiderationsThe owners and designers of composite marine structures have a broad range of materials thatthey can choose from. The vast majority of construction to date has been with fiberglassreinforcement and ortho-polyester resin because of the relative ease of use and low cost. Whenweight, strength, stiffness or durability requirements are at a premium, the use of higherperformance materials can be rationalized.Product Description and Test Data Tables are included at the end of this section to assist in theevaluation of economic differences between commercially available reinforcements based onvarious strength criteria developed in the 1978 ABS Rules for Reinforced Plastic Vessels [2-5]and the 1986 Guide for Offshore Racing Yachts [2-6] and supplier price quotes from Fall,1989. Cost data is presented to compare various products fmm a particular vendor. Manufaetwrsshould consult lewd suppliers to get current regional pricing information.53

Composite MaterialsAJwineCom~osifeslaminate Property AssumptionsEach Data Table includes a set of variables that remain constant for the range of reinforcementsin the table. The key variable is the selection of a resin system. All entries within a giventable should have a common resin system used for test data derivation. A resin system isusually determined before reinforcement selection based on cost, builder’s capabilities, barrierperformance, toughness and shear strength. Resin cost is entered into the Data Table on a perpound basis to compare laminates that require different amounts of resin.Laminate schedules in the marine industry are necessarily specified by thickness to conformwith established shipbuilding practices. Dry reinforcement material undergoes some degree ofcompaction during the laminating process. This value is dependent upon the specificmanufacturing process utilized and is input in the form of a percentage. Resin also changesdensity from the published “neat” value when cured. This phenomena, known as shrinkage, isalso represented as a percentage.Labor variables include the hourly wage rate ad the rate at which material can be assembled.The latter is expressed in terms of hours to laminate one squsre foot of one ply. A value of .05hours per square foot equates to about 12 pounds per hour of the Base Laminate. This is thevalue that Scott gives for single skin military boats (see Table 2-10). A difficulty factor isassigned for materials other than standsrd fiberglass products. This factor takes into accounthan~ing and wet-out procedures.Table 2-10. Hand Layup Production Rates for 10 or More Identical Hulls[Scott, Fiberglass Boat Constmctjon]Type of Construction Type of Boat Lbs/Hour* Ft2/Hourt Hours/Ft2*Single Skin with FramesSandwichConstruction* Based on matiwoven roving laminatet Single ply of mat/woven roving laminate* Time to laminate one ply of mat/woven rovingRecreational 20 33 .03Military 12 20 .05Recreational 10 17 .06Military 6 10 .10Since all calculated data is thickness and density dependent, an estimate for void volume isincluded. This value is used to modify the total estimated laminate weight, but is not includedin any derived strength calculations.Reinforcement DescriptionThe manufacturer’s designation is used here to identify the commercial product represented.Refer to pages 60-67 for composition and construction information about these products. Thebase laminate consists of one layer of woven roving and one mat to form what is considered asingle ply.54

Chapter TwoMATERIALSTest AngleSince the majority of materials listed are anisotropic, information on the orientation of testspecimens is included. Much care shotid be taken in interpreting the comparative data,especially with unidirectional reinforcements. Most material testing is done along axes ofprimary reinforcement.Fiber Weight PercentageThe percentage of reinforcement fiber in a given laminate is determined by burnout tests andreported as a weight percentage. Mechanical properties will vary widely with varying fiberratios. Strength data is often given as a function of fiber ratio, which is why this descriptormust be included in the Data Table entry.Fiber Volume PercentageThe percentage of fiber by volume is given by the following relationship presented by Chamis:[2-7]where:“=*‘V = void volumePf = fiber densityPm = resin densityl.f = percentage of fiber by weightDry Fiber and Uncured Resin DensityDensities are presented in pounds per square foot for one inch thickness. This base, unit isbetter for visualization purposes than cubic feet or cubic inches. Data is derived from virginmaterial properties.Cured laminate DensityThe cured laminate density is derived as follows:where:pl=~vxpfx(l +Apf)+’mxpm x(l+Apm)A Pf= fiber compaction expressed as a percentageA ~ = resin shrinkage expressed as a percentagekm = resin volumeDry Fiber ThicknessThis value, given in roils, is representative of the reinforcement material alone without resin andbefore any mechanical compaction such as vacuum bagging, rollering, squeegeeing or otherprocessing.55

Composite MaterialsMarine CompositesFiber WeightThis valu~ is merely the product of fiber volume and fiber density.Resin WeightTo calculate resin weight, a value for resin volume must be derived. This is simply:( 1- kf- k, ). This value is multiplied by the resin density to get the resin weight.Laminate WeightThe laminate weight is the sum of the fiber weight and the resin weight.Reinforcement Cost DataCurrent pricing is entered either on a per pound basis or per linear yard, based on a 50” wideroll. Cost data for reinforcing material is based on 1000 square yard quantities as ofNovember, 1989.Total Material CostThe material cost per square foot is calculated on a weight basis for reinforcementThe sum is presented as ply cost per square foot,and resin.Labor CostThe input labor rate is multiplied by the productivity valuelabor factor.(ft2/hr) and the assigned materialTotal and Relative Ply CostThe total cost per ply is the sum of material and labor costs. This data is also represented as apercentage relative to the base laminate in the form of cost required to achieve an equalthickness.Strength DataDerived strength and stiffness properties are from tests performed according to ASTMstandards (see Chapter Six). Single skin laminates of at least %s inch should be tested withsufficient numbers of specimens to produce statistical agreement. Hand laid up test samplesfabricated under the guidelines recommended by the resin manufacturer are to be used.Single Skin Strength Criteria Thickness ComparisonThe required thickness for the candidate material is expressed in terms of percentage of thebase laminate. The relationship used is:where:c‘f,m‘f‘fk,‘f= flexural strength of the base laminate= flexural strength of the subject laminate56

Composite MaterialsMarine CompositesSandwich Construction Compression Criteria Thickness ComparisonThe compression criteria is based on the ABS inner skin section modulus formula in a similarfashion to that detailed above. The relationship reduces to:where:(~j,x6XUCOf)‘1 = SikfImerB&do = compressive strength of subject laminatecSM1m,, =Bauinner skin section modulus required for 1“ wide sandwich panelto match Sill of 1“ thick single skin base laminatethe above expression is based on the following relationship:SM1~,, =(tzxOf)6x a=Sandwich Construction Stiffness Criteria lhickness ComparisonTo achieve a sandwich structure from alternate materiaJ with stiffness equal to a panel withbase material skins, the relationship presented in Section 7.3.2.c of the ABS Guide [2-6] isused. As with the section modulus comparison developed above, equivalent moments of inertiaare compared linearly to represent alternate material skin thickness for a given core dimension.The mathematical relationship used is:where:(t;Nx Et)* 12 XV2X(E; +EC)tl =I BaseEt = tensile modulus of subject laminateEC= compressive modulus of subject laminateI B&e=required moment of inertia of base laminate for 1“ wide strip tomatch 1 of 1“ thick single skin laminatethe above expression is based on the following relationship:(t3x E)I Sandwich = 12xv2x(E, +Ec]58

Chaoter TwoMATERIALSCost ComparisonsAll of the above five thiclmess comparison criteria are further reduced to cost equivalents bymultiplying the thickness relationship to the base material by the relative equivalent thicknesscost relationship data.These relationships are developed for the purpose of material comparison at the preliminarydesign stage. The strength data is derived from test specimens which may have propertiessignflcantly different from an as-built lamhate. Samples should always be tested to verify thephysical properties of a laminate produced by the builder under conditions similsr to that of theFinal product. Additionally, the comparisons developed for sandwich psnels were independentof core thiclmess and properties. Response prediction procedures for cored panels are presentedin Chapter Three. This type of analysis is essential for predicting sandwich panel response. Itwill be shown that different core materials snd dimensions are required to achieve truecompatibility with the variety of reinforcement materials presented in the Data Tables.However, the analysis presented does give a good relative indication of skin contribution topanel response.Additional equations relating to sandwich properties are given in the Sandwich ConstructionSection of Chapter Three. Readers may also refer to specific requirements of governingregulatory bodies or national standards outlined in Chapter Seven.Costing information is provided for engineering purposes only. Data is current as of August,1990. Quotations were based on 1000 pound purchases of material. The cost per lineal yard isbased on 50 inch wide reinforcement material. Builders should of course consult their localsuppliers for current regional pricing, as msrket fluctuations are common.59

ReinforcementDescriptionManheCon@tes60

Chapter TwoMATERIALS61

Reinforcement DescriptionMarine Composites.62

mwProduct Descriptionsfor Various RelntorcementMaterialsUsed in Marine ConstructIonTnde t4ame Product Descrlptfon CodeWeight ThickcostMaterlai Weaveoz/yd21g/m2 roils $/yd I $/lbTf3EVARN0 Boat and Tooling Fabric 7533 5.9 198 10 E-Glass Plain 2.76 5.44TREVARNO Boat and Tooling Fabric 7544 19.2 651 22 E-Glass Plain 6.12 3.67TREVA13N0 Boat and Toofing Fabric 7587 20.7 700 30 E-Glass Mock Leno 7.16 3.99TREVARNO Boat and Tooling Fabitc 7597 39.2 1328 45 E-Glass Satin 13.52 3.98TREVARNO Advanced Composite Fabrics 4522 3.7 125 5.5 S-Glass Plain 5.56 17.31TREVARNO Advanced Composite Fabrics 4533 5.8 197 9 S-Glass Plain 6.83 13.57TREVA13N0 Advanced Composite Fabrics 282 5.7 193 7.2 Cartmn Plain 27.43 55.44TREVARNO Advanced composite Fabrics 584 10.9 370 13.5 Catin Satin 52.35 55.33TREVARNO Advanced Composite Fabrics 613 Ia.o 373 13.5 Carbon 51-IS 33.10 34.66TF?EVARNO Advanced Composite Fabrics 690 19.0 644 24 Cadre Plain 34.94 21.18TREVARNO Advanced Composite Fabfics 716 4.6 156 6.1 Carbon Plain 13.99 35.04TREVARNO Advanced Composite Fabrics 120 1.8 61 4.5 Kevlar Plain 20.17129.09TREVARNO Advanced Composite Fabrics 281 5.0 170 10 Kevlar Plain 23.50 54.14TREVARNO Advanced Composite Fabrics 285 5.0 170 10 Kevlar Cnwfoot 17.99 41.45TREVARNO Advanced Composite Fabrics 500 . 5.0 170 10 Kevlar Plain 14.67 33.80TREVARNOAdvanced Composite Fabrics 900 9.0 305 13 Kevlar Satin 19.05 24.38TREVARNO Advanced Coqosite Fabrics 1350 13.5 458 26 Kevlar Basket 25.52 21.78HERCULES Graphite Woven Fabrics A193-P 5.7 193 10.5 AS4 Carhan Plain 23.22 47.00HERCULES Graphite Woven Fabrics A280-5H 8.3 280 16 AS4 Cartxm 5H Satin 33.69 47.00HERCULES Graphite Woven Fabrics A370-5H 10.9 370 21 AS4 Carbon 5H Satin 36.00 38.00HERCULES Graphite Woven Fabrics A370-8H 10.9 370 21 AS4 Carbon 8H Satin 44.5247.00HERCULES Graphite Woven Fabrics 1360-5H 10.6 360 20.4 IM6 Carbon 5H Satin 50.6955.00PRECOM InternationalAEROTEX Vertex R-Glass Unidirectional VRX 16-300 4.7 160 RGlass Unidirectional 7.86 19.21AEROTEX Vertex R-Glass Unidirectional VRX 28-300 8.3 280 R-Glass Unidirectional 10.88 15.18AEROTEX Carbotex Carbon Unidirectional Cx 10-300 3.0 100 int Mod Cartmn Unidirectional 13.00 50.73AEROTEX Carbotex Carbon Unidirectional CX IM 12-267 3.5 120 HTX Carban Unidirectional 25.75 83.74AEROTEX Carbatex Carbon Unidirectional Cx 16-300 4.7 160 tiTX Carbon Unidirectional 16.63 40.55AEROTEX Carbatex Carbon Unidirectional CX 22-300 6.5 220 HTX Carbon Unidirectional 19.25 34.t5AEROTEX Carbotex Carbon Unidirectional CX 32-300 9.4 320 HTX Carbon Unidirectional 23.38 28.55Anchor Reinforcements, Inc.ANCAREF Unidirectional G135 4.0 136 E-Glass Unidirectional 4.62 13.30ANCAREF Unidirectional G300 8.8 298 E-Glass Unidirectional 5.08 6.65ANCAREF Unidirectional G600 17.7 600 E-Glass Unidirectional 6.41 4.17Ahlnnnrr *F i*- .** . --- .-.. --- . . . .. . . . . . ..— ——fultimma- +4’3,-4a UDUUA 1{.{ mm b-tilass umawecllonal 11.11 7.23

Reinforcement DescriptionMarine Composites

Chapter TwoMATERIALS.... . . -. ...

ReinforcementDescriWion Marina Cmnnnc[fes66

at4Product Descriptions for Various Reinforcement Materials Used in Marine ConstructionTfade Name Product Description CodeWeight ThickMatedai Weaveoz/yd2]g/m2 mi!s $/y~;/ibVECTORPLY Double Bias w/ mat Vxl 808 24.0 814 43 E-Glass Stitch-bonded 4.63 2.22VECTORPLY Knit Warp Triaxial TW36 36.0 1221 62 E-Glass Stitch-bonded 6.72 2.15VECTORPLY Knit Warp Triaxial TW24 24.0 814 40 E-Glass stitch-bonded 5.71 2.74VECTORPLY Knit Fill Triaxial TF36 36.0 1221 62 E-Glass Slitch-bondecf 6.72 2.15VECTORPLY Knit E-glass (O,90) w/ mai V1808 24.0 814 43 E-Glass Stitch-bonded 3.54 1.70VECTORPLY Knit E-glass (O,90) w/ mai Vlalo 27.0 915 48 E-Glass Stitch-bonded 3.94 1.68Low profile 24 oz. Woven Roving 3 24.0 814 40 E-Glass Woven Roving 2.08 1.00Low profile 18 oz. Woven Roving 11 18.0 610 30 E-Glass Woven Roving 1.63 1.04Low profiie Fine weave Roving Roving 1109 10.0 339 17 E-Glass Woven Roving 1.87 2.15THREE PLY Mat/18 oz. Knit {0, 90)/Mal V1808-08 31.0 1051 80 E-Glass Stiictl-bonded 5.09 1.89WOVMAT Woven Roving/chopped fibers 1010 20.0 678 32 E-Glass WR/chopped fbrs 2.95 1.70WOVMAT Woven Roting/chopped fibers 1524 38.0 1288 66 E-Glass WR/chopped fbrs 3.99 1.21BGF Industries, Inc.ReinforcedPlastics WovenCloth 1522 11.9 402 5.6 E-Glass Plain 3.00 2.92Reinforced Plastics Woven Cloth 2532 7.3 246 10 E-Glass Plain 3.36 5.34Reinforced Plastics Woven Cloth 3733 5.8 197 8 E-Glass Plain 2.97 5.90Reinforced Plastics Woven Cloth 7500 9.6 325 12 E-Glass Plain 4,49 5.39North American TextilesNORTEX Woven Fabric N120 2.0 68 5 Kevlar Plain 15.10 86.98NORTEX Woven Fabric N281 5.0 170 11 Kevlar Plain 13.00 29.95NORTEX Woven Fabric N285 5.0 170 9 Kevlar Cmwfoot 13.00 29.95NORTEX Woven Fabric NI118 3.0 102 6 Carbon Plain 48.33185.59NORTEX Woven Fabtic N1122 3.5 119 7 Catin Plain 59.06194.39NOf3TEX Woven Fabric N3113 6.0 203 11 Carbon Plain 25.00 48.00NORTEX Woven Fabric N3118 8.5 288 11 Carbon 4 x 4 Twill 35.87 48.61NORTEX Woven Fabric N3125 12.0 407 16 Carbon 8 I-fS 49.83 47.84NORTEX Woven Fabric N611 1 10.5 356 14 Carbon Plain 25.78 28.28NORTEX Woven Fabrfc N2577 20.0 678 30 Catin Plain 34.17 19.68NORTEX Woven Fabric N3376 3.5 119 8 CarbotiE-Glass Plain 27.28 89.79NORTEX Woven Fabric N3375 4.5 153 8 Catin/E-Glass Plain 18.58 47.56NORTEX Woven Fabric MI-476 7.5 254 12 CarboWE-Glass Plain 14.95 22.96NORTEX Woven Fabric NI 222 3.0 102 6 Carkn/Kevlar Plain 19,25 73.92NORTEX Woven Fabric N2312 6.0 203 11 Carbon/Kevlar Plain 14.26 27.38NORTEX Woven Fabric N4375 5.0 170 8 Kevlar/E-Glass Plain 8.13 18.73.. ---— . . ... —. .. —- -- .-. ——. —. . —NW? I kX Woven Fi3bIiC N4475 12.5 424 12 Kevfar/E-Glass Plain 7.01 6.46

Advanced Textiles Reinforcements Tested at FIT Structural Composites Lab with FRP A 100 Polyester Resin—c p $ guq~ z ;$ 3 n g g ~ ;fla gm ~$ gg g~ gg gg& Gn 9 $4

Chapter TwoMATERIALSDescrlptlonSandwichStiffnessCrlterlaSandwichCompressiveStrengthCrlterlaSandwichTensileStrengthCrlterlaSingle SkinStiffnessCriteriaSingle $klnStrengthCrlterlaSandwichStiffnessCrlterlaSandwichCompressiveStrengthCrlterlaS;::sl:hStrengthCrlterlaSingle SkinStiffnessCrlterlaSingle SkinStrengthCrlterlaCompressiveStrengthTensileModulusTensileStrengthFlexuralModulusFlexuralStrength69

Reinforcement Engineering PropertiesMarine CompositesCost Relatlveto $ gBase Laminateper Thlcknesa ~ G~I IFiber Cost by a k?!?Weight g g ‘7Cured Laminate :Density*UncuredResin = x g ~Density~ ~Dry Fiber qDensity . ml%vgggy $ $0 r+ml ml5%0Fiber by $ $Weight ~ qHTesl Angle 00I70

Chapter TwoMATERIALS$ $Sandwich s 3Stiffness Crlterla ~ -1 #Sandwich ~ * *CompressiveStrength Crlterla ~ $ ~Y! ‘‘Strength Crlterla ~ ~ ~SandwichStlffnees CrlterlaSandwichCompressiveStrengthCrlterlaSandwichTensileStrengthCrlterlaSingle SkinStiffness Crlterlaco;qn&sgveo 0 0a o0 w 1-- OJ 7CompressiveStrength ~ $ ~IIllFlexuralStrengthm mN w 371

Reinforcement Engineering PropertiedMarine CompositesCost Relative toBase Laminate z 5 2per Thlcknese 0 . .* a.$0mIIcoq0C9 CD CQ03 m av q q0 0 0w1-15Cured LaminateDensitym o 0y Lqqm m m$ticoqN1 I II‘/0 Fiber byVolume~ ~ Em m m$NP)YOFiber by g g gWeight m U3mIITest Angle 900972

——Chapter TwoMATERIALSSkinCrlterla2~N1--l”l=l’Single SkinStrength CrlterlaSandwichStiffness CrlterlaSandwichCompressiveStrength CrlterlaS;&d;w:hStrength CrlterlaSingle SkinStiffness Crlterlau“Single SkinStr$ngth CrlterlaLz CompressiveStrengthTensileModulusTensileStrengthFlexuralModulusFlexuralStrength73

Composite MaterialsMarine CompositesThis pageintentionally left blank74

Chapter ThreeDESIGNHull as a longitudinalGhderClassical approaches to ship structural design treat the hull structure as a beam for purposes ofanalyticsilevaluation. [3-1] Obviously, the vtidity of this approach is related to the vessel’s lengthto beam and length to depth ratios. Consequently, beam analysis is not the primary analyticalapproach for small h Nevertheless, it is imructive to regard hull structme as a beam whenconsidering frees that act on the vessel’s overall length. By determining which elements of the hullare primmily in tension, compression or shear, scantling determination can be approached in a momrational manner. This is particularly important when designing with misotrophic materisls whereorientation aikcts the structure’s load carrying capabilities to such a great extent.A variety of different phenomena contribute to the overall longitudinal bending momentsexperienced by. a ship’s hull structure. Analyzing these global loading mechanisms statically isnot very realistic with smaller craft. Here, dynamic interaction in a seaway will generallyproduce loadings in excess of what static theory predicts. However, empirical information hasled to the development of accepted safety factors that can be applied to the statically derivedstress predictions. Force producers are presented here in an order that corresponds todecreasing vessel size, ie., ship theory fwstStill Water Bending MomentBefore a ship even goes to sea, somestress distribution profde exists withinthe structure. Figure 3-1 shows howthe summation of buoyancy andweight distribution curves leads to thedevelopment of load, shear andmoment diagrams. Stresses apparentin the still water condition generallybecome extreme only in cases whereconcentrated loads are applied to thestructure, which can be the case whenholds in a commercial vessel areselectively filled. The sdll waterbending moment (SWBM) is animportant concept for composites&sign because fiberglass isparticularly susceptible to creep orfracture when subjected to long termloads. Static fatigue of glass fiberscan reduce their load carryingcapability by as much as 70 to 80%depending on load duration,temperature, moisture conditions andother factors. [3-2]WI Ii~-— ———.— .. ———— L~ ________IL—— -----(u} RECTAW13ULAR mARGIZ-UNLOfiDE+ ‘——————t-) ~ARGE-HALF LOADEDi 1!I OASIELINE\ 1{dl WEIGHT AUD EIUOV+MCY cURVES====5==(0> SHEAR Awn 9ENO!WG MOMENT CURVES~gllre a-l Bending Moment Developmentof Rectangular Barge in Still Water [Principles ofNaval Architecture]75

. ,Loads for FRP Ship DesignMarine CompositesWave Bending MomentA static approach to predicting ship structure stresses in a seaway involves the superposition ofa tcochoidal wave with a wavelength equal to the vessel’s length in a hogging and saggingcondition as shown in Figure 3-2. The trochoidal wave form was originally postulated byFroude as a realistic two-dirnensional profile, which was easily defined mathematically. Theheight of the wave is usually taken as ~ZO,.O&G or 1,1L2, with the latter most applicable tosmaller ships. Approximate calculation methods for maximum bending moments and shearingforces have been developed as preliminary design tools for ships over 300 feet long. [3-3]I(o) VESSEL IN STILL WATERIIItI(b) VESSEL IN SAGGINGCONDITIONI(e) VESSEL IN HOGGINGCONDITIONFigure 3-2 Superposition of Static Wave Profile [FJrh@es of fVava/Architecture]Ship Oscillation ForcesThe dynatnic response of a vessel operating in a given sea spectrum is very difficult to predictanalytically. Accelerations experienced throughout the vessel vary as a function of vertical,longitudinal and transverse location. These accelerations produce virtual increases of theweight of concentrated masses, hence additional stress. The designer should have a feel for atleast the worst locations and dynamic behavior that can combine to produce extreme loadscenarios. Figure 3-3 is presented to define the terms commonly used to describe ship motion.It is generally assumed that combined roll and pitch forces near the deck edge forward areindicative of the extreme accelerations throughout the ship.Dynamic PhenomenaDynamic loading or vibration can be either steady state, as with propulsion inducedphenomena, or transien4 such as with slamming through waves. In the former case, loadamplitudes are generally within the design limits of hull structural material. However. thefatigue process “can lead to premature iailures, especially if structural components axe inresonance with the forcing frequency. A prelitiary vibration analysis of major structural76

Chapter ThreeDESIGNYAWlliEAVE42I“-L --------------1YS WAYFigure 3-3 Principal Axes and Ship Motion Nomenclature [Evans, Sh@ StructuralDesign Concepts]ensure that natural frequencies are not near shsft and blade rate for normal operating speeds.[3-4] The theoretical analysis of vibration characteristics associated with complex compositestructures is problematic, at best. Some consolation can be found in the fact that compositestructures have superior damping properties when compared to metals. This is especially truefor sandwich construction.The transient dynamic loading referred to generally describes events that occur at much higherload amplitu&s. Slammin g in waves is of particular interest when considering the design ofhigh-speed craft. This topic will be covered in detail in the following section on panel loadingas the intense loading is genemilly localized. Applying an acceleration factor to the static wavebending analysis outlined above can give some indication of the overall girder stressesproduced as a high-speed craft slams into a wave. Other hull girder dynamic phenomena ofnote include springing and whipping of the hull when wave encounter frequency is coincidentwith hull natural frequency.Hauling and Blocking LoadsWhen a vessel is hauled and blocked for storage, the weight of the vessel is not uniformlysupported as in the water. The point loading from slings and cradle fmtures is obviously aproblem and will be addressed in the &tail design section. The overall hull, however, will besubject to bending stresses when a vessel is lifted with slings at two points. Except in extremesituations, in-service design criteria for small craft up to about 100 feet should be more severethan this case. When undergoing long term storage or over-land transit, consideration must begiven to what f~tures will be employed over a given period of time. Large unsupportedweights, such as machinery, keels or tanks, can produce unacceptable overall bending momentsin addition to the local stress concentrations. During transportation, acceleration forcestransmitted through the trailer’s support system can be quite high. The onset of fatique damagemay be quite precipitous, especially with cored construction.77

, .Loadsfor FRP Ship DesignMarine CompositesSailing Vessel Rigging LoadsThe major longitudinal load producing element associated with sailing vessels is the mastoperating in conjunction with the headstay and backstay. Upwind sailing performance is oftena function of headstay tension, which can be very demanding on a lightweight, racing structure.The mast works in compression under the combined action of the aforementioned longitudinalstays and the more heavily loaded athwartship shroud system (see Shroud Attachment infollowing section). Hull deflection is in the sagging mode, which can be additive with waveaction response. The characteristic design criteria for high performance sailing vessels isusually deflection limitations.Lateral LoadingLateralloading on a ship’s hull is normally of concern only when the hull form is ve~ long andslender. Global forces are the result of beam seas. In the case of sailing vessels, lateral loads canbe significant when the vessel is sading upwind in a heeled condition. Methods for evaluatingwave bending moment should be used with a neutral axis that is parallel to the water.Lateral loading can also result from docking and tug assisted maneuvers, although the designcriteria will usually be dictated by local strength in these instances.Torsional LoadingTorsional loading of hull structures is often overlooked because there is no convenientanalytical approach that has been documented. Quartering seas can produce twisting momentswithin a hull structure, especially if the hull has considerable beam. In the case of rnultihulls,this loading phenomena often determines the configuration of cross members. Newreinforcement materials are oriented with fibers in the bias direction (+ 450), which makes themextremely well suited for resisting torsional loading.LoadingNormal to Hull and Deck SurfacesThe loads on ship structures me reasonably well established (e.g. PNA, etc), while the loads onsmall craft structures have received much less attention. There are some generalizations whichcan be made concerning these loads, however. The dominant loads on ships are global in-planeloads (loads affecting the entire structure), while the dominant loads on small craft are local outof plane loads (loads normal to the hull surface over very small portions of the hull surface).As a result, structural analysis of ships is traditionally approached through approximating theentire ship as a box beam, while the structural analysis of small craft is approached throughlocal panel analysis. The analysis of large boats (or small ships) must inclu& both global andlocal loads, as either may be the dominant factor. Since out-of-plane loads are dominant forsmall craft, the discussion of these loads will center on small craft, however, much of thediscussion could be applied to ships or other large marine structures. The American Bureau ofShipping provides empirical expressions for the derivation of design heads for sail and powervessels. [3-5, 3-6]Out-of-plane loads can be divided into two categories: distributed loads (such as hydrostatic andhydrodynamic loads) and point loads (such as keel, rig, and rudder loads on sail boats, or stra~rudder or engine mounts for power boats). The hydrostatic loads on a boat at rest are relativelysimple and can be determined from fmt principles. The hydrodynamic loads are very complex,78

Chapter ThreeDESIGNhowever, and have not beenstudied extensively, thus they areusually treated in an extremelysimplified manner. The mostcommon approach is to increasethe static pressure load by a fixedproportion, called the dynamicload factor. [3-7] The sources ofpoint loads vary widely, but mostcan be estimated from firstprinciples by making a few basicassumptions.IIHydrodynamic LoadsThere are several approaches toestimating the hydrodynamicloads for planing power boats,however most are based on thefnst comprehensive work in thisarea, performed by Heller andJasper. The method is based onrelating the strain in a structurefrom a static load to the strain in astructure from a dynamic load ofthe same magnitude. The ratio ofthe dynamic strain to the staticstrain is called the “responsefactor~’ and the maximumresponse factor is called the“dynsmic load factor.” l%isapproach is summarized here as anexample of this type ofcalculation. Heller and Jasperinstrumented and obtained data onan aluminum hull torpedo boat(Y’P 110) and then used this dataas a basis for the empirical aspectsof their load calculation. Anexample of the data is presented inFigure 3-4. The dynamic loadfactor is a function of the impactpressure rise time, to, over thenatural period of the structure, T,and is presented in Figure 3-5,where C/cC is the fraction ofcritical damping.The theoreticalAte*IeromettrFigure 3-4 Pressures Recorded in Five and SixFoot Waves at a Speed Of 28 Knots [Heller andJasper, On the Structural Design of Planing Cra~0 I&TR9Ure s-s Dynamic Load FactorsTime Varying Impact Loads [Heller andthe Structural Design of Planing Cramfor TypicalJasper, On279

Loads for FRP Ship DesignMarine Compositesdevelopment of the load prediction leads to the following equations:Maximum Impact Force Per Unit Length:where:PO= maximum impact force per unit lengthw= hull beamL= waterline lengthY~~ = vertical acceleration of the CGg = gravitational accelerationMaximum Effective Pressure at the Keel3P0——’01 – Gwhere:P~j = maximum effective pressure at the keelG = half girthMaximum Effective Pressurewhere:~ = the maximum effective pressure for designDLF = the Dynamic @ad Factor from Figure 3-5 (based on known ormeasured crItIcal damping)An example of the pressure calculation for the YPl 10 is also presented by Heller and Jaspe~Maximum Force Per Unit Length:PfJ= 3 ; :~~~(1 + 4.7) = 1,036 lbs~mMaximum Effective Pressure at the Keel:1036 X3’01 = 96= 32.4 psi80

. ...-Chapter ThreeDESIGNMaximum Effective Pressure:p= 32.4x 1.1= 35.64 psiThis work is the foundation for most prediction methods. Other presentations of loadcalculation, measurement, or design can be found in the following: Jones (1984), Reichard(1985), Savitsky (1964), Savitsky and Brown (1978), Savitsky (1985), American Bureau ofShipping Guidelines, Lloyd’s Register of Shipping Rules, and Det Norske Veritas Rules.Point LoadsOut-of-plane point loads occur for a variety of reasons. The largest loads on a boat often occurwhen the boat is in dry storage, transported over land, removed from the water or placed into thewater. The weight of a boat is distributed over the hull while the boat is in the water, but isconcentrated at support points of relatively small area when the boat is out of the water. As anexample, an 80 foot long 18 foot wide power boat weighing 130,000 pounds would probably onlyexperience a hydrostatic pressure of a few psi. If the boat was supported on land by 12 blockswith a surface area of 200 square inches each, the support areas would see an average load of 54psi. Equipment mounting, such as rudders, struts, engines, mast and rigging, booms, cranes, etc.can also introduce out-of-plane point loads into the structure through mechanical fasteners.General Res~onse of FRP Marine StructuresHull Girder Stress DistributionWhen the primary load forces act uponthe hull structure as a long, slenderbeam, stress distribution patterns looklike Figure 3-6 for the hoggingcondition with tension and compressioninterchanged for the sagging case. Themagnitude of stress increases withdistance from the neutral axis. On theother hand, shear stress becomesmaximum at the neutral axis. Figure3-7 shows the longitudinal distributionof principal stresses for a long, slendership*The relationship between bending momentand hull stress can be estimated fromsimple beam theury for the purposes ofprdiminary design. The basic relationshipis stated as follows:M Mc Figure 3-6 Theoretical and MeasuredStress Distribution for a Cargo Vessel MidshipSection [R7nciples of Naval Architecture]81

Loads for FRP Ship DesignMarine Compositeswhere:a = unit stressM = bending momentSikl = section modulusc = distance to neutral axisI = moment of inertiaThe neutral axis is at the centroid of all longitudinal strength members, which far compositeconstruction must take into account specific material properties along the ship’s longitudinal axis.The actual neutral axis rarely coincides with the geomettic center of the vessel’s midship section.Hence, values for o and c will be different for extteme fibers at the deck and hull bottom.PRINCIPAL STRESSES, TENSILE and COMPRESSIVEMAXIMUM SHEARING STRESSESPRINCIPAL STRESSES, TENSILE and COMPRESSIVEMAXIMUM SHEARING STRESSESFigure 3-7 Longitudinal Distribution of Stresses in a Combatant [Hovgaard, StrLIcturalDesign of Warships]Buckling of Hat-Stiffened PanelsFRP laminates generally have ultimate tensile and compressive strengths that are comparablewith mild steel but stiffness is usually only 5V0to 10%. A dominant design consideration thenbecomes elastic instability under compressive loading. Analysis of the buckling behavior ofFRP grillages common in ship structures is complicated by the anisotrophic nature of thematerials and the stiffener configurations typically utilized. Smith [3-8] has developed a seriesof data curves to make approximate estimates of the destabilizing stress, OX,required to producecatastrophic failure in transversely framed structures (see Figure 3-8). Theories for sandwichlaminates will be presented in the section covering sandwich construction.82

Chapter ThreeDESIGNfigure 3-8 Transversely Stiffened Panel [Smith, Buck/ing Problems in the Design ofFiberglass-Reinforced Plastic Ships]The lowest buckling stresses of a transversely framed structure usually correspond to one of theinterframe modes illustrated in Figure 3-9.The frrst type of buckling (a) involves maximum flexural rotation of the shell/stiffener interfaceand minimal displacement of the actual stiffener.This action is dependent upon the restraining stiffness of the stiffener and is independent of thetransverse span.The buckling phenomena shown in (b) is the result of extreme stiffener rotation, and as such, isa function of mnsverse span which influences stiffener torsional stiffness.The third type of interframe buckling depicted (c) is unique to FRP structures but can oftenproceed the other failure modes. In this scenario, flexural deformation of the stiffenersproduces bending of the shell plating at a half-wavelength coincident with the stiffener spacing.Large, hollow top-hat stiffeners can cause this effect. The restraining influence of the stiffeneras well as the transverse span length are factors that control the onset of this type of buckling.All buckling modes are additionally influenced by the stiffener spacing and dimensions and theflexural rigidity of the shell.Buckling of the structure may also occur at half-wavelengths greater than the spacing of thestiffeners. The next mode encountered is depicted in Figure 3-9 with nodes at or betweenstiffeners. Formulas for simply supported orthotropic plates show good agreement with morerigorous folded-plate analysis in predicting critical loads for thisapproximate formula is:type of failure. [3-8] The83

Loads for FRP Ship DesignMarine Compositeswhere:N=&D] =Dv =L=critical load per unit widthflexural rigidity per unit widthflexural rigidity of the shell in the x-directionstiffened panel rigidity = 1A(C=+ CY) with C = torsional rigidity per unitwidth and C~ = twisting rigidity of the shell (~st term is dominant)buckling wavelengthLongitudinally framed vessels are also subject to buckling failure, albeit at generally higher criticalloads. If the panel in question spans a longitudinal distance L, a suitable formula for estimatigC1’itiCdbucldhg Stfe~S,~w, based on the assumption of simply supported end conditions is:where:$EIAL2a= ycr “ n2EI1 -1--L~(-AsEI =A=GA, =flexural rigidity of a longitudinal with assumed effective shell widthtotal cross-sectional area of the longitudinal including effective shellshear rigidity with A.= area of the stiffener webs-a-DJ--(a)I[NODE LINES OCCiIkBETwEEN FwUWS7-—.— .1I(b)Io~NODE LINE$ COINCIUwITHFwAMESu- ‘L ‘w ~(c)~gure 3-9 Interframe BucklingModes[Smith, Buckling Problems in theDesign of Fiberglass-Reinforced PlasticSh@]Figure 3-10 Extraframe BucklingModes [Smith, Buckling Problems in theDesign of Fiberg/ass-Reinforced P/asticSh@sJ84

Chapter ThreeDESIGNBuckling failure can occur at reducedprimary criticzil stress levels if thestructure is subjected to orthogonalcompressive stresses or high shearstresses. Areas where biaxialcompression may occur include sideshell where lateral hydrodynamic loadcan be signhlcant or in way of framesthat can cause secondary transversestress. Areas of high shear stressinclude side shell near the neutral axis,bulkheads and the webs of stiffeners.Large hatch openings are notorious forcreating slmss concentrations at theircorners, where stress levels csn be 3-4times greater than the edge midspan.Large cut-outs reduce the compressivestability of the grillage structure andmust therefore be carefully analyzedSmith [3-8] has proposed a method foranalyzing this pmtion of an FRP vesselwhereby a plane-stress analysis isfollowed by a grillage bucklingcalculation to determine the distributionof destabilizing forces (see Figure 3-11).Figure 3-12 shows the fwst two globalfailure modes and associated averagestress at the structure’s mid-length.Shl P’s SIOE~. _., ._. -– . —T –--– - -, —. .— . .. . . . . . .,-. ..~.. - --—1❑ . 4: nx—x.- .- :: —. \ \– \ +/’ /,::.— - —.■~1. . —.I1 1------- . . . .... .- .-— -— . -.(d) FINITE ELEMEN1 lBEAkliArl ON.—. LCL{b) blSTRllU?lON OF LONGl?UblNAL $Tnt$$fi9Ure q-l 1 Plane Stress Analysis of HatchOpening [Smith, Buckling Problems in the 12esignof Fiberglass-Reinforced Plastic Ships]II1-4Ia. ❑figllre $1 z Deck Grillage Buckling Modes Near Hatch Opening [Smith, Buck/ingProblems in the Design of Fiberglass-Reinforced Plastic Sh(os]85

Mechanics of Composite MaterialsMarine CompositesThe physical behavior of composite materials is quite different from that of most coramonengineering materials that are homogeneous and isolropic. Metals will generally have the samecomposition regardless of where or in what orientation a sample is taken. On the other hand,the makeup and physical properties of composites will vary with location and orientation ofprincipal axes. These materials are termed anisotrophic, which mesns they exhibit differentproperties when tested in different directions. Most composite structures me, however,orthotropic having three mutually perpendicular planes of symmetry.The mechanical behavior of composites is traditionallyevaluated on both microscopic and macroscopicscsle to take into account inhomogeneity. Microrrdsnics attempts to quant@ the interactions offiber and matrix @enforcement and resin) on a microscopic scsle on par witi the diamet~ of a singlefiber. Macrornechanics treats composites as homogeneous materials with mechanical proptztiesrepresentative of the medium as a whole. The latter analytical approach is more realistic for the studyof tie laminates that arEoften thick and laden with tbrough-laminate inconsistencies. However, itis instructive to undmtand the concepts of micromechanics as the basis fur macromechanic properties.The designer is again cautioned to verify all analytical work by tdng builder’s specimens.MicromechanicTheorvGeneral Fiber/Matrix RelationshipThe theory of micromechanics was developed about 30 yesm ago to help explain the complexmechanisms of stress and strain transfer between fiber and matrix within a composite. [3-9]Mathematical relationships have been developed whereby knowledge of constituent materialproperties can lead to behavior predictions. Theoretical predictions of composite stiffness havetraditionally been more accurate than predictions of ultimate strength. Table 3-1 describes theinput and output variables associated with micromechanics.Table 3-1. Micromechanics Concepts[Chamis, AS/1#Engineers’ Guide to Composite Materials]InputFiber propertiesMatrix propertiesEnvironmental conditionsFabrication process variablesGeometric configurationoutputLfniaxial strengthsFracture toughnessImpact resistanceHygrothermai effectsThe basic principles of the theory can be illustrated by examining a composite’ element un&r auniaxial force. Figure 3-13 shows the state of stress and transfer mechanisms of fiber andmatrix when subjected to pure tension. On a macroscopic scale, the element is in simpletension, while internally a number of stresses can be present. Represented in Figure 3-13 arecompressive stresses (vertical SITOWSpointing inwards) and shear stresses (half arrows along thefiber/matrix interface). This combined stress state will determine the failure point of the86

Chapter ThreeDESIGNmaterial. The bottom illustration inFigure 3-13 is representative of a poorfiber/matrix bond or void within thelaminate. The resulting imbalance ofstresses between the fiber and matrix canlead to local instability causing the fiberto shift or buckle. A void along 1% ofthe fiber surface generally reducesinterracial shear strength by 7%. [3-9]Fiber OrientationOrientation of reinforcements in alaminate is widely known to dramaticallyeffect the mechanical performance ofcomposites. Figure 3-14 is presented tounderstand tension failure mechanisms inunidirectional composites on amicroscopic scale. Note that at an angleof U, the strength of the composite isalmost completely dependent on fibertensile strength. The following equationsrefer to the three failure mechanismsshown in Figure 3-14:Fiber tensile failure:a=c cMatrix or interracial shew‘c= a sin@ CosalComposite tensile failure:where:0= ua= c0=0=‘c=au =composite tensilestrengthapplied stressangle between thefibers and tensile axisshear strength of thematrix or interfacetensile strength ofthe matrixFigure 3-I 3 State of Stress and StressTransfer to Reinforcement [Materia/ Engineering,May, 1978 p. 29]Tensilefailurein fiber4- u=uc.~ 0.s$Shear failure in matrix-fiber$ I~0102030 40606070 BOXIFiber alinement to tensile axis, #r degfi9Ure $14 Failure Mode as a Functionof Fiber Alignment [ASM Engineers’ Guide toComposite Materials]P87

Mechanics of Composite MaterialsA4arineCompositesMicromechanics GeometryFigure 3-15 shows the orientationand nomenclature for a typicalfiber composite geometry.Properties along the fiber or xdirection (l-axis) are calledlongitudinal; transverse or y(2-axis) are called transverse; andin-plane shear (l-2 plane) is alsocalled intralaminar shear. Thethrough-thickness properties inthe z direction (3-axis) are calledinterlaminar. Ply properties aretypically denoted with a letter todescribe the property withsuitable subscripts to describe theconstituent material, plane,direction and sign (withstrengths). As an example, S~ ~1~indicates matrix longitudinaltensile strength.The derivation of micromechanicsequations is based on theassumption that 1) the ply and itsconstituents behave linearlyelastic until fracture (see Figure3-16), 2) bonding is completebetween fiber and matrix and 3)fracture occurs in one of thefollowing modes: a) longitudinaltension, b) fiber compression, c)delamination, d) fibermicrobuckling, e) transversetension, or f) intralaminar shear.[3-2] ThB following equationsdescribe the basic geometricrelationships of compositemicromechanics:Partial volumes:kf+km+k, = 1Angla.plieImninataPly1=z34r3tv2—-. ___.—. . .————. . ___———_ .—————— ___——— ____———— ———ShearTransverseFiberMatrix~ LongitudirdFigure 3-15 Fiber Composite Geometry[Chamis, ASM Engineers’ Guide to Composite Materials]/$0---Wn 2‘1 – t’”’Strain~IntrdarrdnarshearFigure 3-16 Typical Stress-Strain Behavior ofUn~directional Fiber’ Composites [Chamis, ASM En-gineers’ Guide to Composite Materia/s]88

.=,Chapter ThreeDESIGNPly density:Resin volume ratio:1+= kj Pf+ km Pmkm=Fiber volume ratio:(1-k)P1+= +-1Pf mmWeight ratio:kf =(1-k)PI1++ —-1~ Lfmwhere:f = fiber,m= matrixv = void1 = plyk = weight percentElastic ConstantsThe equations for relating elastic moduli and Poisson’s ratios are given below. properties inthe 3-axis direction are the same as the 2-axis direction because the ply is assumed transverselyisotropic in the 2-3 plane (see bottom illustration of Figure 3-15).Longitudinal modulus:Transverse modulus:“’’”*’E’”\ 1Shear modulus:89

—Mechanics of Composite MaterialsMarine CompositesPoisson’s ratio:‘112= kf v112+ kmvm= V[13In-Plane Uniaxial StrengthsThe equations for approximating composite strength properties are based on the fracturemechanisms outlined above undm micromechanics geometry. Three of the fracture modes fallunder the heading of longitudinal compression. It should be emphasized that prediction ofmaterial strength properties is currently beyond the scope of simplifkd mathematical theory.The following approximations aredominate particular failure modes.Approximate longitudinal tension:presentedto give insight into which physical propertiess ~llT=kS.ffTApproximate fiber compression:s IHc=~fsjcApproximate delamination/shear:s~~lc= 10 S/lX + 2.5S~TApproximate rnicrobuckling:Gms lIIC=l–kf 1->T1f12Approximate transverse tension:s mT90

.Chapter ThreeDESIGNApproximate transverse compression:‘22c=[’-($-’f)p-2]]’~Approximate intralaminar shear:Approximate void influence on matrix:Through-Thickness Uniaxiai StrengthsEstimates for properties in the 3-axis directionam given by the equations below. Note that theinterlarrinar shear equation is the same as that for in-plane. The short beam shear depends heavily onthe resin shear strength and is about 1Y2times the interlamimr value. Also, the longitudinal flexuralstrengthis fiber dominated while the transverseflexural strengthis mm sensitiveto matrix strength.Approximate interlaminar shear:s 113s=s 123S=Approximate fkxuralstrength:s lllF=s 122F=91

Mechanics of Composite MaterialsMarine CompositesApproximate short-beam shear:s 113SB = 1.5 S1~3~s 123SB =1“5‘123sUnlaxial Fracture ToughnessFracture toughness is an indication of a composite material’s ability to resist defects ordiscontinuities such as holes and notches. The fracture modes of general interest include:opening mode, in-plane shear and out-of-plane shear. The equations” to predict longitudinal,transverse and intralaminar shear fmcture toughness are beyond the scope of this text and canbe found in the cited reference. [3-2]In-Plane Unlaxial Impact ResistanceThe impact resistance of unidirectional composites is defined as the in-plane uniaxial impactenergy density. The five densities are: longitudinal tension and compression; transverse tensionand compression; and intralaminar shear. The reader is again directed to reference [3-2] forfurther elaboration.Through-Thickness Uniaxial Impact ResistanceThe through-thickness impact resistance is associated with impacts normal to the surface of thecomposite, which is generally of particular interest. The energy densities are divided asfollows: longitudinal interlaminar shear, transverse interlaminar shear, longitudinal flexure, andtransverse flexure. The derivation of equations and relationships for this and the remainingrnicromechanics phenomena can be found in the reference.ThermalThe following thermal behavior properties for a composite are derived from constituent materialproperties: heat capacity, longitudinal conductivity, and longitudinal and transverse thermalcoefficients of expansion.Hygral PropertiesThe ply hygral properties predicted by micromechanics equation include ditfusivity andmoisture expansion. Additional equations have been derived to estimate moisture in the resinand composite as a function of the relative humidity ratio. An estimate for moisture expansioncoefficient is also postulated.Hydrothermal EffectsThe combined environmental effect of moisture and temperature is usually termedhydrothermal. All of the resin dominated properties me particularly influenced by hydrothermalinfluences. The degraded properties that are quantified include: glass transition temperature ofwet resin, mechanical characteristics, and thermal behavior.92

Chapter ThreeDESIGNMacromechanicTheoryLaminae or PliesThe most elementary level considered by macromechanic theory is the lamina or ply. Thisconsists of a single layer of reinforcement and associated volume of matrix material. Inaerospace applications, all specifications are expressed in terms of ply quantities. Marineapplications typically involve thicker laminates and are usually specifkd according to overallthickness, especially when successive plies are identical.For most polymer matrix composites, the reinforcement fiber will be the primary load carryingelement because it is stronger and stiffer than the matrix. The mechanism for transferring loadthroughout the reinforcement fiber is the shearing stress developed in the matrix. Thus, caremust be exercised that the matrix material does not become a strain limiting factor. As anextreme example, if a polyester reinforcement with an ultimate elongation of about 2070 wascombined with a polyester resin with 1.5V0elongation to failure, cracking of the resin wouldoccur before the fiber was stressed to a level that was 109i0of its ultimate strength.LaminatesA laminate consists of a series of laminae or plies that are bonded together with a materi@ thatis usually the same as the matrix of each ply. Indeed, with contact molding, the wet-out andlaminating processes are continuous operations. A potential weak area of laminates is the shearstrength between layers of a laminate, especially when the entire lamination process is notcontinuous. This concept is further described in the Design of Details section and ChapterFive.A major advantage to design and construction with composites is the ability to varyreinforcement material and orientation throughout the plies in a laminate. In this way, thephysical properties of each ply can be optimized to resist the loading on the laminate as awhole, as well as the out of plane loads that create unique stress fields in each ply. Figure 3-17illustrates the concept of stress field discontinuity within a laminate.Laminate PropertiesPredicting the physical properties of laminates based on published data for the longitudinaldirection (l-axis) is not very useful as this data was probably derived from samples fabricatedin a very controlled environment. Conditions under which marine laminates are fabricated canseverely limit the resultant mechanical properties. To date, safety factors have generally beensufficiently high to prevent widespread failure. However, instances of stress concentration,resin-rich areas and voids can negate even large safety factors.There are essentially three ways in use today to predict the behavior of a ltiated structureunder a given loading scenario. In all cases, estimates for Elastic properties are more accuratethan those for Strength properties. This is in part due to the variety of failure mechanismsinvolved. The analytical techniques currently in use include:. Property charts called “Carpet Plots” that provide mechanical performancedata based on orientation composition of the laminate;93

Mechanics of Composite MaterialsMarine CompositesGENERAL UMINATE STRUCTURE, WITH L0406u“ 4 4% dw’”>–’ ““ev1PLY FISERS.,~’=< “ ,xANDY ARE LAMWJATE,OR GEOMETRIC2 OIRECTI~S: 1 AND zFIBERs ARE ●RINCIPALDIFIECTIONSOF4W’” FIBERDiRECTl~ % h _ . . .. .k‘* STRESSFIELD IN PRINCIPAL1 AND 2DIRECTIONS FOR EACH LAYER4~gure s-l 7 Elastic Properties of Plies within a Laminate [Schwartz, CompositeMaterials Handbook]“ Laminate analysis software that allows the user to build a laminate from amaterials database and view the stress and strain levels within and betweenplies in each of the three mutually perpendicular axes;●Test data based on identical laminates loaded in a similar fashion to thedesign case.Carpet PlotsExamples of Carpet Plots based on a Carbon FiberEpoxy laminate are shown in Figures 3-18,3-19 and 3-20 for modulus, strength and Poisson’s ratio, respectively. The resultant mechanicalproperties are based on the assumption of uniaxial loading (hence, values are for longitudinalproperties only) and assume a given design temperature and design criterion (such as B-basiswhere there is 90~0 confidence that 95% of the failures will exceed the value). [3-2] StephenTsai, an acknowledged authority on composites design, has dismissed this technique as a validdesign tool in favor of the more rigorous laminated plate theory. [3-10]94

.Chapter ThreeDESIGNCarpet plots have been a commonpreliminary design tool within theaerospace industry where laminatestypically consist of a large number of thinplies. Additionally, out of plane loads arenot of primary concern as is the case withmarine structures. An aerospace designeressentially views a laminate as ahomogeneous engineering material withsome degraded mechanical propertiesderived from carpet plots. Typical marinelaminates consist of much fewer plies thatare primarily not from unidirectionalreinforcements. Significant out of planeloading and high aspect ratio structuralpanels render the unidirectional data fromcarpet plots somewhat meaningless fordesigning FRP maxine structures. oi___“. J . . .J.__llo 20 4;4$p!lms, %15007 -, ~’ “---- -“~ ‘ +MFigure 3-18 Carpet plot illustratingLaminate Tensile Modulus [ASM EngineeredMaterials Handbook]01- .J_l-l_lao 40 00 40 10044”Plkl, %Figure 3-19 Carpet plot II-Iustrating Tensile Strength [ASM EngineeredMaterials Handbook ]oL-L~LJo m 411 K! In mw mm,%Figure 3-20 Carpet plot Illustrating Poisson’sRat io [ASM Engineered MaterialsHandbook ]95

Mechanics of Composite MaterialsMarine CompositesComputer laminate AnalysisThere are a number of structural analysis computer programs available for mainframecomputers that use finite-element or finite-difference numerical methods and are suitable forevaluating composites. In general, these programs will address: [3-2]o Structural response of laminated and multidirectional reinforced composites●Changes in material properties with temperature, moisture and ablativedecomposition. Thin-shelled, thick-shelled, and/or plate structuresc Thermal-, pressure- traction-, deformation- and vibration-induced load states. Failure modes. Non-linearity. Structural instability. Fracture mechanicsThe majofity of these codes for mainhnes are quite expensive to acquire and operate, whichprecludes their use for general marine structures. Specialized military applications such as apressure hull for a torpedo or a highly stressed weight critical component might justify analysiswith these sort of programs.More useful to the marine designer, are the PC based laminate analysis programs that allow anumber of variations to be evaluated at relatively low cost. The software generally costs lessthan $500 and can run on hardware that is probably already integrated into a design office. Thebetter programs are based on laminated plate theory, which treats each ply as aquasi-homogeneous material. Prediction of ultimate strengths with materials that enternon-elastic regions, such as foam cores, will be of limited accuracy. Some other assumptions inlaminated plate theory include: [3-2]. The thickness of the plate is much smaller than the in-plane dimensions. The strains in the deformed are small compared to unity●Normals to the undefomned plate surface remain normalplate surface. Vertical deflection does not vary through the thickness. Stress normal to the plate surface is negligibleto the deformedFor a detailed description of laminated plate theory, the reader is advised to refer toIntroduction to CompositeMaterials, by S.W. Tsai and H.T. Hahn, Technornic, Lancaster, PA(1985).96

Chapter ThreeDESIGNTable 3-2 illustrates a typical range of input and output variables for computer latninate analysisprograms. Some programs are menu driven while others follow a spreadsheet format. Oncematerial properties have been specifkd, the user can “build” a laminate by selecting materialsand orientation. As a minimum, stresses and strains failure levels for each ply will becomputed. Some programs will show stress and strain states versus design allowable based onvarious failure criteria. Most programs will predict which ply will fail fit and provide someroutine for laminate optimization. In-plsne loads can usually be entered to compute predictedstates of stress and strain instead of failure envelopes.Table 3-2.Typical Input and Output Variables for Laminate Analysis ProgramsInputoutputLoadCondltlons MaterialProperties Ply Properties LaminateResponseLongitudinal In-Plane Modulus of Elasticity Thicknesses* Longitudinal DeflectionLoadsTransverse In-PlaneLoadsVertical In-PlaneLoads (shear)Long$::;t:lBendingPoisson’s Ratio Orientation* Transverse DeflectionShear Modulus Fiber Volume* Vertical DeflectionLongitudinal Strength Longitudinal Stiffness Longitudinal StrainTriw#vmsvd:BendingVertical Moments(torsional)Failure CriteriaTemperature ChangeTransverse Strength Transverse Stiffness Transverse StrainShear StrengthLongitudinal Poisson’sRatioVertical StrainThermal Expansion Tran~:rse Poisson’s Longitudinal StressCoefficientsper PlyLon&ujd# Shear Transverse Stress perPlyTrann$ Shear Ve:~j~ress (shear)‘These ply properties are usually treated as input variablesFirst Ply to FailSafety FactorsFailure CriteriaFailure criteria used for analysis of composites structures sre similar to those in use forisotropic materials, which include maximum stress, maximum strain and quadratic theories.[3-10] These criteria me empirical methods to predict failure when a laminate is subjected to astate of combined stress. The multiplicity of possible failure modes prohibits the use of a morerigorously derived mathematical formulation. The basic material data required for all thecriteria is longitudinal and transverse tensile, and compressive as well as longitudinal shearstrengths. Two-dimensional failure theory is based on these properties.97

Mechanics of Composite MateriaisMarine CompositesMaximum Stress CriteriaEvaluation of laminated structures using this criteria begins with a calculation of thestrengtldstress ratio for each stress component. This quantity expresses the relationshipbetween the maximum, ultimate or allowable strength, and the applied corresponding stress,The lowest ratio represents the mo& that controls ply failure. This criteria ignores thecomplexities of composites failure mechanisms and the associated interactive nature of thevarious stress components.Maximum Strain CriteriaThe maximum strain criteria follows the logic of the maximum stress criteria. The maximumstrain associated with each applied stress field is merely the value calculated by dividingstrengths by moduli of elasticity. The dominating failure mode is that which produces thehighest strain level. Simply stated, failure is controlled by the ply that first reaches its elasticlimit. This concept is important to consider when designing hybrid laroinates that contain lowstrain materials, such as carbon fiber.Both the maximum stress and maximum strain criteria can be visualized in two-dimensionalspace as a box with absolute positive and negative values for longitudinal and transverse axes.This failure envelope implies no interaction between the stress fields and material response.Quadratic Criteria for Stress and Strain SpaceOne way to includ~ the coupling effects (Poisson phenomena) in a failure criteria is to use atheory based on distortional energy, The resultant failure envelope is an ellipse which is veryoblong. A constant, called the normalized empirical constant, which relates the coupling ofstrength factors, generally falls between -!/2 (von Mises criteria) and O (moditkd Hill criteria).[3-10] A strain space failure envelope is more commonly used for the following reasons:cPlotted data is less oblong. Data does not vary with each laminate. Input properties are derived more reliably. Axes are dimensionlessFirst- and Last-Piy to Faiiure CriteriaThese criteria are probably more relevant with aerospace structures where laminates mayconsist of over 50 plies. The theory of fist-ply failure suggests an envelope that describes thefailure of the i%st ply. Analysis of the lmninate continues with the contribution from that andsuccessive plies removed. With the last ply to failure theory, the envelope is developed thatcorresponds to failure of the ilnal ply in what is considered analogous to ultimate failure. Eachof these concepts fail to take into account the contribution of a partially failed ply or thegeomernc coupling effects of adjacent ply faihrre.ThicknessDesign CriteriaMany components and smaller hull structures in the marine industry are designed using purelyempirical methods. The spectilcation criteria is usually based on satisfactory in-service98

Chapter ThreeDESIGNperformance of similar structure. This method is normally only applied to productionfiberglass parts that are fabricated by hand lay-up or spray-up techniques where builders haveestablished a working criteria for minimum thickness. Owens-Coming [3-11] has developed asimple methodology for relating laminate thickness to the amal weight of fiberglass applied andthe fiberglass weight percent. The following relationship based on factors from Figure 3-21 ispostulated:where:~_wz100T= w.laminate thickness in inchesmount of fiberglass used in ounces per square footfactor from Figure 3-21766z4Fact3or. . . . .~. . . . . .. . . . . . . . . . . . . . .. . . . . . ... . . . . .\. . . . . ... . . . .. . . . . . ... . . . . .. . . . . .. . . . . .,. . . . ... . ...+. . . . . . ... . . . . ./. . . . .. . . . .21.612. . . . . ... . . . . . . . . . . . . ... . . . . .\.. . . . .\.. . . . . ... . . . . ... . . . . .. . . . .D.610316 20 24 28 32 36 40 44 48 62 58 60Fiberglass Relnfomement% by WeightI~ Z Factor — Speclflc Gravity IFigure 3-21 Z-Factor and Approximate Laminate Specific Gravity for FiberglassLaminates with Unfilled Resin Systems [Owens-Corning Fiberglas, The Hand Lay-Up andSpray-Up Guide]99

Mechanics of Composite MaterialsMarine CompositesConventional Laminate Pro~eW DataIt has been emphasized throughout this document that accurate design engineering can only beaccomplished if material property data is determined from laminate testing using shipyardsamples. However, the designer must have some starting point for the purposes of conductingpreliminary design or trade-off studies. In the early 1970’s, Owens-Coming Fiberglas inconjunction with Gibbs & Cox published a document entitled Design Propem”esof MarineGrade Fiberglas bninates. [3-12] The laminates considered were manufactured by the handlayup method and generally utilized orthophthalic polyester resin. The following materialswere considered in the study:. Chopped Strand Mat - ?4 oz/f# to 3 oz/ft2 with data also relevant for“spray-up” laminates.●Woven Roving - Most laminates used 24 oz/yd2, with some data on 18 and40 oz/yd2 material included. Fabric construction is 5 x 4, accounting forsuperior petiormance in the warp direction. Most U.S. Navy constructionuses only woven roving.*Mat-Woven Roving Laminate - Most data is for alternating layers of 24oz/yd2 woven roving and Ilh oz/ft? rrwt. This construction technique hastraditionally been the most popular with recreational boat builders, in partbecause interlmnimr shear strength is perceived to be better than purewoven roving laminates. The data presented here does not support this,although fabrication considerations still favor this technique.Data for “wet strength” was used whenever possible, although the authors point out that thestate-of-the-art for general purpose polyester resin at that time had reduced “wet” versus “dry”prope~ differences to about 5 to 7%. In the twenty years that have elapsed since most of thisdata was collected, resins have improved further as has sizing agents on fiberglass.The Gibbs & Cox data is being reproduced in this document not so much for the absolutematerial properties that can be extracted but more to show the range of data accumulated andthe graphical method chosen for representation. The variety of data sources and statisticalprocessing techniques varied to the point where the compiled data was not suitable forstatistical analysis. References [3-13] through [3-20] were cited as sources for the materialproperty data.100

Chapter ThreeDESIGNTENSILE STRENGTH AT 0“ (WARP)MAT ldA7.i30WN0 WOVEN KWlNL3-4lAhllMATE6 INMATES* ‘ LAMINATkS/TENS4LE MODULUS AT W (WARP)MAT MAT-ROVING WOVEN ROVING4LAMINATE6 LAMINATES LAMINATES40.MDkA3.0 ,-I+o20 so 40 50 en 70I+OVERALLAVEIWGEOUW CONTENl %TENSILE STFiENGTFI AT 9W [FILLI1‘ ‘ii 1MAT-BOVIMGI wOVEN FIOVlmj I I I 1LAMINATESI LAMINATFfl- 1AMINA7ES 1 1I40,000 I I I I I I I I ITENSILE MODULUS AT SW (FILL)MAT MAT-SOVINQ WUVEN ROVINGdLAMINATE9 LAMINATES UMINATCS3.0S5.90,2.0 .—--26,i?*$~$20,~zk ,s,1.0.= /’/ \10.6,20 30 40 60 80 70GbWSGON1tNT ‘#+OVEEALLAVERAGE020 Sn 40 60 60 70GIASS CONTENT %+OVERALLAVERAGE~gure 3-22 On-Axis Tensile Properties of 11A oz Mat and 24 oz Woven Roving[Gibbs and Cox, Design Properties of Marine Grade Fiberglass Laminates]101

Mechanics of Composite MaterialsMarine CompositesFLEXURAL sTRENGTH AT W (WARPIMAT ~AT-UOVINQ WOVEN ROVING4LAMINATES LAMINATES LAMINATESFLEXURAL MODULUS AT 0° (WARP)MAT MAT.ROVINQ WOVEN RoVINQ●LAMINATES LAMINATES- “ LAMINATES50,000 _ _ . _ _ _S.O\ — — —/:a/t /$;b sa,ouo / 7 [ .— —.A J/L / /:x~~.as0z2,02 /:/F 10 Ab /// .+OVERALLAVERAGE/yy+OVERALLAVERAGEZo,m__20 “’ 3i“ 40 so m ‘mGLASS CONTENT %o.20 2Q 40 60 80 70GLASS CONTENT xFLEXURAL STFIENINH AT SO. (FILL)MAT MAT+iOVING wovkN ROVING -4LAMINATSS LAMINATE~ - UMINATESFLEXURAL MO13ULU$ AT 90° (FILL]MAT MAT.ROVINQ WoVEN ROVING4UMINATES U2AINATES L4MINATESSo,wo3,0@J,MOg. 2.0~$F1i~i SO.WO//F~~ozi/3 /t1.0 / 9 +’ Yk/+0VER4LLAVHIAGE+OVHIALLAVERAGE20 20 40 50 so 70GLASS CONSENT %o20 30 40 50 so 10GL4SSaTENT %Figure 3-23 On-Axis Flexural Properties of IYZ oz Matand240z Woven Roving[GibbsandCox, Design Properties of Marine Grade Fiberglass Laminates]102

Chapter ThreeDESIGNCOMPRESSIVE STRENGTH AT Oh AND 20*MAT ~ ~NT.ROVlN13 WOVEN ROVTNO4LAMINATES L4MINATE8F “ UJJINATE9COMPRESSIVE MowLus AT o? AND 90”40.0003,0-—~ 30000g2.0~fk$ 20,0mo1,0—+OVERALLAVERAQEYI-+OVERMLAVER4GE10,OMJJo 30 40 60 so 70GLAS9CONTENT %o20 30 40 50 Cu 70QLASSCONTENT %COMPRESSIVE STRENGTH AT 46*MAT MAT-ROVINQ WOVEN ROVINGdLAMINATES UMINATE8 LAMINATESICOMPRESSIVE MODULUS AT 45*MAT MAT-ROVlffi WOVEN ROVING4bUAINATES LAMINATE6 LAMINATESI1Ig ~qo~EggE$% 20,0w \~ L\ \\~1.0+OVERALLAVERAGE+OVERALLAVERAGE10,00030 2n 40 m m 70.3LASSaNTENT %020 00 40 a ml 70C+ASS CONTENT %Figure 3-24 Compressive Properties of 11A oz Mat and 24 oz Woven Roving [Gibbsand Cox, Design Properties of Marine Grade Fiberglass Laminates]103

Mechanics of Composite MaterialsMarine CompositesTENSILE STRENGTH AT4s0MAT MAT~OVING WOVEN ROVINQ4 .,. -IAMINATES LAMINATES IAMINATESTENSILE MoDULUS AT 459MAT MAT-ROVING ~VEtJ ROVINQ+1AMlt4ATES LAMIt4ATEfi LAMINATES.WOW _., .26,000 .-~ 2C,000~w2.0~IR~2 ,,0I“b’u””mmzh I I I I I I{/~ L--;E$I ,UYA_- -4 F------ -~-6 -6,200+OVERALLAVERAGE+OVERAILAVERAOE1o20 20’ 40 60 Eo 70QLABS CONTENT %020 30 40 so 00 70G@SCCINTENT ?,FLEXURAL sTREN9w AT 4s’MAT MAT-R(WING WOVFN ROVING4UIMINATES LAMINATES UMINATESFLEWJRAL MODULUS AT 45°MAT MAT-ROVING WOVEMROVING+LAMINAW9 LAMINATES LAMINATESI1 1 I # 1 I 1 1 Ig 4!2,000Za~$; - ––$m ~:. ,. . .“gso ~oo~ ~-’r 1 I I IIyJ*+OVERALLAVERAGE, 1 I 1 1 1 1I OvmA1 .. -,.,-. IW’E~GE20,03020 m 40 50 SJl 70GMSS CONTENT %o20 30 40 50 so ToGU9SQNTENr %Figure 3-25 Off-Axis Properties of 1VP oz Mat and 24 oz Woven Roving [Gibbs andCox, Design Properties of Marine Grade Fiberglass Laminates]104

Chapter ThreeDESIGNPARALLEL SHEAR STRENGTHMAT ~ ~AT-ROMNG WOVEN RWINGdLAMINATES UMINATES- “ L4MlNATzaPER PENDICUMR SHEAR STRENGTHMAT MAT-ROVING WOVEN HOVINGdLAMW4ATS6 IAMINATES IAMINA7SSE 16,0002zE3&04~ ,“,,,W\v \ \ \l 1 1[ ,0,0,01 1 1 1 [ I I I I& 7OVERALLAVEFIAGE+OVERALLAVER4GE6.MO20 30 40 50 so ToGLASS CONTENT %20 so 40 60 m 70QLASSCONTENT t,TIIICKNES6 PER PAIR-ALTERNATING PLIESOF 1-112 Oz. MATAND 24 OZ WOVEN ROVINGMT J MAT-ROVING WQVSN flQvlNG4lAMl NATES7 LAMINATES LAMINATESTHICKNESS PERPLY-1-1/2 OZ. MAT OR24 OZ. WOVEN ROVINGMAT MAT-ROVING WOVEN ROWNG4LAMINATES UMINATE8 LAMINATES.13.C71,12 _ _1.06.11 _ _.03! ~A.10.04\.09\ g I,09,08-\+OVERALLAVERAGE.02 +OVERALLAVERAQE.0720 30 40 m 50 70GLAS$WNTENTx,0120 30 40 50 E4 70GLASS CONTENT %Figure 3-26 Shear and Thickness Properties of 11A oz Mat and 24 oz WovenRoving [Gibbs and Cox, Design Properties of Marine Grade Fiberglass Laminates]105

Sandwich ConstructionMarine CompositesThe structure of most small craft is designed to withstand high localized forces normal to thehull panels, as this is the dominant loading of the structure. Therefore, the structure must bedesigned with relatively higher flexural stiffness and strength than in-plane stiffness andstrength. This is especially true when comparing sandwich to solid laminates, along withcorresponding frame spacing. Sandwich construction is often used in high performance boatsbecause good out-of-plane flexural properties can be achieved at relatively low weights. Table3-3 developed for honeycomb core structures illustrates the potential gains of utilizing sandwichconstruction.Table 3-3. Strength and Stiffness for Cored and Solid Construction[Hexcel, The 13aslcson Bonded Sandwich Construction]IRelative StiffnessRelativeStrength1001007003503700925RelativeWeight100103106Sandwich panels consist of thin, high stiffness and strength skins over a thick, low density corematerial. The behavior of sandwich beams and panels is quite different from “solid” beams andpanels, with higher flexural stiffness and strength relative to in-plane properties. Mostdesigners have substantial experience with solid GRP, aluminum, or steel construction, andthere are a number of widely accepted scantling rules for these materials. However, theexperience base for sandwich construction is relatively small, and although there has been somework on sandwich scantling rules, there is at present no widely accepted scantling rule forsandwich construction,Flexural Stiffnessof a BeamThe flexural stiffness of a beam is a function of the elastic modulus, which is similar for thesolid beam and the sandwich skins, and the moment of inertia, which is ve~ different for solidand sandwich beams. The moment of inertia for the two types of beams are:Solid Beam Moment of Inetia= bh3Ig =106

chapterThreeDESIGNApproximateSandwich Beam Skins Momentof Inetiia2b+ ~ 2bt&+=— —12 4Approximate Sandwich Beam Core Moment of Inertiawhere:J=tic12b = the width of the beamh = the height of the beamr = the thiclmess of the sandwich skinsd = the thickness of the core, as per Figure 3-27F@Ure 3-27 Geometryof Sandwich Beams [Hexcel, The Basics on Bonded SandwichConstruction]The flemrral stiffness is the product of the modulus of elasticity and the moment of inertiaSolid Beam Flexural StiffnessEbh3EgI~ = -&107

SandwichConstructionMarine CompositesApproximate Sandwich Beum Flexural Stiffnesswhere:E~= the modulus of the solid beamE~= the modulus of the sandwich facing materialEC= the modulus of the core materialThese expressions can be simplified by neglecting the smaller terms. The followingcommon to sandwich construction, can be used to determine the relative magnitudeterms:ratios,of thet– = 0.1d:=200cSubstituting these ratios into the expression for the flexural stiffness of a sandwich bea.rmit canbe seen that the fist and tid tern-s contribute less than 1% of the flexural stiffness, thus theycan be neglected with little error. The resulting expression is:Simplified Sandwich BeamUsing this mpressio~ the ratio of the flexural stiffnessesof a solid beam and a sandwich beam i~When there is no core, t = ?2 and when E~= E , the bending stiffness ratio is 1.0. If thesandwich beam is at least as thick as the solid b~am, and Ef = E~, then this ratio is alwaysgreater than 1.0, thus for a given weight, a sandwich beam is stiffer than a solid beam. As anexample, let E~=E~, d=h=l, mdt=0.2h:# = (1)~= 1728h3SgThus the sandwich beam, which is 20% thicker than the solid beam, has a flexural stiffness1.73 times greater than the solid beam If the facing density is ten times the core density, thesandwich beam would weigh only 4890 of the solid beam weight108

Chapter ThreeDESIGNFlexural Strengthof a BeamThe flexural stmgth of the solid andsandwich beams is a function of thestress distribution in the beams and thelimiting material slrength. The generalstress distribution in sandwich beamssubjected to a moment M is presented inFigure 3-28. The maximumtensile/compressive stresses in the twobeams are:Solid Beam= 6Ms— 8 bh2Ḃ/‘IJ -— i2jlQ0 TAssumed Stress Distributionin theClassical Sandwich TheorySandwich Beamwhere:‘f=M(d+t)bts = the maximum stressg in the solid beamsf = the maxinmm stressin the sandwich beamM = the applied momentThe resulting ratio of maximum stress is:u ‘TMore Realistic Stress Distributionin a Sandwich ElelmentFigure 3-28 Stress Distribution Within aSandwich Beam [Rasmussen and Baatrup,Rational Design of Large Sandwich Structures]When no core is presen~ h = 2t, d = Oand Ef = E~, the maximum stress ratio approaches ~.This ratio should be 1.0, but the stress was assumed constant, rather than linearly varying,through the face thickness. This emor is largest for the case with no core, but becomesnegligible when the core thickness is much greater than the facing thiclmess. The sameexample used previously, with t = 0.2h and d = h, yields the following maximum stress ratio:: = 0694&’109

Ssndwich ConstructionAMine CmmusifesIf the limiting failure mechanism is tensile/compressive strength of the fachgs, the sandwichbeam has a flexural strength 1.44 times that of the solid beam. Thus the flexural strength of thesandwich beam is also greater than that of the solid beam for this example, although not asdramatic as the increase in flexural stiffness.Summary of Beam ComparisonSandwich beams can be designed to have higher flexural strength and stiffness at lower weigh~but the in-plane stiffness and strength per unit weight are lower than for solid beams. Theflexural stiffness of a sandwich beam is a linear function of the face thickness and the modulusof the face material, but the stiffness increases with the square of the core thickness. Thus,doubling the skin thickness or facing modulus will double the flexural stiftness, but doublingthe core thiclmess will increase the flexural stiffness by a factor of 4.0. The flexural stiffness ofa solid beam is a linear function of the modulus of the material, and a function of the cube ofthe beam thiclmess, The flexural strength of a sandwich beam is a linear function of the facingthickness, facing strength and core thiclmess. The strength of a solid beam is a linear functionof the material strength and is proportional to the square of the beam thiclmess. Figure 3-29illustrates some basic structural design concepts applicable to sandwich construction.SandwichPanel Flexural StiffnessThe primary use of sandwich laminates, with high flexural stiffness and strength, is for largeunsupported panels, such as hulls, decks and bulkheads. Bwun theory is commonly used in thedesign of these panels, since this type of theory is successfully utilized for steel construction.This theory does not work well for sandwich panels, however, since it does not considermembrane effects. Finite element method @EM) analysis can be used to predict the behaviorof the sandwich panels, but this method also has Iirnitations. Deflection or strain predictionsfor loads where the structural response of the materials is linear are generally satisfactory,however, these predictions are usually not very good for the non-linear or plastic responseregion. Strength prediction, or failure anilysis, is a problem when failure occurs outside theelastic response range of the materials, which is usually the situation. Also, the accuracy of theFEM predictions is highly dependent on material properties, which must be obtained fromtesting. Thus FBM is useful for analyzing the structural response to working or design loads,but is of limited use in predicting structural response to extreme loads.The limitations of analytical approaches to the problem leads to a reliance on mechanicaltesting of both the materials and the structure. Materials testing is based on standard tests, suchas ASTM tests, which are developed to provi& industry wide standards. The marine industryhas not played an active role in developing these standard tests, thus most of the tests which areused have been developed by and for other industries, and are not necessarily applicable to themarine industry. In particular, almost all of the material tests are uniaxial load tests, while thematerials in marine structures are usually subjected to multi-axial loads. As an example, beamflexural tests are used to determine flexurd stiffness and strength of sandwich laminates. Thistest method can lead to large errors when considering pressure loaded sandwich panels, such asthose in boat hulls. Figures 3-30 through 3-33 present relative flexural stiffness and strengthsof several sandwich laminates obtained by testing sandwich beams using ASTM C 393 andstructural testing of sandwich panels constructed of the same laminates using distributed110

—Chapter ThreeDESIGN1.The facings should be thick enoughwithstand the tensile, compressiveand shear stresses induced by thedesign load.to2.The core should have sufficientstrength to withstand the shearstresses induced by the designloads. Core bonding material musthave sufficient strength to carryshear stress in the core,3.The core should be thick enough and -have sufficient shear modulus toprevent overall buckling of thesandwich under load, and to prevent - ~crimping.+Hllllll, .4.Comtxessive modulus of the core andthe compressive modulus of thefacings should be sufficient toprevent wrinkling of the faces underdesign load.-HIIIIHT7TIIIIHH+5.With honeycomb cores, the cellstructure should be small enough toprevent intracell dimpling of thefacings under design load.+ +I6.7.The core should have sufficientcompressive strength to resistcrushing by design loads actingnormal to the panel facings or bycompressive stresses inducedthrough flexure,The sandwich structure should havesufficient flexural and shear figidity -to prevent excessive deflectionsunder design load,tFigure 3-29 Basic Santilch Structural Criteria [ASM Engineered Maferia/s Handbq111

SandwichConstructionMarine Composites100%Rolatlve Roam Stlt?neSQ100%Relatlve Panel Stlftrmss00%80%60%60%40%40%20%20%0%Alrex H-60 H-80 H-1OO R-76 R-1OO EtaloaGom Mmt~rlml0%Alrex H-60 H-BO H-1OO R-76 R-1OO BalsaCOr.MmtorlmlFigure 3-30 ReIative Stiffness forFRP Beams with DifferentCores [Reich~Fi9Ure S-31 Relative Stiffness forFRP Panels with DifferentCores [Reichard]1Ooqdatlvo Pmnml StrenothIeo%60%40%20%‘- AlrOX H-60 H-SO H-100 R-76 R-100 BaleaCormMatorlml0%Airox H-60 H-EO H-1OO R-76 R-1OO BalaaCoroMmtmrlalfigllrea-sz Relative Strength forFRP Beams with 13ifferent Cores [Reichard]Figure 3-33 Relative Strength forFRP Paneis with Different Cores [Reichard]112

Chapter ThreeDESIGNpressure loading. The core materials tested included products fiorn. Airex‘, Divinycell@,Klegecell” and Baltek. It is obvious that there are sigrdlcant differences between beam andpanel testing.The primary obstacles to the use of sandwich construction for retie structures are thelimitations of the analytical methods and the lack of appropriate test methods. Both of theseareas are presently being addressed by individual researchers, but a coordinated, industry wideeffort is necessmy to adequately address these problems. Some forrdulas are presented herethat relate sandwich properties to an equivalent solid skin thiclmess, t~~.for skins in tension:[1tF tc+f T = ~t2xafor skins in compression:t2) ox a cwhere:tF =tc =af =at=(3C=Sandwich skin thiclmessCore thicknessSingle skin flexural strengthSandwich skin tensile strengthSandwich skin compressive strengthsandwich bending stiffness:t~: x EI sandwich = 12x 0.5 (Et+ qwhere:Et =E, =EC =Single skin flexural modulusSandwich skin tensile modulusSandwich skin compressive modulus113

Design of DetailsA.@ineCompositesIn reviewing the past three decades of FRP boat construction, very few failures can beattributed to the overall structural collapse of the structure due to primary hull girder loading.This is in part due to the fact that the overall size of FRP ships has been limited, but alsobecause safety factors have been very conservative. In contrast to this, numerous failuresresulting from what is termed “local phenomena” have been observed, especially in the earlyyears of FRP development. As high-strength materials sre introduced to improve vesselperformance, the safety cushion associated with “bulky” laminates diminishes. As aconsequence, the FRP designer must pay carefal attention to the structural performance ofdetails.Details in FRP construction can be any area of the vessel where stress concentrations may bem present. These typically include areas of discontinuity and applied load points. As an example,failures in hull panels generally occur along their edge, rather than the center. [3-21] FRPconstruction is particularly susceptible to local failure because of the difficulty in achievinglaninate quality equal to a flat panel. Additionally, stress concentration areas typically havedistinct load paths which must coincide with the directional strengths of the FRP reinforcingmaterial, With the benefit of hindsight knowledge and a variety of reinforcing materialsavailable today, structural detail design can rely less on “brute force” techniques.Secondary BondingFRP structures will always demonstrate superior structural properties if the part is fabricated inone continuous cycle without total curing of intermediate plies. This is because interlaminsrproperdes are enhanced when a chemical as well as mechanical bond is present. Someties thepart size, thickness or manufacturing sequence preclude a continuous layup, thus requiring theapplication of wet plies over a previously cured laminate, known as secondary bonding.Much of the test data available on secondary bonding performance dates back to the early1970’s when research was active, supporting an FRP minesweeper program. Frame andbulkhead connections were targeted as weak points when large hulls were subjected to extremeshock from detonated charges. Reports on secondtuy bond strength by Owens-ComingFiberglas [3-22] and Della Rocca & Scott [3-23] are summarized below:●Failures were generally cohesive in nature and not at the bond interface line.A clean laminate surface at the time of bonding is essential and can best beachieved by use of a peeling ply. A peeling ply consists of a dry piece ofreinforcement (usually cloth) that is laid down without being wetted out.After cure, this strip is peeled away, leaving a rough bonding surface withraised glass fibers.c Filleted joints proved to be superior to right-angle joints in fatigue tests. Itwas postulated that the bond angle material was stressed in more of a pureflexural mode for the radiused geometry.●Bond strengths between plywood and FRP laminates is less than that ofFRP itself. Secondary mechanical fasteners might be considered.114

Chapter ThreeDESIGN. In a direct comparison between plywood frames and hat-sectioned stiffeners,the stiffeners appear to be superior based on static tests.. Chopped strand mat offers a better secondary bond surface than wovenroving.Table 3-4. SecondaryBond Technique Desirability [DellaRoccaandScott, Mhtsrii#sTest Progmm for Application of fiberglass Plastics to U.S. N&y Minesweepws]Preferable BondingAcce table Bonding UndesirableTechniques f echnlques ProceduresBondresin:either general purpose orfire retardant, resilientSutiace treatment:roughened with apneumatic saw tooth hammer, peel ply,or continuouscure of rib to panel; oneply of mat in way of bondStitiener faying flange thickness:minimum consistent with rib strengthrequirementBolts or mechanical fasteners arerecommended in areas of high stressBond resin: general pumose orfire retardant,rigid air inhibitedNo surfaceSurfacetreatment:rough smcfifq l~eatnlenlExcessivestiffenerfaying flangethicknessDeck Edge ConnectionSince the majority of FRP vessels are built with the deck and hull coming from diHerent molds, thebuilder must usually decide on a suitable technique for joining the two. Since this connection is atthe extm.mefiber location for both vertical and transverse hull girder loading, alternating tensile andcompressive stresses are expected to beat a maxkmun. The integrity of this \-DEcK LOADl NGconnection is also responsible formuch of the torsional rigidityexhibited by the hull. Secon@y deckand side shell loading shown in Figure1 BONOEO LAM I NATES3-34 is often the design limiting—. /’TEND To PEEL APARTcondition. Other &signconsiderations include: maintainingz,Ifiwatertight in~grity under stress,SHAPEzresisting local impact from docking,//!11 ~,, ,1 .=.. !personnel footing assistance andj]appearance (faking of shear). Figures4:3-35 through 3-45 show someS1 DE SHELLtraditional deck edge connectionLOADINGtechniques for various side shell anddeck constructions, Open FRP boatsgenerally require some stiffening at ~gllr’e 3-34 Deck Edge Connection - NormalDeck and Shell Loadina Produces Tensionthe gunwale. Figures 3-46 throughat the Joint [Gibbs and ~ox, Marine Design3-49 depict some wuiations on theManual for FRPjtreatment of smaU boat gunwales.115

Design of DetailsMarine CompositesPREDECKD CONINGOEDI NATE -]il i PRE-UOLDEOSHELL LAMINATEOtCKFigure 3-35 Shaped Wood GunwaleClamp [Gibbs and Cox, MarineDesign Manual for FRPlLAMINATEFI BEuGLA5sdOINTUE I NFORCEL4ENTCOhU 1N’S MOLDEDVEE OR SCfiRFS.IELL LA#l NATEFigure 3-36 Wood Coaming and “Joint in Deck [Gibbs and Cox, Marine DesignManual for FRPjSNAt IN PLAcERUBB ING STRIP==,+ }/7 ,. /-,II,“’vb~~,’:-: i1 PLY t4ht IN JOINT*IF I BERGLASS JO I NL—------- ‘/,(’ ---THROUGH BOLTS1,, . -’ y]HEI NFORCEMENT;~ +“-5J::”RHTE/.-,,r& .!.ALTERNATE COW TWCTI ON SPLAY I NGENDs 10 TAKE SNAP ON STRIPFigure 3-37 Coaming with Joint inShell [Gibbs and Cox, Marine DesignManual for FRPlFigure 3-38 Small Boat Type withSnap in Plaoe Rubbing Strip [Gibbs andCox, Marine Design Manual for FRflDECKP RE-MoLLAMIRUBBINHsTRlp1 PLLTl+Pm5+IELlGNINa STRIP2ES I REDW SI+ELL LAW NATEfigure 3-39 Combining Bonding &Mechanical Fastening [Gibbs and Cox,Marine Design Manual for FF?flFigure 3-40 Sandwich Deck withWood Coaming and Joint in Deck [Gibbsand Cox, iWfne Des&n Manual for FRPj116

Chapter ThreeDESIGNPRE-MOLDEO,SANDWI CH CONSTRUCT 10N./’1 /1I N DECKa-l C14 CON61WJImmlm DECK//7- OPT 10NAL EXTERIORF I BERQLASS .JO1NTRE I NFORCEMENlSANMI Cl! CORE CUFAXMl m’ms 0WEnFigure 3-41 Sandwich Deck withMolded-In Coaming and Joint in ShellFigure 3-42 Interior Deck to Shell\~~bb:~d Cox, Marine Design Manual/’----PRE.MOLDEDDECK LAMI NATE_—-.—————— _.—. .—. ,__THROW3H BOLTSOR BONDED CONNEC1 i ON SHELL LAM I MATEF I BERGLASSREi NCOROEMENTJOINTPRE-WOLDEO5tIELL LAM I NATEFigure 3-43 Simple Molded-InCoaming with Mechanical Fastenings[Gibbs and Cox, Marine Design Manualfor FRPlFigure 3-44 Deck Edge Connection- Simple Butt Joint [Gibbs and Cox,Marine Desi@ Manual for FRP’jPRE-MOLUODECK LAMI N*TESNAP I N PLAcc RUBBI Na5TR 1P ON OVERHANGSEPARATELYMOLOEtI----., = = =----,, ~-::F letRoLAss ,101N1 -.+; PR L-MOL DEDRE I NFORCDAEN1? SVLLL LAMI NATEGUNWALE“-~‘S1 DE SHELL1 Ly:&yY’--’””Figure 3-45 Modified Butt Joint withOverhana for Snap in Place RubbingStrip [Gibbs and Cox, Marine DesignManual for FRIJlFigure 3-46 SeDeratelv MoldedFi~erglass Gunwa(e [Gibb~ and Cox,Marine Design Manual for FRPl117

Design of DetailsEach builder develops their own methodfor deck edge connection that suits theirparticular needs. In lieu of specifyingone particular conilguration, Gibbs &Cox [3-13] offered the followingguidelines that have relevance today:.,. A joint should develop maximumefficiency or the full strength ofthe weaker of the two pieces beingjoined....*A joint must be easy to fabricateto ensure quality control in areasnot easily accessed for inspection.A joint should be compatible withmolding methods used andconsistent with overall hull “fabrication requirements.Exterior reinforcement is essentiaJto resist loads normal to the sideshell and deck.Exposed edges, if unavoidable,should always be sealed to preventdelamination.S I DESVELL—Figure 3-47[Gibbs and Cox,/-–7V ,.Marir?e Composites“’k %EAL EDGE OF LAM I NATEWITH REsi MIntegrally Molded GunwaleMarine Des@nManual for FR~4-SEAL EDGE OF LAM I NATEWITH PESlt+WOOD CLAW kRUBBING STRIP---s1 DE Si-tELLTHROUGH BOLTSFigure 3-48 Wood Gunwale [Gibbs andCox, Marine Design Manual for FRFl-LJEAL EDGE OF LAMI NATEWITHRESINALUM I t#JMEXTRUS 10NRUBBINGSTRIPALUMINUMEXTRUS i ONTHROUGH BOLTS *. -S1 (JE SHELLTHROUGH BOLTS=.- S! DE SHELL+“3Figure 3-49Aluminum Gunwale [Gibbs and Cox, Marine Design Manual for F/?~Centerline JointsTo facilitate hand layup fabrication, some builders produce hulls from separate female moldsfor each side of the hull. This enables the laminators to work on a more horizontal surface.When such a technique is used, some form of butt joint must be utilized to join the two hull118

Chapter ThreeDESIGNhalves. This highly stressed portion ofthe hull must be fabricated with care,especially since secondary bonding isinvolved. Builders rarely skimp onmaterial since this joint is low in thevessel where weight is desirable. Inaddition to adequate strength and goodadhesion, the joining laminate shouldinclude sufficient mat reinforcements tocreate a superior water permeationbarrier, Figures 3-50 through 3-52 showtypical connection configurations forvarious size boats. Figure 3-53 shows atypical centerboard trunk that may befound in a small sailboat As will beshown for bulkheads, the connectionillustrated in Figure 3-53 could beimproved with the addition of a radiusedfillet. Figure 3-55 is a detail sketch forrecommended butt joining techniqueswith single skin laminates.Keel AttachmentExternally mounted ballasted keels forsailboats have traditionally been fastenedto a matching FRP stub as pictured inFigure 3-54. This technique may still bevalid for a few cruising type designs thatsport such a fat-sectioned keel.However, performance sailboats sincethe 1970’s have had much higher aspectratio keels with very fine root sections.The current go-fast theory has led tokeels where the root section is thinnestat the top and meets the hull at a cleanright-angle when viewed in transversesection. Needless to say, these high liftkeels produce tremendous moments atthe faying region that, at times, is onlytwo to three inches wide. ABS providesgood guidance [3-5] for the selectionand arrangement of keel bolts associatedwith externally mounted fin keels.Adequate solid FM skin thiclmess andinternal transverse structure must beFI BERQLAsS JOINTTHROUfiH BOLTS ORRIVETS~ PRE-MOLDEDTROWELED I N PLAOEFILLEO RESINFigure 3-50 Connection of Shell Halves -Centerline Skeg [Gibbs and Cox, Marine DesignManual for FRflVI EIERGLN3S JOINREINFORCEMENTF t OERQLASS JOINTREINFORCEMENT \I NBoARD ANO @JTBOA!J;~RE-MOLDEDHALVESO OR CASTSHELLI ROM OALLASTI N RESIN I MPREQNATEDREINFORCEMENTFigure 3-51 Connection of Shell Halves -Cruising Sailboat with Ballast [Gibbs and Cox,Marine Design Manual for FR~FI EIERGLASSRE I NFOROEMENTJO I t4T/“. ..- ——-SHELL‘1 PLY LIGHT MAT ANDVEE JOINT 1 pLY CLOTHHALVESFigure 3-52 Connection of Shell HaIves -Small Boats Only [Gibbs and Cox, Marine DesignManual for FRPl119

Design of DetailsMarine CompositesPFIE4JOLDE0F 10ERGLAS~E 1NFORCLOCALFIBEBQLASSREINFORCEMENT —1 ● LY L1tiH1 MAT -- “AND ‘1 PLY CLOTVLARGEWASHER+&lWJNK AND SHELL MOLnE> SEPARA1 ELYFigure 3-53 Connection of Shelland Centerboard Trunk [Gibbs andCox, Marine Design Manual for FRPlFigure 3-54 Ballast to Hull Connection[Gibbs and Cox, Marine DesignManual for FRflSAND OR GRIND TO:l:Ml:O’E7/BACKING PLATESTO Ix REUOVECICELLOPHANE/SEPARATINGOR OTHERFILMPRE~OED J L MOL13ED IN PLACE L.-mmmII NATE dOINT REINFORCEMENT LAMI NATE& PBEFERRED CONSTRUCTION~TIWL EIACK,W PLATEPW-mLmoJ LSMXING PLATE L MOLDED IN kRE+OLOEDLAwINATE ‘- TO BE REMoVED PLAcE dOINT LAM I NATEREINFORCEMENTh.ACCEPTABLEALTEPNATEFigure 3-55Butt Joints [Gibbsand Cox, Marine Design ManualforFR~120

Cha@erThreeDESIGNprovided to support hydrodynamic lift and grounding forces that are transmitted through thebolts. Installation of propeller struts, especially single foil types popular on sailboats and somepowerboats, should be treated with similar caution as shaft or propeller imbalance, as well aslateral shaft resonances, can create large alternating moments.BulkheadsThe scantling for actual bulkheads are usually determined from regulatory body requirements orfirst principals covering flooding loads and in-plane deck compression loads. Design principalsdeveloped for hull panels are also relevant for determining required bulkhead strength. Ofinterest in this section is the connection of bulkheads or other panel stiffeners that are normal tothe hull surface. In addition to the joint strength, the strength of the bulkhead and the hull inthe immediate area of the joint must be considered. Other design considerations include:●●●●●Some method to avoid creation of a “hard” spot should be usedStiffness of joint should be consistent with local hull panelAvoid laminating of sharp, 90° cornersGeometry should be compatible with fabrication capabilitiesCutouts should not leave bulkhead core material exposedAn acceptable configuration for use with solid FRP hulls is shown in Figure 3-56. As a generalrule, tape-in material should be at least 2 inches along each leg have a thickness half of thesolid side she~ taper for a length ecpd to at least three times the tape-in thiclmess; and includesome sort of filletmaterial. Figure 3-57shows an example of\elastomeric support underthe bulkhead inconjunction with a hullof sandwich construction. THESE DI MENw10t#3 SHOULDBE MI NIWM CONSISTENTDouble bias knitted tapes./WITH STRENGTH REQUI REMENTowith or without a matF I SERGLASS ANGLESzfl MI NIWM REcOMNENDEDOTO FORM00NNECT10Nbacking are excellentchoices for tape-inmaterial. With primaryreinforcement oriented atY 45°, all fiberglass addsto the strength of thejoint, while at the sametime affording moreflexibility. Figure 3-58shows a comparisonbetween double-bias tapeinversus conventionalwoven roving tape-in.,2,.”: /-.A,1:~;L.l,EXTRA PLIES Of F I BEROLASS MATJ’!!-.-—/“ ,.4 .,, TO REINFORCE SHELL - OPT10tL4L,/.” ~ ●“I>,,,.;\ SHELL OR DECK - I LLET CORES - USE CONTINUOUSLAUIN4TE STRIP WITH I NCOWRESSIBLEBULKWAD OR fW4EFigure 3-56 Connection of Bulkheads and Framing toShell or Deck [Gibbs and Cox, Marine Design Manua/ forFRq121

Designof Details Akrhe CompositesStiffenersStiffeners in FRP construction caneither be longitudinal or transverseand usually have a non-structural corethat serves as a form. In general, GLEcontinuity of longitudinal membersshould be maintained withappropriate cut-outs in transversemembers. These intersections shouldbe completely bonded on both theH9UW 3-57 Elastomericfore snd aft side of the transversement [USCG NVIC No. 8-87]member with a schedule similar toBulkhead Attatch-that used for bonding to the hall.B ;‘..Traditional FRP design philosophy :.. Double Bias Tape Woven Roving ;produced stiffeners that were verynarrow and deep to take advantageof the increased section modulus andstiffness produced by this geometry.The current trend withhigh-perfommnce vehicles is towardshallower, wider stiffeners thatreduce effective panel width andminimize stress concentrations.Figure 3-59 shows how panel spancan be reduced with a low aspectratio stiffener. Some builders - areFigure 3-58 Double Bias and Woven Rovinginvestigating techniques to integrally Bulkhead Tape-In [Knytex]mold in stiffeners alongwith the hull’s primaryinner skin, - thusSPAN OR SPACING .elirninadng secondary l+- FOR STIWENERS Ibonding problemsaltogether.Regulatory agencies,such as ABS, typicallyspecify stiffenerSPAN FOR Ascantlings in terms of 1- PLATE PANEL~required- section moduliand moments of inertia.[Refi 3-5, 3-6, 3-24] Figure 3-59 Illustration of Referencemensions [USCG NVIC No. 8-87]Exarnples of a singleStiffener Span DiskinFRP stiffener and a high-strength material stiffener with a cored panel are presented alongwith sample property calculations to illustrate the design process. These examples aretaken from USCG NVIC No. 8-87. [3-24]i122

Chapter ThreeDESIGN‘~w”: :,B5.5”6S)”O.j’ D - &q~.fl+~+YtL 4 ,::=,4. ● ‘:

Design of DetailsAMne CompositesAIThree inch wide layer ofKevla# in the topflange of the stiffener0.5”7.5”6.5’42?Dc0.5”1—Figure 3-61 Stringer Geometry for Sandwich Construction including High-StrengthReinforcement [USCG NVIC No. 8-87]Table 3-6. High Strength Stiffener with Sandwich Side ShellItem b h A=bxh d Ad Ad2 IAl 3.70 0.50 3.29* 7,25 52.56 381.08 0.039A2 3.80 0.50 1.90 6.75 12,83 86.57 0.040B 0.50 5.00 2.50 4.00 10.00 40.00 5.208B 0.50 5.00 2,50 4,00 10.00 40.00 5.208c 2.00 0.50 1.00 1.75 1.75 3.06 0.021c 2.00 0.50 1.00 1.75 0.75 0.56 0.021D 3,00 0.50 0.75 0.67 0.50 0.33 0.01El 28.94 0.25 7.23 1.375 9.95 13.68 0.038E2 28.94 0.25 7.23 0.125 0.90 0.11 0.038Totals: 27.40 99.24 565.39 10.620m-INA = ~iO+ ~d2– [Ad2] = 10.86+ 115.92- [16.85X (1.81)2] = 71.58 ti4SM,OP= +=‘A tOJ7SM&tO~= ~ INAbdtom71.58—=4.1930.26 in3= 71.58—=1.8139.55 ins124

ChqXerThreeDESIGN●●SYM130LS:b= width or horizontal dimensionh = height or vertical dimensiond = height tQcenter of A from reference axisNA = neutral axisi= oitem moment of inertia= bhxzd NA =distance from reference axis to real NAI NA =moment of inertia of stiffener and plate about the real neutral axisThe assumed neutral axis is at the outer shell so all distances are positive.●Note how the stiffened plate is divided into discreet areas and lettered.●Items B and C have the same effaton section properties and are counted twice.●Some simplifications were made for the vertical legs of the stiffener, item B.The item io was calculated using the equation for the 1 of an inclined rectangle.Considering the legs as vertical members would be a further simplification.●Item D is combined from both sides of the required bonding angle taper.●EKeVZa@ = 9.8 msiRatio of elastic mochdi E = E@$~S 5.5 msi✎☛Effective area of Kevlar@ compared to the E-glass = 3.7 x 0.5 x 1.78 = 3.29●The overall required section modulus for this example must also reflect the mixedmaterials calculated as a mtiler to the required section modulus:E ● UltimateStrength~_~l&,sMKo,ar9= sME_gh~x EK’’l”’x~~b~ UltimateS*engthK~Vk,*E KevkraUlti17UUt? Strength~_~~~ 9.8 m~i ~lo ksiE x UltimateNrengthK,VbP= 5.5 rnsi x 196ksi = 1.0.l-glmsReinforcing fibers of different strengths and different moduli can be limited in the smountof strength that the fibers can develop by the maximum elongation tolerated by the resinand the strain to failure of the surrounding laminate. Thmefore, the slrength of the overalllaminate should be amdyz@ and for marginal safety factor designs or arrangementsmeeting the minimum of a rule, tests of a sample laminate should be conducted to provethe integrity of the design. In this example, the required section modulus was unchsngedbut the credit for the actusl section modulus to meet the rule was significant.125

Design of DetailsMarine CompositesEngine BedsIf properly fabricated, engine beds in FRP vessels can potentially reduce the transmission ofmachinery vibration to the hull. Any foundation supporting propulsion machinery should begiven the same attention afforded the main engine girders.As a general rule, engine girdersshould be of sufficient strength,stiffness and stability to ensureproper operation of rotatingmachinery. Proper bonding to thehull over a large area is essential.Girders should be continuousthrough transverse frames andterminate with a gradual taper.Laminated timbers have been usedas a core material because ofexcellent damping properties and theability to hold lag bolt fasteners.Consideration should be given tobedding lag bolts in resin to preventwater egress. Some builders includesome metallic stock between thecore and the laminate to acceptmachine screws. If this is done,proper care should be exercised toguarantee that the metal remainsbonded to the core. New, highdensity PVC foam cores offer anattractive alternative that eliminatesthe concern over future wood decay.Figures 3-62 through 3-64 showsome typical engine mountingconfigurations.HardwareThrough-bolts are always moredesirable than self-tapping fasteners.Hardware installations in single skinlaminates is fairly straightforward.Backing plates of aluminum orstainless steel are always preferableover simple washers. If using onlyoversized washers, the localthickness should be increased by atleast 25%. [3-25] The strength ofhardware installations should beENG I NE HOLD-DOWN ---.— .-. %‘0’--—————i,FlaERGLASS ANGLE ,=PRE4,10LDEDTRANSVERSEANDctiQwiSWITAWEE$- - ._-_—_. =\ IIv~ I 2ERGLASSCONNECT I NG ANGLESi— ENGINE(j\/I‘oA;j::L::o:T”pSHELLFigure 3-62 Engine Bearer - Pre-MoldedFiberglass Angle Bonded to Shell [Gibbs and Cox,Marine Design Manual for FRflENGINE HOLD-DOWN ~.. -------- -— ENGINE00LT3STEELTHROUGH BWITH METANON-STRUCTURALCOPEORLATORHELLsTRIPEB WITHFigure 3-63 Engine Bearer - Steel AngleBolted to Hat Stiffener [Gibbs and Cox, MarineDesign Manual for FRfli! STEEL CLIP IN WAY OF\, ENGINE HOLO-DOWNL.–.JFt BERGLASS ST IFFENERNOWSTRUCTURALCOPEBOLTSWI THFigure 3-64 Engine Bearer - Steel ClipBolted to Hat Stiffener [Gibbs and Cox, MarineDesign Manual for FRfl126

Chapter ThreeDESIGNconsistent with the combined load on a particular piece of hardware. In addition to shear andnormal loads, applied moments with tall hardware must be considered. Winches that aremounted on pedestals are examples of hardware that produce large overturning moments.Hardware installation in cored construction requires a little more planning and effort. Lowdensity cores have very poor holding power with screws and tend to compress under the load ofbolts. Some builders simply taper the laminate to a solid thiclmess in way of planned hardwareinstallations. This technique has the drawback of generally reducing the section modulus of thedeck unless a lot of solid glass is used, A more efficient approach involves the insertion of ahigher density core in way of planned hardware. In the pas~ the material of choice wasplywood, but high density PVC foam will provide superior adhesion. Figure 3-65 illustratesthis technique.UPPERSKINof SANDwl CHMOLDED- I N OR PRE-MOLDEDF 18EF?GLASSINSERT I NWAYOF THREADEDFASTENER.. .. . . . . . .LOWERSKI N OFFigure 3-65 Fiberglass Insert for Threaded or Bolted Fasteners in Sandwich Construction[Gibbs and Cox, Marine Design Manual for F/?PlHardware must often be located and mounted after the primary laminate is complete. Toeliminate the possibility of core crushing, a compression tube as illustrated in Figure 3-66should be inserted.Non-essential hardware and trim,especially on small boats, is oftenmounted with screw fasteners.Table 3-7 is reproduced toprovide some guidance indetermining the potential holdingforce of these fasteners. Thistable is suitable for use with matand woven roving type laminatewith tensile strength between 6and 25 ksi; compressive strengthbetween 10 and 22 ksti and shearstrength between 10 and 13 ksi.ANDw I cl-l SKINSCORE MATER I AALLY REI hIFORCEDI NGREASED BEARINGENGTH I F NECESSARYFITTIEuFigure 3-66 Through Bolting in Sandwich Construction[Gibbs and Cox, Marine Design Manua/ forFRPl127

Design of DetailsMarine CompositesTable 3-7. Holding Forces of Fasteners in Mat/Polyester Laminates[Gibbs and Cox, Marine Design Manual for FRPJAxial Holdlng ForceLateral Holdlng ForceT&d Mh’ilmum Maximum Mlnlmum MaximumDee::Force(Ibs)YW)hyi$Machine ScrewsDen~\hForoe Depth Force(Ibs) (ins) (Ibs)4-40 .125 40 .3125 450 .0625 150 .125 2906-32 ,125 60 ,375 600 ,0625 180 .125 3808-32 .125 100 .4375 1150 .0625 220 .1875 75010-32 .125 150 .5 1500 ,125 560 .25 13501/4 -20 .1875 300 .625 2300 .1875 1300 .3125 1900!3@-18 .1875 400 .75 3600 .1875 1600 .4375 290094-16 .25 530 .875 5000 .25 2600 .625 40007/16.14 .25 580 1.0 6500 .3125 3800 .75 5000l&.13 .25 620 1.125 8300 .375 5500 ,875 60009/16.12 ,25 650 1,25 10000 .4375 6500 .9375 8000‘%-11 .25 680 1,375 12000 .4375 6800 1.0 11000W4- 10 .25 700 1.5 13500 .4375 7000 1.0625 17000—Self Tapping Thread Cutting Screws4-40 .125 80 ,4375 900 ,125 250 .1875 4106-32 .125 100 .4375 1100 ,125 300 .25 7008-32 .25 350 .75 2300 .1875 580 .375 130010-32 .25 400 .75 2500 .1875 720 .4375 17501/4-20 .375 600 1.0625 4100 .25 1600 .625 3200Self Tapping Thread Forming Screws4-24 .125 50 .375 500 .125 220 .1875 5006-20 .1875 110 .625 850 .125 250 .25 6008-18 .25 180 ,8125 1200 .1875 380 .3125 85010-16 .25 220 .9375 2100 .25 600 .5 150014-14 .3125 360 1.0625 3200 .25 900 .6875 28005/16.18 .375 570 1.125 4500 .3125 1800 .8125 4400%-12 .375 700 1,125 5500 .375 3600 1.0 6800128

Chapter ThreeDESIGNThickness TransitionFRP construction gives the designer the Horn to tailor skin thiclmesses very precisely. Theefficiency of cored structures in resisting normal loads makes this type of construction popular.These two advantages of FRP construction csn lead to stress concentrations if thicknessvariations are not - adequatelytapered. Figure 3-67 illustrates arecommen&d taper equal to threetimes the core thiclmess. When ~+ 3tapering from a cored laminate to asolid area, consideration should be /Eaz;] .~.*,*.O.*.f.*.f..*.9.*:”?*;+;+:, J.,.,.J.f. CQRE;.;*x.”b”.’given to the m.iluced sectionmodulus that will occur withoutadditional reinforcement material.Figure 3-67 Recommended Core Taper forHatches and Potilights Transition to Single-Skin [USCG NVIC No. 8-87]Stress concentrations - around deckand hull openings are a problem with metal as well as FRP hulls. Ship designers are acutelyaware of this problem when desi@ng containerships with large hatch covers. The designer isexpected to make allowances for the loss of longitudinal and torsional strength. Corners ofopenings should be radiused to relieve undue smess concentrations.Openings in smaller crtit are usually cut as the vessel news completion. In the case of FRPconstructed vessels, reinforcement fibers can be cut in a fashion that causes excessivedeterioration of global strengths. Just as additional framing is usually added around an openingin a metal ship, perimeter reinforcement is required with FRP. Restoration of reinforcement inthe direction that was severed is a primary goal Unidirectional and hi-axial tapes are usefulmaterials for local reinforcement.Care should always be exercised in the planning phases of a deck layout, especially when highperformance laminates are utiized. At a recent conference, a naval architect recounted a storyof how a deck on a racing sailboat collapsed just aft of the deck partners after a pair ofcompasses were flush mounted. The point was made that the scantlings should not have beenso marginal as to fail when two simple four inch diameter holes were drilled. It was also notedthat such a modification to the deck is actwilly quite extreme when the amount of unidirectionalfiber that was severed is considered.Through-HullsThrough-hull fittings represent a specisl case of hull opening in that they are usually locatedbelow the waterline. These fittings must exhibit the highest degree of both watertight andstructural integrity. NonmetaUic fittings are gaining popularity because of their noncorrosiveand inert electrical properties. Any fitting will have a flat flange and a similsr mating surfaceshould be molded or machined into the hull.129

Designof DetailsMarine CompositesWith single skin laminates, holes are normally drilled after the hull is completwl Carefulattention must be paid toward the sealing of the laminate edges after the hole is drilled.Bedding and installation of the fitting is accomplished with the accompanying hardware.Through-hull fittings in sandwich can be installed a number of ways. One involves the taper toa solid section with installation as per above. An alternative method uses a high density insertin way of the fitting. Extreme care must be taken to seal the edge of the core and potting isusually suggested. Potting is similar to encapsulating, except that steps are taken to insurecomplete penetration of all the voids before the resin catalyzes. The high density core can alsobe installed by drilling an oversize hole and laminating it in place.Shroud AttachmentLoads at shroud and stay chaiuplates can be very grea~ wpecially with tall rigs.High-performance racing sailboats typically have very narrow spreader and shroud basedimensions to improve closewindedness. Extreme tensile and deck compressive loads are thuscreated. As a design starting point, the breaking strength of all shrouds and stays combinedthrough vector addition should be considered. Figure 3-68 shows an installation for a cruisingtype sadboat where the chainplates may be mounted to the shell plating. More often than not,chainplates are located further inboard than this. Nevertheless, installation details remainsimilar if tying into a bulkhead or longitudinal frame.Local reinforcement of thepanel should extend bothfore and aft of the mast agood distance. An effectiveinsert capable of resistingbolt compression and shesrloads should be present.Secondary stabilizingstructure as well as deckstrengthening in way of themast partners are required.Bolted connections throughFRP should not load thematerial for greater thanabout 20q0 of its ultimatestrength if creep is to beavoided.SANDWICHCORE DECKWEB FRAME4~REINFORCED\BACKINGPLATESANDWICHCORE SHELLxEFFECTIVEINSERTFigure 3-68 Typical Shroud Attachment to Side Shellwith Sandwich Construction [USCG NVIC No. 8-87]RuddersRudders and supporting structure represent one of the most challenging design problems facinga nawd architect. High aspect ratio spade rudders are an extreme example. Hydrodynamicperformance criteria dictates the use of a rather nmrow foil section. The high aspect ratioproduces an enormous transverse moment about the lower bearing. The rudder post itself mustadditionally resist torsional loads and rotate freely. Figure 3-69 is included to illustrate thestress distribution resulting from bending moment and torque.130

...Chapter ThreeDESIGNmIiTransve&e Section‘7i\ IProfileBending MomentDistributionTo&eDistributionFigure 3-69 Typical Force Distribution within a Spade Rudder [A13SGuide for Bui/dingand Classing Offshore Racing Yachts]Rudder weight is usually offset by its buoyancy. The rnass, however, still exists and Wincrease the vessel’s radius of gyration. Prudent design practice would strive to maintain agood safety factor for the rudder structure because even minor failures can incapacitate a vessel.The commercial marine industry recognizes this fact, but the competitive yachting market wascompelled to experiment with exotic materials such as carbon fiber in the late 1970’s. Thefailure rate in the 1979 Fastnet Race has become one of the most notorious cases of poorcomposite ‘design and process engineering. Those failures were primarily due to fibermisalignment with principal stresses and manufacturing inconsistencies. More thoroughengineering, greater selection of reinforcement cordlguration and improved manufacturingprocesses have virtually eliminated failures in exotic lightweight rudder posts.Bearing foundations within the hull structure must be of sufficient strength to resist themoments transmitted through the bearings. Transverse ring frames are typically included toincrease torsional stiffness. ABS rules give good guidance on rudder stock and bearingsupport.131

.Design of DetailsMarine CompositesThis page Intentionally left blank132

ChapterFourPERFORMANCEAfundamental problem conceding the engineering uses of fiber reinforced plastics (FRP)isthe determination of their resistance to combined states of cyclic stress. [4-1] Compositematerials exhibit very complex failure mechanisms under static and fatigue loading because ofanisotropic characteristics in their strength and stiffness. [4-2] Fatigue causes extensive damagethroughout the specimen volume, leading to failure from general degradation of the materialinstead of a predominant single crack. A predominant single crack is the most cormnon failuremechanism in static loading of isotropic, brittle materials such as metals, There are four basicfailure mechanisms in composite materials as a result of fatigue: matrix cracking, delamination,fiber breakage and interracial debonding. The different failure modes combined with theinherent anisotropies, complex stress fields, and overall non-linear behavior of compositesseverely limit our ability to understand the true nature of fatigue. [4-3] Figure 4-1 shows atypical comparison of the fatigue damage of composites and metals over time.Many aspects of tension-tension and tension-compression fatigue loading have beeninvestigated, such as the effects of heat, frequency, pre-stressing samples, flawing samples, andmoisture [4-5 through 4-13], Mixed views exist as to the effects of these parameters oncomposite laminates, due to the variation of materials, fiber orientations, and stackingsequences, which make each composite behave differently.uATmlRCahcaweo~~oslfccnAcrumOC~ONDCVOID,FATtGtJE CYCLES OR TIME~gllre g-l Typical Comparison of Metal and Composite Fatigue Damage [Salkind,Fat@ue of Composites]133

FatigueMarine CompositesExtensive work has been done to establish failure criteria of composites during fatigue loading[4-1, 4-5,4-14, 4-15]. Fatigue failure can be defied either as a loss of adequate stiffness, or asa loss of adequate strength. There sre two approaches to determine fatigue life; constant stresscycling until loss of strength, and constant amplitude cycling until loss of stiffness. Theapproach to utilize depends on the design requirements for the laminate.In general, stiffness reduction is an acceptable failure criterion for many components whichincorporate composite materials, [4-15] Figure 4-2 shows a typical curve of stiffness reductionfor composites and metal’. Stiffness change is a precise, easily measured and easily interpretedindicator of damage which can be directly related to microscopic degradation of compositematerials. [4-15]In a constant amplitude deflection loading situation the degradation rate is related to the stresswithin the composite sample. hitidy, a larger load is required to deflect the sample. Thiscorresponds to a higher stress level. As fatiguing continues, less load is required to deflect thesample, hence a lower stress level exists in the sample. As the stress within the sample isreduced, the amount of deterioration in the sample decreases. The reduction in load required todeflect the sample corresponds to a reduction in the stiffness of that sample. Therefore, inconstant amplitude fatigue the stiffness reduction is dramatic at first, as substantial matrixdegradation occurs, and then quickly tapers off until only small reductions occur.sTIFPNESSLQa cYcLgsFigure 4-2 Comparison of MetalFatigue of Composites]andCompositeStiffness Reduction [Salkind,134

ChapterFourPERFORMANCEIn a unidirectional fiber composite, cracks may occur along the fiber axis, which usuallyinvolves matrix cracking. Cracks may also form transverse to the fiber direction, which usuallyindicates fiber breakage and matrix failure. The accumulation of cracks transverse to fiberdirection leads to a reduction of load carrying capacity of the laminate and with further fatiguecycling may lead to a jagged, irregular failure of the composite material, This failure mode isdrastically different from the metal fatigue failure mode, which consists of the initiation andpropagation of a single crack, [4-1] Hahn [4-16] predicted that cracks in composite materialspropagate in four distinct modes. These modes are illustrated in Figure 4-3, where region Icorresponds to the fiber and region It corresponds to the matrix.IIIlltIIII-——(a)[b) (c) (d)Figure 4-3 Fatigue Failure Modes for Composite Materials - Mode (a) remesents atough matrix where the crack is forced to propagate through the fiber. Mode “(b)occurswhen the fiber/matrix interface is weak. This is, in effect, debonding. Mode (c) resultswhen the matrix is weak and has relatively little toughness. Finally, Mode (d) occurs witha strong fiber/matrix interface and a tough matrix. Here, the stress concentration is largeenough to cause a crack to form in a neighboring fiber without cracking of the matrix.Mode (b) is not desirable because the Iamlnate acts like a dry fiber bundle and the potentialstrength of the fibers is not realized. Mode (c) is also undesirable because it is similarto crack propagation in brittle materials. The optimum strength is realized in Mode (a) asthe fiber strengths are fully utilized. [Hahn, Fatigue of Composites]Minor cracks in composite materials may occur suddenly without warning and then propagateat once through the specimen. [4-1] It should be noted that even when many cracks have beenformed in the resin, composite materials may still retain respectable strength propefies. [4-17]The retention of these strength properties is due to the fact that each fiber in the laminate is aload-carrying member, and once a fiber fails the load is redistributed to another fiber.135

FatigueA&fine CompositesComposite Fatigue TheoryThere are many theories used to describe the composite material strength and fatigue life.Since no one analytical model can account for all the possible failure processes in a compositematerial, statistical methods to describe fatigue life have been adopted. Weibull’s distributionhas proven to be a useful method to describe the material strength and fatigue life. TheWeibull distribution is based on three parameters; scale, shape and location. Estimating theseparameters is based on one of three methods: the maximum-likelihood estimation method, themoment estimation method, or the standardized variable method. These methods of estimationare discussed in detail in references [4-18, 4-19], It has been shown that the moment estimationmethod and the maximum-likelihood method lead to lage errors in estimating the scale and theshape parameters, if the location parameter is taken to be zero. The standardized variableestimation gives accurate and more efficient estimates of all three parameters for low shapeboundaries. [4-19]Another method used to describe fatigue behavior is to extend static strength theory to fatiguestrength by replacing static strengths with fatigue functions.The power law has been used to represent fatigue data for metals when high numbers of cyclesare involved. By adding another term into the equation for the ratio of oscillatory-to-meanstress, the power law can be applied to composite materials. [4-20]Algebraic and linear first-order differential equations can also be used to describe the compositefatigue behavior. [4-14]There are many different theories usedto describe fatigue life of compositematerials. However, given the broadrange of usage and diverse variety ofcomposites in use in the marineindustry, theoretical calculations as tothe fatigue life of a given compositeshould only be used as a ilrst-orderindicator. Fatigue testing of laminatesin an experimental test program isprobably the best method of determiningthe fatigue properties of a candidatelaminate. Further testing anddevelopment of these theories must beaccomplished to enhance their accuracy.Despite the lack of knowledge, empiricaldata suggest that composite materialsperform better than metals in fatiguesituations. Figure 4-4 depicts fatiguestrength characteristics for some metaland composite materials. [4-21]100—80 — -80 - -40—-20- -0— 1@Cycle+10failure~gure 4-4 Comparison of FatigueStrengths of Graphite/Epoxy, Steel, Fiberglass/Epoxyand Aluminum [Hercules]136

ChapterFourPERFORMANCEFatiaue Test DataAlthough precise predictions of fatigue life expectancies for F~ laminates is currently beyondthe state-of-the-art of analytical techniques, some insight into the relative performance ofconstituent materials can be gained from published test data. The InterPlastic Corporationconducted an exhaustive series of fatigue tests on mat/woven roving laminates to comparevtious polyester and vinyl ester resin formulations. [4-22] The conclusion of those tests isshow in Figure 4-5 and is summarized as follows:“Cyclic flexural testing of specific polyester resin types resulted in predictabledata that oriented themselves by polymer description, i.e., orthophthalic wasexceeded by isophthalic, and both were vastly exceeded by vinyl ester typeresins. Little difference was observed between the standard vinyl ester and thenew preaccelerated thixotropic vinyl esters.”+- curw?FllIEquatim:-D1~1 {04 ;.s /06PFK)JECIHS CYCLES T(IFAILUREiolFigure 4-5 Curve Fit of ASTM D671 Data for Various Types of Unsaturated PolyesterResins [Interplastic, Cycle Test Evacuation of Various Polyester Types and a MathematicalModel for Predicting Flexural Fatigue Endurance]With regards to reinforcement materials used in marine laminates, there is not a lot ofcomparative test data available to illustrate fatigue characteristics. It should be noted thatfatigue performance is very dependent on the fiber/resin interface performance. Tests by137

FatigueMarine Compositesvarious investigators [4-23] suggest that a ranking of materials from best to worst would looklike:oHigh Modulus Carbon Fiber. High Strength and Low Modulus Carbon. Kevlar/Carbon Hybrid*Kevlar●Glass/Kevlax Hybrids S-GlassoE-GlassThe construction and orientation of the reinforcement also plays a critical role in determiningfatigue performance, It is generally perceived that larger quantities of thinner plies performbetter than a few layers of thick plies. Figure 4-23 shows a comptison of various fabricconstructions with regard to fatigue performance.60 -——— Flexuralfatiguaat23‘C (73 OF)— Axial fatigue at 23 % (73 OF).=xi~=502 40:E- 30 \.:~dJ220 -‘~’\“’”’’--i%>-~-

ChapterFourPERFORMANCEThe introduction of FRP and FRP sandwich materials into the boating industry has led tolighter, stiffer and faster boats. This leads, in general, to reduced impact performance, sincehigher speeds cause impact energy to be higher, while stiffer structures usually absorb lessimpact energy before failure. Thus, the response of a FRP composite marine sh-ucture toimpact loads is an important consideration.The complexity and variability of boat impacts makes it very difficult to define an impact loadfor design purposes. There is also a lack of information on the behavior of the FRP compositematerials when subjected to the high load rates of an impact, and analytical methods are, atpresent, relatively crude. Thus, it is difficult to explicitly include impact loads into thestructural analysis and design process. Instead, basic knowledge of the principles of impactloading and structural response is used as a guide to design structures for relatively betterimpact performance,The impact response of a composite structure can be divided into four categories. In the first,the entire energy of the impact is absorbed by the structure in elastic deformation, and thenreleased when the structure returns to its original position or shape. Higher energy levelsexceed the ability of the structure to absorb the energy elastically. The next level is plasticdeformation, in which some of the energy is absorbed by elastic deformation, while theremainder of the energy is absorbed through permanent plastic deformation of the structure.Higher energy levels result in energy absorbed through damage to the structure. Fimilly, theimpact energy levels can exceed the capabilities of the structure, leading to catastrophic failure.The maximum energy which can be absorbed in elastic deformation depends on the stiffness ofthe materials and the geometry of the structure. Damage to the structural laminate can be in theform of resin cracking, delamination between plies, &bonding of the resin fiber interface, andfiber breakage for solid FRP laminates, with the addition of debonding of skins from the core insandwich laminates. The amount of energy which can be absorbed in laminate and structuraldamage depends on the resin properties, fiber types, fabric types, fiber orientation, fabricationtechniques and rate of impactImpact Design ConsiderationsThe general principles of impact design are as follows. The kinetic energy of an impact is:where:K.E. = $v = the collision velocity and m is the mass of the boat or the impactor,whichever is smaller.The energy that can be absorbed by an isotropic beam point loaded at mid-span is:r K.E. = — o 2%21”139

ImpactMarine Compositeswhere:L= the span lengthM = the momentE = Young’s Modulus1 = moment ofinmtiaFor the small deformations of a composite panel, the expression can be simplified to:where:K.E. = S2AL~6EC2s = the stressA = cross-sectional arear = the depth of the beamc = the depth of the outermost fiber of the beamFrom this relationship, the following conclusions can be dram.●Increasing the skin laminate modulus E causes the skin stress levels to increase.The weight remains the same and the flexural sdfFnessis increased.. Increasing the beam thickness r &creases the skin stress levels, but it alsoincreases flexural stiffness and the weigh~●Increasing the span length L decreases the skin stress levels. The weightremains the same, but flexural stiffness is decreased.Therefore, increasing the span will decrease skin stress levels and increase impact energyabsorption, but the flexural stiffness is reduced, thus increasing static load stress levels.For a sandwich structure:where:~= btd22s = skinstressd = core thicknessb = beam widtht = skin thickness140

ChapterFourPERFORMANCEThus the energy absorption of a sandwich beam is:~E = S2btL. .4EFrom this relationship, the following conclusions can be drawn:● Increasing the skin laminate modulus E causes the sldn stress levels toincrease. The weight remains the same and the flexural stiffness isincreased.●Increasing the skin thickness tdecreases the skin stress levels, but it alsoincreases flexural stiffness and the weight.c Increasing the span length L decreases the skin stress levels. The weightremains the same, but flexural stiffness is decreased.●Core thickness has no effect on impact energy absorption.Therefore, increasing the span will decrease sldn stress levels and increase impact energyabsorption, while the flexural stiffness can be maintained by increasing the core thickness.An impact study investigating sandwich panels with different core materials, different fibertypes and different resins supports some of the above conclusions. [4-24] This study found thatpanels with higher density foam cores performed better than identical panels with lower densityfoam cores, while rigid cores such as balsa and Nomex@did not fare as well as the foam. Thisindicates that strength is a more important property than modulus for impact performance ofcore materials. The difference in performance between panels constructed of E-glass, Kevlar@,and carbon fiber fabrics was small, with the carbon fiber panels performing slightly better thanthe other two types. The reason for these results is not clear, but the investigator felt that thehigher flexural stiffness of the carbon fiber skin distributed the impact load over a greater areaof the foam core, thus the core material damage was lower for this panel. Epoxy, polyester andvinyl ester resins were also compared. The differences in performance were slighq with thevinyl ester providing the best performance, followed by polyester and epoxy. Impactperformance for the different resins followed the strength/stiffness ratio, with the bestperformance from the resin with the highest strength to stiffness ratio.General impact design concepts can be summarized as follows:. Impact Energy Absorption Mechanisms*Elastic deformation. Matrix cracking. Delaminationc Fiber breakage. Interracial debonding●Core shear141

ImpactMarine CompositesThe failure mechanism is usually that of the limiting material in the composite, however,positive synergism between spectic materials can dramatically improve itnpact perbrrnance.General material relationships are as follows:. Kevlar@and S-glass are better than E-glass and carbon fibers.●●Vinyl ester is better than epoxy and polyester.Foam core is better than Nomex@and Balsa.. Quasi-isotropic laminates are better than Orthotropic laminates.●●High fiber/resin ratios are better than low.Many thin plies of reinforcing fabric are better than a few thicker plies.TheoreticalDevelopmentsTheoretical snd experimental analysis have been conducted for ballistic impact (high speed, smallmass projectile) to evaluate spedic impact events. The theory can be applied to lower velocity,larger mass impacts acting on marine structures as summarized in Figure 4-7 and below.1. Determine the surface pressure and its distribution induced by the impactor as a functionof impact parameters, laminate and sncture properties, and impactor properties.2. Determine the internal three dimensional stress field caused by the surface pressure.3. Determine the failure modes of the laminate and structure resulting from the internalstresses,and how they interact to cause damage.duProjectileD=nTargetlmp~:tlri::csd(timedependent)Resultantsims*sFailureCaused bvStresses-Figure 4-7 Impact Initiation and Propagation [Jones, Impact Analysis of CompositeSandwich Panels as a Function of Skin, Core and Resin Materials]142

ChapterFourPERFORMANCEInterlaminar stress in composite structures usually results from the mismatch of engineeringproperties between plies. These stresses are the underlying cause of delamination initiation andpropagation. Delamination is deilned as the cracldng of the matrix between plies. meaforementioned stresses are out-of-plane and occur at structural discontinuities, as shown inFigure 4-8. In cases where the primary loading is in-plane, stress gradients can produce anout-of-plane load scenario because the local structure may be discontinuous.FreeedgeBoltedjoint.. #11-11PFigure 4-8 Sources of Out-of-Plane Loads from Load Path Discontinuities [ASM, Engi~eeredMaterials HandbooKjAnalysis of the delamination problem hasidentiled the strain energy release rate, G, as akey parameter for characterizing failures. Thisquantity is independent of layup sequence ordelamination source. [4-25] NASA and Armyinvestigators have shown from finite elementanalysis that once a delamination is modeled a fewply thiclmesses from an edge, G reaches a plateaugiven by the equation shown in Figure 4-9.where:hG=$ttaIn energyrdwmralomt =&=EM =laminate thicknessremote strainmodulus beforedelaminationmodulus afterdelaminationFigure 4-9 Strain Energy ReleaseRate for Delamination Growth10’Brien, Delamination Durability ofComposie Materials for Rotorcra~143

Delamination#Marine CompositesYYIYiMode 1Mode IIMode IllFigure 4-10 Basic Modes of Loading Involving Different Crack Surface Displacements[ASM,Engineered Materials Handbook]Linear elastic fracture mechanics identies three distinct loading modes that correspond todifferent crack surface displacements. Figure 4-10 depicts these different modes as follows:. Mode I - Opening or tensile loading where the crack surfaces move directlyapart●●Mode II - Sliding or in-plane shear where the crack surfaces slide over eachother in a direction perpendicular to the leading edge of the crackMode Ill - Tearing or antiplane shear where the crack surfaces moverelative to each other and parallel to the leading edge of the crack(scissoring)Mode I is the dominant form of loading in cracked metallic structures. With composites, anycombination of modes may be encountered. Analysis of mode contribution to total strainenergy release rate has been done using finite element techniques, but this method is toocumbersome for checking individual designs. A simplified technique has been developed byWrgia Tech for NASA/Army whereby Mode II and III strain energy release rates arecalculated by higher order plate theory and then subtracted from the total G to determine ModeI contribution.Delamination in tapered laminates is of particular interest because the designer usually hascontrol over taper angles. Figure 4-11 shows delamination initiating in the region “A” wherethe first transition from thin to thick laminate occurs. This region is modeled as a flat laminatewith a stiffness discontinuity in the outer “belt” plies and a continuous stiffness in the inner“core” plies. The belt stiffness in the tapered region, lIz, was obtained from a tensortransfomnation of the thin region, El, transformed through the taper angle, beta. As seen in thefigure’s equation, G will increase as beta increases, because the belt stiffness is a function ofthe taper angle. [4-25]Lately, there has been much interest in theresin systems that resist impact damage.aerospace industry in the development of “tough”The traditional, high-strength epoxy systems are144

ChapterFourPERFORMANCEDelamination ~--:“’’’”w●15 x 104 - [09’(*45’d,~& .10“N2 x .5 -0 510152025Taperangle,~, degIG=$(:-+JBeltE core + Nx\tEl1% I BeltDelamination~‘2 = F (~) E* =t‘2 5 +‘core coreFigure q-l 1 Strain Energy Release Rate Analysis of Delamination in a TaperedLaminate [0’Brien, Delamination Durability of Composie Materia/s for Rotorcraftltypically characterized as brittle whencompared to systems used in themarine industry. In a recent test ofaerospace matrices, little difference indelamination durability showed up.However, the tough matrix compositesdid show slower delamination growth. lq ~Figure 4-12 is a schematic of a log-logplot of delamination growth rate, ‘Ydv,where:BrittlemstdxToughmetrixGC = cyclic strainenergy releaserateGt~ = cyclic threshold‘th ‘th ‘log GIIGcFigure 4-12 Comparison of DelaminationGrowth Rates for Composites with Brittle andTough Matrices [0’Brien, Delamination Durabilityof Composie Materials for Rotorcrat7J145

Water AbsorptionMarine CompositesWhen an organic matrix composite is exposed to a humid environment or liquid, both themoisture content and material temperature may change with time. These changes usuallydegrade the mechanical properties of the laminate. The study of water absorption withincomposites is based on the following parameters as a function of time: [4-26]...●✎✎The temperature inside the material as a function of positionThe moisture concentration inside the materialThe total amount (mass) of moisture inside the materialThe moisture and temperature induced “hydrothermal” stress inside thematerialThe dimensional changes of the materialThe mechanical, chemical, thermal or electric changesT,hT, ‘$ ‘1Figure 4-13 Time Varying Envir~nmentalConditions in a M-ultilayeredComposite [Springer, Ew4fmvnental Effectson Composite Materia/s]To determine the physical changes within acomposite laminate, the temperature distributionand moisture content must be determined.When temperature varies across the thicknessonly and equilibrium is quickly achieved, themoisture and temperature distribution process iscalled “Fickian” diffusion, which is analogousto Fourier’s equation for heat conduction.Figure 4-13 illustrates some of the keyparameters used to describe the Ficldandiffusion process in a multilayered composite.The letter T refers to temperature and the letterC refers to moisture concentration.Fick’s second law of diffusion can berepresented in terms of three principal axes bythe following differential equation: [4-27]ac a% a2c a2cx = “ axxz+ ‘Y q+ “ 3X,2Figure 4-14 shows the change in moisture content, M, versus the square root of tie. Theapparent plateau is characteristic of Fickian predictions, although experimental procedures haveshown behavior that varies from this. Additional water absorption has been attributed to therelaxation of the polymer matrix under the influence of swelling stresses. [4-28] Figure 4-15depicts some experimental results from investigations conducted at elevated temperatures.146

ChapterFourPERFORMANCEMm.-- ——-— --——— - — -——- .MaI------- 1M,.— -fi ~s~L F tmSQUARE ROOTW TIME,fiFiqure 4-I 4 Charme of Moisture Content with the SauareRo~t of Time for “Fic~an”Diffusion[Springer,Environrnenti/Effects on Composite Materials]Water temperature {’C)● 30A 45● 605 10 15 20 25 30/immersiontime -s}Figure 4-15 Laminate Water AbsortMion Kinetios for ExperimentalLaminate Specimens [Pritchard, The L/se of Water A&-sorbtion Kinetic Data to Predict Laminate Property Changes]AStructural designers areprimarily interested inthe long termdegradation ofmechanical propertieswhen composites areimmersed in water. Byapplying curve-fittingprogramstoexperimental data,extrapolations about longterm behavior can bepostulated. [4-28]Figure 4-16 depicts a 25year prediction of shearstrength for glasspolyester specimensdried after immersion.Strength valueseventually level off atabout 60q0 of theiroriginal value, with thedegradation processaccelerated at highertemperatures. Figure4-17 shows similar datafor wet tensile strength.Experimental data at thehigher temperatures is inrelative agreement forthe f~st three years.Table 4-1 shows theapparent maximummoisture content and thetransverse diffusivitiesfor two polyester and ‘one vinyl ester E-glasslaminate. The numericaldesignation refers tofiber content by weightLaminate water contents cannot be compared directly with cast resin water contents, since thefibers do not absorb water and the water is concentrated in the resin (approximately 75% byvolume for bidirectional laminates and 67% by volume for unidirectional ones). [4-28]147

Water AbsorptionMarine CompositesI 1 I I I I I 1 I I I I2 5 10 25 2 5 10 25Time(ycarslTim- (YoardFigure 4-16 Predicted Dry Shear Figureq-lv Predicted Wet TensileStrength versus Square Root of lmmer- Strength versus Square Root of immersionTime [Pritchard, The Use of Water sion Time [Pritchard, The Use of WaterAbsorption Kinetic Data to Predict Lami- Absorbtion Kinetic Data to Predict LaminateProper?yChanges]nate Property Changes]-—m–m– a A ----- —------ . . . . . . . Wu ● . -.. .- ----- . . .I ame 4-_I. Apparem Maximum Molslure Gontent ana 1ransverse Dmusnmies otSome Polyester E-Glass and Vinyl Ester Laminates[Springer, Environmental Effects on Composite Maferhls]SubstanceT Maximum Moisture Content* Transverse DiffusivitytFEr SMC-R25 VE SMC-R50 SMC-R50 SMC-R25 VE SMC-R50 SMC-R50509!.Humidity23 0.17 0.13 0,10 10.0 10.0 30.093 0.10 0.10 0.22 50.0 50.0 30.010070 23 1.00 0.63 1,35 10.0 5.0 9!0Humidity93 0.30 0,40 0.56 50,0 50.0 50.0Salt WaterDiesel FuelLubricating OilAntifreeze●Values given in percent23 0.85 0.50 1.25 10.0 5.0 15.093 2.90 0.75 1.20 5.0 30.0 80.023 0.29 0.19 0.45 6.0 5.0 5.093 2.80 0.45 1.00 6.0 10.0 5.023 0.25 0.20 0.30 10.0 10,0 10.093 0.60 0,10 0.25 10.0 10.0 10,023 0.45 0,30 0.65 50.0 30.0 20.093 4.25 3.50 2.25 5.0 0.8 10.0‘Values given are Dz12x 107 mm2/sec148

ChapterFourPERFORMANCEThe blistering of gelcoated, FRPstructures hasrOceived much attention ti recent years. Thedefect manifests itself as a localized raised swelling of the laminate in an apparently randomfashion after a hull has been immersed in water for some period of time. When blisters arerupture~ a viscous acidic liquid is expelled. Studies have indicated that one to three percent ofboats surveyed in the Great Lakes and England, respectively, have appreciable blisters. [4-29]There are two primary causes of blister development. The fwst involves vsrious defectsintroduced during fabrication. Air pockets can cause blisters when’ a part is heated underenvironmental conditions. Entrapped liquids are also a source of blister formation. Table 4-2lists some liquid contaminate sources and associated blister discriminating features.Table 4-2. Liquid ContaminateSources During Spray-Up That Can Cause Blistering[Cook, Po/ycor Polyester Gel Coats and Resh]CatalystWaterSolventsOilLlquld Common Source Dlstlngulshing CharacterlstlcsUncatalyzed ResinOverspray, drips due to leaks ofmalfunctioning valves.Air lines, improperly storedmaterial, perspiration.Leaky solvent flush system,overspray, carried by wet rollers.Compressor seals leaking,Malfunctioning gun or ran out ofcatalyst.Usually when punctured, the blister has avinegar-like odor; the area around it, if inthe laminate, is browner or burnt color.If the part is less than 24 hours old, wetstarch iodine test paper will turn blue.No real odor when punctured; areaaround blister is whitish or milky.Odor; area sometimes white in color.Very little odor; fluid feels slick and willnot evaporate.Styrene odor and sticky,Even when the most careful fabrication procedures are followed, blisters can still develop overa period of time. These type of blisters are caused by osmotic water penetration, a subject thathas recently been examined by investigators. The osmotic process allows smaller watermolecules to penetrate through a particular laminate, which react with polymers to form lsrgermolecules, thus trapping the larger reactants inside. A pressure or concentration gradientdevelops, which leads to hydrolysis within the laminate. Hydrolysis is defined asdecomposition of a chemical compound through the reaction with water. Epoxide andpolyurethane resins exhibit better hydrolytic stability than polyester resins. In addition to thecontaminants listed in Table 4-2, the following substances act as easily hydrolyzableconstituents: [4-30]. Glass mat binder. Pigment carriers. Mold release agents149

—..BlistersMarine Composites. Stabilizers*Promoters●●CatalystsUncross-linked resin componentsBlisters can be classfied as either coating blisters or those located under the surface at substrateinterfaces (see Figure 4-18). The blisters under the surface are more serious and will be ofprimary concern. Some features that distinguish the two typs include:....Diameter to height ratio of sub-gel blister is usually greater than 10:1 andapproaches 40:1 whereas coating blisters have ratios near 2:1,Sub-gel blisters are much larger than coating blisters.The coating blister is more easily punctured than the sub-gel blister.Fluid in sub-gel blisters is acidic (pH 3.0 to 4.0), while fluid in coatingblisters has a pH of 6.5 to 8.0.lA’Rs’DEtINSIDE OF HULL~ Air-laminae Bounda~Coatin substrate> Inte aces~ Waier-G,C. BoundaryLAYER A+ LAYER B {OUTSIDE HULLt DIRECTION OF tWATER PENETRATIONFigure 4-18 Structure Description for a Skin Coated Composite with: Layer A = GelCoat, Layer B = lnterlayer and Layer C = Laminate Substrate [Interplastic, A Study ofPermeation Barriers to Prevent Blisters in Marine Composites and a Novel Technique forEvaluating Blister Formation]Both types of blisters are essentially cosmetic problems, although sub-gel blisters do have theability to compromise the laminate’s integrity through hydrolytic action. A recent theoreticaland experimental investigation [4-31] examined the structural degradation effects of blisterswithin hull laminates. A finite element model of the blister phenomena was created byprogressively removing material from the surface down to the sixth layer, as shown in Figure4-19. Strain gage measurements were made on sail and power boat hulls that exhibited severeblisters. The field measurements were in good agreement with the theoretically determinedvalues for strength and stiffness. Stiffness was relatively unchanged, while stiength valuesdegraded 15% to 30%, well within the margin of safety used for the laminates..-150

ChapterFourPERFORMANCE250@pressureduetoFigure 4-19 InternalBlister AxisymetricFiniteElementModel[KokarakisandTaylor,Theoretical and Experimental Investigation of Blistered Fiberglass Boa@The fact that the distribution of blisters is apparently random hasprecluded any documentedcases of catastrophic fsilures attributed to blistering. The repair section of this document willdeal with comective measures to remove blisters.As was previously mentioned, recent investigations have focused on what materials performbest to prevent osmotic blistering. Referring to Figure 4-18, Layer A is considered to be thegel coat surface of the laminate. Table 4-3 lists some permeation rates for three types ofpolyester resins that are commonly used as gel coats.----- - . .. .- — —I ame 4-s ~omposmon and Permeation Rates for Some Polyester Resins usedin GelCoats [Crump,A Study of IWster Formation in Ge/ Coated Laminates]Resin Glycol Sat#aJed Uns~W~ated PermeationRate*H O @ 77*F H20 @ 150”FNPG ISONPG OrthoNeopentyl Isophthalic Maleicglycol acid anhydrideNeopentyl Phthalic Maleicglycol anhydride anhydrideGeneral Propylene Phthalic MaleicPurpose glycol anhydride anhydride●grams/cubic centimeter per day x 1040.25 4.10.24 3.70.22 3.6Investigators at the Interplastic Corporation concentrated their efforts on determining anoptimum barrier ply, depicted as Lay~r B in Figure 4-18. Their tests involved the completesubmersion of edge-sealed specimens that were required to have two gel coated surfaces. Theconclusion of this study was that a vinyl ester cladding applied on an orthophthalic laminatingresin reinforced composite substantially reduced blistering.Investigators at the Univmsity of Rhode I&u@ under the sponsorship of the U.S. Coast Gusr~conducted a series of experiments to test various coating materials and methods of application.Table 4-4 summmizes the results of tests performd at 65”C. Blister severity was subjectivelyevaluated on a scale of Oto 3. The polyester top coat appeared to be the best perbming scheme.151

BlistersMarine CompositesTable 4-4. Results from URI Coating Investigation[Marine, The Effects at Coating on Blister Formation]Coating Scheme SurFace Treatment lnitl%~’rneBilsterSeverityBllstersPresent?Epoxytop coatnone 5 3 Yessanding 5 1 Yesacetonewipe 5 1 Yesboth 5 1 Yesnone 5 2 YesPolyurethane top sanding 14 1 Yescoatacetone wipe ~ 1 YesPolyestertop coatboth ? 1 Yesnone . 0 Nosanding . 0 Noacetonewipe . 0 Noboth . 0 Nonone 8 3 YesEpoxy top coat sanding 8 1 Yesover epoxyacetone wipe 8 2-3 Yesboth 8 2 Yesnone 7 1 YesPolyurethane topcoat oversanding 7 1 Yespolyurethane acetone wipe 7 1 Yesboth 7 1 Yesnone 8 3 NoPolyester top coat sanding . 0 Noover polyesteracetone wipe 8 2 Noboth 8 1 Nonone 8 3 YesEpoxy top coat sanding 8 2 Yesover polyurethaneacetone wipe 17 1-2 7both 19 2 Yesnone 11 3 YesPolyurethane top sanding . 0 Yescoat over epoxyacetonewipe 11 1-3 Yesboth . 1 Yes152

ChapterFourPERFORMANCEBl[sterCoatlngScheme Surface Treatment Inltlatlon Time(days)BllsterSeverityBlistersPresent?none 6 3 YesPolyurethane top sanding 6 3 Yescoat over polyesteracetone wipe 6 3 Yesboth 6 1 Yesnone 9 3 YesEpoxytop coat sanding 9 3 Yesover polyesteracetonewipe 9 3 Yesboth 9 3 YesBllster Severity ScaleO no change in the coated laminate1 questionable presence of coating blisters; surface may appear rough, with rare,small pin size blisters2 numerous blisters are present3 severe blistering over the entire laminate surface153

Cass HistoriesMarine CompositesAdvocates of fiberglass construction have often pointed to the long tarn maintenance advantages ofFRP materials. Wastage allowances and shell plating replacement associated with corrosion andgalvanic action in metal hulls is not a consideration when designing fiberglass hulls. However,concern over long term degradation of strength properdes due to in-service conditions promptedseveril studies in the 60’s snd 70’s. The results of those investigations along with some casehistories that illustrate common FRP structural failures are presented in this section. It should benoted that documented failures are usually the result of one of the following. Inadequate design●Improper selection of materials. Poor workmanshipUS Coast Guard 40 foot Patrol BoatsThese multipurpose craft were developed in the early 1950’s for law enforcement and search andrescue missions. The boats were 40 feet overall with an 11 foot beam and displaced 21,000pounds. Twin 250 horsepower diesel engines produced a top speed of 22 lmots. Single skin FRPconstruction was reinforced by transverse aluminum frames, a decidedly conservative approach atthe time of construction. Lsminate schedules consisted of alternating plies of 10 ounce boat clothand 1~2 ounce mat to thicknesses of %4inch for the bottom and %i inch for the sides.In 1962, Owens-Corning Fiberglass and the US Coast Guard tested psnels cut from three boatsthat had been in service 10 years. In 1972, more extensive tests were performed on a largerpopulation of samples taken from CG Hull 40503, which was being retired after 20 years inservice. It should be noted that service included duty in an extremely polluted ship channelwhere contact with sulfuric acid was constant and exposure to extreme temperatures during onefire fighting episode. Total operating hours for the vessel was 11,654. Visual examination ofsliced specimens indicated that water or other chemical reactants had not entered the larainate.The comparative physical test data is presented in Table 4-5.Table H. Physical Property Datafor 10 Year and 20 Year Tests of USCG Patrol Boat[Owens-CorningFiberglas,Fiber Glass Mufne Laminates,20 Y- of Proven Dumbi/i@Hull CG 40503 I 10 Year Tests I 20 Year TestsTensile StrengthCompressive StrengthFlexuralStrengthShear StrengthAverage psi 5990 6140Number of samples 1 10Average psi 12200 12210Number of samples 2 10Average psi 9410 10850Numberof samples 1 10Average psi 6560 6146Numberof samples 3 10154

ChapterFourPERFORMANCESubmarine FairwaterIn the early 1950’s, the U.S. Navy developed a fiberglass replacement for the aluminum fairwatersthat wem fitted on submarines. The fairwater is the hydrodynamic cowling that surrounds thesubmarine’s sail, as shown in Figure 4-20. The motivation behind this program was electrolyticcomosion and maintenance problems. The laminateused consisted of style 181 Volan glass cloth ina general purpose polyester resin that was nixedwith a flexible resin for added toughness.Vacuum bag molding was used and curing tookplace at room temperature.The fairwater installed on the U.S,S. Halfkak wasexamined in 1965 after 11 years in semice. Thetested material’s physical properties are shown inTable 4-6. After performing the tests, theconclusion that the materials were not adverselyaffected by long term exposure to weather wasreached. It should be noted that a detailed analysisof the component indicated that a safety factor offour was maintained throughout the service Me ofthe part. Thus, the mean stress was kept below thelong term static fatigue strength limit, which atthe time was taken to be 20 to 25 percent of theultimate strength of the materials mentioned.Figure 4-20 Submarine Fairwaterfor the US.S. Halfbeak [Lieblein, Surveyof Long-Term Durability of Fiberglass-/reinforced Plastic Simotures]Table 4-6. Property Tests of Samples from Fainivaterof US.S. Halfbeak[Fried & Graner, Durability of Reinforced Plastic Sfrucfuraflkktefials in Il@ine Service]PropertyConditionog#rJal1965 Data(1954)’ Ist Panel 2hdPanel AverageFlexuralStrength, Dry 52400 51900 51900 51900psiWet+ 54300 46400 47300 46900FlexuralM~ulus, Dry 2.54 2.62 2.41 2.52psi x 10-Wet 2.49 2.45 2.28 2.37Compressive Strength, Dry — 40200 3800 39100pslWet — 35900 35200 35600Barcol Hardness Dry 55 53 50 52Specific Gravity Dry 1.68 1,69 1.66 1.68Resin Content Dry 47.6?4. 47.470 48.2?40 47.8?40* Average of three panelst Specimen boiled for two hours, then cooled at room temperature for one hour prior to testing155

Case HistoriesMarine CompositesGel Coat CrackinaHairline cracks in exterior gel coat surfaces are traditionally treated as a cosmetic problem.However, barring some deficiency in manufacturing, such as thickness gauging, catalyzation ormold release technique, gel coat cracks often are the result of design inadequacies and can leadto further deterioration of the laminate.Gel coat formulations represent a finebalance between high gloss propertiesand material toughness. Designers mustbe constantly aware that the gel coatlayer is not reinforced, yet it canexperience the highest strain of the entirelaminate because it is the farthest awayfrom the n@mil axis.This section will attempt to classify tyyx ofget coat cracks and describe the stress fieldassociated with them [4-32] Figwe 4-21shows a schematic repmentation of threetypes of gel coat cracks that wae analyzedby Smith using microscopic andfractographic techniques. That investigationlead to the following conclusions:Type IThese are the most prevalent type ofcracks observed by marine surveyors andhave traditionally been attributed tooverly thick gel coat surface or impactfrom the opposite side of the laminate.Although crack patterns can becomerather complex, the source can usually betraced radially to the area of highestcrack density. The dominant stress fieldis one of highly localized tensile stresses,which can be the result of internal braces(stiffener hard spots) or overload inbending and flexing (too large a panelspan for laminate). Thermal stressescreated by different thermal expansioncoefficients of materials within a laminatecan create cracks. This problem isespecially apparent when plywood isused as a core. Residual stress can alsoinfluence the growth of Type I cracks.‘ Adjacent stress fieldsinfluence patternType Radialor DivergentConfiguration1111I4I? IIIm=nm ,Ilall- M41m nbmt mm muI 1CIKLUnctnIType II Randomly Spaced Parallel and Vertical FracturesType Ill Cracks at Hole of Other Stress ConcentrationFigure 4-21 Schematic Representationsof Gel Coat Crack Patterns [Smith, Crackingof Ge/ Coated Composites]156

ChapterFourPERFORMANCECracks tend to initiate at points of non-uniformity in the laminate, such as voids or areas thatare resin rich or starved. The propagation then proceeds in a bilateral fashion, fmlly into thelaminate itself.Type IIType II cracks are primarily found in hull structures and transoms, although similar fractureshave been noted along soles and combings [4-33]. In the latter instance, insufficient supporthas been cited as the contributing cause, with the pattern of cracking primarily attributable tothe geometry of the part. The more classical Type II cracks are the result of thermal fatigue,which is the dominant contributing factor for crack nucleation. The parallel nature of thecracks makes it difficult to pinpoint the exact origin of the failure, although it is believed thatcracks nucleate at fiber bundles perpendicular to the apparent stress fields. Other factorscontributing to this type of crack growth are global stress fields and high thermal gradients.Type IllCracking associated with -holes drilled in the laminate are quite obvious. The hole acts as anotch or stress concentrator, allowing cracks to develop with little externally applied stress.Factors contributing to the degree of crack propagation include:. Global stress field●Method of machining the hole. Degree of post cureCore Separation in Sandwich ConstructionIt has been shown that sandwich construction can have tremendous strength and stiffnessadvantages for hull panels, especially when primary loads are out of plane. As a rule, materialcosts will also be competitive with single-skin construction, because of the reduced number ofplies in a laminate. However, construction with a core material requires additional labor skill toensure proper bonding to the skins. Debonding of skins from structural cores is probably thesingle most common mode of laminate failure seen in sandwich construction. The problemmay either be present when the hull is new or manifest itself over a period of time underin-service load conditions.Although most reasons for debonding relate to fabrication techniques, the designer may also beat fault for specifying too thin a core, which intensifies the interlaminar shear stress field whena panel is subject to normal loads. Problems that can be traced to the fabrication shop include:...●✎Insufficient preparation of core surface to resist excessive resin absorptionImproper contact with f~st skin, especially in female moldsApplication of second skin before core bedding compound has curedInsufficient bedding of core jointsContamination of core material (dirt or moisture)157

CassHistorissMarine CompositesSelection of bonding resin is also critical to the performance of this interface. Some transitionbetween the “soft” cores and relatively stiff skins is required This can be achieved if a resinwith a reduced modulus of elasticity is selected.had sources that can exacerbate a poorly bonded sandwich panel include wave skunming,dynamic deck loading from gear or personnel, and global compressive loads that tend to seekout instable panels. Areas that have been shown to be susceptible to core debonding include:...●✎✎Stress concentrations willoccur at the face to core,:::;::\ ::::: !,:.:.., ....... ,.:,:~jj::..,,,. ,,,,,, ,,,:~:-joint of scrim-cloth orcontoured core material ifthe voids are not filled with Figure 4-22 Illustration of Stressa bonding agent, as shownConcentration Areas in Unfilled ContouredCore Material [Morgan, Designin Figure 4-22to the Limit: Optimizing Core and SkinAreas with extreme Properties]curvature that can causedifficulties when laying thecore in placePanel locations over stiffenersCenters of excessively large panelsCockpit floorsTransomsFailures in SecondaryBondsSecondary bond failures are probably the most common structural failure on FRP boats. Forreasons outlined in the Detail Design section of this document, complete chemical bondingstrength is not always obtained. Additiomdly, geometries of secondarily bonded componentsusually tend to create stress concentrations at the bond line. Some specific areas wheresecondary bond failures have been noted include:. Stiffeners and bulkhead attachments. Furniture and floor attachment. Rudder bearing and steering gear supportUltravioletExposureThe three major categories of resins that are used in boat building, polyester, vinyl ester andepoxy, have different reactions to exposure to sunlight. Sunlight consists of uhraviolet rays andheat.158

ChapterFourPERFORMANCEEpoxies are generallyve~ sensitive touhraviolet (UV) light andifexposed to UV rays for anysignMcant period of time the @ns will degracb to the point where they have little, if any, strengthleft to them The vinyl esters, because there m epoxy linkages in them are also sensitive to Wand will degrade with time, although in general not as rapidly as an epoxy. Polyester, although it issomewhat sensitive to W degradation, is the least sensitive of the three to W lightThe outer surface of most boats is covered with a gel coat Gel coats are based on ortho orisopolyester resin systems that are heavily filled and contain pigments. In addition, often thereis a UV screen added to help protect the resin, although for most gel coats the pigment itselfseines as the W protector.In general, the exposure of the gel coats to W radiation will cause fading of the color which isassociated with the pigments themselves and their mtction to sunlight but also on white or off-whitegel coats W exposure can cause yellowing. The yellowing, in genera is a degradation of the resinrather than the pigments and will finally lead to the phenomenon known as “chalking.” Chalkingoccurs when the very thin outer coating of Esin degrades under the W light to the point where itexposes the ~er and some of the pigment in the gel coat The high gloss finish that is typical of gelcoats is due to that thin layer. Once it degrades and disappears the gloss is gone, and what’s left isstill a cola-d surface but it is no longer shiny. Because the pigments are no longer sealed by thethin outer coating of resin, they actually can degrade and lose some of their color and theyeventually loosen up fmm the fish to give a kind of a chalky surface effect.There are some gel coats that are based on vinyl ester resin. These are not generally used inthe marine industry, but some boat manufacturers are starting to use them below the water lineto prevent blistering, since vinyl ester resins are not typically susceptible to blistering.However, if these resins are used on the top side or the decks of a boat, they will sufferyellowing and chalking very quickly as compared to a good orrho or isopolyester gel coat,Tempercrture EffectsIn addition to this type of degradation caused by sunlight, the other problem that must beconsidered is the effects of heat, The sun will actually heat up the gel coat and the laminatebeneath i~ The amount of damage that can be done depends on a number of factors. First, thethermal expansion coefficient of fiberglass is very different from that of resin. Thus, when alaminate with a high glass content is heated significantly the fiberglass tends to be relativelystable, whereas the resin tries to expand but can’t because it’s held in place by the glass. Theresult of this is that the pattern of the fiberglass will show through the gel coat in many cases, aphenomenon known as “print through.” Of course, if reinforcing fibers are used which havethen-ml expsnsion coefficients similar to the resins, it is less likely that print through will occur.Another consideration in addition to the thermal coefficient of expansion is the temperature atwhich the resin was cured Most polyester resins have a heat distortion temperature of around150-20WF. This means that when the resin becomes heated to that temperature it has gone abovethe cure tempermure, and the resin will become very soft When resin becomes soft the laminatebecomes unstable. The resin can actually cure further when it’s heated to these temperatures.When it cools down the resin will try to S- but since it’s been set at the higher temperatureand the glass doesn’t change dimensions very much, the resin is held in place by the glass,159

Case HistoriesMarine Compositesthereby creating very large internal sttwses solely due to these thermal effects. This canhappen also in a new laminate when it’s cured, but this is also something that can happen to alaminate that’s exposed to the sun and is heated higher than its heat distortion temperature.This can be a problem with all room temperature therrnosetting resins, polyester vinyl ester andepoxies, although it is less likely to be a problem with vinyl ester and epoxy than withpolyester, because the vinyl esters and epoxies usually cure at a higher exotherm temperature.As mentioned above, the heat distortion temperature of polyester resins can range born about15~-200”. In Florida or the tropics it’s not uncommon to get temperatures in excess of 15W onboats with white gel coats. Temperatures have been measured as high as 18(Yon the decks ofboats with red gel coat, close to 200” on the decks of boats with dark blue gel coat and wellover 200” on the decks of boats with black gel coat. That’s one of the reasons why there arevery few boats with black gel coat. Some sport fishing boats or other boats are equipped with awind screen which, rather than being clear, is actually fiberglass coated with black gel coat fora stylish appearance. This particular part of these boats suffers very badly from print throughproblems because the heat distortion temperature or the resin in the gel coat is exceeded.Obviously, during each day and night much temperature cycling occurs; the laminate will gethot in the day, cool off at nigh~ get hot again the next day, etc. The resin will already bepostcured to some extent, however it will still suffer from this cyclic heating and cooling.These temperature cycles tend to produce internal stresses which then cause the laminate tofatigue more rapidly than it normally would.Another thermal effect in fatigue is caused by shadows moving over the deck of a boat that’ssitting in the sun. As the sun travels overhead, the shadow will progress across the deck. Atthe edge of the shadow there can be a very large temperature differential on the order of2(Y-3~. As a result, as that shadow line travels there is a very sharp heating or cooling at theedge, and the differential causes signiilcant stress right at that point That stress will result infatigue of the material. Boats that are always tied up in the same position at the dock, so thatthe same areas of the boat get these shadows traveling across them, can actually suffer fatiguedaruage with the boat not even being usecLAnother environmental effect, which sometimes is considered by boat designers and sometimes isnot heat, but cold Most resins will absorb some amount of moisture, some more than others. Alaminate which has absorbed a significant amount of moisture will experience severe stresses ifthe laminate becomes frozen, since water expands when it freezes. This expansion can generatesignificant pressures in a laminate amdcan actually cause delamination or stress cracking.Another problem with cold temperatures concerns the case of a laminate over plywood.Plywood is relatively stable thermally and has a low coefficient of thermal expansion ascompared to the resins in the fiberglass laminated over it. If the fiberglass laminate is relativelythin and the plywood fairly thick, the plywood will dominate. When the resin tries to contractin cold temperatures, the plywood will try to prevent it from contracting and local cracking willoccur in the resin because the plywood is not homogeneous. There is a grain to the w@ sosome areas won’t restrain the contracting resin and other areas wilL As a result, spidenvebcracking can occur. This effect has been noted on new boats that have been built in warmerclimates and sent to northern regions.160

ChapterFourPERFORMANCEFaihrresi nFRPconstructedv esselsf allintoo neoftwocaEgoties. Firsgthe faih.rrecanbetheresult of a collision or other extreme force. Secondly, the failure may have occurred because ofdesign inadequacies. In the case of the latter, the repair should go beyond restoring thedarnaged srea back to its original strength, The loads and stress distributions should bereexamined to determine proper design alterations. When the failure is caused by an unusualevent, it should be kept in mind that all repair work relies on secondary bonding, which meansthat stronger or additional replacement material is needed to achieve the original strength. Ingeneral, repair to FRP vessels can be easier than other materials. However, proper preparationand working environment are critical.Major Single-SkinDamageDamage to the hull or deck structure is considered major when the structural integrity of thevessel is compromised. If the damage is extensive, provisions must be made to adequatelysupport the vessel to insure the restoration of the original form. The as-built lsminate scheduleshould be determined in order to reproduce strength and orientation properties. The followinggeneral repair procedure should be followed [4-34]Edge and Surface Preparation: The area to be repaired should be defied by athorough suxveyof the damage. The lsminate should be cut back to au area tlyt hasbeen determined to be sound The edges of the sound laminate should be taped backto a slope of 1:12 as shown in Figure 4-23b. Surface preparation with coarsesandpaper is recommended to produce a roughened area for secondarybond adhesion.Molding: The method of creating a female mold for repairing a damaged areadepends greatly on the extent of the damage. In the case of a 75 foot GulfShrimper that collided with a barge, the entire bow section of the vessel wasreplaced using a female mold taken from a sistership. [4-35] When damage toan area is not too extensive, the general form can be temporarily recreated usingauto body fdler, thus enabling a mold to be fabricated in place. The area issubsequently cut back to sound laminate, as outlined above. Large molds mayrequire stiffeners to maintain their form.Laminating: Laminated qairs have traditionally been done using a ply tapersequence illustrated in Figure 4-23& It has been determined that this techniqueproduces relatively weak resin rich areas at the repair interface. As an alternative, itis recommended to iirst apply a layer that completely covers the work ~ followedby successively tapered layers. The plies should be slightly larger then necessarywhen laminated to allow for subsequent grinding. Also note the extension of thefirst and last layers over the sound laminate illustrated in Figure 4-23b.Finishing: When fairing the repair job in preparation for gel coat or paintapplication, extreme care should be exercised to insure that the laminated sldnsof the repair reinforcements are not compromised.161

,RepairMarine Compositesa) Conventlotml Taper Sequence for FRP RepairsMATCHEDLAMINATE PLIES.MOLD ORBACKJNGRESIN RICH AREAb) RecommendedTaper Sequeneefor FRP RepairsFIRST LAYER COVERS GROUNDFULL REPAIR JOINT FLUSH 12 TO 1 TAPER 0.75 tI /+“t 4Figure 4-23 Illustrations of Conventional and Preferredfor Single-Skin Construction [USCG NVIC No. 8-87]FRP Hole Repair TechniquesMajor Damage in Sandwich ConstructionDeterminingg the extent of darnage with sandwich construction is a bit more difficult becausedebonding may extend far beyond the area of obvious visual darnage. The cut back area shouldbe increasingly larger proceeding from the outer to the inner skin as shown in Figure 4-24.Repair to the skins is generally similar to that for single-skin construction. The new core wiUnecesstuily be thinner than the existing one to accommodate the additional repair laminatethickness. Exireme care must be exercised to insw that the core is properly bonded to bothskins and the gap between new and old core is illled.162

ChapterFourPERFORMANCE/\ /\ ~R SKINOUTER SKINMOLD OR BACKINGFigure 4-24 Technique for Repairing Damage to Sandwich Construction [USCGNVIC No. 8-87]Core DebondingRepairing large sections of laminate where the core has separated from the skin is costly andwill generally result in a structure that is inferior to the origimd design, both from a strengthand weight standpoint. Pilot holes must be drilled throughout the structure in the areassuspected to be debonded. These holes will also serve as ports for evacuation of any moistureand injection of resin, which can restore the mechanical aspects of the core bond to a certaindegree. In most instances, the core never was fully bonded to the skins as a result ofmanufacturing deficiencies.Small Non-PenetratingHolesIf the structural integrity of a laminate has not been compromised, a repair can be accomplishedusing a “structural” putty. This mixture usually consists of resin or a gel coat formulationmixed with milled fibers or other randomly oriented ffler that contributes to the mixture’sstrength properties.For minor surface damage, filler is only required to thicken the mixture for workability.following general procedure [4-36] can be followed:The●Clean surface with acetone to remove all wax, dirt and grease.. Remove the damaged material by sanding or with a putty knife or razorblade. Wipe clean with acetone, being careful not to saturate the area.. Fonmdate the putty mixture using about 1% MEICPcatalyst.. Apply the putty mixture to the damaged area to a thickness of about ~lb”.. If a gel coat mixture is use~ a piece of cellophane should be placed overthe gel coat and spread out with a razor’s edge. After about 30 minutes, thecellophane can be removed.●Wet-sand and buff gel coated surface or sand and paint when matching apainted finish.163

RepairMarine CompositesBlistersThe technique used to repair a blistered hull depends on the extent of the problem. Whereblisters are few and spaced far apart, they can be repaired on an individual basis. If areas of thehull have a cluster of blisters, gel coat should be removed from the vicinity surrounding theproblem. In the case where the entire bottom is severely blistered, gel coat removal over theentire surface is recommended. The following repair procedure [4-37] is advised:Gel Coat Removal: Sand blasting is not recommended because it shatters theunderlying laminate, thus weskening the structure. Also, the gel coat is harderthan the laminate, which has the effect of quickly eroding the laminate once thegel coat is removed. Grinding or sanding until the laruinate has a “clear” qualityis the prefemed approach.Laminate Preparation: It is essential that the laminate is clean. If the blistercan not be completely removed, the area should be thoroughly washed withwater and treated with a water soluble silane wash. A final wash to removeexcess silane is recommended. The laminate is then required to be thoroughlytied. Vacuum bagging is an excellent way to accomplish this. In lieu of this,moderate heat application and fans can work.Resin Coating: The final critical element of the repair procedure is the selectionof a resin to seal the exposed laminate and create a barrier layer. As illustratedin the Blisters section, vinyl ester resins are superior for this application and arechemically compatible with polyester laminates, which to date are the onlymaterials to exhibit blistering problems. Epoxy resin in itself can provide thebest barrier performance, but the adhesion to other materials will not be as good.Epoxy repair might be most appropriate for isolated blisters, where the increasedcost can be justified.164

ChapterFiveFABRICATIONThe various fabrication processes applicable to marine composite structures are summarized inthe tables at the end of this section. The most common technique used for large structures suchas boat hulls, is the open mold process. Specifically, hand lay-up or spray-up techniques axeused. Spray-up of chopped fibers is generally limited to smaller hulls and parts. Figure 5-1shows the results of an industry survey indicating the relative occurrence of variousmanufacturing processes within the marine industry.The most popular forms of open molding in the marine industry are single-skin from femalemolds, cored construction from female molds and cored construction from male mol~ Industrysurvey results showing the pwpuhrity of these techniques is shown in Figure 5-2.ProoesssHand Layup81ngie-t3kinVacuum BagAutoclave Cure$prayupt1I!Cored w/ Male MoldGored w/ Female Mold!RIM or RTMOthnrOthero% 20% 405 60% 80% 100%10% 20% 40% 60% 80% 100%Peroant of Companlaa In surveymFigure 5-1 Marine Industry ManufacturingProcesses [EGA Survey]Figure 5-2 Marine Industry ConstructionTechniques [EGA Survey]Mold BuildingAknost all production hull fabrication is done with female molds that enable the builder toproduce a number of identical parts with a quality exterior ftish. It is essential that molds arecarefully constructed using the proper materials if consistent ftish quality and dimensionalcontrol are desired.165

. lManufacturing ProcessssMarine CompositesPlugsA mold is built over a plug that geometrically resembles the fished pm The plug is typicallybuilt of non-porous wood, such as oak, mahogany or ash, The wood is then covered with aboutthree layers of 7.5 to 10 ounce cloth or equivalent thickness of mat. The surface is faired andftished with a surface curing resin, with pigment in the first coat to assist in obtaining auniform surface. After the plug is wet-sanded, three coats of carnauba wax snd a layer of PVAparting fti can be applied by hand.MoldsThe fwst step of building a mold on a male plug consists of gel coat application, which is a criticalstep in the process. A non-pigmented gel coat that is specifically fomnulated for mold applicationsshould be applied in 10 mil layers to a thickness of 30to40 roils. The characteristics of tooling gelcoats incluck toughness, high heat distortion, high gloss and good glass retention. A back-up layerof gel that is pigmented to a dark color is then applied to enable the laminator to detect air in theproduction laminates and evenly apply the production gel coat surfaces.After the gel coat layers have cured overnigh~ the back-up laminate can be applied, startingwith a surfacing mat or veil to prevent print-through. Reinforcement layers can consist ofeither mat and cloth or mat and woven roving to a minimum thickness of 1/4inch. Additionalthickness or coring can be used to stiffen large molds. Framing and other stiffeners arerequired to strengthen the overall mold and permit handling.The mold should be post cured in a hot-air oven at 1O(YFfor 12 to 24 hours. After this, wetsandingand buffing can be undertaken. The three layers of wax and PVA are applied in amanner similar to the plug. [5-1]Single Skin ConstructionAlmost all marine construction done h female molds is fished with a gel coat surface, therefore,this is the first procedure in the fabrication sequence. Molds must first be carefully waxed and coatedwith a parting agent Gel coat is spmyed to a thickness of 20 to 30 roils and allowed to cure. Aback-up reinforcemen~ such as a surfacing mat, veil or polyester fabric is then applied to tiuceprint-through. Recent testing has shown that the polyester fabrics have suptior mechanical pmpmtieswhile possessingthermal expansion coefkients similarto common resin systems. [5-2]Resin can be delivered either by spray equipment or in small batches via buckets. If individualbuckets are used, much care must be exercised to ensure that the resin is properly catalyzed.Since the catalyzation process is very sensitive to temperature, ambient conditions should bemaintained between 60” snd 85”F. Exact formulation of catalysts and accelerators is required tomatch the environmental conditions at hand.Reinforcement material is usually precut outside the mold on a flat table. Some material supplyhouses are now offering precut kits of reinforcements to their customers. [5-3] After a thinlayer of resin is applied to the mold, the reinforcement is put in place and resin is drawn up byrolling the surface with mohair or grooved metal rollers, or with squeegees. This operation isvery critical in hand lay-up fabrication to ensure complete wet-out, consistent fiber/resin ratio,and to eliminate entrapped air bubbles.166

ChapterFiveFABRICATIONAfter the hull laminating process is complete, the installation of stigers and frames can start.The hull must be supported during the installation of the interior structure because the laminatewill not have sufficient stiffness to properly support themselves, Secondary bonding shouldfollow the procedures outlined in the section on Details.Cored Constructionfrom Female MoldsCored construction from female molds follows much the same procedure as that for single skinconstruction. The most critical phase of this operation, however, is the application of the coreto the outir laminate. The difficulty stems from the following:●✎✎✎✎Dissimilar materials are being bonded togetherCore materials usually have some memory and resist insertion into concave moldsBonding is a “blind” process once the core is in placeContoured core material will produce voids as the material is bent into placeMoisture contamination of smfacesInvestigators have shown that mechanical properties can be severely degraded if voids are presentwithin the sandwich structure. [5-4] Most suppliers of contoured core material also supply aviscous bedding compound that is specially formulated to bond these cores.Whenever possible, non-contoured core material is preferable. In the case of PVC foams,preheating may be possible to allow the material to more easily conform to a surface withcompound curves. Vacuum bag assistance is recommended to draw these cores down to theouter laminate and to pull resin up into the surface of the core.Cored Constructionover Male PlugsWhen hulls are fabricated on a custom basis, boat builders usually do not go through theexpense of building a female mold. Instead, a male plug is constructed, over which the corematerial is placed directly. Builders claim that a better laminate can be produced over a convexrather than a concave surface,Figure 5-5 shows the various stages of one-off construction from a male plug. (A variation ofthe technique shown involves the fabrication of a plug finished to the same degree as describedabove under Mold Making. Here, the inner skin is laminated f~st while the hull isupside-down. This technique is more common with balsa core materials.) A detail of the coreand outer skin on and off of the mold is shown in Figure 5-3.With linear PVC foam, the core is attached to the battens of the plug with either nails from theoutside or screws from the inside, as illustrated in Figure 5-4. If nails are used, they are pulledthrough the foam after the outside laminate has cured. Screws can be reversed out from insidethe mold.167

Manufacturing ProcessesMarine CompositesMale PlugLongitudinal Battens Stationsor FramesSequence Shows FinishedLaminate and Removal fromthe Male PlugAMale Plug With Core And OutsideSkin.Outer kinfCore MaterialFigure 5-3 Detail of SandwichConstruction over Male Plug [Johannsen, One-Off Alrex Fiberglass SandwichConstruction]I,/-,’ -\ReceivingMold with Hull Consisting OfCore and Outside Skin.~9Ure s-a Detail of Foam Placementon Plugs Showing Both Nailsfrom the Outside and Screws from theInside [Johannsen, One-Off AirexFiberglass Sandwich Construction]Figure 5-5 Simple, Wood Frame MalePlug used in Sandwich Construction [Johannsen,One-0t7 Airex Fiberglass SandwichConstruction]168

ChapterFive.FABRICATIONEquipmentVarious manufacturing equipment is used toassist in the laminating process. Most devicesare aimed at either reducing man-hourrequirements or improving manufacturingconsistency. Figure 5-6 gives a representationof the percentage of marine fabricators that usethe equipment described below.Chopper Gun and Spray-UpA special gun is used to deposit a mixture ofresin and chopped strands of fiberglassfilament onto the mold surface that resembleschopped strand mat. The gun is called a“chopper gun” because it draws continuousstrands of fiberglass from a spool through aseries of whirling blades that chop it intostrands about two inches long. The choppedstrands are blown into the path of two streamsof atomized liquid resin, one accelerated andone catalyzed (known as the two-pot gun).When the mixture reaches the mold, a randompattern is produced.1Realn Spray GunChopper GunQel Coat Spray GunImpregnator0% 20% 40% 60% 80% 100%-Hull =Deck ~PertsAlternately, catalyst can be injected into aFigure 5-6 Marine Industry ManufacturingEquipment [EGA Survey]stream of promoted resin with a catalystinjector gun. Both liquids are delivered to asingle-head, dual nozzle gun in proper proportions and are mixed either internally or externally.Control of gel times with this type of gun is accomplished by adjusting the rate of catalystflow.Spray systems may also be either airless or air-atomized. The airless systems use hydraulicpressure to disperse the resin mix. The air atomized type introduces air into the resin mix toassist in the dispersion process. Figures 5-7 and 5-8 illustrate the operation of air-atomizingand airless systems.Resin and Gel Coat Spray GunsVolume production shops apply resin to laminates via resin spray guns. A two-part system isoften used that mixes sepmate supplies of catalyzed and accelerated resins with a gun similar toa paint sprayer. Since neither type of resin can cure by itself without being added to the other,this system minimizes the chances of premature cure of the resin. This system providesuniformity of cure as well as good control of the quantity and dispersion of resin. Resin sprayguns can also be of the catalyst injection type described above. Table 5-1 provides a surnmsryof the various types of spray equipment available. Air atomized guns can either be the internaltype illustrated in Figure 5-9 or the external type shown in Figure 5-10.169

Manufacturing ProcessesMarine CompositwFigure 5-7 Air Atomizing Gun ShowingPossible “Fog” Effect at Edge ofSpray Pattern [Venus-Gusmer]21. Annular nng around llle fluld nozzle tIP.2. Conlamment holes.3. Wngs. hornsor ears.4, Side-port holes,5. Angularconverging hales.AIR NOZZLEISIDE PORTCONTROL STEMFigure 5-8 Airless Spray Gun ShowingPossible Bounce Back from the Mold[Venus-Gusmer].,. ,FIGURE 2FLhINLETFigure 5-9 Internal AtomizationSpray Gun [Binks Mfg.]Figure 5-10 External AtomizationSpray Gun [Binks Mfg.]170

ChapterFiveFABRICATIONTable 5-1. Description of Spray Equipment[Cook, i%/ycor Po/yester Gel Coats and Resins]Process Technique DescrlptlonGravityThe material is above the gun and flows to the gunnot commonly used for gel coats - sometimes usedIor more viscous materials).The material is picked up by passing air over a tubeMaterial Delivery suction inserted into the material (no direct pressure on thematerial). Not commonly used for making productionparts due to slow delivery rates,Method ofCatalyzatlonAtomizationThe material is forced to the gun by direct air pressurePressure or by a pump. Pressure feed systems - mainly pumps- are the mam systems used with gel coats.Hot PotCatalyst InjectionInternalExternalAirless AtomizationAir Assist AirlessCatalyst is measured into a container (pressure potand mixed by hand. This is the most accurate metkodbut requires the most clean up.Catalyst is added and mixed at or in the gun headrequiring Cypriot lines and a method of meteringcatalyst and material flow. This is the most commonsystem used in larger shops.Air and resin meet inside the gun head and come outa single orifice, This system is not recommended forgel coats as it has a tendency to cause porosity andproduce a rougher film.Internal mix air nozzles are typically used in highproduction applications where finish quality is notcritical, The nozzles are subjecl to wear, althoughreplacement is relatively inexpensive. Some materialstend to clog nozzles.Air and resin meet outside the gun head or nozzle,This is the most common type of spray gun. The resinis atomized in three stages:First Stage Atomization - fluid leaving the nozzleorifice is immediately surrounded by an envelope ofpressurized air emitted from an annular ring,Second Stage Atomization- the fluid stream nexlintersectstwo streamsof air from wnverging holesindexedto 90” to keep the stream from spreading.Third Stage Atomization - the Wings” of the gunhave air orifices that inject a final stream of airdesigned to produce a fan pattern.Resin is pressurized to 1200 to 2000 psi via a highratio pump. The stream atomizes as d asses throu hthe sprayer orifice. This system is usexfor large an8high volume operations, as it is cleaner and moreefficient than air atomized systems.Material is pressurized to 500 to 1000 psi and furtheratomized with low pressure air at the gun orifice torefine the spray pattern.171

Manufacturing ProcessesMarine CompositesImpregnatorImpregnators are high output machinesdesigned for wetting and placingwoven roving and other materkds thatcan retain their integrity when wetted.These machines can also processreinforcements that combine mat andwoven roving as well as Kevlar.@Laminates are layed into the moldunder the impregnator by usingpneumatic drive systems to move themachine with overhead bridge-crane organtries. Figure 5-11 shows aconfiguration for a semi-gantryimpregnator, which is used when thespan between overhead structuralmembers may be too great.Roll goods to 60 inches can be wettedand layed up in one continuousmovement of the machine. Theprocess involves two nip rollers thatcontrol a pool of catalyzed material oneither side of the reinforcement &additional set of rubber rollers is usedto feed the reinforcement through thenip rollers and prevent thereinforcement from being pulledthrough by its own weight as it dropsto the mold. Figure 5-12 is a schematicrepresentation of the impregnatormaterial path.Impregnators are used for large scaleoperations, such as minecountermeasure vessels, 100 footyachts and barge volume production ofbarge covers. In addition to thebenefits achieved through reduction oflabor, quality control is improved byreducing the variation of laminate resincontent. High fiber volumes and lowvoid content are also claimed byequipment manufacturers. [5-5]Figure 5-11 Configuration of Semi-GantryImpregnator ~enus-Gusmer]q@#FiberglassFeed RollsNip RollsFigure 5-12 Impregnator Material Path[Raymer, Large Scale Processing Machineryfor Fabrication of Composite Hulls and Superstructures]ap172

ChapterFiveFABRICATIONHealth ConsiderationsThis document’s treatment of the industrial hygiene topic should serve only as an overview.Builders are advised to familiarize themselves with all relevant federal, state and localregulations. An effective in-plant program considers the following items: [5-6]oExposure to styrene, solvents, catalysts, fiberglass dust, noise and heat. The use of personal protective equipment to minimize skin, eye andrespiratory contact to chemicals and dust. The use of engineering controls such as ventilation, enclosures or processisolation. The use of administrative controls, such as worker rotation, to minimizeexposures Work practice control, including material handling and dispensing methods,and storage of chemicalss A hazard communication program to convey chemical information and safehandling techniques to employeesSome health related terminology should be explained to better understand the mechanisms ofworker exposure and government regulations. The relationship between the term “toxicity” and“hazard” should fist be defined. All chemicals are toxic, if they are handled in an unsafemanner. Alternatively, “hazard” takes into account the toxicity of an agent and the exposurethat a worker has to that agent. “Acute toxicity” of a product is its harmful effect aftershort-term exposure. “Chronic toxicity” is characterized by the adverse health effects whichhave been caused by exposure to a substance over a significant period of time or by long-termeffects resulting from a single or few doses. [5-7]Exposure to agents can occur several ways. Skin and eye contact can happen when handlingcomposite materials. At risk are unprotected areas, such as hands, lower arms and face.“Irritation” is defined as a localized reaction characterized by the presence of redness andswelling, which may or may not result in cell death. “Corrosive” materials will cause tissuedestruction without normal healing. During the manufacturing and curing of composites, therelease of solvents and other volatiles from the resin system can be inhaled by workers. Fiberand resin grinding dust are also a way that foreign agents can be inhaled. Although not widelyrecognized, ingestion can also occur in the work place. Simple precautions, such as washing ofhands prior to eating or imoking can reduce this risk.Worker exposure to contaminants can be monitored by either placing a sophisticated pump andair collection device on the worker or using a passive collector that is placed on the worker’scollar, Both techniques require that the interpretation of data be done by trained personnel.Exposure limits are based on standards developed by the American Conference ofGovernmental Industrial Hygienists (ACGIH) as follows:173

Manufacturing ProcessesMarine CompositesThreshold Limit Value - Time Weighted Average (TLV-TWA) - the timeweightedaverage for a normal 8-hour workday and a 40-hour workweek, towhich nearly all workers may be exposed, day after day, without adverse effectThreshold Limit Value - Short Term Exposure Limit (TLV-STEL) - theconcentration to which workers can be exposed continuously for a short periodof time (15 minutes) without suffering from (1) imitation, (2) chronic orirreversible tissue darnage, or (3) narcosis of sufficient degree to increase thelikelihood of accidental injury, impair self-rescue or materially reduce workefficiency, and provided that the daily TLV-TWA is not exceeded.Threshold Limit Value - Ceiling (TLV-C) - the concentration that should notbe exceeded during any part of the working day.The occupational Safety and Health Administration (OSHA) issues legally binding PermissibleExposure Limits (PELs) for various compounds based on the above defined exposure limits.The limits are published in the Code of Federal Regulations 29 CFR 19100.1000 and arecontained in OSHA’S revised Air Contaminant Standard (OSHA, 1989). Table 5-2 lists thepermissible limits for some agents found in a composites fabrication shop.Table 5-2.Permissible Exposure Limits and Health Hazards of Some Com~ositeMaterials [SACMA, Safe Handling of Advanced Compos!fe “Material Components: Health Information]Component I Primary Health Hazard I TLV-TWA I TLV-STELStyrene MonomerAcetoneStyrene vapors can cause eye and skinirritation. It can also cause systemiceffectson the central nervoussystem,Overexposureto acetone by inhalationmaycause irritationof mucousmembranes,headacheand nausea.50 ppm750 ppmMethyl ethylkeytone (MEK) I I Eye, nose and throat irritation, 200 ppmIPolyurethaneResinCarbon andGraphite FibersThe isicyanates may strongly irritate the skinand the mucous membranes of the eyes andrespiratory tract,Handlingof carbon and graphite fibers cancause mechanicalabrasion and irritation.100 ppm1000 ppm300 ppm0.005 ppm 0.02 ppm10 mg/m3’ —FiberglassMechanical irrigation of the eyes, nose andthroat.10 mg/m3t —1 1Aramid Fibers Minimalpotential for irritation to skin. 5 fibrils/cm3* I, 1—Value for total dust - natural graphite is to be controlled to 2.5 mg/m3T Value for fibrous glass gust - Althou h no standards exist for fibrous glass, a TWA of 15 mym3(total dust) and 5 mg/m (respirable ? raction) has been established for “particles not othervwseregulated* Acceptable exposure limit established by DuPont based on internal studies174

Chapter FiveFABRICATIONThe boat building industry has expressed concern that the PEL’s for styrene would beextremely costly to achieve when kuge parts, such as hulls, are evaluated. In a letter to theFiberglass Fabrication Association, OSHA statedOSHA also“The industry does not have the burden of proving the technical unfeasibility ofengineering controls in an enforcement case....The burden of proof would be onOSHA to prove that the level could be attained with engineering and workpractice controls in an enforcement action if OSHA believed that was the case.”[5-8]stated that operations comparable to boat building-. may comply -. with the PEL’sthrough the use of respiratory protection-when they:“(1) employ the manual or spray-up process, (2) the manufactured items utilizethe same equipment and technology as that found in boat building, and (3) thesame consideration of large part size, cotiguration interfering with air-flowcontrol techniques, and resin usage apply.”The use of proper ventilation is the primsrytechnique for reducing airbornecontaminants, There are three types ofventilation used in polyester fabricationshops:Good System - flesh air oarriesfumes away fromworkerGeneral (Dilution) Ventilation. Theprincipal of dilution ventilation is to dilutecontaminated air with a volume of fresh air.Figure 5-13 shows good and bad examplesof general ventilation systems. These typesof systems can be costly as the totalvolume of room air should be changedapproximately every 2 to 12 minutes.Local Ventilation. A local exhaust systemmay consist of a capture hood or exhaustbank designed to evacuate air from aspeciilc area. Spray booths are an exarapleof local ventilation devices used in shopswhere small parts are fabricated.Directed-Flow Ventilation. These systemsdirect air flow patterns over a part inrelatively small volumes. The air flow isthen captured by an exhaust bank locatednear the floor, which establishes a generaltop-to-bottom flow. [5-6]Bad System- inoomingair drawsva ors past workers.Movingthe benchWOUI $ help.Figure s-ls General Ventilation Techniquesto Dilute Airborne Contaminantsthrough Air Turnover [FRP Supply, Hea/th,Safety and Environmental Manuaij175

Manufacturing ProcessesMarine CompositesOne yard in Denmark, Danyard Aalbmg A/S, has invested a significant amount of capital toreach that country’s standards for styrene emission during the fabrication of fiberglassmultipurpose navy vessels, Total allowable PELs in Denmark are 25 ppm, which translates toabout 12 ppm for styrene when other contaminants are considered. The air-handling systemthat they’ve instilled for a 50,000 square foot shop moves over 5 million cubic feet per hour,with roughly two thirds dedicated to styrene removal and one third for heating. [5-9]Many U.S. manufacturers are switching to replacement products for acetone to clean equipmentas an effort to reduce volatiles in the workplace. Low-styrene emission laminating resins havebeen touted by their manufacturers as a solution to the styrene exposure problem. An exampleof such a product is produced by USS Chemicals and is claimed to have a 2070 reduction instyrene monomer content. [5-10] To document company claims, worker exposure in Floridaand California boat building plants were monitored for an 8-hour shift. In the Florida plant,average worker exposure was 120 ppm for the conventional resin and 54 ppm for thelow-styrene emission resin. The California plant showed a reduction of 31% between resinsystems. Table 5-3 is a breakdown of exposure levels by job description.Table 5-3. Personnel Exposure to Styrene in Boat Manufacturing [ModernPlastics, Low-Styrene Emission Laminating Resins Prove it in the Workplace]Worker OccupationFlorldaPlant$tyrene Exposure, TLV-TWAStandard ResinLow-StyreneEmission ResinHull gun runner 113.2 64.0Gun runner 1 158.2 37.7Gun runner 2 108.0 69.6Gun runner 3 80.3 43.9Roller 1 140,1 38.4Roller 2 85.1 43.6Roller 3 131,2 56.9CaliforniaPlantForeman (chopper) 30 7Chopper 2 106 77Chopper 3 41 47Roller 1 75 37Roller 2 61 40Roller 3 56 42Area sampler 1 18 12Area sampler 2 19 4Area sampler 3 9 13Area sampler 4 30 16176

Chanter FiveFABRICATIONFuture TrendsOpen Mold Resin Transfer Molding (RTM)Seemann Composites of Gulfport, Mississippi has developed a vacuum assisted RTM processthat utilizes a single open-mold. Resin is injected under a vacuum illrn, thus elirninadng theneed for a second mold. Figure 5-14 shows the various elements of the process. The processis patented, primarily because of the uniqueness of the resin distribution medium. Parts up to1000 pounds have been manufactured by the process. Materials tested include polyester, vinylester phenolic and epoxy resins and E-glass, carbon fiber and Kevlar@reinforcementBecause reinforcement material is layed up dry and resin infusion is controlled, fiber volumesto 75% with wovens and 80% with unidirectional have been achieved. Correspondingly,tensile strengths of 87 ksi and flexural strengths of 123 ksi have been documented with E-glassin vinyl ester resin. Additional advantages of the process include enhanced quality control andreduced volatile emissions. [5-11]1,J’ {2[’or’Figure 5-14 Seemann Composites Resin Infusion Molding Process (SCRIMP@)Showing: 1. Fluid Impervious Outer Sheet, 2. Sealing Tape, 3. Rigid Mold, 4. ResinInlet, 5. Helical Spring Extension, 6. Vacuum Outlet, 7. Continuous PeripheralTrough, 8. Dry Lay-Up of Reinforcement Material, 9. Distribution Medium, 10, Peel Ply[Seemann Composites, US Patent # 4,902,215]177

Manufacturing ProcessesMarine CompositesThermoplastic-Yhermoset Hybrid ProcessA company called Advance USA is currently constructing a 15 foot racing sailboat called theJY 15 using a combination of vacuum forming, injection foam and resin transfer molding.Designed by Johnstone Yachts, Inc. the boat is a very high-performance planing boat.The hull is essentkdly a three-element composite, consisting of a laminated thermoplastic sheeton the outside, a polyurethane foam core and an inner skin of RTM produced, reinforcedpolyester. The 0.156 inch outer sheet is vacuum formed ~d consists of pigmented Revel@ (aweatherable rubber-styrene copolymer made by Dow Chemical and used for hot tubs, amongother things) covered with a scratch resistaut acrylic film and backed by an impact grade ofDow’s Magnum AIM. The foam core is a two part urethane that finishes out to be about threepounds per cubic foot. The inner skin is either glass cloth or mat combined with polyesterresin using an RTM process.The hull and deck are built separately and bonded together with epoxy as shown in Figure5-15. Although investment in the aluminum-filled, epoxy molds is si@lcan~ the builderclaims that a lighter and stronger boat can be built by this process in two-thirds the timerequired for spray-up construction. Additionally, the hull has the advantage of a thermoplasticexterior that is proven to be mom impact resistant than FRP. Closed-mold processes alsoproduce less volatile emmisions. [5-12]figure S-15 Schematicof JY-15 ShowingHull and Deck Parts prior to Joining withEpoxy ~achting, Yachting-k 7990 Honor Ro//j178

Chapter FiveFABRICATIONPost CuringThe physical propernes of polymer laminates is very dependent upon the degree ofcross-hiking of the matrices during polymerization. Post curing can greatly influence thedegree of cross-linking and thus the glass-transition temperature of thermoset resin systems,Some builders of custom racing yachts are post curing hulls, especially in Europe whereepoxies sre used to a greater extent. An epoxy such as Gougeon’s GLR 125 can almost doubleits tensile strength and more than double ultimate elongation when cured at 25~F for threehours, [5-13]Owens-Corning performed a series of tests on several resin systems to determine the influenceof cure cycle on material properties. Resin castings of isophthalic polyester, vinyl ester andepoxy were tested, with the results shown in Table 5-4.Table 5-4. Effect of Cure Conditions on Mechanical Properties[Owens-Corning, ~ostcur~ng Changes Polymer Pfapertles]Tensile PropertiesFlexural PropertiesResin System Cure Youn ‘S Ultlmate Ultimate Youn ‘s UltlmateCycle Modu~~$ Stren th Defo&~;tion Y(Xlo) (pslj y:;o~; ‘t&llthA 3.61 8000 7.0 2.0 7000Owens-Corning E-737Polyester16%CobaltlDMA/ B 4.80 13500 3.4 5.0 18900MEKP(1OO:2:I:2)c 4,80 13400 3.4 5.0 18900A 2.71 3000 9.0 2.8 6500Dow 411-415 Vinyl Ester B(100:0.4) 2.80 3400 6.8 4.0 15600c 4.20 9500 4.2 4,8 17000D 3.72 12700 7.0 4.0 15600Dow DER-331Epoxy/MDA (100:26.2) E 3.72 12700 6,5 4,1 15600F 4.39 13300 6.0 4.4 16200A 24 hours@ 72-FCure CyclesB 24 hours@ 72°F plus 1 hour@ 225°Fc 24 hours@ 72-F plus 2 hours @ 225°FD2 hours @I250”FE 2 hours@ 250”F plus 1.5 hours@ 350”FF 2 hours@ 250”F plus 2.5 hours@ 350”F179

Manufacturing ProcessesMarine CompositesHAND LAY-UPA contact mold method suitable for making boats, tanks, housings and building panels forprototypesand other large parts requiringhigh strength. Productionvolume is low to medium.bminntContact moldGel coatProcess DescrlptlonA pigmented gel mat is first applied to the mold by spray un for a hi h-quality surface. When thegel coat has beoome tacky, fiberglass reinforcement (usua7 Iy mat or cYoth) is manually placed onthe mold. The base resin is a plied by pouring, brushin or sprayinq, Squeegees or rollers areused to densify the laminate, tEoroughly wetting the reinvorcement wdh the resin, and removingentrapped air. Layers of fiberglass mat or woven roving and resin are added for thickness.Catalystsand acceleratorsare added to the resin systemto allow the resinto cure without externalheat. The amounts of catalyst and accelerator are diotated by the working time necessary andoverall thickness of the finished part.The laminate may be cored or stiffened with PVC foam, balsa and honeycomb materials to reduceweight and increase panel stiffness.Resin SystemsGeneral-purpose,room-temperaturecuring polyesterswhich will not drain or sag on verticalsurfaces. Epoxiesand vinyl esters are also used.MoldsSim Ie, single-cavity,one-piece,either male or female, of any size. Vacuumbag or autoclavemetRods may be used to speed cure, increase fiber content and improve surface finish,Major AdvantagesSimplest method offering low-cost tooling, simple processing and a wide range of parl sizes.Design changes are readily made. There is a minimum investment in equipment. With goodoperator skill, good production rates and consistent quality are obtainable.180

Chmter FiveFABRICATIONSPRAY-UPA low-to-medium volume, open mold method similar to hand lay-up in its suitability for makingboats, tanks, tub/shower units and other simple! medium to large size shapes such as truck hoods,recreational vehicle panels and commercial refrigeration display cases. Greater shape complexityis possible with spray-up than with hand lay-up.CatalyContinuous Chopper/spray mold coatstrand rovinggunProcess DescrlptlonFiberglasscontinuousstrand roving is fed through a combination chopper and spra gun. Thisdevice simultaneouslydepositschopped roving and catalyzed resin onto the mold. ! he laminatethus deposited is densifiedwith rollersor squeegeesto removeair and thoroughlywork the resininto the reinforcingstrands. Additionallayers of chopped roving and resin may be added asrequiredfor thickness. Cure is usually at room temperature or may be accelerated by moderateapplication of heat.As with hand lay-up, a superior surface finish maybe achieved by first spraying gel coat onto themold rior to spray-up of the substrate. Woven roving is occasionally added to the iaminate forspecific strength orientation, Aiso, core materialsare easily incorporated.Resin SystemsGeneral-purpose,room-temperaturecuring polyesters,iow-heat-curingpolyesters.MoldsSimpie, sin ie-cavity, usuaiiy one-piece, either maie or femaie, as with hand iay-up moids.Occasional Fy molds maybe assembied in several pieces,then disassembledwhen removing thepart. This technique is usefui when pad complexity is great.Ma]or AdvantagesSimpie, low-cost tooling, simple processing; portabie equipment permits on-site fabrication; vitiuallyno parl size imitations, The process may be automated,181

Manufacturing ProcessesMarine CompositesCOMPRESSIONMOLDINGA high-volume, high-pressure method suitable for moldin complex, high-stren hfiberglass-reinforced plastic parts. Fairl large parts can \ e molded with excelrent surface finish.Thermosetting resins are normally use J .Femalemold halfMoldingcompound/ H&t and pressureMale mold halfProcess DescrlptlonMatched molds are mounted in a hydraulic or mechanical molding press. A weighed charge ofsheet or bulk molding compound, or a “preform” or fiberglass mat with resin added at the press, islaced in the open mold. In the case of preform or mat molding, the resin maybe added eitherBefore or after the reinforcement is positioned in the mold, depending on part configuration. Thetwo halves of the mold are closed, and heat (225 to 320”F) and pressure (150 to 2000 psi) areapplied. Depending on thickness, size, and shape of the part, curing cycles range from less than aminute to about five minutes. The mold is opened and the finished part is removed. Typical partsinclude: automobile front ends, appliance housings and structural components, furniture, electricalcomponents, business machine housings and parts.Resin SystemsPolyesters (combined with fiberglass reinforcement as bulk or sheet molding compound, preform ormat), eneral purpose flexible or semirigid, chemical resistant, flame retardant, high heat distortion;also pienolics, rrrelamines, silicones, dallyl phtalate, some epoxies.MoldsSingle- or multiple-cavity hardened and chrome plated molds, usually cored for steam or hot oilheating; sometimes electric heat is used. Side cores, provisions for inserts, and other refinementsare often employed. Mold materials include cast of forged steel, cast iron and cast aluminum.Major AdvantagesHighest volume and highest part uniformity of any thermoset moldin~ method. The process can beautomated. Great part design flexibility, good mechanical and chemical propetiies obtainable.Inserts and attachments can be molded in. Superior color and finish are obtainable, contributing tolower part finishing cost. Subsequent trimming and machining operations are minimized.182

Chapter FiveFABRICATIONFILAMENT WINDINGA process resulting in a high degree of fiber orientation and high fiber loading to provide extremelyhigh tensile strengths in the manufacture of hollow, generally cylindrical products such as chemicaland fuel storage tanks and pipe, pressure vessels and rocket motor cases.bminateMandrel/Cctntinuous strand Rasin applicatorroving\Process DescriptionContinuous strand reinforcement is utilized to achieve maximum laminate strength. Reinforcementis fed through a resin bath and wound onto a suitable mandrei (pre-impregnated roving may also beused), Special winding machines iay down continuous strands in a predetermined pattern toprovide maximum stren th in the directions required. When sufficient layers have been applied, thewound mandrel is cure3at room temperature or in an oven. The molding is then stripped from themandrel. Equipment is available to perform filament winding on a continuous basis.Polyesters and epoxies.Resin SystemsMoidsMandrels of suitable size and shape, made of steel or aluminum form the inner surface of thehollow part, Some mandrels are collapsible to facilitate part removal.Major AdvantagesThe process affords the hi best strength-to-weight ratio of any fiberglass reinforced plasticmanufacturing practice an%provides the highest degree of controi over uniformit y and fiberorientation. Filament wound structures can be accurately machined. The process may beautomated when high volume makes this economically feasible. The reinforcement used is low incost, Integral vessel closures and fittings may be wound into the laminate.183

Manufacturing ProcessesMarine CornposjfesPULTRUSIONA continuous process for the manufacture of products having a constant cross section, such as rodstock, structural shapes, beams, channels, pips, tubing and fishing rods.Pullingdevice\, “m//l\\\\ll/~$+.fi~+?1:,’ ~;~,y.~:: ~,.:,,-.,.~~ ;i,+:~$.: . ‘ ,;@wX@,~f+@@!..,,+,,.WJW&*g&*.x.xp?XjE$* ,Vx: ;.%+:}:: ,-4,$.*,x@$J?++i~j+mi.; ..‘ w%Heat sourceFinished stock~\ Resin applicatorContinuous strand roving,mat, or clothProcessDescrlptlonContinuous strand fiberglass roving, mat or cloth is impregnated in a resin bath, then drawn througha steel die, which sets the shape of the stock and controls the fiberhesin ratio. A portion of the dieis heated to initiate the cure. With the rod stock, cure is effected in an oven. A pulling deviceestablishes production speed.General-purpose polyesters and epoxies.Hardenedsteel dies.Resin SystemsMoldsMa]or AdvantagesThe process is a continuous operation that can be readily automated, It is adaptable to shapeswith small cross-sectional areas and uses low cost reinforcement. Very high strengths are possibledue to the length of the stock being drawn. There is no practical limit to the length of stockproduced by continuous pultrusion.184

Chapter FiveFABRICATIONVACUUM BAG MOLDINGMechanicalpropertiesof open-moldlaminatescan be improvedwith a vacuum-assisttechnique.Entrappedair and excess resin are removedto producea productwith a higher percentageof fiberreinforcement,~minateFlexible filmProcessDescrlptlonA flexible film (PVA or cellophane is placed over the completed lay-u , its joint sealed, and avacuum drawn. A bleeder.ply of fiLerglasscloth, non-wovennylon, poYyester cloth or otherabsorbentmaterialis first placed over the laminate. Atmospheric ressure eliminatesvoids in thelaminate, and forces excess resin and air from the mold. The adzition of pressure further results inhi h fiber concentration and provides better adhesion between layers of sandwich construction.d en laying non-contoured sheets of PVC foam or balsa into a female mold, vacuum bagging isthe technique of choice to ensure proper secondary bonding of the core to the outer laminate.Resin SystemsPolyesters,vinyl esters and epoxies.MoldsMolds are similarto those used for conventional open-mold processes,Major AdvantagesVacuum bag processing can produce laminates with a uniform degree of consolidation, while at thesame time removing entrapped air, thus reducing the finished void content. Structures fabricatedwith traditional hand lay-up techniques can become resin rich, especially in areas where puddlescan collect. Vacuum bagging can eliminate the problem of resin rich laminates. Additionally,complete fiber wet-out can be accomplished if the process is done correctly. Improvedcore-bonding is also possible with vacuum bag processing.185

Manufacturing ProcessesMarine CompositesAUTOCLAVE MOLDINGA pressurized autoclave is used for curing high-quality aircraft components at elevatedtemperatures under very controlled conditions. A greater laminate density and faster cure can beaccomplished with the use of an autoclave.Air or vacuumProcessDescrlptlonMost autoclaves are built to operate at 200”F, which will process the 250. to 350”F epoxies used inaerospace applications. The autoclaves are usually pressurized with nitrogen or carbon dioxide toreduce the fire hazard associated with using shop air. Most autoclaves operate at 100 psi undercomputer control systems linked to thermocouples embedded in the laminates.Resin SystemsMostly epoxies incorporated into prepreg systems.MoldsLaminatedstructurescan be fabricated using a variety of open- or close-mold techniques.MajorAdvantagesVery precise quality control over the curing cycle can be accomplished with an autoclave. This isespecially important for high temperature cure aerospace resin systems that produce superiormechanical properties. The performance of these epoxy systems is very much dependent on thetime and temperature variables of the cure cycle, which is closely controlledduring autoclavecure.186

Chapter FiveFABRICATIONRESIN TRANSFER MOLDINGResin transfer molding is an intermediate-volume molding process for producing reinforced plasticparts, and a viable alternative to hand lay-up, spray-up and compression molding.ALaid-Up Mat or Wcwen ReinforcementProcess DescrlptlonMost successful production resin transfer molding RTM) operations are now based on the use ofresin/catalyst mixing machine~ using positive dispIacement piston-type pumping equipment toensure accurate control of resWcatalyst ratio. A wnstantly changing back pressure conditionexists as resin is forced into a closed tool already occupied by reinforcement fiber.The basic RTM molding process involves the connection of a meter, mix and dispense machine tothe inlet of the mold. Closing of the mold will give the redetermined shape with the inlet injectionporl typically at the lowest point and the vent ports at tIe highest.ResinSystemsPolyesters, vinyl esters, polyurethane,epoxies and nylons.MoldsRTM can utilize either “hard” or “soft” tooling, depending upon the expected duration of the run,Hard tooling is usually machined from aluminum while soft tooling is made up of a laminatedstructure, usually epoxy.MajorAdvantagesThe close-mold process produces parts with two finished surfaces. By laying up reinforcementmaterial dry inside the mold, any combination of materials and orientation can be used, including3-D reinforcements. Part thickness is also not a problem as exotherm can be controlled.Carbon/epoxy structures up to four inches thick have been fabricated using this technique.187

Quality AssuranceMarine CompositesUnlike a structure fabricated from metal plate, a composite hull achieves its form entirely at thetime of fabrication. As a result, the overall integrity of an FRP marine structure is verydependent on a successful Quality Assurance Program (QAP) implemented by the builder. Thisis especially true when advanced, high-performance craft are constructed to scantlings thatincorporate lower safety factors, In the past, the industry has benefited horn the process controlleeway afforded by structures considered to be “overbuilt” by today’s standards. Increasedmaterial, labor and fuel costs have made a comprehensive QAP seem like an economicallyattractive way of producing more efilcient marine structures.The basic elements of a QAP include:●●Inspection and testing of raw materials including reinforcements, resins andcoresIn-process inspection of manufacturing and fabrication processes. Destructive and non-destructive evaluation of completed composite structuresThe last topic will be covered in the section on Testing of Marine Composites. Each buildermust develop a QAP consistent with the product and facility. Figure 5-16 shows the interactionof various elements of a QAP. The flowing elements should be considered by managementwhen evaluating alternative QAPs: [5-14]. Program engineered to the structure●$ufilcient organization to control labor intensive nature of F’RI?constructionc Provide for training of production personnelwTimely testing during production to monitor critical stepss Continuous production process monitoring with recordkeeping●Simple, easily implemented program consistent with the product. Emphasis on material screening and iu-process monitoring as laminates areproduced on sitewThe three sequences of a QAP, pre, during and post construction, should beallocated in a manner consistent with design and production philosophy●Specifications and standards for composite materials must be tailored to thematerial used and the applicationoThe balance between cost, schedule and quality should consider the designand performance requirements of the productTable 5-5 lists some questions that engineering personnel must evaluate when considering thedesign and implementation of a QAP. [5-14]188

Chapter FiveFABRICATION1LbFacilities ApprovaliStorage Controland TestingTool Proof ofCure CycleITooling InspectionSurface ConditionCompatibilityDimensional Control b~I +Lsy-Up inspectionOrientation of PiiesSequence of PliesInspection forContaminantsProcess Verification CouponsLaminate InspectIonProcess RecordsNon-Destructive EvaluationDimensional ControlCoupon ResuitsmIFigure 5-16 Inspectionvanced Composite Design]Requirements for Composite Materials [U.S. Air Force, Ad-189

Quality AssuranceMarine CompositesTable 5=5. Engineering Considerations Relevant to an FRP QualityAssurance Program [Thomas and Cable, Qualify Assessment of GlassReinforced Plastic Ship Hulls in Naval Applications]EngineeringConslderatlonsDesign CharacteristicsMaterial,Design ParametersStress Critical AreasVariablesLongitudinal bending, panel deflection, cost, weight, damage toleranceInterlaminarshear strength, compressive strength, shear stre h, tensilestrength, impact strength, stiffness, material cost, material proYuction wst,material structuralweight, material maintenance requirementsKeel area, bow, shell below waterline, superstructure, load pointsDelamination, voids, inclusions, uncured resin, im roper overallglass to resin ratio?local omission of layers of reinforcement,Important Defects discoloration, cram , btisters, print-through, resin starved or richareas, wrinkles, reinYorcement discontinuities, impro er thickness,foreign object damage, construction and assembly f efectsProper supervision, improving the production method, materialDefect Prevention screening, training of personnel, inwrporation of automation toeliminate the human interface in labor intensive production processesDefect DetectionDefect CorrectionDefect EvaluationEffort AllocationEvaluation of sample plugs from the structure, testing of built-in testtabs, testing of cutouts for hatches and ports, nondestructive testingof laminated structurePermanent repair, replacement, temporary repairComparison with various standards based on: defect location,severity, overall impact on structural performancePreconstruction, construction, post-constructionQuality assurance of raw materials can consist of qua.litigation inspections or qualityconformance inspections. Qualiilcation inspections serve as a method for determining thesuitability of particular materials for an application prior to production. Quality conformanceinspections are the day-to-day checks of incoming raw material designed to insure that thematerial conforms with minimum standards. These standards will wry, depending on the typeof material in question.Reinforcement MaterialInspection of reinforcement materials consists of visual inspection of fabric rolls, tests on fabricspecimens and tests on lmninated samples. This section will concentrate on visual inspection asit represents the most cost effective way an average boat builder can insure raw materialconformance. Exact inspection requirements will vary depending upon the type of material (EandS-Glass, Kevlar@,carbon fiber, etc.) and construction (mat, gun-roving, woven roving, kni~unidirectiontil, prepreg, etc.). As a general guideline, the following inspection criteria should b~used for rolled goods: [5-15]c Uncleanliness (dirt, grease, stains, spots, etc.)r190

Chapter FiveFABRICATION●✎●✎✎Objectionable odor (any odor other than finishing compounds)Color not characteristic of the finish or not uniformFabric brittle (fibers break when flexed) or fusedUneven weaving or knitting throughout clearly visibleWidth outside of specfled toleranceThe builder will also want to make sure that rolls are the length specified and do not contain anexcessive number of single pieces. As the material is being rolled out for cutting or use, thefollowing defects should be noted and compared to established rejection criteria:oFiber ply misalignment~Creases or wrinkles embeddedDAny knots. Any hole, cut or tear●Any spot, stain or streak clearly visibleDAny brittle or fused area. Any smashed fibers or fiber bundles. Any broken or missing ends or yarnsoAny thickness variation that is clearly visible●Foreign matter adhering to the surface. Uneven finish●Damaged stitching or knitted threadsAs part of a builder’s’ overall QAP, lot or batch numbers of all reinforcements should berecorded and correlated with the specific application. The following information shouldaccompany all incoming reinforcement material and be recordd. Manufacturer. Material identification●●●✎✎✎✎Vendor or supplierLot or batch numberDate of manufactureFabric weightFabric widthType or style of weaveChemical finish191

QualityAssuranceMarineCompositesThe handling and storage of reinforcement material should conform with the manufacturer’srecommendations. Material can easily be damaged by rough handling or exposure to water,organic solvents or other liquids. Ideally, reinforcement material should be stored undercontrolled temperature and relative humidity conditions, as some are slightly hydroscopic.Usually room temperature conditions with adequate protection from rain water is sufilcient forfiberglass products. Advanced materkils and especially prepregs will have specific handlinginstructions that must be followed. If the ends of reinforcement rolls have masking tape toprevent fraying, all the adhesive must be thoroughly removed prior to lamination.ResinLaminating resin does not reveal much upon visual inspection. Therefore, certain tests of thematerial in a catalyzed and uncatdyzed state must be performed The following tests can beperformed on uncatalyzed resin:Specific Gravity - The specific gravity of resin is determinedweighing a known volume of liquid.by preciselyViscosity - The viscosity of uncatalyzedresin is determined by using a calibratedinstrument such as a MacMichael orBrooldeld viscometer, like the oneshown in Figure 5-17.Acid Number - The acid nurnkr of apdyemr or vinyl ester lesin is an indictorof the relative reactivity of the resin. It isdefied as the numbm of milligrams ofpotassium hydroxide required to newralizeone gtmn of polyester. It is &tmmined bytitrating a suitable sample of material as asolution in neutral acetone with 0.1 nomnalpotassium hydroxide usingphenolphthalein as an indicator. Mostbuilders will instead rely on the gel testof catalyzed resin to determine reactivity.figure S-IT BrookfieldModel LVF Viscometer andSpindles [Cook, Po/ycor Pm’yesterGel Coats and Resins]The testing of catalyzed resin using the following tests will provide more information, as thetests reflect the specific catalysts and ambient temperature conditions of the builder’s shop.Gel Time - The gel time of a resin is an indicator of the resin’s ability topolymerize and harden and the working time available to the manufacturer. TheSociety of the Plastics Industry and ASTM D-2471 specify alternative butsimilar methods for deteti g gel time. Both involve the placement of a fixedamount of catalyzed resin in a elevated temperature water bath. Gel time ismeasured as the time required for the resin to rise from 150”F to 19~F withtemperature measurements made via an embedded thermocouple.192

Chapter FiveFABRICATIONAn alternative procedure that is coomonly used involves a cup gel titner.Catalyzed resin is placed in a cup and a motorized spindle is activated with atimer. As the resin cures, the spindle slows and eventually stalls the meter at agiven torque. Gel time is then read off of the unit’s timer device.Peak Exotherm - The peak exotherm of a catalyzed resin system is an indicatorof the heat generation potential of the resin during polymerization, whichinvolves exothermic chemical reactions. It is desirable to minimize the peakexotherm to reduce the heat build-up in thick laminates. The peak exotherm isusually determined by fabricating a sample laminate and recording thetemperature rise and time to peak. ASTM D-2471 provides a detailed procedurefor accomplishing this.Barcol Hardness - The Barcol hardnessof a cured resin sample is measuredwith a calibrated Barcol impresser, asshown in Figure 5-18. This test willindicate the degree of hardness achievedduring cure as well as the degree ofcuring during fabrication.Manufacturer’s will typically specify aBarcol hardness value for a particularresin.Specific Gravity - Measurement of Figure 5-18 Barcollmpresspecificgravityofcured,unfilled resinsor (Model934 or 935 for readingsover 75) [Cook, Po/ycorsystem involves the weighing of lmown Polyester Gel Coats and Revolumeof cured resti.sins]The following information should accompany all incoming shipments of resin and be recordedby the manufacturer for futare reference:. Product name or code number and chemical type. Limiting values for mechanical and physical properties. Storage and handling instructions●●●Maximum usable storage life and storage conditionsRecommended catalysts, mixing procedure; finishes to use inreinforcements; curing tine and conditionsSafety informationThe storage and handling of resin is accomplished either with 55 gallon drums or via speciallydesigned bulk storage tanks. Table 5-6 lists some precautions that should be observed for drumand bulk storage.193

Quality AssuranceMarine CompositesTable 5-6. Precautions for Storage and Handling of Resin[SNAME, Guide for Quality Assured Fiberglass Reinforced Plastic Structures]Drum StorageBulk StorageDate drum upon receipt and store using first-infirst-out systemto assure stock rotationUse a strainerto prevent impuritiesfrom eitherthe tank truck or to delivery linesDo not store materialmore than three months Install a vacuum pressurerelief valve to allow(or per manufacturer’s recommendation)air to flow during tank filling and resin usageKeep drums out of dkect sunlight, using covers Use a manhole or conical tank bottom to permitif outdoors, to prevent water contamination periodic cleanoutStore drums in well ventilated area betvmen Phenolic and epoxy tank liners prevent the32*F and 77°F attack of tank metal by stored resinIf drums are stored at a temperatureA pump should provide for both the deliverysubstantially different from laminating area, resin through the lines and the circulation of resin totemperature must be brought to the temperature. prevent sedimentation, which can also beof the laminating area, which usually requires a controlled with a blade or propeller type stirringcouple of daysdeviceKeep drums sealed until just prior to useElectrically ground tank to filling truckJust prior to insertion of a spiqot or pump, make Throttling valves are used to control resin flowsure that the top of the drum is clean to reduce rates and level indicators are useful for showingthe risk of contaminationthe amount of material on handCore MaterialIn general, core material should be visually examined upon receipt to determine size,uniformity, workmanship and correct identification. Core material can be tested to determinetensile, compressive and shear strength and moduli using appropriate ASTM methods. Densitysnd water absorption, as a minimum, should be tested.Manufacturers will supply storage requirements specific to their product. All core materialsshould be handled and stored in such a way as to eliminate the potential for contact with watersnd dirt. This is critical during fabrication as well as storage. Perspiration from workers is amajor contamination problem that seriously effects the quality of surface bonds.In-ProcessQuality ControlIn order to consistently produce a quality laminated product, the fabricator must have somecontrol over the laminating environment. Some guidelines proposed by ABS [5-16] include:●●Premises are to be fully enclosed, dry, clean, shaded from the sun, andadequately ventilated and lighted.Temperature is to be maintained adequately constant between 60”F and90”F. The humidity is to be kept adequately constsnt to preventcondensation and is not to exceed 80%. Where spray-up is taldng place, thehumidity is not to be less than 40%.194

ChapterFiveFABRICATIONc Scaffolding is to be provided where necessary so that all laminating workcsn be carried out without standing on coxes or on laminated surfaces.An in-process quality control program mustbe individually tailored to the project andpersonnel involved. Smaller jobs with highlytrtied laminators may proceed flawlesslywith little oversight and controls. Big jobsthat utilize more material and a large workforce typical need more built-in controls toinsure that a quality laminate is constructed.Selection of materials also plays a critical rolein the amount of in-process inspectionrequired Figure 5-19 gives an indication ofsome techniques used by the boat buildingindustry. The following topics should beaddressed in a quality control program●●●Mold inspection prior toapplying releasing agentand gel coatGel coat thiclmess,uniformity of applicationand cure check prior tolaminatingCheck resin formulationand nixing check andrecord amounts of baseresin, catalysts, hardeners,accelerators, additives andfillersMaterialTechniqueAcceptanceBarcol HardneesMechanicalTeatTestingBurn Out or AddVlaual Ply InspactTadnoor Lnmlnatat Check that reinforcements are uniformly imp~gnatedthat lay-up is in accordance with spectications.●✎●Check and record fiber/resin0% 20% 40% 60% 80% 100%Peroent of Companies in Surveyfigure &19 Marine Industry QualityControl Efforts [EGA Survey]and well wet-out andCheck that curing is occurring as specified with immediate remedial actionif improper curing or blistering is notedOverall visual inspection of completed lay-up for defects listed in Table 5-7that can be corrected before release from the moldCheck and record Barcol hardness of cured part prior to release from moldFinished ltinates should be tested to guarantee minimum physical pi-operties. This can bedone on cut-outs, run-off tabs or on test panels fabricated s-ti”dtan~usly with the hull on asurface that is 45* to the horizontal. Burn-out or acid tests are used to determine the fiber/resin195

Qualhy AssuranceMarine Compositesratio. Thickness, which should not vary more than 15%, can also be checked from thesespecimens. With vessels in production, ABS requires the following testing schedule:Table 5-6. Pro~osed Test Schedule for ABS Inspected Vessels [ABS, ProposedGuide for Bufiding and Classing High-Speed and Displacement Mot&r Ya_chts]Vessel Length (feet)Under30Frequency of TestingEvery 12* vessel30 to 40 Every 10th vessel40 to 50 Every 8ti vessel50 to 60 ~60 to 70 Every 4* vessel70 to 80 Every other vessel80 and over Every vessel[SNAME,Table 5-7. Defects Present in Laminated StructuresGuide for C?uaiityAssured Fiberglass Reinforced Piastic Structures]Defect DescrlptlonAir Bubble or Voids - May besmall and non-connectedorlarge and interconnectedDelamlnatlons - This is theseparationof individuallayersin a laminateand is probablythe most structurallydamagmgtype of defectCrazing - Minuteflaws orcracks m a resinWarping or ExcessiveShrinkage - Visible change insize or shapeWashing- Displacementoffibersby resin flow duringwet-out and wiping in the lay-upResin Rich - Area of highresin contentResin Stained - Areaof lowresin contentSurface Defects - Flaws thatdo not go beyond outer plyProbable CauseAir entrapment in the resin mix, insufficient resin or poor wetting,styreneboil-off from excessiveexotherm,insufficientworkingofthe plies or porous moldsContaminated reinforcemen~, insufficient pressure during wet-out,failure to clean surfaces during multistage la -ups, forcefulremoval of a part from a mold, excessive drii’Iing pressure,damage from sharp impacts, forcing a laminate into place duringassembly or excessive exotherm and shrinkage in heavy sectionsExcessive stresses in the laminate occurring during cure or bystressing the laminateDefective mold construction, change in mold shape duringexotherm, temperature differentialsor heat contractionscausinguneven curing, removal from mold before sufficient cure, excessstyrene, cure temperature too high, cure cycle too fast or extremechanges in part cross sectional areaResinformulationtooviscous,looselywovenor defectivereinforcements, wet-out procedure too rapid or excessive forceused during squeegeeingPoor resin distribution or imperfections such as wrinkling of thereinforcementPoor resin distribution, insufficient resin, poor reinforcement finishor too high of a resin viscosityPorosity,roughness,pitting,alligatoring,orange peel, blistering,wrinkles, machining areas or protruding fibersTackiness or Undercure - Low concentrationof catalyst or accelerators,failure to mix theIndicated by low Barcol reading resin properly, excessive amounts of styrene or use ofor excessive styrene odor deteriorated resins or catalysts196

Chapter SixTESTINGIdeally, all testing should be conducted using standardized test methods. Standardized testprocedures have been established by the American Society for Testing Materials (ASTM), theU.S. Military (MlL), various industrial associations, as well as foreign agencies andorganizations. The individual tests have been established for specific purposes andapplications. The tests may or may not be applicable to other applications, but must beevaluated on a case by case basis. The test methods for FRP materials have been developedprimarily for the aerospace industry, thus they may or may not be applicable to the marineindustry.There are three major types of testing: 1) tests of the individual FRP components, 2) tests of theFRP laminates, 3) tests of the FRP structure. In general, the tests of individual FRPcomponents tend to be application independent, however, some of the properties may not beuseful in certain applications. Tests of the FRP lamhates tend to be more applicationdependent, and tests of FRP structures are heavily application dependent. ASTM tests whichare applicable to the marine industry are examined, and their limitations are discussed.ASTM FRP Material TestsResins~~ D-rA “onof PlastiThis test is commonly used to determine the water absorption characteristics of neat resins andFRP materials. The test results are often used to compare the water absorption rates of differentresin systems.~44This test can used to obtain the tensile modulus and strength of cured resins, but is mostcommonly used to obtain tensile properties of FRP laminates. The principal difficulty withtensile tests is casting pure resin samples of appropriate dimensions without introducing stressand stress cracks during the resin cure process.. . .e Pronerhes of RWd PlasncsThis test can used to obtain the compressive modulus and strength of cured resins, but is mostcommonly used to obtain compressive properties of FRP laminates. One difficulty with thistest is casting pure resin samples of appropriate dimensions without introducing slress andstress cracks during the resin cure process. Another difficulty is actually obtaining acompression failure for calculation of compressive strength. The samples are restrained fromEuler buckling and shear failure by a test jig, which is bolted to the sample. If this jig is notpositioned and tightened correctly, failure modes other than pure compression failure mayoccur. Also, if the jig is too tight it could effect the modulus values.ASTM D 792-66 Test Methods for $necific Gravitv and Densitv of Plastics bv DimlacementThis test can be used to determine the specif3c gravity or density of cured resin or FRP samples.It is not suitable for most sandwich laminates due to water absorption and/or trapping of airbubbles by the core materials.197

Mechanical TestinfiMarine Composites. . .D 1201-81 Sp~osetiu~ Polyester ~These speciilcations apply only to reinforced polyester compression molding compounds, butsimilar guidelines could be developed for polyester thermosetting resins and FRP laminates.ASTM ~ 1652 Test Mdd for EPOXYContent of FFc@l@bsThis test is used to determine the purity of epoxy resins. It is often used as psrt of the materialacceptance/rejection testing in a quality control program.ASTM D 1763-81 Spedld.mb@oxy MUṀThese specifications apply to epoxy resins, and can be used to establish materialacceptance/rejection criteria for quality control programs.~Variations of this test are commonly used to determine appropriate catalyst levels, working timeand cure times by fiberglass fabricators. This test can also be used as part of the materialacceptance/rejection testing for a quality control program.Fibers and Fabric~STM D 191O-XXTest Methods for Construction Characteristics of Woven FabricsThis test deals with inspection of the fabric with respect to thread count, width and weight ofthe fabric. This test should be included as part of the material acceptance/rejection testing of aquality control program.ASTM D 2150-81 Specific ation for Woven Rovirwm Fab~“cfor Polvest er-Glass LaminatesThis test establishes specifications for woven roving glass fabric and appropriate testingprocedures for the material acceptance/rejection testing of a quality control programASTM D 2343-67Test Method for Tensile Propert ies of Glass Fiber Strands. Yams. andThis test is commonly used to determine fiber properties before the glass fiber is converted intofabric. This data should be supplied to the boat builder from the converter as part of fabricdocumentation. This test can be used to determine the stiffness and strength of unidirectionaltapes.ASTM D 2408-87. .Test Method for Fmlsh content.of Woven Glass Fab~c. Clemed andThis test evaluates the amount of amino-silane finish, or sizing, applied to lass fabric.Arnino-sihme finished fabric is used with epoxy and phenolic resin systems. The data is useful,since the sizing is applied to enhance the bonding between the glass fibers and the resin system.ASTM D 2409-84 Test Method for Finish Content of Woven Glass Fabric. Cleaned and After-Finished with Vinvl-Silane Tkoe Finishes for Plastic LaminahMTMs test evaluates the amount of vinyl-silane finish, or sizing, applied to glass fabric.Vinyl-silane finished fabric is used with polyester resin systems. The data is useful, since thesizing is applied to enhance the bonding between the glass fibers and the resin system.198

Chapter SixTESTING. .D 7.41O-R7. Test Me-for F@ Co~. Cleaned and.ed with _ Co~This test evaluates the amount of chrome complex finish, or sizing, applied to glass fabric.Chrome complex finished fabric is used with polyester, epoxy and phenolic resin systems. Thedata is useful, since the sizing is applied to enhance the bonding between the glass fibers andthe resin system. .TM D 7660-84 Test -d for F~ of Woven G~ Cletmed and. . ,. . . .ter-Fuushed with A@mSdaW Tyye Flh for Pl~tic JiammaksThis test evaluates the amount of acrylic-silane finish, or sizing, applied to glass fabric.Acrylic-silane finished fabric is used with polyester resin systems. The data is useful, since thesizing is applied to enhance the bonding between the glass fibers and the resin system..133317-~1 Spec~This standard sets specifications for high modulus organic yarn and roving (i.e. carbon fiber).The spectilcation can be used as a guide for acquisition specifications and for materialacceptance/rejection testing.~ A -TfHi h “rThis test method is used to establish the density of fibers. This information is of use toconverters (manufacturers of fabric) and direct users of tow, such as filament winding.~d AsTMD 41- TsMf Contin ilamen naphite Yarns. Strands. Rovings and TowsThis test method is used to establish the tensile modulus and strength of carbon fiber tow. Thisinformation is of use to converters (manufacturers of fabric) and direct users of tow, such asfilament winding.Core MaterialsAST M C 271-6 1 Test Method for De nsitv of co re Materials for Structu ral SandwichConstruetion~This test is commonly used to determine the density of core materials. The test is simple,however hand measurement of the samples can be inconsistent, which may lead to errors indensity. Also, the test does not make provision for testing of sandwich specimen, thus theeffects of the face/core adhesive on apparent core density are not included. (see ASTM D1622-83)ASTM C 272-53 Test Method for Water Absom-ion of Core Mat~ rilfrSandm“chConstxuctionsThis test is used to determine the water absorption properties of core materials such as fo~honeycomb and balsa. The test is conducted on sandwich core materials without faces or othermethods of sealing the surfaces. Also, the duration of the test is only 24 hours. These factorsmake this test inappropriate for direct use in the marine industry. However, the mechanicalproperties of the core materials are often a function of the water content. This test can be usedto determine the water content levels of the core materials before mechanical testing todetermine the variation of the mechanical properties as a function of water content.199

Mechanical TestingMarjne CompositesC 7.73-61 Mew of Shear ~ in Flatwiwme of Flat ~wjch C~This test is commonly used to determine the shear properties of various core materials. Thetest has some serious flaws, but can yield useful information. The shear modulus is dependenton the stiffness of the mounting plates, therefore, the specifications for these plates must beclosely followed. The test specimen shape is such that stress concentrations are produced at theedge of the specimen, which may l~ad to premature failure and artificially low strength.Materials with high strain to failure undergo a transition from dominant shear stress at lowstrains to dominant tensile stress at high strains, thus the shear strengths of these materials arehighly suspect.. .C 365-57 Test Me~latwise C~~ve Stre#h of Wdwlch C!oresThis test is commonly used for quality assurance/material acceptance testing, since thespecimen preparation is quite simple, Cylindrical or rectangular samples are used, howevercylindrical samples appear to yield more consistent results. The material properties aredependent on the load or strain rate, thus the load rate or strain rate must be controlled withinthe guidelines of the test procedures.ASTM C 366-57 Methods for MeasWement of Thickness of Sandwith CoresThis test can be used to measure the thickness and variation in thickness of various corematerials. The test is simple, but requires special apparatus, which is not commonly availablein the marine industry.ASTM C 394-62 Test Method for Shear Fatkme of Sandwith Core MaterialsThis test was designed to measure shem fatigue of sandwich core materials. The test apparatusis similar to ASTM C 273-61, thus ASTM C 394-62 is subject to some of the same problems.The dominant problem is the stress concentrations which occur at the edge of the test sample.Most fatigue failures begin at these locations and propagate into the core material fairly rapidly,thus this test is not representative of core fatigue phenomena in sandwich constructions.~d 1 21-ce~l ar PlasticsThis test is commonly used to determine the compressive properties of foam core materials.Procedure A, utilizing cross-head motion for the strain calculation, yields significantly differentmodulus values and strain to failure values than procedure B, which utilizes direct strainmeasurement. Also, samples may be either square or cylindrical. There can be substantiallydifferent modulus, strength and strain to failure values between the two sample shapes. Thereappears to be general agreement between experts in the field of foam core testing thatprocedure B with cylindrical samples is the preferred test. Care must be taken when cutting thesamples to avoid damaging the surface of the foam, since this can alter test results dramatically.Foam material properties are strongly dependent on strain rate, thus strain rate or loading ratemust carefully controlled within the guidelines of the test method.ASTM D 1622-83 Test Method for Apparent De~sitv of Ritid Cellular PlasticsThis test is commonly used to determine the density of foam core materials. The testis simple,however hand measurement of the foam samples can be inconsistent, which may lead to errorsin density. The test does make provision for determining the apparent density of sandwichconstructions, thus the effects of the face material and the face/core adhesive material ondensity can be determined.200

ChapterSixTESTINGThis test is commonly used to determine tensile properties of foam core materials and face/coretensile adhesion strength of foam sandwich conshwctions. There are tlqee specimen types, twofor tensile properties snd one for face/core tensile adhesion strength.Type A specitnens are tapered cylinders, which are mounted in matching tapered collars. Thefabrication of these specimen is more involved than the other specimen, thus is more subject toerror. The tapered collars introduce compression stresses into the ends of the specimen, whichcan lead to premature failure, however, this type of failure can be determined through locationof the failure in the region of the collsr. Tensile modulus and strain to failure can be&termined using extensometer data, but cross-head motion is not suitable for calculating theseparameters.Type B specimen are square or cylindrical in shape, and are bonded to face plates. Cylindricalspecimen appear to yield more consistent results. Strength calculations can be affected by thefailure mode (adhesive failure or tensile fosrn failure), therefore extra sqmples must be tested toinsure sufficient data for strength calculations. The failure mode is easily determined, however,the tensile strength can be calculated using only samples with tensile foam failures. Modulusand strain to failure can be calculated from extensorneter da~Type C specimens are similar to Type B specimens, except that the specimen is a sandwichlaminate, and is used only for strength calculations. An additional failure mode (face/coreadhesion failure) is possible, thus care must be taken to identify the failure mode accurately.Also, if the face/core adhesion strength is greater thsn the face/test fmture adhesion or the foamcore tensile strength, it can not be determined using this test. The properties of foam aredependent on strain rate, thus strain rate or load rate must be carefully controlled within theguidelines of the test method.Solid FRP LaminatesASTM D 638-84 Test Method for Tensile Properties of PlasticsThis test can used to obtain the tensile modulus amd strength of cured resins, but is mostcommonly used to obtain tensile properties of FIW laminates. The principal difficulty with thistest is that the sample is cut to a dog bone shape, asshown in Figure 6-1. This causes stressconcentrations in the area of the taper, with failureoften occurring in this area instead of the testsection, making determination of tensile strengthimpossible (see ASTM D 3039). This test isappropriate for (0°, 9~) and rsndomly orientedreinforcing fabrics, and the laminates must besymmetric. Off-axis fibers (directions other thanO“ or 90°) introduce stress concentrations into thelsminate, which lowers the ultimate smngth.FlexUral stresses occur in unsymmetrical laminatessubjected to uniaxial in-plane loads, which cancause premature failure of the test samples.+L+~ LO JFigure 6-1 Dogbone TensileTest Specimens [ASTM D638]201

Mechanical TestingMarine Compositese of Pk@cs bv Co~de .-of F-This test is commonly used to determine the flexural fatigue properties of FRP laminates. Thetesting is conducted at 30 Hz, which is representative of the natud frequency of many boatstructures. This frequency is high enough to heat up the sample,thus this will have an effect onthe data. The test samples are machined with a tapered “neck.” There is a tendency for stressconcentrations and premature failures in the taper due to the cut fibers, thus the failures must beexamined and recorded., . .D 695-85 Test Method for C_sslve Proper&s of ~This test can used to obtain the compressive modulus and strength of cured resins, but is mostcommonly used to obtain compressive properties of FRP laminates. The principal difllcultywith this test is actually obtaining a compression failure for calculation of compressive strength.The samples are restrained from Euler buckling and shear failure by a test jig which is bolted tothe sample. If this jig is not positioned and tightened correctly, failure modes other than purecompression failure may occur. Also, if the jig is too tight, it could effect the modulus values.This test is appropriate for (0,90) and randomly oriented reinforcing fabrics, and the laminatesmust be symmetric. Off-axis fibers (directions other than O or 90 degrees) introduce stressconcentrations into the laminate which lowers the ultimate strength. Flexural stresses occur inunsymmetrical laminates subjected to uniaxial in-plane loads, which can cause premature failureof the test samples..ASTM D 732-85 Test Method for Shear Strength of PINUCSb v Punch ToolThis test is used to determine out-of-plane shear strength, thus it is representative of “punchthrough” or impacts with sharp edged objects. There are so many factors which contribute tothe out-of-plane shear strength that test results are most commonly used to directly compare theshear resistance of two or more laminates.ASTM D 790-84 Test Method s for Flex@ Pro~er&iesof 1Unreinforcedand Remforced Plasticsand Electrical Insulatirw MaterialaThis test is one of the most commonly used tests in the marine industry. The dominate loadson boats are often localized loads which introduce bending stresses into the laminate, thusflexural stiffness and strength are important properties for marine laminates, The test is also agood quality control test, since the laminate is subjected to all three major stresses: tensile,compressive, and shear. The test is not used to determine material properties, but is often usedto compare candidate laminates.~- 244-4 frShear Strenpth of Parallel Fiberco mnosites bv Short-Beam MethodThis test is similar to ASTM D 790, except that the span is very short, thus the shear stressesare dominant. The test is used to determine the iuterlarninar shear strength developed by theresin, thus it is most commonly used as a quality control test for evaluating the resin.ASTM D 2583-81 Test Method for In den-“ Hardness of Rl“gid Plastics bv~eans of aBarCO1ImmessorThis is probably the most common test in the marine industry. Barcol hardness can be used todetermine the state of cure of the resin at intermediate steps in the fabrication process. It canalso be used to monitor the rate of cure of the resin. It is simple and inexpensive, thus itprovides an excellent quality control test..202

ChapterSixTESTING. . .D 2584-68 Te~ of Cured Raced RemFiber-resin ratio is one of the most important quality control tests. This data is also necessaryfor interpretation of physical and mechanical test data. This testis the most common method ofobtaining the fiber-resin ratio for GRP laminates.. .ASTM D 2587-68 Test = for Ace~mon of GIMS Fiber S-This test is an alternate method for obtaining fiber-resin ratios for GRP huninates (see ASTM D2584).D 3039-76 Test ~es. .of Flbain C~This is the preferred test for determiningtensile modulus and strength of FRPlaminates. The test samples utilize adhesivelybonded tabs shown in Figure 6-2, instead of adog bone taper, to obtain a high stress testsection. Failures can still occur outside of the1 I Itest section, but these failures are usmdly tab‘AIdebonding, thus it is easy to determine iffailure data should be included iu the uMmate‘-ltensile strength calculation. This test isappropriate for (O”, 90°) and randomlyoriented reinforcing fabrics, and the laminatesmust be symmetric. Off-axis fibers(directions other than (Y or 90”) introducestress concentrations into the laminate whichlowers the ultimate strength. Flexural stressesoccur in unsymmetrical laminates subjected to Figure 6-2 Tensile Test Specimenuniaxial in-plane loads which can cause with Tabs [ASTM D 3039]premature failure of the test samples.~fent 1 1- Mhof Resin-Matrix Composites bv MatrixLThis test is an alternate method for obtaining fiber-resin ratios for GRP laminates (see ASTM D2584), but is the primary method for obtaining fiber-resin ratios for carbon fiber or graphitefiber reinforced laminates.ASTM D 3410-75 Test Method for Comnre ssive Frot)erties of Unidirectional or CroSs~lV~~This test yields more consistent results than ASTM D 695, but the test jig, shown in Figure 6-3,is very complicated and the tolerances on sample size are very tight, thus it is not as commonlyused as ASTM D 695. This test is appropriate for ((Y, 90”) and randomly oriented reinforcingfabrics, snd the laminates must be symmetric. Off-axis fibers (directions other than 0° or 90°)introduce stress concentrations into the laminate, which lowers the ultimate strength. Flexuralstresses occur in unsymmetrical laminates subjected to uniaxial in-plane loads, which can causepremature failure of the test ssmples.203

Mechanical TestingMarine Compositeso e*C?d EFigure 6-3Restraining Fixture for Testing Compressive Properties of Unidirectionalor Crossply Fiber-Resin Composites [ASTM ~3410]A~tl4- M Tni - inF” “n-~This test is designed to provide fatigue data for designers so that laminates can be designed to apredetermined life span. The test is tension-tension, thus it is an in-plane fatigue test withoutreversing loads. This limits the usefulness of the data, because most parts of the boat structureare subjected to tension-compression loading or flexural loading. Samples must not be cycledtoo quickly (

ChapterSixTESTING. .364-61 ~ww ~ve S~This test is commonly used to determine the in-plane strength of sandwich constructions. Thereare several different failure mechanisms which can limit the in-plane strength of sandwichconstructions: general column buckling (Euler Buckling), wrinkling, dimpling, and crimping.There are established equations for the critical stress for each type of failure mode, but theseequations assume a high quality laminate. Therefore, this test can be used to determine thequality of the laminate, as well as to check the results of the predicted failures. Thus it isimportant to know the failure mode, as well as the mechanical properties of the face and corematerials used in the predictive equations, to make use of the results of this tes~. .c 393-~This test is commonly used to determine the flexural properties of a sandwich construction.The main advantage of sandwich construction is to enhance flexural stiffness and strength, andsince all the important factors, such as face stiffness and strength, fa~e/core bond, and shearstiffness and strength contribute to the overall flexural stiffness and strength, this test is anexcellent quality control/quality assurance test The test can also be used as an alternative toASTM C 273-61 for calculating the shear properties of the core material. The procedures forobtaining the shear properties of the core material are quite involved, but appear to yieldexcellent results. Investigations into the possibility of using this test method for fatigue testingof core materials shows great potential, but a standard test needs to be established.~@T) TM 4-2T() f Sandw “ch ConStt’Uc tionSThis test is used to determine deflection as a function of time for sandwich constructionssubjected to long duration static loading (creep). This test is one of the few which addressestesting at different temperatures, an kportant feature for marine laminates. The mathematicsassociated with the test are very limited, however, it is difficult to extend test data thoughpredictions, which is important when examinin g creep phenomena.ASTM FRP Structure Tests~ ATM 2 - R-fr o Classifyirw Visual Defects in Glass-Reinforced?klstl“cLaminate PartsThis test sets standards for visual inspection and classillcation of defects in GRP laminates.Most boat builders utilize visual inspection as the primary structural quality control test, but theresults are not lmnsferable due to lack of standardization. Use of this stantid practiceguideline would allow this information to be used quantitatively.SACMA FRP Material TestsThe Suppliers of Advanced Composite Materials Association (SACMA) has developed a set ofrecommended test methods for oriented fiber resin composites. These tests are similar toASTM standard tests, and are either improvements on the corresponding ASTM standard testsor are new tests to obtain data not covered by ASTM standard tests. The tests are intended foruse with prepreg materials, thus some modifications may be necessary to accommodatecommon marine laminates. Also, the tolerances on fiber orientations (10, and specimen size(approximately 0.005 inch) are not realistic for marine laminates.205

Mechanical TestingMarine Compositesd Test _ for ~~ive Prrqties of ~Fibfir—~ . .This test corresponds to ASTM D 695, Test for Compressive Properties of Plastic Materials.The major difference between the two tests is that the SACMA test calls for tabs to be bondedto the ends of the specimen to minimize the possibility of premature failure of the sample at theends where the load is introduced. Thus one of the major problems with using the ASTM D695 test for FRP materials is eliminated. SRM 1-88 and ASTM D 695 both rely on a metal jigto prevent buckling of the sample. The sample must be installed in the jig very carefully toavoid biasing the results,thus leaving the repeatability and reliability of the test open toquestion. This also makes determination of the compressive modulus very difficult and timeconsuming, since it can only be done by use of strain gages. SRM 1-88 should yield bettercompressive data for marine laminates than ASTM D 695.ed Te~ for Co~act -ies ofThis test has no corresponding ASTM test. The method involves determination of thecompression after impact properties of fiber-resin composites reinforced by oriented highmodulus fibers. The method specifies impact and compression testing procedures for specimen4 x 6 inches in size, with a thickness of 0.18 to 0.22 inches. The sample size limits theapplicability to msrine laminates, since thick laminates (greater than 0.22 inches) can not betested. Also, the method does not allow testing of sandwich laminates. Another potentialproblem is that the impact level is determined from the energy of the impact, however, researchhas shown that low velocity and high velocity impacts at the same energy levels cause differenttypes and amounts of damage. The loading is uniaxial, while most marine laminates aresubjected to multi-axial loads. Use for marine applications appesrs to be extremely limited.SRM %88 SARCMA ecomnx@ed Test Wod for Ouen-Hole Commess ion nerhes ofOriented Fiber-Resin Comnosi@This test has no corresponding ASTMtest. The method involves determinationof the compression properties of fiberresincomposites reinforced by orientedhigh modulus fibers containing a circularhole. The recommended specimen size is1.5 inches wide by 12 inches long with a0.25 inch hole, but other sizes can betested as long as the 6:1 specimen widthto hole diameter ratio is maintained. Thetest fmture is shown in Figure 6-4. Thetest method does not allow testing ofsandwich laminates, and specties aquasi-isotropic laminate (+45°, W, -45”,90”), but should be useful for solid FRPm~e laminates.Figure 6-4 Test Fixture for CompressionTesting of Composites with Holes [SACMA 3-206

Chapter SixTESTINGM8~.of~ C!!.This test corresponds to ASTM D 3039, Test for Tensile Properties of Oriented FiberComposites. The major difference between ASTM D 3039 and SRM 4-88 is specification ofthe specimen tabs. SRM 4-88 specties tabs with a more gradual taper (15”) than ASTM D3039, thus it should yield more consistent strength data. The major difficulty with this test, aswith ASTM D 3039, is that the testis a uniaxial test, and while it works well for unidirectionaland (0,90) laminates, it does not work well for multi-axial laminates containing bias fibers.for ~e.Prop-.of ~co-This test has no comesponding ASTM test The method involves determination of the tensileproperties of fiber-resin composites reimforcd by oriented high modulus fibers containing a circularhole. The recommended specimen size is 1.5 inches wide by 12 inches long with a 0.25 inch hole.The test method does not allow testing of sandwich laminates, and specifies a quasi-isotropiclaminate (+45”,0’,45”, 90’’)s,but should be useful for solid FRP marine laminates.Stress-Slud.UProperties qffh-iented Fiber-Resin Composite~This test corresponds to ASTM D 3518, Test for In-plane Shear Stress-Strain Response ofUnidirectional Reinforced Plastics. The method involves determination of the in-plane sheaxstress-strain properties of fiber-resin composites reinforced by oriented continuous highmodulus fibers. The method is based on the uniaxial tensile stress-strain response of a i45°laminate, which is symmetrically laminated about a mid-plane. There does not appear to beany signiilcant enhancement over ASTM D 3518.R.~~:TestM:(A,~:k~=sv@ofThis test ~~sponds tomASTM D2344, Standard Test Method forApparent InterlaminarStrength of ParallelComposites by Short-Beam Shear ~mmlmllmMethod. SRM 8-88 does notI~~appear to contain any significant ~9’EumMmcenhsmcement over ASTM D 2344, (y&c5TaTm ~ ~“however the discussion on failure mmmodes, shown in Figure 6-5, is Figure 6-5 Typical Load-Deflection Curvesvery useful. and Failure Modes [SACMA 8+8]SW 10-88 sACMA Recomme nded Method for Calculation of Fiber Volume of ConmositeLaminatesThere is no ASTM test cmresponding to SRM 10-88. This method sets procedures forcalculation of fiber volume content as a percentage of reinforcing fiber volume versus the totallaminate volume. This is a simple procedure, but it will not be accurate for most marinelaminates as there is no allowance for air trapped in the laminate. The errors depend on theamount of trapped air (more air, larger errors), the ratio of the fiber density to the resin density(lower ratios, larger emrs), and the fiber content (lower fiber content, larger errors). Thiscalculation method is not likely to be useful for marine laminates.207

Mechanical TestingMarine CompositesSandwichPanel TestingBackgroundFiite elermmtmodels can be used to calculate panel deflections for various hminates under worst caseloads [61, 6-2], but the accuracy uf these prdcdom is highly dependent on test data for the laminates.Ttitional test methods [6-3] involve testing narrow stips, using ASTM standards outlined above.UsE of these tests assumes that hull panels can be amurately modeled as a beanz thus ignoring themembrane effec~ which is particularly impmtant in sandwich panels [6-4]. The traditional tests alsocause much higher stressesin the core, thus leading to pmnatwe failure [651.A student project at the Florida Institute of Technology investigated three point bending failure stresslevels for sandwich panels of various laminates and span to width ratios. The results were ffilyconsistent for biaxial ((T, W) hminates, but considerable variation in deflection and failure stress fordouble bias (m4Y) laminaies was observed as the aspct ratio was changed TIWSwhile the traditionaltests yield mnsistent results for biaxial laminates, the test pmprties may b significantly lower thanactual properties, and test results for double bias and trimial laminates are generally inaccurate.Riley and Isley [&51 addmsed these problems by using a new test prmdrte. They pressure loadedsandwich panels, which wem clamped to a rigid frame. Ilffemt panel aspect ratios we~ investigatedfor both biaxial and double b~ sandwich laminates. The results showed tit the double bias laminateswere favmwl for asp ratios less than two, while biaxial laminates @ornMl bettm with aspect ratiosgreater than three. Finite element models of three tests indicated similar results, however, themagnitude of the deflections and the pressure at failure was quite difikrent. This was probably due tothe method of fastening the edge of the paneL The nwhod of clamping of the edges probably causedlocal stress concentmtionsand could not be modeled by either pinned-or fied-end conditions.Pressure Table DesignThe basic concept of pressure loading test panels is sound, however, the edges or boundaryconditions need to be treated more realistically. In an actual hull, a continuous outer skin issupported by longitudinal and transverse framing, which defines the liull panels. Theappropriate panel boundary condition is one which reflects the continuous nature of the outerskin, while providing for the added stiffness and strength of the frames. One possible solutionto this problem is to include the frame with the panel, and restrain the panel from the frame,rather than the panel edges. Also, extending the panel beyond the frame can approximate thecontinuous nature of the outer skin.A test apparatus, consisting of a table, a water bladder for pressurizing the panel, a frame toconstrain the si&s of the water bladdm, and framing to rwrain the test panel, was developed andis shown in Figure 6-6. The test panel is loaded on the “outside,” while it is restrained by meansof the integral frame system The pressurization system can be operated either manually or undercomputer control, for pressure loading to failure or for pressure cycling to study fatigue.Test ResultsSandwich laminates using four different reinforcements and three aspect ratios were constructedfor testing. All panels used non-woven E-glass, vinyl ester resin and cross-linked PVC foamcores over fm frames and stringers. The panels were loaded slowly (approximately 1 psi perminute) until failure.208

Ch@er SixTESTINGApplledPrsssursLoad W7 4Figure 6-6Schematic Diagram of Panel Testing Pressure Table [Reichard]MSC/NASTRAN, a finite element structural analysis program, was used to model the paneltests. The models were run using two different boundary conditions, pinned edges and fixededges. The predicted deflections for freed- and pinned-edge conditions along with measuredresults are shown in Figure 6-7.The pinned-edge predictions most closely model the test results.made as a result of early pressure table testing include:Other conclusions that can be●Quasi-isotropic laminates are favored for square panels.. Triaxial laminates are favored for panels of aspect ratios greater than two.. Deflection increase with aspect ratio until asymptotic values are obtainedAsymptotic values of deflection are reached at aspect ratios between 2.0 and3.5.Material Testing ConclusionsIn theprevious text there is a review of ASTM and SACMA test procedures for determiningphysicaJ and mechanical properties of various laminates.In order to properly design a boat or a ship, the designer must have accurate mechanicalproperties. The properties important to the designer are the tensile strength and modulus, thecompressive strength and modulus, the shear strength and modulus, the interply shear strength,and the flexural strength and modulus.The ASTM and SACMA tests are all uniaxial tests. There are some pints of a boat’s structurethat are loaded uniaxially, however, much of the structure, the hull, parts of the deck andbulkheads, etc., receive multiaxial loads. One factor which is very important to determine in209

.Mechanical TestingMarine CompositesIIm lY by 128# 12’ by z#n12’ by4Y1 1I I i I Io 60 100 160 200 260 300 S60 400 460 500~ Pinned-End _ Find-End ~ MeasuredFigure 6-7 Theoretical and Measured Deflections (roils) of PVC Foam Core PanelsSubjected to a 10 psi Load [Reichard]composite materials is the interaction between loads in more than one axis. Poisson’s ratio isnot something which is easily &temained. The effects of stress in the x and y directionscombined are difficult to detemnine for composites, although they me relatively easy todetermine for isotropic materials. Therefore, one thing that really needs to be done before adesigner can design with confluence snd using reasonable factors of safety is to determine theinteraction between muhiaxial stresses for given laminates. This is not possible using thesestandard tests, since they are all uniaxial in nature.It’s going to be very important for the marine industry to develop a set of tests which yield theright type of data for the marine designer. Once this has been accomplished and an industrywide set of accepted tests has been developed, then a comprehensive testing program, testing allthe materials that are cornmordy used in the marine industry, would be very beneficial to thedesigners to try to yield some common data. Meanwhile, until these tests sre developed, andthis development could take a number of years, there is still a need for some corntnon testing.In particular, the tests recommended to be performed on laminates are the ASTM D3039 tensiletest or the appropriate SACMA variation of that, SRM 4-88. The ASTM compressive tests, allof them, leave something to be desired for marine laminates. However, the SACMAcompression test looks like it might yield some useful uniaxial compressive load data formarine laminates, and therefore, at this time would probably be the reconunended test forcompression data. Flexural data should be determined using ASTM D790. This is a fairlygood test. As far as shear is concerned, there is really no good test for determining the inplane210

Chapter SixTESTINGshear properties. The ASTM test (D35 18) is basically a 3039 tensile test performed on a fabricthat has been laid up at a bias so that all the fibers are at *45”. This has a number of problems,since the fibers are not continuous, and the results are heavily dependent on the resin, muchmore so than would be in a continuous laminate. So this test isn’t particularly good. Currently,there is not a test that would yield the right type of data for the inplane shear properties. Forthe interply shear, about the only test that’s available is the short beam shear test (ASTMD2344). The data yielded there is more useful in a quality control situation. It may be,however, that some of the other tests might yield some useful information. There’s a shear testwhere slots are cut half way through the laminate on opposite sides of the laminate (ASTMD3846). This one might yield some useful information, but because they’re cutting into thelaminate and there’s some variability involved in that it’s difficult to come up with consistentdata.In summary, what is recommended as a comprehensive laminate test program is the AST’MD3039 tensile tes~ the SACMA compressive test, ASTM D790 flexural test and a panel testusing the method developed at FIT. It’s not clear whether or not this will become an industrystandard, but at this point it’s the best test that’s available for looking at the out of planeloading and muhkxial loading.Accelerated TestingThere are two mechanisms to accelerate tests for water absorption over normal speeds. One isto elevak the temperature of the water, the other is to increase the pressure of the water.Neither of these methods work particularly well. Increasing the temperature is unrealistic andaffects the resin, softening it and making it more susceptible to hydrolysis or water attack,therefore, more water will be absorbed than would normally occur with a regular laminate.Resins which may be highly resistant to absorption may become very susceptible to it fromraising the temperature. Increasing the pressure of the water will cause water absorption inlaminates that would not normally absorb water because of the high pressure. The main issuehere, however, is not so much absolute data but relative data, and it may be that increasing thepressure could give fairly good relative data between the different resins, since a resin that ismore porous, with the higher pressure, would tend to take on even more water than a laminate,which is not quite so porous.The second type of accelerated testing that’s often done pertains to blistering. The commentshere are very sirailar to those above for the accelerated water absorption tests, except thathigher pressure is not an issue, since increasing the pressure tends to mihimize the effects of theosmotic pressure, which causes the blistering. By using higher pressure to try to acceleratewater absorption, which one might think would accelerate blistering, the formation of blisters isactually reduced or eliminated . It appears that the only viable method for accelerated blistertesting is to elevate the temperature of the water, which is a common method throughout theindustry. There are some problems with doing this, but it might yield reasonable relativeresults. One of the things that has been a problem in the past is the use of differenttemperatures. It’s relatively easy to hold the water at boiling temperatures, but boiling is 212”F,which is well above the heat distortion temperature of all the polyester resins. Therefore, youwill see a si~cant breakdown of the resin and blistering is much more likely to occur in thelaminate. Recently, the industry seems to have settled on 65°C (149”F) for this testing, and theresults seem to be more reasonable at 65”C.211

—.Fire TestingMarine CompositesComposite materials based on organic matrices are flammable elements that should beevaluated to determine the potential risk associated with their use. In a iire, general purposeresins will burn off, leaving only the reinforcement, which has no inherent structural strength.Vessels inspected by the U.S. Coast Guard must be fabricated using ilre retardant resins. Theseresins usually have additives such as chlorine, bromine or antimony. Physical properdes of theresins are usually reduced when these compounds are added to the formulation. There is alsosome concern about the toxicity of the gases emitted when these resins are burned.The fire resistance of individual composite components can be improved if they are coated withintumescent paints or foaming agents that will char and protect the component during minorfwes. This consideration is generally only relevant to rnilitsry projects where composites maybe integrated into larger steel structures. The commercial designer is primarily concerned withthe following general restrictions (see appropriate Code of Federal Regulation for detail):...Subchapter T - Small Passenger Vessels: Use of fire retardant resinsSubchapter I - Cargo Vessels: Use of incombustible materials - constructionis to be of steel or other equivalent materialSubchapter H - Passenger Vessels: SOLAS requires non-combustiblestructural materials or materials insulated with approved non-combustiblematerials so that the average temperature will not rise above a designatedtemperatureMore detail will be given on SOLAS requirements later in this section. The industry iscurrently in the process of standardizing tests that can quantify the performance of variouscomposite material systems in a fm. The U.S. Navy has taken the lead in an effort to certifymaterials for use on submarines. Table 6-7 at the end of the section presents some compositematerial test data compiled for the Navy. The relevant properties and associated test methodsare outlined in the following topics. No single test method is adequate to evaluate the firehazard of a particular composite material system. The behavior of a given material system in afm is dependent not only on the properties of the fuel, but also on the fme environment towhich the material system may be exposed. ,The proposed standardized test methods [6-7] forflammability and toxicity characteristics cover the spectrum from small scale to large scaletests.Small Scale TestsSmall scale tests are quick repeatable ways to determine the flammability characteristics oforganic matetiik. Usually, a lot of information can be obtained, using relatively snxdl testspecimens.Oxygen-Temperature Limiting Index (LOI) Test - ASTM D 2863 (Modified)The Oxygen Temperature Index ProFde method determines the minimum oxygen concentrationneeded to sustain combustion in a materiil at temperatures from ambient to 570”F. During afm, the temperature of the materials in a compartment will increase due to radiative and212

Chapter SixTESTINGconductive heating. As the temperature of amaterial increases, the oxygen level requiredfor ignition decreases. This test assesses therelative resistance of the material to ignitionover a range of temperatures. The -testappsratus is shown in Figure 6-8.Apprmdmately (40) V4° to ~“ x lA” x 6“ ,samples are needed for the test Testapparatus consists of an OxygenfNitrogenmixing system and anslysis equipment. Thetest is good for comparing similar resinsystems, but may be misleading when vastlydifferent materials are compared.N.B.S. Smoke Chamber - ASTM E662This test is used to determine the visualobscuration due to fue. The saraple isheated by a small furnace in a lsrge charribersnd a photocell arrangement is used todetermine the visual obscuration due tosmoke from the sample.(33--. .-..- Piloi flameBurningSvecimenThe test is performed in flaming andnon-flaming modes, requiring a total of (6)~!, x 3!1 x M“ samples. Specific OpticalDensi~, which is a dimensionless number, isrecorded. The presence of toxic gases, suchas CO, COZ, HCN and HC1 can also berecorded at this time. Table 6-1 shows sometypical values recorded using this testFigure 6-8 Sketch of the FunctionalParts of the Limiting Oxygen Index Apparatus[Rollhauser, Fire Tests of JoinerBulkhead Panels]Table 6-1.Results of Smoke Chamber Tests (E-662) for Several Materials[Rollhauser, Fire Tests of Joiner Bulkhead Pane/s]MaterialPhenolic Composite -ExposursFlaming 7Nonflaming 1Optical Density Optlca] Density20 minutes 5 minutesPolyester Flaming 660 321CompositeNonflaming 22Plywood Flaming 45Nylon Carpet Flaming 270Red Oak Flooring Flaming 300213

Fire TestingMarine CompositesCone Calorimeter - ASTM P 190This is an oxygen consumption calorimeter that measures the heat output of a burning sample bydetermining the amount of oxygen consumed during the burn and calculating the amount of enmgyinvolved in the process. The shape of the heating coil resembles a truncated cone. The testapparatus may be configured either vertically m hcrrizmtally, as shown in Figure 6-9. The device isused to dmmnine the hmt flux needed to ignite a sample, the mass loss of the sample, the sample’sheat loss generation and smoke and toxic gas generation. This is a new test procedure that usesrelatively small (4” x 4“) test specimens, usually m@ring (24) for a full series of tests.laBI ri=7-TOPOFFURNACEOPENTO----- -.. .— / AUOWGASESTOPASSTHROUBIMilr‘E”n’4””R”cETlzzisk4 COILEOELI%-- 4 RESIHANCEWIm ’“2:12-..-UERTEMmosuREliORIZONTAL EKPOSUREFigure 6-9 Sketch of the Functional Parts of a Cone Calorimeter [Rollhauser, FkeTests of Joiner Bulkhead Panels]Radiant Panel - ASTM E 162This test procedure is intended to quantify theL21ExhauSlho~~surface flammability of a material as a functionof flame spread and heat contribution. Theability of a panel to stop the spread of fm andlimit heat generated by the material is measured.A 6’ x 18“ specimen is exposed to heat from a— Radimtl psnGI12” x 18” radiant heater. The specimen is heldSpecimenat a 45” angle, as shown in Figure 6-10.The test parameters measured include the timerequired for a flame front to travel down thesample’s surface, and the temperature rise in thestack. The Flame Spread Index is calculatedfrom these factors. The Flame Spread Index forRed Oak is 100 and Ofor asbestos.Fi9UW6-10 Sketch of theFunctional Parts of the NBS RadiantPanel Test Configuration [Rollhauser,Fire Tests of Joiner Bulkhead Panels]214

Chapter SixTESTINGIntermediate Scale TestsIntermediate scale tests help span the gap between the uncertainties associated with small scaletests and the cost of full scale testing. Three tests used by the U.S. Navy sre described in thefollowing.DTRC Burn Through TestThis test determines the timerequired to burn throughmaterials subjected to 200WFunder a controlled laboratoryfii condition. This is atemperature that may resultfrom fluid hydrocarbon fueledfues and can simulate theability of a material to contisuch a h to a comparbnen~Figure 6-11 shows themrangement of specimen andflame source for this test (2)24” x 24” samples are neededfor this test. Burn throughtimes for selected material ispresented in Table 6-2.Figure 6-11 Sketch of the DTRC Burn ThroughSample and Holder [Rollhauser, Fire Tests of JoinerBulkhead Panels]Table 6-2.Plywood 1Plywood 2DTRC Burnthrough Times for Selected Materials [Rollhauser, F..reTests of Joiner Bulkhead Panels]❑Burn~.

..-Fire Testing /Wne CompositesU.S. Navy Quatter Scale Room Fire TestThis test determines the flashover potential of materials in a mom when subjected to fueexposure. The test reduces the cost and time associated with full scale testing. A 10’ x 10’ x8’ room with a 30” x 80” doorway is modeled. (1) 36” x 36” and (3) 36” x 30” samples arerequired.One Meter Furnace Test - ASTM E 119 (Modified)This test subjects one side of a specimen to a small Class A h. The samples are about 40square feet, which yields more realistic results than small scale tests, but at a greater cost. Thistest is not widely used outside of the Navy.Large Scale TestsThese tests are designed to be the most realistic simulation of a shipboard fm scenmio. Testsare generally not standardized, instead designed to comptwe several material systems for aspecific application.Corner TestsCornertests are used to observe flame spread, structural response and fue extinguishment of thetested materials. The test was developed to test joiner systems. The geomelry of the insidecorner creates what might be a worst case scenario where the draft from each wall converges.7’ high by 4’ wide panels are joined with whatever connecting system is part of the joinery.Approximately two gallons of hexane fuel is used as the source fwe burning in a 1‘ x 1‘ pan.Room TestsThis type of test is obviously the most costly and time consuming procedure. Approximately98 square feet of material is required to construct an 8’ x 6’ room, Parameters measuredinclude: temperature evolution, smoke emission, structural response, flame spread and heatpenetration through walls. Instrumentation includes: thermocouples and temperatures recorders,thermal imaging video cameras and regular video cameras.Summary of Proposed MIL-STD-2202 (SH) RequirementsAlthough MIL-STD-X108 (SH), ‘Tire and Toxicity Test Methods and Qualification Procedurefor Composite Materkd Systems used in Hull, Machinery, and Structural Applications insideNaval Submarines” is still in draft form, it is instructive to look at the requirements proposedby this standard. The foreword states:“The purpose of this standard is to establish the fire and toxicity test methods,requirements snd the qualification procedure for composite material systems toallow their use in hull, machinery, and structural applications inside navalsubmarines. This standard is needed to evaluate composite material systems notpreviously used for these applications.”Table 6-3 summarizes the requirements outlined in the new military standard.216

Chapter SixTESTINGTable6-3. ProposedGeneralRequirementsof MIL-STD-2202(SH), FWaand ToxicityTest Methods and Qualiiiation Procedure for Composite il&teriai Systems Used inHuii, il&whinery and structural Applications-inside iWvai Submarines~~~FireTest/Characterlstlcak~gw~-The minimumconcentration of oxygenin a flowing oxygennitrogen mixture capablem- of supporting flamingk combustion of a material.RequirementMlnlmum‘A oxygen @ 25°C 35YO oxygen @ 75°C 30YO oxygen @ 300°C 21Test MethodASTM D 2863(modified)A number orclassifica~on indicating aa=~ comparative measureE~~a derived from~ ~= observations madeduring the progress ofthe boundary of a zoneof flame under definedtest condfiions.%-~w=Q The ease of ignition, assemeasured by the time to~ ~ ignite in seconds, at ag~ specified heat flux with apilot flame.Maximum20Mlnlmum100 kW/m2 irradiance 6075 kW/m2 irradiance 9050 kW/m2 irradiance 15025 kW/m2 irradiance 300ASTM E 162ASTM P 190Maximum100 kW/m2 irradiancePeak150Average 300 sees120f8tzaHeat produced by amaterial, expressed perunit of exposed area, perunit of time.75 kW/m2 irradiancePeakAverage 300 sees50 kW/m2 irradiance100100ASTM P 190Peak65Average 300 sees5025 kW)m2 irradiancePeak50Average 300 sees50217

Fire TestingMarine CompositesFire Test/Characterlstlc Requirement Test MethodMaximum~g~Reductionof light DSduring300 sees 100 ASTM E 662transmission by smokeE~ as measured by light Dmm occurrence2240 seesWgattenuation.o25 kW/m2 irradiance: Maximum~ ~ Rate of production ofZ$!lcombustion ases (e.g.co200 ppmco, C02, H!?1,HCN, ASTM P 190g~:C024% (Vol)NOX, SOX, halogen, acidses and total HCN 30 ppmg U fl~drocarbons.HCL100 ppmc m Test method to determinea % the time for a flame tokl- burn through a compositel-a) material system underGk&ii controlled fire exposure: conditions.No burn through in 30 minutesDTRC BurnThrough Fire Test~Test method to determinel?lh-the flashover potential ofmaterials in a room whenNaNo flashover in 10 minutes{f subjected to a fireProceYureexposure.a:g Method to test materialsat full size of theirtig~~ intended applicationunder controlled firego.: + exposure to determine95 fire tolerance of ease ofextinguishment.~~ Method to test materials~~gusing an enclosedm~+ compartment in asimulated environment~~ “g :;;:::re. controlled fireY&’PassPassNavProceJureNavProceJurea 5~ ~ ~~ Test method to determine- ~ the potential toxic effects,- -of combustion products~ 6 ~ ~ (smokeand fire gases)+ $! ‘S’ng ‘aboratow ‘ats”PassNavyProcedure218

Chapter SixTESTINGReview of SOLAS Requirements for Structural Materials in FiresSOLAS is the standard that all passenger ships built or converted after 1984 must meet.Chapter II-2 Fire Protection, Fire Detection and Fire Extinction defines minimum fire standardsfor the industry. SOLAS divides ships into three class divisions and requires different levels offire protection, detection and extinction. Each class division is measured against a standard firetest. This test is one in which specimens of the relevant bulkheads or decks are exposed in afm test furnace to temperatures corresponding approximately to the StandardTime-Temperature Curve of ASTM El 19, which is shown in Figure 6-11 along with otherstsndards. The standard time-temperature curve for this purpose is developed by a smoothcurve drawn through the following temperature points measured above the initial furnacetemperature:. at the end of the first 5 minutes 556°C (1032T). at the end of the frost 10 minutes 659°C (1218”F)* at the end of the first 15 minutes 7 18°C (1324”F). at the end of the first 30 minutes 821“C (1509”F)●at the end of the first 60 minutes 925-C (1697”F)— ASTME 119(SOLAS) + lJL 1709 (Proposed)m :.,,:,,,,,,,.,.,.,., ##~~ ASTMP 191RangeFigure 6-11 Comparison of Three Fire Tests [Rollhauser, Integrated TechnologyDeckhouse]219

Fire TestingMarineCompositesNon-combustible materials are identified for use in construction and insulation in all three classdivisions. Non-combustible material is a material which neither burns nor gives off flammablevapors in sufllcient quantity for se~-ignition when heated to approximately 750*C (1382T), thisbeing determined to the satisfaction of the adminis~tion by an established test procedure. AnYother material is a combustible material.The actual class divisions are A, B, and C.bulkheads and decks which:a. shall be constructed of steel“A” class divisions are those divisions formed byor other equivalent materi~b. shall be suitably stiffene@c. shall be so constructed as to be capable of preventing the passage of smokeand flame to the end of the one-hour standard fue tes~d. shall be insulated with approved non-combustiblematerials such that the averagetemperature of the unexposed side will not rise more ti 13YC (282T) above theoriginal temperatum,nur will the temperature, at any one poin~ including any join6 risemo~ than 18(YC(356T) above the original temperature,within the time listed below.●●●Class “A-60” 60 minutesClass “A-30” 30 tiutesClass “A-15” 15 minutes. Class “A-O” Ominutes“B” class divisions are those divisions formed by bulkheads, decks, ceilings or linings whichcomply with the following:a. shall be constructed as to be capable of preventing the passage of smoke andflame to the end of the first half hour standard ilre tests;b. shall have an insulation value such that the average temperature of theunexposed side will not rise more than 130’C (282”F) above the originaltemperature, nor will the temperature at any point, including any joint, rise morethan 225*C (437”F) above the original temperature, within the time listed below:. Class “B-15” 15 minutes●Class “B-O” Orrrhmtesc. they shall be constructed of approved non-combustible materials and allmaterials entering into the construction and erection of “B” class divisions shallbe non-combustible, with the exception that combustible veneers may bepermitted provided they meet other requirements of the chapter.220

Chapter SixTESTINGTable 6-4. Heat Release Rates and Ignition Fire Test Data for CompositeMaterials [Hughes Associates, Heat Release Rates and Ignition FireTest Data for Representative Building and Composite Materiais]Material/ReferenceA IledAverage Heat Release Rate -1? eat Peak HRR HRR (kW/m2)(kW/m2)(k%#2) 1 mln 2 mln 5 mlnEpoxy/fiberglass A 25,50,75 32,8,5. . . .Epoxy/fiberglass B 25,50,75 30,8,6Epoxy/fiberglass7mm C 25,50,75 158,271,304Epoxy/fiberglass7mm D 25,50,75 168,238,279Epoxy/filwglass 7mm E 26,39,61 100,150,171EWxy/fiberglass7mm F 25,37 117,125Epxy/fiberglass 7mm G 25,50,75 50,154,117E~xy/fiMglass 7mm H 25,50,75 42,71,71Epoxy/fiberglass7mm I 35 92Phenolic/fiberglass A 25,50,75 28,8,4Phenolic/fiberglass B 25,50,75 NI,8,6Phenolic/FRP7mm C 25,50,75 4,140,204Phenolic/FRP 7mm D 25,50,75 4,121,171. . .Phenolic/FRP 7mm E 26,39,61 154,146,229PhenoIic/FRP 7mm F 25,37 4,125Phenolic/FRP 7mm G 25,50,75 4,83.71 . .Phenolic/FRP7mm H 25,50,75 4,50,63Phenolic/FRP 7mm I 35 58Polyester/fiberglass J 20 138FRP J 20,34,49 40,66,80GRP J 33.5 81Epoxy/Kevlar@ 7mm A 25,50,75 33,9,4Epoxy/Kevlar@ 7mm B 25,50,75 36,7,6Epoxy/Kevlar@ 7mm C 25,50,75 108,138,200Epoxy/Kevlarw 7mm D 25,50,75 100,125,175Epoxy/Kevla~ 7mm E 26,39,61 113,150,229Epoxy/Kevlar@ 7mm F 20,25,27 142,75,133Epoxy/Kevla~ 7mm G 25,50,75 20,83,83Epoxy/Kevla~ 7mm H 25,50,75 20,54,71Epoxy/Kevla~ 7mm I 35 71Phenoli@Kevi~ 7mm A 25,50,75 NI,12,6221

Fire Testing A&he CompositesMaterial/ReferenceA liedAverage Heat Release Rate -F eat Peak HRR HRR (kW/m2) I ;l&n(kW/m2) %(k~;2)1 min 2 mln 5 mln3henoliiKevi# 7mm B 25,50,75 NI,9,6~henolidKevia~7mm C 25,50,75 0,242,333‘henolidKevia~ 7mm D 25,50,75 0,200,250ahenoli~evia~ 7mm E 26,39,64 100,217,300‘henolidKevl@7mm F 30,37 147,1253henolidKevl~ 7mm G 25,50,75 13,92,1173henolidKetifl 7rnrn H 25,50,75 13,75,92ahenolidKevifl 7mm I 35 83%ermWGraphiie7mm C 25,50,75 4,183,233WerdWGraphiie7mm D 25,50,75 0,196,200TmdidGt@iie 7mm E 39,61 138,200%erdidGraphiie 7mm F 20,30,37 63,100,142YwmWG&ie 7mm G 25,50,75 13,75,1083herdidGmphiie 7mm H 25,50,75 13,63,88%enoWGraphiie7mm I 35 71WenolidGmphiie7mm A 25,50,75NI,12,6WerdidGraphiie 7mm B 25,50,75 NI,1O,6Epoxy K 35,50,75 150,185,210155,170,190 75,85,100 116,76,40@xy/Nexiel-Prepreg K 35,50,75 215,235,255195,205,240 95,105,140 107,62,31Bismaleimide (BMI) K 35,50,75 105,120,140130,145,170 105,110,125 211,126,54BMl/Nextel-Prepreg K 35,50,75 100,120,165125,135,280 120,125,130 174,102,57BM1/Netiel-Dry K 35,50,75 145,140,150150,150.165 110.120{ 125 196,115,52Koppers 6692T L 25,50,75 263,60,21

ChapterSixTESTINGMaterial/ReferenceA +fdAverageHeat ReleaseRatel?Peak HRR HRR (kW/m2) 1 ~lgn(kW/m2) %(k%;2) 1 mln 2 mkt 5 mln~~b Epoxy/Graphite L 35,50,75 150,185,210155,170,190 75,85,100Lab BMI 3mm L 35,50,75 211,126,54Lab BM1/Graphite L 35,50,75 105,120,140130,145,170 105,110,125Glass/Vinylester M 25,75,100377,498,557 290,240,330 180,220,— 281,22,11Graphite/Epoxy M 25,75,100 0,197,241 0,160,160 o,90,— NI,53,28Graphite/BMl M 25,75,100 0,172,168 0,110,130 0,130,130 NI,66,37Graphite/Phenolic M 25,75,100 0,159,— 0,80,— 0,80,— Nl,79,—Designation Furnace ReferenceA Cone - H Babrauskas, V. and Parker, W.J., “lgnitabili!y Measurementswith the Cone Calorimeter,” Fire and Ma.tmds , Vol. 11, 1987,B Cone - V pp. 31-43.cDCone - VCone - HE FMRC - H Babrauskas, V., “Comparative Rates of Heat Release f~~ FiveDifferent Types of Test Apparatuses,” Journal of Fire Sc e ces,F FlaMsHeig~ - V Vol. 4, March/April 1986, pp. 146-159.G 0SW02 - vHIJOSU - V (a)OSU - V (b)Osu “ vSmith, E.E., ‘Transit Vehicle Material Specification UsingRelease Rate Tests for Flammability and Smoke,”Re ort No.IH-5-76-I, American Public Transit Association, Was 1! ington,DC, Oct. 1976.Brown, J , E ., “Combustion Characteristics of Fiber ReinforcedK Cone Resin Panels,” Reporl No. FR3970, U.S.Department ofCommerce, N.B.S,, April 1987.LH = horizontalV = verticalConeBrown, J . E., Braun, E. and Twilley, W.H., “Cone CalorimeterEvaluation of the Flammability of Composite Materials,” USDe artment of the Navy, NAVSEA 05R25,Washington, DC,Fe E.1988,Sorathia, U., “Sutvey of Resin Matrices for IntegratedM Cone Deckhouse Technology,” DTRC SME-88-52, David TaylorResearch Center, August 1968.NI = not ignited(a) = initial test procedure(b) = revised test procedure223

Nondestructive TestingMarine CompositesUnlike metallic structures, composites may have a variety of different defects that are either dueto fabrication inconsistencies or from in-semice damage. A variety of specializednondestructive testing (NDT) techniques have evolved that can characterize defects present incomposite structures. The U.S. Coast Guard Research Center in New London, CT is currentlyinvestigating a range of NDT techniques as applied to typical marine laminates for detection ofthe following defects:. Resin rich/poor areas. Excessive moisture*Voids●Delamination*Impact Damage. Shear FailureA total of (40) panels are being fabricated for the effort. The report should be available to thepublic through the National Technical Information Service in the Spring of 1991. This sectionwill briefly describe some of NDT techniques in use today.RadiographyTechniquesRadiography includes a number of different techniques such as X-rays, gamma rays, neutrons,radiation backscatter and flouroscopy. Each method uses a radiation beam that passes throughthe material, whereby varying amounts of radiation are absorbed by different sections of thelaminate and discontinuities within the laminate.Radiography is primarily used to determine fiber alignment, bond integrity and defects insandwich structures, [6-8] X-ray radiography is unable to detect fiber breaks in graphite oraramid fiber. Very low-energy sources of about 15 to 25 kV must be used with graphitecomposites, otherwise the material would appear completely transparent. Often imageenhancing penetrants are used to obtain good information about interior damage, [6-9]Ultrasonic InspectionUltrasonic techniques are the most common form of NDT used with composites. In ultrasonicinspection, a beam of ultrasonic energy is directed into the laminate, and the energy is eithertransmitted or reflected. The laminate is usually immersed in water to direct sound waves.Ultrasonic transducers are placed on each side of the laminate that convert electric energy intomechanical vibrations, which are then transmitted through the laminate, Table 6-5 shows theapplications of various types of ultrasonic techniques.224

Chapter SixTESTINGTable 6-5. Ultrasonic Inspection Techniques[M.M. Schwartz, International Product News]Ultrasonic TechniquePulse EchoPulse Echo Refleotor PlateThrough TransmissionApplicationFiberglass-fiberglass bonds; delaminationin fiberglass laminates up to %!4”thick;and facing to core unbendsDelamination in thin fiberglass or boronI laminatesInspect sandwich constructions and thickfiberglass laminatesIDeteetunbends in fiberglass-metal bondsResonant Frequency and fiberglass-fiberglass bonds where theexposed layer is not too thickAcousticEmissionThe acoustic emission from composites under load is a research tool under development forassessing damage. Researchers have postulated that acoustic emission signals can becategorized by energy levels indicating fiber breakage, matrix cracking and delamination. Thetechnique is most widely accepted in the tlkunent wound pressure vessel industry.ThermographyThermographic analysis of composite materials uses thermal gradients in either a passive oractive mode, to delineate defects or damage. In the passive method, an external heat source isapplied to the laminate. Heat may be conducted either into or away from the laminate by anexternal heat source of either higher or lower temperature. In the active method, meehanicd orelectrical energy is applied, Video-thennographic cameras are the most efficient way ofrecording therrnographic phenomena. Vibrothmnography uses mechanical vibrational energythat is applied to the laminate, which is transformed into heat at damage sites.225

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ChapterSevenREFERENCEThe U.S. Coast Guard is statutorily charged with administering maritime safety on behalf of thepeople of the United States. In carrying out this function, the Coast Guard monitors safetyaspects of commercial vessels from design stages throughout the vessel’s useful life. Oftendesign standards such as those developed by the American Bureau of Shipping are used. Codesare referenced directly by the U.S: Code of Federal Regulations (CFR) [7-1]. Other countries,such as England, France, Germany, Norway, Italy and Japan have their own standards that areanalogous to those developed by ABS. Treatment of FRP materials is handled differently byeach country. This section will only describe the U.S. agencies.U.S. Coast GuardThe Coast Guard operates on both a local and national level to accomplish their mission. Onthe local level, 42 Marine Safety Offices (MSOS) are located throughout the country. Theseoffices are responsible for inspecting vessels during construction, inspecting existing vessels,licensing personnel and investigating accidents. The Office of Marine Safety, Security andEnvirontnent Protection is located in Washington, DC. This ofllce primfilydisseminatespolicy, directs marine safety training, oversees port security and responds to the environmentalneed of the country. The Marine Safety Center, also located in Washington, is the office wherevessel plans are reviewed. The Coast Guard’s technical staff revieyw machinery, electricalarrangement, structural and stability plans, calculations and instructions for new constructionand conversions for approximately 18,000 vessels a year.The Coast Guard has authorized ABS for plan review of certain types of vessels. These do notinclude Subchapter T vessels and novel craft. The following section will attempt to describethe various classifications of vessels, as defined in the CFR. Table 7-1 summarizes some ofthese designations. Structural requirements for each class of vessel wiU also be highlighted.Subchapter C - Uninspected VesselsThe CFR regulations that cover uninspected vessels are primarily concerned with safety, ratherthan structural items. The areas covered include:●●●Life presemers and other lifesaving equipmentEmergency position indicating radio beacons (fishing vessels)Fire extinguishing equipment. Bacldre flame control●●VentilationCooking, heating and lighting systems. Garbage retention.227

Rules and RegulationsMarine ComposlesOrganizations that sre cited for reference:American Boat and Yacht CouncilP.O. Box 747Millersville, MD 21108-0747National Fire Protection Association (NFPA)60 Batterymsrch ParkQuincy, MA 02260Table 7-1. Summary of CFR Vessel Classiflcatlons[46 CFR, Part 2.01- 7(a)]Subchapter H - Subchapter T -S$@&h~~~; ISize or Other Passenger Small PassengerMlsce7IaneousLlmltatlons46 $FO~8%ahS 46 ~~~&tS46 CFR, Part 175 .Vessels over 100 Vessels under~~~;~~over 9~ss tons 100 gross tonsSubchapter CUnlnspected46 CFR, Parts24-26All vessels carrying more than 12tons exceptpassengers on an mtemational voyage,~~t~ingexcept yachts.vessels ofAll vesselsAll vessels not over 65 feet in lengthk 300 gross carrying freight All vesselswhich carry more than 6 passengers.tons andfor hire except except those# over.those covered covered b H, TAll other vessels of over 65 feet in by Hor T or I vessesrlength cartying passengers for hire. vessels=r!!~o~~ing All vessels cartying more than 12passengers on an international voyage,vessels of except yachts.300 grosstons and All other vessels carving passengersover.except yachts.Vessels over 100 Vessels underVessels not gross tons100 gross tonsover 700gross tons. All vessels carrying more than 6None Nonepassengers.Vessels over700 gross All vessels carrying passengers for hire, None Nonetons.Part 72 of CFR 46 is tid-d Construction and Arrangement. Subpsrt ~72.01-15 StructuralStandards StateS:In general, compliance with the stamiards established by ABS will be consideredsatisfactory evidence of structural efficiency of the vessel. However, in specialcases, a detailed analysis of the entire structure or some integral psrt may bemade by the Coast Guard to determine the structural requirements.228

Chapter SevenREFERENCELooking at Subpart 72.05 - Structural Fire Protection, under ~72.05-10 Type, location andconstruction of f~e control bulkheads and decks, it is notedThe hull, structural bulkheads, decks, and deckhouses shall be constructed ofsteel or other equivalent metal construction of appropriate scantlings.The section goes onto define different types of bulkheads, based fm performance.Subchapter I - Cargo and Miscellaneous VesselsThe requirements for “I” vessels is slightly different than for “H”. Under Subpart 92.07 -Structural Fire Protection, $92.07-10 Construction states:The hull, superstructure, structural bulkheads, decks and deckhouses shall beconstructed of steel. Alternately, the Commandant may permit the use of othersuitable materials in special cases, having in mind the risk of fire.Subchapter T - Small Passenger VesselsSubpart 177.10- Hull Structure is reproduced herein its entirety:5177.10-1 Structural standardsS177.1O-5Fire Protection(a) In general, compliance with the standards established by a recognizedclassification society (Lloyds’ “Rules for the Construction and Classiilcation ofComposite and Steel Yachts” and Lloyds’ “Rules for the Construction andClassification of Wood Yachts” are acceptable for this purpose.) will beconsidered satisfactory evidence of the structural adequacy of a vessel. Whenscantlings differ from such standards and it can be demonstrated that craftapproximating the same size, power tmd displacement have been built to suchscantlings and have been in satisfacto~ service insofar as structural adequacy isconcerned for a period of at least 5 years, such scantlings may be approved Adetailed structural analysis may be required for specialized types or integral partsthereof.(b) Special consideration will be given to:(1) The structural requirements of vessels not contemplated by the standards of arecognized classiilcation society; or(2) The use of materials not spec~lcally included in these standards.(a) The general constmction of the vessel shall be such as to minimize firehazards insofar as reasonable and practicable. Vessels contracted for on or afterJuly 1, 1961, which carry more than 150 passengers shall meet the requirementsof Subpart 72.05 of Subchapter H (Passenger Vessels) of the chapter. The229,,,,, ,--,.,,,, ‘,,’;,,,

Rules and RegulationsManhe Compositesapplication of these requirements to specific vessels shall be as determined bythe Officer in Charge, Mtuine Inspection.(a-1) Except for a vessel complying with the requirements contained inparagraph (a-2) of this section, each hull, structural bulkhead, deck, or deckhousemade of fibrous glass reinforced plastic on each vessel that carries 150passengers or less must be constructed with fm retardant resins, laminates ofwhich have been demonstrated to meet rnilitmy specification MIL-R-21607 afterl-year exposure to weather. Military specification MIL-R-21607 may beobtained from the Commanding Officer, Naval Supply Depot, 5801 TaborAvenue, Philadelphia, PA 19120.(a-2) Each hull, structural bulkhead, deck, or deckhouse, made of fibrousreinforced plastic on a vessel that cmries 150 passengers or less, that wascertificated on July 11, 1973, and remains certificated may continue in service.Any repairs must be as follows:(1) Minor repairs and alterations must be made to the same standard as theoriginal construction or a higher standa@ and(2) Major alterations and conversions must comply with the requirements of thissubpart.(b) Internal combustion engine exhausts, boiler and galley uptakes, and similarsources of ignition shall be kept clesr of and suitably insulated from snywoodwork or other combustible matter.(c) Lamp, paint, snd oil lockers and similar compartments shall be constructed ofmetal or lined with metal.AmericanBureau of ShippingThe American Bureau of Shipping (ABS) is a nonprofit organization that develops rules for theclassification of ship structures and equipment. Although ABS is primarily associated withlarge, steel ships, their involvement with small craft dates back to the 1920’s, when a set ofrules for wood sailing ship construction was published. The recent volume of work done forFRP yachts is summarized in Table 7-2. The publications and services offered by ABS aredetailed below. [7-2]Rules for Building and Classing Reinforced Plastic Vessels 1978These give hull structure, machinery and engineering systim requirements for commercialdisplacement craft up to 200 feet in length, and special requirements for limited service craftsuch as yachts and ferries etc. They contain comp~hensive sections on materials andmanufacture and are essentially for E-glass chopped strand mat and woven roving laminateswith a means of approving other laminates given.230

Chapter SevenREFERENCEThesegeneral Rules have served and condrme to semice industry and AIM ve~ well - they areadopted as AustrsJisnGovmnment Regulations aud sre used by the USCG. They are applied currentlyby ABStoall mmmercd displacement crall in unrwmictedocesn service, and to limited service croftsuch as ssillng yachts ova 100 fmt in len~ faries, passenger vessels, and fibing vessels.Table 7-2. Statistics on ABS Services for FRP Yachts Duringthe Past Decade[Curry, AmericanBureau of Shipping] -ABS Service Saillng MotorYachts YachtsCompleted or contracted for class orhull certification as of 1989336 94Plan approval service only as of 1989 160 9Currently in class 121 164Plan approval service from 1980 to1989390 35Guide for Buiiding and Ciassing Offshore Racing Yachts, 1986These were devel~ by ABS at the ~uest of the OHshm-Racing C&ncil (ORC) 1978-1980out oftheir concern for ever lighter advanced cornposim boats snd the lack of suitable standards. At thatlime, several boats and lives had been lost ABS staff mfemedto the design and construction practicefor offshore racing yachts, reflected in designws’ and builders’ practice and to limited full scslemeasured load data d refined the results by tWdySiSof Illatly existing pen boats, and @ySiS ufdarnaged boat stmcturm. Advice and @dance on the scope, &tad and needs of the standmds weregiven by the Chahman aud two membtm of the International Technical Committee of the ORC,rwpmtively Olin Stephens,Gary Mull and Hans Steffensen.As the Guide was to provide fm sll possible hull materials, including advsnced cornposims, it wasessential that it be given in a direct engintig furmat of design loads and design stresses, based onply, laminate and COIEmaterhd mechmical propmties. Such a forrrwtpermits the designer to -ysee the influence of design loads, matmial mechanical propwties and structural arrangement on therequirements,thereby giving as much freedom as possible to achieve optimum use of rnatmials.The Guide gives hull structural design and construction stamkuds for tishore racing yachts and forcruising yachts. Boats that am to receive the ABS classification ~Al Yachting Semite, are m@rml tohave enginewing systems such as bilge system fuel oil system electrical system frm protection inwordance with the ABYC rwomrnendations. For sailing yachts over 100 feet in length the Guideand the ABYC standmds am augmented by parts of the Rules for Building snd Classing ReinforcedPlastic vessels.All Rules and Guides m in a continuous state of development to reflect exp-ience, advances intechnology, new mataiak, changes in building pmcdurw and occasionally to curtail exploitation ofloopholes. This is nowhtzt mm true than in the use of advanced composites for offshore racingyachts - slrwdy the development of additional in-house guidance to augment the Guide, suggests athird edition in the near future. It should be noted that the Coast Gusrd does not yet recognize theGuide as sn acceptable standard for a vessel to meet the requirements of Subchapter T.231 #~, , ,,.,-.,,. .

Rules andRegulationsMarine CompositesProposed Guide for Building and Classing High Speed Craft (Commercial,Patrol and Utility Craft)Since 1980, ABS has had specflc in-house guidance for the hull structure of planing sndsemi-planing crtit in commercial and governrmmt service.This Guide, for vessels up to 200 ft. in length, covers glass fiber reinforced plastic, advancedcomposite, ihwninum and steel hulls. Requirements are given in a direct engineering formatexpressed in terms of design pressures, design stresses, and material mechanical properties.Design planing slamming pressures for the bottom structure have been deve~oped for the workof Heller and Jasper [7-3] Savitsky and Brown, [7-4] Allen and Jones [7-5], and Spencer [7-6].Those for the side structure are based on a combination of hydrostatic Wd speed inducedhydrodynamic pressures. In establishing the bottom design pressures and dynamic componentsof side structure, distinction is made for example between passenger-carrying craft, generalcorrunercial craft, and mission type craft such as patrol boats. Design pressures for deckssuperstructures, houses and bulkheads are from ABS and industry practice.Design stresses, have been obtained from the ABS in-house guidance and from applying thevarious design pressures to many existing, proven vessels processed over the years by AIM. Inproviding requirements for advanced composites, criteria are given for strength in both 0° and9W axes of structural panels.Anticipating the desirability of extending the length of boats using standard or advancedcomposites, the Guide contains hull-girder strength requirements for vessels in both thedisplacement and planing modes. The former comes from current ABS Rules. The latter fromHeller and Jasper bending moments together with hull-girder bending stresses obtained byapplying these moments to many existing, proven planing craft designs. As might be expected,design stresses for the planing mode bending moments are datively low, reflecting design forfatigue strength. Particularly for fiber reinforced plastic boats, criteria were established forhull-girder stiffness, by which, one of the potential limitations of fiber reinforced plastic, lowtensile snd compressive modulii, can be avoided by proper design.Again, primarily for fiber reinforced plastic construction, there are extensive sections onmaterials and manufacturing.Requirements for structural detail considering local structural stability and local shear strengthare also included. For the frost time in any set of ABS standards, the Guide contains proposedcriteria for pordights and windows - for which, bmause of the empirical nature of development,we are seeking a comprehensive ~view and comment participation by industry. Distribution ofthe Guide for industry rwiew is imminent.Although the Guide contains speciiic, detailed stsndards for planing craft hull structures, it isnot confined to these form hulls and operational modes. Brief, general requirements for surfaceeffect, air cushion and hydrofoil craft are also included and will be developed into morespecfic detailed criteria over the next few years.232

Chapter SevenREFERENCEProposed Guide for High Speed and Displacement Motor YachtsAs with high speed commercial and government service craft, ABS has had in-house guidancefor many years for planing motor yachts. This has also been developed over the last few yearsinto the Guide for High Speed and Displacement Motor Yachts.The standards for high speed motor yachts parallel those for high speed commercial andgovernment service craft and the preceding description of the Guide for the high speedcommercial, patrol, and utility craft is equally applicable with the qualification that the designpressures for motor yachts reflect the less rigorous demands of this service.Probably, 80% to 90%, of the motor yachts today are, by dellnition of this Guide, high speed.However to provide complete standards, the Guide also includes requirements for displacementmotor yachts. Design loads and design stresses for these standards are essentially developedfrom ABS Rules for Reinforced Plastic Vessels, modified appropriately for advancedcomposite, aluminum and steel hulls and fine-tuned by review of a substantial number ofexisting proven, displacement hull motor yacht designs.In addition to hull structural standards, this Guide includes requirements for propulsion systemsand essential engineering systems. The hull part of this Guide is now complete and distributionfor industry review is imminent.ClassificationThis entails plan approval of the hull structural plans, including the building processdescriptions, essential engineering systems for both sail and power craft, and for power craft,plan approval of the main propulsion system.Following plan approval, the ABS surveyor inspects the boat during construction to verifycompliance with these approved plans, and with the appropriate ABS Rules or Guide. TheSurveyor also witnesses material tests, installation and testing of the propulsion system (formotor craft) and engineering systems (for sail and motor craft). The symbol ~ in front of AMSis required for commercial craft but is optional for recreational and certain government servicecraft. The symbol m indicates that the main propulsion engine, reduction gear, shafting,propellers and generators (over 100 kw) have been inspected by the ABS surveyor during theirconstruction, and certificates for their construction have been issued by ABS, On completionof the boat and compliance with all of the conditions of classification the boat is issued with aClassiilcation Certificate and bronze plaque. The boat is also included in the ABS Record ofClassed Vessels.In service, vessels are required to have ABS annual and special periodic surveys, as well assumeys after damage, to retain classification,Table 7-3 shows basic ABS classification symbols and various ABS classification notations.Figure 7-1 shows a flow chart outlining the classtilcation process.233

Rules and RegulationsMarine CompositesTable 7-3.SymbolKAlAl~ AMSAMSo EABS Classification Symbols [ABS]DeflnltlonHullplanapproval;hullconstructionandhullmaterialtestingunderABS surveyHull plan a proval; special ABS survey ofcompleted \ uIIPropulsion and essential engineering systemsapproval; repulsion system units manufacturedunder AB!survey, propulsion and engineeringsystems installed and tested under ABS surveyPropulsion and essential engineering systemsapproval; propulsion and en ineering systemsinstalled and tested under A%S surveyEquipment of anchors, cables and windlassesapproved in accordance with ABS Rules orGuide; materialand equipmenttested andinstalledunder ABS surveyApptOVadDesignerCODie8 GI [LHull& oo 3opieaPABS Technical StaffBuilder~4 Performanceo 7 ABS Survey StaffApproved1 Machinery Plans of Plan*9“ApprovedCopiesof PlansBoat DuringConstruction““7ln*pectlOn DuringConstruction &ITests and Trialsro 4[+ Engine Builder, etc. 1.v~gure 7-IShipping]Flow Chart for ABSClassificationProcess [Curry, American Bureau of,,.234,’J/ ,i” ;, .,.”!

Chapter SevenREFERENCEHull CertificationHull certification comprises plan approval of the hull structural plans, including the buildingprocess description and inspection of the hull during construction to verify compliance withthese approved plans, and with the appropriate Rules or Gujde. The Smrveyor also witnessesrequired hull material tests.On completion of the boat and compliance with all of the requirements for hull certification, theboat is issued with a Hull Construction Certificate and bronze plaque.Hull certification is confined to the hull construction and there are no ABS surveys of thevessel in service. Figure 7-2 shows the hull certdlcation procedure.Plan ApprovalPlan approval entails approval of hull structural plans and if desired, plan approval of thepropulsion system (for motor vessels) and engineering systems (for sail and motor vessels).There is no inspection by an ABS Surveyor during construction.IApprovedcopiesof PlansIDesignerABS Technical Staff 1l“ ‘d o2’Laminate MaterialTo&t ReportsApnrovedCopiesof Plan*I3o~>Approvedo Hull Construction, Opiee1 Sea Cock, Engineof PlansExhaust system plansITBuildero4InspectionDuringI Boat in Service IFigure 7-2Shipping]Flow Chart for ABS Hull Certification Process [Curry, American Bureau of,,.,235, ,+”!~,,=.

Conversion FactorsMarine CompositesLENGTHMultlply: By: To Obtain:Centimeters 0.0328 FeetCentimeters 0.3937 InchesFeet 30.4801 CentimetersFeet 0.30480 MetersInches 2,54 CentimetersMeters 3.28083 FeetMeters 39,37 InchesMeters 1.09361 YardsMils 0.001 InchesMils 25.40 MicronsMultiply:GramsGramsKilogramsKilogramsKilogramsKilogramsLongTons’Long Tons*Metric TonsOunces*Pounds*Pounds*Pounds*Pounds*Pounds*Tons*Tons*MASSBy:0.035272,205 X 10-335,272.2051.102 XI O-39.839 X 10-4101622402204,628.35453.60.45360.00054.464X 10-44.536 X 10-4907.22000Ounces*Pounds*Ounces*Pounds*Tons*Long Tons*KilogramsPounds*Pounds*GramsGramsKilogramsTons*Long Tons*Metric TonsKilogramsPounds’To Obtain:* These quantities are not mass units, but are often2used as such. Theconversion factors are based on o = 32.174 ftkec .236

Chapter SevenREFERENCEAREAMultlply: By: To Obtain:Squarecentimeters 1.0764 x 10-3 SquarefeetSquarecentimeters 0,15499 SquareinchesSquare centimeters 0.02403Square inches2(moment of area)(moment of area)Square feet 0.09290 Square metersSquare feet 929.034 Square centimetersSquare feet2 Square inches220736(moment of area)(moment of area)Square meters 10.76387 Square feetSquare meters 1550 Square inchesSquare meters 1.196 Square yardsSquare yards 1296 Square inchesSquare yards 0.8361 Square metersVOLUMEMultlply: By: To Obtain:Cubiccentimeters 3.5314 x 10-5 CubicfeetCubic centimeters z.~17 x 10-4 GallonsCubic centimeters 0.03381 OuncesCubic feet 28317.016 Cubic cmtirnetersCubic feet 1728 Cubic inchesCubic feet 7.48052 GallonsCubic feet 28,31625 LinersCubic inches 16.38716 Cubic centimetersCubic inches 0.55441 OuncesCubic meters 358314 Cubic feetCubic meters 61023 Cubic inchesCubic meters 1,308 Cubic yardsCubic meters 264.17 GallonsCubic meters 999,973 LitersCubic yards 27 Cubic feetCubic yards 0.76456 Cubic meters237 ,“

Conversion FactorsMarine CompositesIMultlply:Gramsper centimetersGrams per centimetersKilograms per meters3Kilograms per meters3Pounds per inches3Pounds per inchessPounds per feetaPounds per feet3DENSITYBy:0.0361362.4283.613 X 10-50,062432.768 X 104172816.025.787 X 10-4To Obtain:Poundsper inches3Pounds per feet3Pounds perinches3Pounds perfeet3Kilograms per meters3Pounds perfeet3Kilograms per meters3Pounds perinches3IFORCEMultiply: By: To Obtain:Kilograms-force 9.807 NewtonsKilograms-force 2.205 PoundsNewtons 0,10197 Kilograms-forceNewtons 0.22481 PoundsPounds 4.448 NewtonsPounds 0.4536 Kilograms-forcePRESSUREMultlply:Feetof saltwater(head)Feetof saltwater(head)Feetof saltwater(head)InchesofwaterInchesofwaterInchesofwaterPascalsPascalsPoundsperfeet2Poundsper feet2Pounds per inches2Pounds perinches2By:3064,32640.44444249,0825.2020.036130.020891.4504X 10-447.886.944 X 10-36895144To Obtain:PascalsPoundsperfeet2Poundsperinches2PascalsPoundsperfeet2Poundsperinches2Poundsperfeet2Poundsperinches2PascalsPounds perinches2PascalsPounds perfeet2Pascals= Newtons permeters2238

Chapter SevenREFERENCEWeights and Conversion Factors [Prhc@esof Naval Architecture]QuantityWatersalt Fresh Fuel I)lesel LubeoilGasollneCubicfeet perlongton 35 36 38 41.5 43 501I Gallons per long ton — 269,28 284.24 310.42 321,64 374.00Pounds per gallon — — 7.881 7.216 6.964 5.989Pounds per cubic feet 64 62.222 58.947 53.976 52.093 44.800Pounds per barrel — — 331 303 292.5 251.5Gallons605550454036302520151050— Verticalto Bottom ~ Vwticalto Top‘----’Horizontalto Bottom– - Horizontalto TopFigure 7-3 Volume Remaining in 55 Gallon Drums Based on Ruler Measurementsfrom the Top and Bottom for Drums in Vertical and Horizontal Positions [Cook, %’ycorPolyester Gel Coats and Resins]239

Conversion FactorsMarine CompositesPolyester Resin Conversion Factors[Cook, Po/ycor Polyester Gel Coats and Reshw]Multiply: By: To Obtain:Fluidounces MEK Peroxide* 32.2 Grams MEK Peroxide*Grams MEK Peroxide* .0309 Fluid ounces MEK Peroxide*Cubic centimetersMEK Peroxide*Grams MEK Peroxide’ 0.901.11 Grams MEK Peroxide*Cubic centimetersMEK Peroxide*Fluid ounces cobalt”” 30.15 Grams cobalt**Grams cobalt** 0,033 Fluid ounces cobalt**Grams cobalt** 0.98 Cubic centimeters cobalt**Gallon polyester resin+ 9.2 PoundsGallon polyester resint 13.89 Fluid ouncesGallon polyester resin+ 411 Cubic centimeters* 9% Active Oxygen** 6~0 Solution+ UnpigmentedMaterial Coverage Assuming No Loss[Cook, Polycor Polyester Gel Coats and l?eslns].00111600,00.63.0033534.01.90.0055320.03.10.01010160.06.30.01515107,09.40.0181889.011.20.0202080.012.50.0252564.015.60,.0303053.019.00,0313151.019.50.0606027.038.00,0626226.039.00240, “,.,, .,,. ., ,:‘!. . .

Chapter SevenREFERENCENon-woven E“Glass Reinforcement Designation ComparisonAdvance&Textlles, Brunswick. Technologies, Inc.Hexcel KnytexFiber OrlentatlonProduct %& Product %GF Product %&NEMP090 9.5 DB 090 9.3 *45°~ NEMP 120 12.4 DB 120 12.0 *45”~ NEWF 120 12.1 c 1200 1280 o“, 90”mNEMP 170 17,6 X 1800 18.0 DB 170 18.0 *45”I , INEWF 180 17.7 C 1800 18.0 0’,90”I NEMP240 24,2 I X 2400 24.0 I DB 240 25,2 I h45”NEWMP 230 22.8 CDB 200 22.7 ()”,*45”~ NEFMP230 22,8 DDB 222 22.5 90”, &45”g NEWMp 340 33,1 l-v 3400 34.0 CDB 340 33,9 l)”, ?45”+ NEFMP 340 33.1 DDB 340 34.7 90”, *45°I NEMPC 1208 19.2 I I DBM 1208 19.7 I *45”, 3/4 oz. matI NEWFC 1208 I CM 1208 18.8 I I 0“, 90”, 3/402, matI NEMPC 1708 24.4 I XM 1808 24.8 I DBM 1768 25.7 I +45”, 3/4 oz. mat1 I 1* NEMPC 1715 31.1 XM 1815 31,5 DBM 1715 31.2 I +45”, 11A oz. matI 1~ I N~wFc 1808 24.4 i CM 180824.8 CDM 1808 26.6 I 0°, 90°, 3/4oz. mat, 1 1gNEWFC 1810 26.6 I CM 1810 27.0 CDM 1810 28.8 0“, 90”, 1 oz. matI 1 1~. NEWFC 1815 31.2 CM 1815 31,5 I CDM 1815 33.4 O“, 90’, 1 Vz oz. matI , I~ NEMPC 2408 31.0 I XM 2408 30.8 I DBM2408 32.8 ~45”, 3/4oz. matI NEMPC 2415 37.8 I XM 2415 37.5 I DBM 2415 38.3 I A45”, 1M oz. matI NEWFC 2308 29.0 I CM 2408 30.8 I CDM 2408 33.6 t 0“, 90°, 3/4 oz. matNEWFC 2310 32.2 CM 2410 33,0 CDM 2410 35.9 0“, 90”, 1 oz. matI NEWFC 2315 36.7 I CM 2415 37,5 I CDM 2415 40.4 I 0°,90°, 114 oz. mat1 I 1NEWMPC 2308 29,5 CDBM 2008 30.4 I O“,+45”, %4oz. mat, 1 INEWMPC3408 40.2 I TVM 3408 40.8 I CDBM3408 42.1 0°,+45”, 3/4oz. mat241,,~,.

GlossatyMarine Compositesablation Tl_Edegradation,decompositionanderosionof materialcausedby high temperature,pressure, time, percent oxidizing species andvelocityof gas flow, A controlledlossof materinltoprotecttheunderlyingstructure.ablative plastic A materialthat absorbsheat(witha lowmateriallossandcharrate)throughadecompositionprocess (pyrolysis) that takesplaceat or nearthesurfaceexposedto theheat.absorption The penetrationinto the mass ofonesubstanceby another.Thecapillaryor cellularattmctionofadherendsurfacesto drawoff theliquidadhesivefilmintothesubstrate,accelerated test A test procedure in Whichconditionsare increasedin magnitudeto reducethe time requiredto obtaina result, To reproducein a short time the deterioratingeffect obtainedundernormalserviceconditions.accelerator A materialthat, when mixed with acatalystor resin, will speed up the chemicalreactionbetween the catalyst and the resin (eitherpolymerizing of resins or vukanization of robbers).Alsocalledpromoter.acceptance test A test, or series of tests, conductedby the procuring agency upon receipt ofan individual lot of materials to determinewhetherthe lot conformsto the purchaseorder orcontractor to determinethe degree of uniformityof the materialsuppliedby the vendor,or both.acetone In anFRPcontex~acetoneis primarilyuseful as a cleaning solvent for removal of uncuredresin from applicatorequipmentand clothing.This is a very flammableliquid.acoustic emission A measureof integrity of amaterial,as determinedby sound emission whena material is stressed. Ideally, emissions can becorrelatedwith defectsand/orincipientfailure.activator Anadditive used to promote and reducethe curingtime of resins. See also accelerator.additive Any substance added to another substance,usually to improve properties, such asplasticizers,initiators, light stabilizersand flameretardants.adherend A body that is held to another body,usuallyby an adhesive. A detail or part preparedfor bonding.advanced composites Strong,tough materialscreatedby combiningone or more stiff, highstrengthreinforcing fiber with compatible resinsystem, Advancedcompositescan be substitutedfor metals in many structural applications withphysical properties comparable or better thanaluminum.air-inhibited resin A resin by which surfacecures will be inhibitedor stoppedin the presenceof air.aging The effect on materials of exposure to anenvironmentfor an interval of time. The processof exposingmaterialsto an environmentfor a intervalof time.air-bubble void h entrapment within andbetween the plies of reinforcement or within abondline or encapsulatedarm, localized, noninterconnected,sphericalinshape.allowable Propertyvaluesused for designwitha 95 percentconfidenceintervak the “A” aUowableis the minimum value for 99 percent of thepopulation;and the “B” allowable,90 percent.alternating stress A stress varying betweentwo maximum valuw which are equal but withopposite signs, according to a law determinedintermsof the tie.alternating stress amplitude A test paramekrof a dynamic fatigue tEZLone-half thealgebraic difference between the maximum andminimumstressin one cycle.ambient conditions Prevailing environmentalconditions such as the surrounding temperature,pressureand relativehumidity,anisotropic Not isotropic. Exhibiting differentproperties when tested along axes in differentdirections,antioxidant A substance tha~ when added insmall quantities to the resin during mixing, preventsits oxidativedegradationand contributestothe maintenanceof its properties.aramid A type of highly orientedorganic materialderived from polyamide (nylon) but incorporatingaromaticring structure. Used prirnmil~as a high-strengthhigh-modulusfik. Kevlarand Nomex@are examplesof ararnids.areal weight The weight of fiber per unit ar~(widthx length)of tape or fabric.artificial weathering !rh~exposure of plssticsto cyclic, laboratoryconditions,consistingofhigh and low temperatures,high and low relativehumidities,and tdtmvioletradiantenergy,with or242 .,. -’.“* -’”;.,.,,..”,. .,,.,,

Chapter SevenREFERENCEwithout direct water spiny and moving air(wind),in an attempt to produce changesin theirproperties similar to those observedin long-termcontinuous exposure outdoors, The laboratoryexposure conditions are usually intens$led beyondthose encountered in actual outdoor exposure,in an attempt to achieve an acceleratedeffect.aspect ratio The ratio of length to diameter ofa fiber or the ratio of length to width in a structuralpanel.autoclave A closed vessel for conducting andcompleting a chemical reaction or other operation,such as cooling,underpressureand heat.bagging Applyingan impermeablelayer of fdmover an uncured part and sealing the edges wthat a vacuumcan be drawn.balanced construction Equal parts of warpand fill in fiber fabric. Constructionin which reactionstotensionand compressionloads result inextension or compressiondeformationsonly andin which flexuml loads produce pure bending ofequalmagnitudein axial and lateml directions.balanced larnhate A composite in which alllaminae at angles other than 0° and 90° occuronly in + pairs (not necessarilyadjacent)and aresymmetricalaroundthe centerline.Barcol hardness A hardness value obtainedby measuring the resistance to penetmtion of asharp steel point under a spring load. The instrument,called a Barcol impresser, gives a directreading on a scale of O to 100. The hardnessvalue is often used as a measureof the degreeofcure of a plastic.barrier film Thelayer of film used to permitremoval of air and volatiles from a compositelay-upduring cure while minimizingresin loss.bedding compound White lead or one of anumber of commerciallyavailableresin compoundsusedtoforma flexible,waterproofbaseto setfittings,bias fabric Warpand fill fibersat an angletothelengthof thefabric,biaxial load A loading conditionin which alaminateis stressedin twodifferentdirectionsinitsplane,bidirectional laminate A reinforced~lasticlaminate with the fibers oriented in two-directionsin its plane. A cross laminate.binder me resinor cementingconstituent (of aplastic compound) that holds the other componentstogether. The agent applied to fiber mator preforms to bond the fibers before laminatingor molding.bleeder cloth A woven or nonwoven layer ofmaterial used in the manufacture of compositeparts to allow the escape of excess gas and resinduring cure. The bkder cloth is removed afterthe curing process and is not part of the ~alcomposite.blister &I elevation on the surface of an adherendcontainingair or water vapor, somewhatresemblingin sha~ a blister on the human skin.IWboundaries may be indefinitely outlined, andit may haveburst and becomeflattened.bond Theadhesion at the interfacebetween twosurfaces. To attach materials togetherby meansof adhesives.bond strength The amount of adhesion betweenbonded surfaces. The stress required toseparate a layer of material from the base towhich it is bonded as measured by load/bondarea. See also peel strength.bonding angles An additional FRP laminate,or an extensionof the laminate used to make upthe joined member, which extends onto the existinglaminate to attach additionalitems such asMining, bulkheadsand shelves to the shell or toeach other.boundary conditions Load and environmentalconditionsthat exist at the boundaries. Conditionsmust be specifiedto perform stress analysis.buckling A mode of failure generally characterizedby an unstable lateral material deflectiondue to compressiveaction on the structural elementinvolved.bulk molding compound (BMC) Thermosettingresinmixed with strand reinforcement,fillers, etc. into a viscouscompoundfor compressionor injectionmolding.butt joint A type of edge joint in which theedge faces of the two adherendsare at right anglesto the other facesof the adherends.carbon Theelement that provides the backbonefor all organic polymers. Graphite is a moreordered form of carbon, Diamondis the densestcrystallineform of carbon.“,.-.243#J - .,.> .$,

GlossaryMarine Compositescarbon fiber Fiber produced by the pyrolysisof organic precursor fibers, such as rayon,polyacrylonitrile (PAN), and pitch, in an inertenvironment. The term is often used interchangeablywith the term graphite; howevercarbon fibers and graphite fibers differ. Thebasic differences lie in the temperature atwhich the fibers are made and heat treated,and in the amount of elemental carbon produced.Carbon fibers typically are carbonizedin the region of 2400’F and assay at 93 to95% carbon, while graphite fibers are graphitizedbetween 3450° and 4500”F and assay tomore than 99Voelemental carbon.carpet plot A design chart showing the uniaxialstiffnessor strength as a function of arbitraryratios of O,90, and k 45 degreeplies.catalyst A substance that changes the rate ofa chemical reaction without itself undergoingpermanent change in composition or becominga part of the molecular structure of theproduct. A substance that markedly speedsup the cure of a compound when added inminor quantity.cell In honeycombcore, a cell is a single honeycombuni~ usuallyin a hexagonalshape.Cd Size The diameter of an inscribed circlewithin the cell of a honeycombcore.Charpy impact test A test for shock loadingin which a centrallynotchedsamplebar is held atboth ends and brokenby striking the back face inthe sameplane as the notch.chain plates Themetallic plates, emkdded inor attached to the hull or bulkhead, used toevenly distributeloads from shroudsand stays tothe hull of sailing vessels.chopped strand Continuous strand yam orroving cut up into uniformlengths, usually fromW2 inch long. Lengths up to M inch are calledmilled fibers,closed cell foam Cellularplastic in which individualcells are completelysealed off from adjacentcells.cocurirtg The act of curing a composite laminateand simultaneouslybonding it to some otherpreptyedsurface, See also secondarybonding,coin test Using a coin to test a laminate indifferent spots, listening for a change in sound,which wouldindicatethe presenceof a defect. Asurprisingly accurate test in the hands of experiencedpersonnel.compaction The application of a temporaryvacuum bag and vacuum to remove trapped airand compactthe lay-up.compliance Measurement of softness as opposedto stiffne+wof a material. It is a reciprocalof the Young’s modulus, or an inverse of thestiffnessmatrix.composite material A combination of twoor more materials (reinforcing elements,fillers and composite matrix binder), differingin form or composition on a macroscale. Theconstituents retain their identities; that is,they do not dissolve or merge completely intoone another although they act in concert.Normally, the components can be physicallyidentified and exhibit an interface betweenone another.compression molding A mold that is openwhen the material is introduced and that shapesthe materialby the presenceof closing and heat.compressive strength The ability of a material@resist a force that tends to crush or buckle.The maximum compressive load sustained by aspecimen divided by the original cross-sectionalarea of the specimen.compressive stress The normal stress causedby forces dired.ed toward the plane on whichthey act.contact molding A process for molding reinforcedplastics in which reinforcementand resinare placed on a mold, Cure is either at roomtemperatureusing a catalyst-promotersystem orby heating in an oven, without additional pressure.constittIent materials Individual materialsthat make up the composim mate~a.L e.g.,graphite and epoxy are the constituent materialsof a graphite/epoxycompositematerial.copolynler A long chain molecule formed bythe reactionof two or more dissimilarmonomers.core The central member of a sandwich constructionto which tbe faces of the sandwichareattached. A charmelin a mold for circulationofheat-transfermedia. Male part of a mold whichshapesthe inside of the mold.corrosion resistance The ability of a materialto withstand contact with ambient naturalfactors or those of a particular artificiallycreated atmosphere, without degra&tion orchange in properties. For metals, this couldbe pitting or rusting; for organic materials, itcould be crazing.Count For fabric, number of warp and fallingyarns per inch in woven cloth. For yam sizebased on relationof lengthandweight.244 ,,

Chapter SevenREFERENCEcoupling agent Any chemical agent designedto react with b“oththe reinforcementand matrixphases of a composite material to form or promotea strongerbond at the interface.crazing Region of uhrafine cracks, which mayextend in a network on or under the surfaceof aresin or plastic material. May appear as a whi~band,creep The change in dimension of a materialunder load over a period of time, not includingthe initial instantaneous elastic deformation.(Creep at room temperatureis called cmldflow.)The time dependentpart of strain resulting froman appliedstress.cross-linking Applied to polymer molecules,the setting-up of chemical links between themolecular chains. When extensive, as in mostthmrnosettingresins, cross-linkingmakes one infusiblesupermoleculeof all the chains,C-scan The back-and-forthscanning of a specimenwith ultrasonics. A nondestructivetestingtechnique for finding voids, delamination, defectsin fiber distribution,and so forth.cure To irreversibly change the properties of athermosetting resin by chemical reaction, i.e.condensation, ring closure or addition. Curingmay be accomplished by addition of curing(crosslinking)agents,with or withoutheat.curing agent A catalyticor reactive agent that,when added to a resin, causes polymerization.Also called a hardener,damage tolerance A design measure of crackgrowthrate. Cracksin darnagetolerant designedstructures are not permitted to grow to criticalsize duringexpectedserviceMe.delamination Separationof the layers of materialin a laminate,either local or coveringa wi&area. Can occur in the cure or subsequentlife,debond Area of separation within or betweenplies in a laminate, or within a bonded joint,caused by contamination, improper adhesionduring processing or damaging interlaminarstresses.denier A yarn and filamentnumberingsysteminwhich the yarn number is numerically equal tothe weight in grams of 9000 mews. Used forcontinuousfilaments where the lower the denier,the finer the yamdimensional stability Ability of a plastic partto retain the precise shape to which it wasmolded,cast or otherwisefabricated,dimples Small sunken dots in the gel coat surface,generallycausedby a foreignparticlein thelaminate.draft angle The angle of a taper on a mandrelor mold that facilitates removal of the finishedpart.drape The ability of a fabric or a prepreg toconformto a contouredsurface.dry laminate A larninaw containing insufficientresin for completebonding of the reinforcement.See also resin-starvedarea.ductility The amount of plastic strain that amaterial can withstandbefore fracture. Also, theability of a material to &form plastically beforefracturing.E-glass A family of glasses with a calciumaluminolmrosilicatecompositionand a maximumalkali content of 2.0%. A general-purposefiberthat is most often used in reinforcd plastics, andis suitable for electrical laminates because of itshigh resistivity. Also calledelectricglass.elastic deformation The part of the totalstrain in a stressedbody that disappearsupon removalof the stress.elasticity That propertyof materialsby virtue ofwhich they tend to recovertheir original size andshape after removal of a fome causing deformation.elastic limit The greatest shess a material iscapable of sustaining without permanent strainremainingafter the completereleaseof the stress.A material is said to have passed its elastic limitwhen the load is sufficient to initiate plastic, ornonrecoverable,deformation.elastomer A materialthat substantiallyrecoversits original shape and size at room temperatureafterremovalof a deformingforce.elongation Deformation caused by stretching.The fractional increase in length of a materialstressedin tension. (Whenexpressedas percentageof the original gage length, it is called percentageelongation.)encapsulation The enclosure of an item inplastic. Sometimesused spcciiicallyin referenceto the enclosure of capacitors or circuit boardmodules.,--”,245 ,.*” “’1,

GlossaryMarine Compositesepoxy plastic A polymerizablethem-nosetpolymercontainingone or more epoxick groups andcurable by reaction with amines, alcohols,phenols, carboxylic acids, acid anhydrides, andmercaptans. An important matrix resin in compositesand structuraladhesive.exotherm heat The heat given off us the resultof the action of a catalyston a resin,f~hre criterion Empirical description of thefailure of composite materials subjected to complexstate of stresses or strains. The most commonlyused are the maximum stress, the maximumstrain,and the quadraticcriteria.failure envelope Ultimate limit in combinedstress or strain state dei?medby a failurecriterion.fairing A member or structure, the primaryfunction of which is to streamlinethe flow of afluid by producing a smooth outline and to reducedrag,as in aircraftframesand boat hulls,fatigue The failureor decay of mechanicalpropertiesafter repeated applications of stress,Fatigue tests give informationon the ability of amaterial to resist the development of cracks,which eventuallybring about failureas a result ofa large numberof cycles,fatigue life The number of cycles of deformationrequired to bring about failures of the testspecimen under a given set of oscillating conditions(stressesor strains).fatigue limit The stress limit below which amaterial can be stressed cyclicallyfor an infinitenumberof times withoutfailure,fatigue strength The maximumcyclicaIsmessa material can withstand for a given number ofcycles before failure occurs. The residualstrengthafterbeing subjectedto fatigue.faying surface The surfaces of materials incontact with each other and joined or about to bejoined together.felt A fibrous material made up of interlockingfibers by mechanicalor chemicalaction,pressureor heat, Felts may be made of cotton, glass orother fibers.fiber A general term used to refer to filamentarymaterials. Often, fiber is used synonymouslywith filament,It is a general term for a filamentwith a finite length that is at least 100 times itsdiameter, which is typically 0,004 tQ 0.005 inches,In most cases it is prepared by drawingfrom a molten bath, spinning, or depsition on asubstrate. A whisker, on the other han~ is ashort single-crystalfiber or fhrnent made from avarietyof materials,with diametersranging tlom40 to 1400 micro inches and aspect ratios between100 and 15000. Fibers can be continuousor specific short lengths (discontinuous), normallyless than % inch.fiber content The amount of fiber present in acomposite. This is usually expressed as a percentagevolumefractionor weight fractionof thecomposite.fiber courtt fie number of fibers per unitwidth of ply present in a speciiled section of acomposite,fiber direction The orientationor alignmentofthe longitudinalaxis of the fiber with respectto astatedreferenceaxis.fiberglass An individual filament made bydrawingmoltenglass. A continuousHament is aglass fiber of great or indefinitelength. A staplefiber is a glass fiber of relatively short length,generally less than 17 inches, the length relatedto the formingor spinningprocessused.fiberglass reinforcement Major materialused to reinforce plastic. Available as mat,roving, fabric,and so forth, it is incorporatedintoboth thermoses and thermoplastics,fiber-reinforced plastic (FRP) A generalterm for a compositethat is reinforcedwith cloth,mat, strandsor any otherfiber form.fiberglass chopper Chopper guns, long cuttersand roving cutters cut glass into strands andfibers to be used as reinforcementin plastics.Fick’s equation Diffusion equation for moisturemigration. This is analogousto the Fourier’sequationof heat conduction.filament Thesmallest unit of fibrous material.The basic units formed during drawingand spinning,which are gathered into strands of fiber foruse in composites. Filaments usually are of ex-@emelength and very small diameter, usuallyless than 1 roil. Normally,Wunents are not usedindividually. Some textile filamentscan functionas a yarn when they are of sufficientstrengthandflexibility.filament winding A process for fabricating acomposite structure in which continuous reinforcements(filament, wire, yarn, tape or other)either previously impregnated with a matrixmaterial or impregnatedduring the winding, areplaced over a rotating and removable form ormandrel in a prescribed way to meet certain246

Chapter SevenREFERENCEstress conditions. Generally, the shape is a surfaceof revolution and may or may not includeend closures, When the required number of layersis applied, the wound form is cured and themandrelis removed.f“l]l Yarn oriented at right angles to the warp in awovenfabric.filler A relatively inert substance added to amaterialto alter its physical,mechanical,thermal,electricaland other properdes or to lower cost ordensi~. Sometimesthe term is used specticallyto meanparticulateadditives.filk?t A rounded filling or adhesive that fills thecorneror angle wheretwo adherendsarejoined.filling yarn The mnsverse threads or fibers ina woven fabric, Those fibers mnning perpendicularto the warp, Also calledweft.finish A mixture of materials for treating glassor other fibers, It contains a coupling agent toimprove the bond of resin to the fiber, and usuallyincludes a lubricant to prevent abrasion, aswell as a binder to promote strand integrity.With graphite or other filaments, it may performany or all of the abovefunctions.first-ply-failure First ply or ply group thatfails in a multidirectional laminate. The loadcorresponding to this failure can be the designlimit load.flame retardants Certain chemicals that areused to reduce or eliminate the tendency of aresin to bum.fish eye A circularseparationin a gel coat filmgenerally caused by contaminationsuch as silicone,oil, dust or water,flammability Measureof the extent to which amaterialwill supportcombustion,flexural modulus TIIeratio, within the ekwticlimit, of the applied stress on a test specimen inflexure to the correspondingstrain in the outermostfibersof the specimen.flexural strertgth The maximum stiess thatcan be borne by the surface fibers in a beam inbending, The flexural strength is the unit resistanceto the maximum load before failure bybending,usually expressedin forceper unit area.flOW The movement of resin under pressure, allowingit to fdl all parts of the mold. Thegradual but continuous distortion of a materialunder continued load, usually at high temperatures;alsocalledcreep.foam-in-place Refers to the deposition offoams when the foaming machine must bebrought to the work that is “in place: as opposedto bringing the work to the foaming machine.Also, foam mixed in a containerand poured in amold, whereit rises to fill the cavity.fracture toughness A measureof the damagetoleranceof a materialcontiing initial flaws orcracks, Used in akcraft structural design andanalysis.gel The initial jellylike solid phase that developsduring the formationof a resin from a liquicL Asemisolidsystem consistingof a networkof solidaggregatesin which liquid is held.gelation time That interval of time, in connectionwith the use of synthetic thermosettingresins,extendingtim the introductionof a catalystinto a liquid adhesivesystemuntil the start of gelformation, Also, the time under application ofload for a resin to reach a solid state.gel coat A quick settingresin appliedto the surfaceof a mold and gelled before lay-up. The gelcoat becomes an integral part of the ftih larrrinate,and is usually used to improve surface appearanceandbonding.glass finish A materialappliedto the surfaceofa glass reinforcement to improve the bond betweentheglass and the plastic resin matrix.glass transition The reversible change in anamorphouspolymer or in an amorphousregionsof a partially crystalline polymer horn, or to, aviscous or rubbery condition to, or from, a hardto a relativelybrittle one,graphite To crystalline allotropic form of carb-.Gr~n strength The ability of a material,whilenot completelycured,set or sintered,to undergoremoval from the mold and handlingwithoutdistortion.h~d lay-up llw processof placing(andworking)successiveplies of reinforcingmaterialofresin-impregnatedreinforcementin positionon amoldby hand.hardener A substanceor mixtureadded to aplastic compositionto promote or control thecuringactionby takingpm in it.harness satin Weaving pattern producing asatin appearance. ‘Eight-harness”means the247/,~ .”.’,.,‘i ~.’.. ..,.+, ,--

GlossaryMarine Compositeswarp tow crosses over seven fill tows and underthe eighth(repeatedly).heat build-up The temperaturerise in part resultingfrom the dissipation of applied strainenergyas heat.heat resistance The propertyor ability of plasticsand elastomers to resist the deterioratingeffectsof elevatingtemperatures.homogeneous Descriptive term for a materialof uniform compositionthroughout, A mediumthat has no intmal physicalboundaries, A matirialwhose properties are constant at every point,that is, constant with respect to spatial coordinates(but not necessarily with respect todirectionalcoordinates).honeycomb Manufacturedproduct of resin impregnatedsheet material (paper, glass fabric andso on) or metal foil, formed into hexagonalshapedcells. Used as a core material in sandwichconstructions,hoop stress The circumferential stress in amaterial of cylindricalform subjectedto internalor externalpressure.hull liner A separate interior hull unit withbunks, berths, bulkheads, and other items of outfitpreassembledthen insertedinto the hull shell,A liner can contribute varying degrees of stiffnessto the hull through careful arrangementofthe berths and bulkheads.hybrid A composite laminate consisting oflarninaeof two or more composite material systems.A combination of two or more differentfibers, such as carbon and glass or carbon andaramid,into a structure. Tapes, fabricsand otherforms may be combine@usually only the fikersdiffer,hydrothermal effect Change in propertiesdue to moisture absorption and temperaturechange.hysteresis The energy absorbed in a completecycle of loading and unloading. This energy isconverted horn mechanical to frictional energy(heat),under shockloading.illlpact test Measureof the energynecessarytofracture a standard notched bar by an impulseload.impregnate In reinforced plastics, to satumtethe reinforcementwith a resin.inclusion A physical and mechanical discontinuityoccurring within a mataial or parL usuallyconsistig of solid, encapsulated foreignmaterial. Inclusions are often capable of transmittingsome structuralstressesand energyfields,but in a noticeably different degree from theparentmaterial.inhibitor A material added to a resin to slowdown curing. It also retards polymerhtion,therebyincreasingshelf life of a monomer.injection molding Method of forming a plasticto the desired shape by forcing the heat-softenedplastic into a relatively cool cavity underpressure.interlatninar Descriptiveterm pertaining to anobject (for example, voids), event (for example,fracture), or potential field (for example, shearstress) referenced as existing or occurring betweentwoor more adjacentIaminae.i~terlaminar shear Shearingforcetendingtoproduce a relative displacementbetween twolwninaein a laminatealongtheplaneof theirinterface.intralaminar Descriptivetermpertainingto anobject(for example,voids),event(for example,hcture), or potmtial field (for example,temperatm gradient)existingentirelywithin asinglelarninawithoutreferenceto any adjacentlamirlae.isotropic Havinguniformpropertiesin all dirwtions,The measuredpropertiesof an isotropicmaterialareindependentof theaxisof testing.Izod impact test A test for shockloadinginwhicha notchedspecimenbar is heldat oneendandbrokenby striking,and the energyabsorbedis measured.ignition loss The difference in weight beforeand after burning, As with glass, the burning offof the binder or size.impact strertgth The ability of a material towithstand shock loading. The work done onfracturinga test specimen in a spec~led mannerkerf Thewidth of a cut made by a saw blade,torch, waterjet, laser beam and so forth.Kevlar@ An organic polymer composed of ar~matic polyamides having a para-type orientation(parallel chain extending trends from each aromaticnucleus).

Chapter SevenREFERENCEknitted fabrics Fabrics producedby interlopingchainsof yarn.lamina A singleply or layer in a laminatema&up of a series of layers (organiccomposite). Aflat or curvedsurfacecontainingunidirectionalfibers or wovenfibers embeddedin a matrix.laminae Plural of laminalaminate To unite laminae with a bondingmaterial, uswdly with pressure and heat (normallyused with referenceto flat sheets, but alsorods and tubes). A product ma& by such bonding.lap joint A joint made by placing one adherendpartly over another and bonding the overlappedportions.lay-up The reinforcing material placed in positionin the mold, The processof placing the reinforcingmaterial in a position in the mold. Theresin-impregnatedreinforcement. A descriptionof the component materials, gametry, and soforth, of a laminate.load-deflection curve A curve in which theincreasingtension, compression,or flexuralloadsare plotted on the ordinate axis and the deflectionscausedby those loads are plotted on the abscissaaxis,loss on ignition Weightloss, usuallyexpressedas percent of total, after burning off an organicsizing from glass films, or an organicresin froma glass fiber laminate,10W-pI’6’SSUre ktdlI@W In general,laminatesmolded and cured in the range of pressuresfrom 400 psi down to and includingpressureobtainedbythe mere contactof the plies.macromechanics Structural behavior of compositelaminatesusing the laminatedplate theory.The fiber and matrix within eachply are smearedand no longer identifiable,mat A fibrous material for reinforced plasticconsisting of randomly oriented chopped tllamems,short fibers (with or without a carrierfabric),or swirled filaments loosely held toget.lwwith a binder. Available in blankets of v~ouswidths, weights and lengths, Also, a sheetformed by filament winding a single-hoopply of249fiber on a mandrel, cutting across its width andlaying out a flat sheet.matrix The essentially homogeneous resin orpolymer material in which the fiber system of acompositeis embeddecLBoth thermoplasticandthermosetresins maybe used, as well as metals,ceramicsand glass.mechanical adhesion Adhesion between swfaces in which the adhesive holds the parts togetherbyinterlockingaction.mechanical properties The properties of amaterial,such as compressiveor tensile strength,and modulus,thatare associatedwithelasticandinelastic reaction when force is applied. The individualrelationshipbetweenstressandmain.mek peroxide (MEKP) Abbreviation forMethyl Ethyl Ketone PeroxiW, a strong oxidizingagent (freeradical source)commonlyused asthe catalystfor polyestersin the FRP industry.micromechanics Calculation of the effectiveply propertiesas functionsof the fiber and matrixproperties. Some numericalapproachesalso providethe stress and strain within each constituentand those at the interface.mil The unit used in measming the diameter ofglass fiber strands, wire, etc. (1 mil = 0.001inch).milled fiber Continuous glass strands hammermilted into very short glass fibers. Useful as inexpensiveffler or anticrazingreinforcing fillersfor adhesives,modulus of elasticity TIE ratio of stress orload applied to the strain or deformation producedin a materialthat is elasticitydeformed. Ifa tensile strength of 2 hi results in an elongationof l%, the modulusof elastici~ is 2,0 ksi dividedby 0.01 or 200 ksi. Also called Young’s modulus.moisture absorption The pickup of watervapor from air by a material, It relates only tovapor withdrawnfrom the air by a material andmust be distinguished tiom watm absorption,which is the gain in weight due to the take-up ofwatmby immersion.moisture content The amount of moisture ina material determined under prescribed conditionsand expressedas a percentageof the massof the moist specimen, that is, the mass of thedry substanceplus the moisturepresent,mold The cavity or matrix into or on which theplastic composition is placed and from which ittakes form, To shapeplastic pmls or iinished articlesby heat and pressure. The assemblyof all“,... ..~.,/’ .“

GlossaryMarine Compositesparts that function collectively in the moldingprocess.mold-release agent A lubrican~ liquid orpowder (often silicone oils and waxes), used topreventthe stickingof moldedarticlesin the cavity,monomer A single moleculethat can react withlike or unlike moleculesto fonma polymer. Thesmallest repeating structure of a polymer (mer).For additionalpolymers,this repmsemtsthe originalunpolymerizedcompound.sensitivityis usually associatedwith brittle materisls.orange peel Backside of the gel coatod surfacethat takes on the rough wavy textureof an orangepeel,orthotropic Having three mutually perpendicularplaues of elasticsymmetry,netting analysis Treatingcompositm likefibers without matrix, It is not a mechanicalanalysis,and is not applicableto composites.non-air-inhibited resin A resin in which thesurface cure will not be inhibited or stopped bythe presence of air. A surfacingagent has beenadded to exclude air from the surface of theresin.nondestructive evaluation (NDE) Broadlyconsidered synonymous with nondestructive inspection(NIX). More specifically,the analysisof NDI findings to determinewhether the materialwill be acceptablefor its function.nondestructive inspection (NDI) Aprocessor procedure,such as ultrasonicor radiographicinspection,for determiningthe quality ofcharacteristics of a material, part or assembly,without permanently altering the subject or itsproperties, Used to find internal anomalies in astmcturewithoutdegradingita properties,nonwoven fabric A planar textile structureproducedby loosely compressingtogetherfibers,yarns, rovings, etc. with or without a scrirnclothcarrier. Accomplishedby mechanical,chemical,thermal, or solvent means and combinationsthereof,non-volatile material Portion remaining assolid under specific conditions short of decomposition,normal stress The stress component that isperpendicularto the plane on which the forcesact.notch sensitivity The extent to which the sensitivityof a material to fracture is increased bythe presence of a surface nonhomogeneity,suchas a notch, a stiddenchangein section,a crackora scratch. Low notch sensitivity is usually associatedwith ductile materkds, and high notch250PWM1 The designationof a section of FRP shellplating, of either single-skin or sandwich consmuction,bondedby longitudinal and transversestiffenersor other supportingstructures.peel ply A layer of resin-bee material used toprokct a laminatefor later secondarybonding.peel strength Adhesive bond strength, as inpounds per inch of width, obtained by a slressappliedin a peelingmode.permanent set The deformation remainingafter a specimen has been stressed a prescribedamountin tension,compressionor shearfor a definitetime period. For creep tests, the residualunrecoverabledeformationafter the load causingthe creep has been removed for a substantialanddeftite Wriod of time, Also, the increase inlength,by which an elastic materialfails to retarnto original length afterbeing stressedfor a standardperiod of time.permeability The passage or diffusion (or rateof passage)of gas, vapor, liquid or solid througha barrier without physicallyor chemictdlyaffectingit.phe~olic (phenolic resht) A therrnosettingresin produced by the condensation of an aromaticalcohol with an aldehyde, particularly ofphenol with formaldehyde, Used in hightemperatumapplicationswith various tiers andreinforcements,pitch A high molecularweight material left as aresidue from the destructive distillation of coaland petroleumproducts, Pitches are used as basematerials for the manufacture of certain highmoduluscarbon fibers and as matrix precursorsfor carbon-carboncomposites.plasticity A property of adhesives that allowsthe material to be deformed continuously andpermanentlywithoutrupture upon the application.-.“ < ., ..> J., j, “,+’

Chapter SevenREFERENCEof a force that exceeds the yield value of thematerial,plain weave A weaving pattmn in which thewarp and fdl fibers alternate; that is, the reptpattern is warp/fwwarp/13JL Both faces of aplain weave are identical. Propertiesare significantlyreducedrelative to a weavingpat~m withfewercrossovers,p]y In general, fabrics or felts consisting of oneor more layers (laminates). The layers that makeup a stack. A singlelayer of prepreg.PoiSSOrl’s ratio The ratio of the change inlateral width per unit width to change in axiallengthper unit length causedby the axial stretchingor stressing of the matahl. The ratio oftmnsversestrain to the correspondingaxial strainbelow the proportionallimit.polyether etherketone (PEEK) A lineararomatic crystalline thermoplastic. A compositewith a PEEK matrix may have a continuoususetemperatureas high as 480!F.polymer A high molecularweight organiccompound,natural or synthetic, whose structure canbe representedby a repeated small unit, the mer,Examples include polyethylene,rubber and cellulose.Synthetic polymers are formed by additionor condensation polymerization of monomers,Some polymers are elastomem,some areplastics and some are fibers. When two or moredissimilarmonomersare involved,the product iscalled a copolymer. The chain lengths of commercialthermoplasticsvaryfrom near a thousandto over one hundred thousand repeating units,Thermosetting polymers approach infinity aftercuring, but their resin precursors, often calledprepolymers,maybe a relativelyshort six to onehundred repeating units before curing. Thelengths of polymer chains, usually measuredbymolectdar weight, have very signiibnt effectson the performance properties of plastics andprofoundeffectson processibility,polymerization A chemical reaction in whichthe molecules of a monomer are linked togetherto form large moleculw whose molecularweightis a multiple of that of the original substance.When two or more monomers are involved, theprocessis calledcopolymerization.polyurethane A thermosetting resin preparedby the reactionof disocyanatcswith polola,polyamides,alkydpolymersandplyetherpolymers,porosity Having voids; i,e., containing pwketsof trapped air and gas after cure. Its measurementis the same as void content, It is commonlyassumedthat porosityis freelyand uniformlydis-tributedthroughoutthe laminate.postcure Additional elevated-temperaturecure,usuallywithoutpressure,to improvefinal propertiesand/or complete the cure, or decrease thepercentageof volatiles in the compound. In certainresins, complete cure and ultimate mechanicalproperties are attained only by exposure ofthe cured resin to higher mmperaturesthan thoseof curing.pOtlife Thelength of time that a catalyzedthermosettingresin system retains a viscosity lowenough to be used in processing. Also calledworkinglife.prepreg Either ready-to-mold material in sheetform or ready-to-windmaterial in roving form,which may be cloth, mat, unitiectional fiber, orpaper impregnatedwith resin and stored for use.The resin is partially cured to a B-stage and suppliedto the fabricator, who lays up the finishedshape and completesthe cure with heat and pressure,The two distinct types of prepregavailableare (1) commercialprepregs, where the roving iscoated with a hot melt or solvent system to producea specfic product to meet specificcustomerrequirements; and (2) wet prepreg, where thebasic resin is installed without solvents or preservativesbutbaa limitedroom-temperatureshelflife.pressure bag molding A process for moldingreinforcedplastics in which a tailor@ flexiblebag is placed over the contact lay-up on themold, sealed, and clamped in place. Fluid pressure,usually provided by compressed air orwater, is placed against the bag, and the part iscured,pultrusion A continuous process for manufacturingcomposites that have a constant crosssectionalshape. The process consists of pullinga fiber-reinforcingmaterial through a resin impregnationbath and through a shapingdie, wherethe resin is subsequentlycured.quasi-isotropic laminate A laminate approximatingisotropy by orientation of plies inseveralor moredirections.251,,“”.,.-. .......~,, ‘>.~~ ./,,,f+~’ k ,,

GlossaryMarjne Compositesranking Orderingof laminatesby strength,stiffnessor others.reaction injection moldhtg (RIM) Aprocess for molding polyurethane, epoxy, andother liquid chemicalsystems. Mixing of two tofour componentsin the proper chemical ratio isaccomplished by a high-pressure impingementtypemixing head,tlom which the mixed materialis deliveredinto the mold at low pressure,whereit reacts (cures).reinforced plastics Molded, formed filamentwound,tape-wrapped, or shaped plastic partsconsisting of resins to which reinforcing fibers,mats, fabrics, and so forth, have bem addedbefore the forming operation to provide somestrength properties greatly superior to those ofthe base resin,resin A solid or pseudosolid organic material,usually of high molecularweight, that exhibits atendency to flow when subjected to stress. Itusually has a softening or melting range, andfractures conchoidally. Most resins are poly.mers. In reinforcedplastics, the materialused tobind together the reinforcement materia~ thematrix, See also polymer,resin content The amount of resin in a laminateexpressed as either a percentage of totalweightor total volume.resin-rich area Locrdizedareafilled with resinand lackingreinforcingmaterial.resin+tarved area Locdized area of insufficientresin, usually identit%d by low gloss, dryspots, or fiber showingon the surface.resin transfer molding (RTM) A processwherebycatalyzedresin is transferredor injectedinto an enclosed mold in which the fiberglassreinforcementhasbeen placed,roving A number of yarns, strands, tows, orends collectedinto a padlel bundle with little orno twist.sandwich constructions panels composedofa lightweightcore material, such as honeycomb,fOSrned@tiC, and SOforth,to whichtwo relativelythin, dense, high-strengthor high-stiffnessfacesor skins are adhered.252scantling Thesize or weight dimensionsof thememberswhich make up the structureof the vessel,secondary bonding The joining together, bythe process of adhesivebonding, of two or morealready cured composite parts, during which theonly chemical or thermal reaction occurring isthe curingof the adhesiveitself.secondary structure Secondary structure isconsideredthat which is not involved in primarybending of the hull girder, such as &ames,girders, webs and bulkheads that are attachedbysecondarybonds.self-extinguishing resin A resin formulationthat will burn in the presenceof a flame but willextinguishitself within a specilkl time after theflameis removed.set The irrecoverableor pecmanentdeformationor creep *r complete release of the force producingthedeformation.set up To harden, as in curing of a polymerresin.S-glass A magnesium alurninosilicatecompositionthat is especially designed to provide veryhigh tensile strengthglass filaments. S-glassandS-2 glass fibers have the same glass compositionbut differentfinishes (coatings). S-glass is madeto more &manding specifications, and S-2 isconsideredthe commercialgrade.shear h action or stress resulting from appliedforces that causes or tends to cause two contiguousparts of a body to slide relative to each otherin a direction parallel to their plane of contact.In interlarninar shear, the plane of contact iscomposedprimarilyof resin.shell The watertightboundaryof a vessel’shull.skht Generally,a term used to describeall of thehull shell. Forsandwichconstruction,there is animer and outer skin which together are thinnerthan the single-skinlaminatethat theyreplace.skin coat A special layer of resin applied justunder the gel coat to prevent blistering. Itissometimes applied with a layer of mat or lightcloth.shear moduIus The ratio of shearing stress toshearing strain within the proportional limit ofthe material,shear strain The tangent of the angularchange, caused by a force between two linesoriginally perpendicularto each other through apoint in a body, Also called angularstrain.shear strength The maximumshear stress thata material is capable of sustaining. Shear.+..-’”; ““/’:, “’”*”’” + ., ‘

Chapter SevenREFERENCEstrength is calculated from the maximum loadduring a shear or torsion test and is based on theoriginalcross-sectionalareaof the specimen,shear stress me component of stress tangentto the plane on which the forcesact.sheet moldhtg compound (S~C) A compositeof fibers, usually a polyester resin, andpigments, fillers, and other additives that havebeen compoundedand processedinto sheet formto facilitatehandlingin the moldingoperation.shelf life The length of time a material, substance,product, or reagent can be stored underspecified environmentalconditions and continueto meet all applicable specificationrequirementsand/orremain suitablefor its intendedfunction.short beam shear (SBS) A flexura.1 test of aspecimen having a low test span-to-thicknessratio (for example, 41), such that failure is primarilyinshear,size Any treatment consisting of starch, gelatin,oil, wax, or other suitable ingredient applied toyarn or fibers at the time of formationto protectthe surface and aid the process of hancilingandfabricationor to control the fiber characteristics.The treatment contains ingredients that providesurfacelubricity and binding action, but unlike aftish, contains no coupling agen~ Before finalfabrication into a composite, the size is usuallyremovedby heat cleaning,and a finish is applied.skin Therelativelydense materialthat may formthe surfaceof a cellularplastic or of a sandwich.S-N diagram A plot of stress (S) against thenumber of cycles to failure (N) in fatigue testing.A log scale is normally used for N, For S, alinear scale is often used, but sometimes a logscale is used here, too. Also, a representationofthe number of alternatingstress cycles a materialcan sustain without failure at various maximumstresses.specific gravity The density (mass per unitvolume)of any material dividedby that of waterat a standardtemperature,spray-up Technique in which a spray gun isused as an applicatortool, In reinforcedplastics,for example, fibrous glass and resin can bsimultaneouslydeposited in a mold In essence,roving is fed through a chopper and ejected intoa resin stream that is directed at the mold byeither of two spray systems. In foamed plastics,fast-matting urethanefoams or epoxy foams arefed in liquid streams to the gun and sprayed onthe surface,On contact,the liquid starts to foam.Spun roving A heavy, low-cost glass fiberstrand consistingof fdaments that are continuousbut doubledback on each other.starved area An areain a plastic part whichhas an insufilcientamount of resin to wet out thereinforcement completely. This condition maybe due to improper wetting or impregnation orexcessivemoldingpressure.storage life The period of time during which aliquid resin, packaged adhesive, or prepreg canbe stored under specified temperatureconditionsand remain suitable for use. AIso called shelflife.strain Elastic deformation due to stress.Measured as the change in length per unit oflength in a given direction,and expressedin percentageorin./in.stress The internal forceper unit area that resistsa change in size or shape of a body. Expressedin forceper unit area.stress concentration On a macromechanica.1level, the magnblcationof the level of an appliedstress in the region of a notch, void, hole, or inclusion.stress corrosion Preferential attack of areasunder stress in a corrosive environmen~ wheresuch an environment alone would not havecausedcorrosion,stress cracking The failure of a material bycracking or crazing some tie after it has beenplaced under load, Time-to-failuremay rangefrom minutesto years. Causesincludemolded-instresses, post fabrication shrinkage or warpage,and hostile environment,stress-strain curve Simultaneous readings Ofload and deformation, converted to stress andstrain, plotted as ordinates and abscissae,respwtively,to obtaina stress-straindiagram.structural adhesive Adhesive used for t.ELTlSferringrequired loads between adherends exposedto service environments typical for thestructureinvolved,surfacing mat A very thin ma~ usually 7 to 20roils thick, of highly fikunentizedfiberglass,usedprimarily to produce a smooth surfaceon a reinforcedplastic lamina~, or for precise machiningor grinding,symmetrical laminate A composite laminatein which the sequence of plies below the laminatemidplane is a mirror image of the stackingsequenceabovethe midplane.253 ,/~.,,..-.,.

GlossaryMarine Compositestack Stickinessof a prepreg; an important handlingcharacteristic.titp~ A composite ribbon consisdngof continuousor discontinuousfibers that are alignedalongthe tape axis parallel to each other and bondedtogetherby a continuousmatrixphase.tensile strength The maximum load or forceper unit cross-sectionalarea, within the gagelength, of the specimen. The pulling stress requiredtobreak a given specimen,tensile stress The normal stress caused byforces directed away from the plane on whichthey act.thermoformhtg Forming a thermoplasticmaterial after heating it to the point where it ishot enough to be formed without cracking orbreakingreinforcingfibers.thermoplastic polyesters A class of thermoplasticpolymers in which the repeating units arejoined by ester groups, The two importanttypesare (1) polyethyleneterphthalate(PET), which iswidely used as fihn, fiber, and soda bottles; and(2) polybutyleneterephthalate(PBT),primarily amoldingcompound.thermoset A plastic that, when cured by applicationof heat or chemicalmeans, changesinto asubstantiallyinfusibleand insolublematerial.thermosetting polyesters A class of resinsproduced by dissolving unsaturated, generallylinear, alkyd resins in a vinyl-typeactive monomersuch as styrene, methyl styrene, or diallylphthalate. Cure is effected through vinyl polymerizationusing peroxide catalysts and promotersor heat to accelerate the reaction. Thetwo importantcommercialtypes are (1) liquid resinsthat are cross-linkedwith styrene and usedeither as impregnanwfor glass or carbonfiberreinforcementsinlaminates,filament-woundstructures,and other built-up constructions, or asbinders for chopped-fiber reinforcements inmoldingcompounds,such as sheet molding compound(SMC), bulk molding compound (BMC),and thick molding compound(TMC] and (2) liquidor solid resins cross-linkedwith other estersin chopped-fiberand mineral-filledmoldingcompounds,forexample,alkyd and diallylphthalate,thixotropic (thixotropy) Concerning materialsthat are gel-like at rest but fluid when agitated.Having high static shear strengthand lowdynamicshear strengthat the sametime. To loseviscosityunder stress,tooling resin Resins that have applications astooling aids, coreboxes, prototypes, hammerforms, stretch forms, foundry patterns, and soforth, Epoxy and siliconeare commonexamples.torsion Twistingstresstorsional stress The shear stress on a h-ansversecrosssectioncausedby a twistingaction.toughness A pro~~ of a materialfor absorbingwork. The actualworkper unit volumeorunit massof materialthat is requiredto ruptrueit, Toughnessis proportionalto the area underthe load-elongationcurvefromthe originto thebreakingpoint.tow An untwistedbundle of continuous~ments.Commonlyusedin referringto mamnadefibers,particularlycarbonand graphite,but alsoglassandaramid. A towdesignatedas 140Khas140,000fflaments,tracer A fiber,tow,or yarn addedto a prepregfor verifyingfiberalignmentand,in the caseofwovenmaterials,for distinguishingwarp filmshornM fibers.transfer molding Method of molding thermosettingmaterialsinwhichthe plasticis fistsoftenedby heatandpressurein a transferchamberandthenforcedby highpressurethroughsuitablesprues,runners,and gates into the closedmoldforfinalshapingandcuring.transition temperature The temperatureatwhichthe propertiesof a materialchange. Dependingon the material,the transitionchangemayor maynotbereversible.ultimate tensile strength The ultimate orfinal (highest)stress sustainedby a spmirnenin atension test. Rupture and ultimate stress may ormay not be the same.ultrasonic testing A nondestructive test applied to materials for the purpose of locating internalflaws or structural discontimritiesby theuse of high-frequencyreflection or attenuation(ultrasonicbeam).uniaxial load A condition whereby a materialis stressedin only one directionalong the axis orcenterlineof componentparts.unidirectional fibers Fiber reinforcementarrangedprimarilyinone directionto achievemaximumstrengthin that direction,urethane plastics Plastics based on resinsmade by condensation of organic isocyanates254 .“i,,; !+”” !, .,,. .,.

Chapter SevenREFERENCEwith com~unds or resins that contain hydroxylgroups, The resin is famished as two componentliquid monomers or prepolymers that are mixedin the field immediately before application. Agreat variety of materials axe available, dependingupon the monomersused in the prepolyrners,polyols, and the type of diisocyanateemployed.Exwemely abrasion and impact resistan~ Seealsopolyurethane.transmitting structural stresses or nonradiativeenergyfields.volatile content The percent of volatiles thatare driven off as a vapor horn a plastic or animpregnatedreinforcement.volatiles Materials, such as water and alcohol,in a sizingor a resin formulation,that are capableof being driven off as a vapor at room tempemtureor at a slightlyelevatedtemperature.vacuum bag molding A processin whichasheetof flexibletransparentmaterialplusbleederclothandreleasefilmare placedoverthe lay-upon the moldand sealedat the edges. A vacuumis appliedbetweenthe sheetandthe lay:up. Theentrappedair is mechanicallyworkedout of thelay-upandremovedby the vacuum,andthepartis cured with temperature,pressure,and time.Alsocalledbagmolding,veil An ultrathinmat similarto a surfacemat,oftencomposedof organicfibersas wellas glassfibers,vinyl esters A class of thermosettingresinscontainingesters of acrylic and/or methacrylicacids, many of which have been made ftomepoxyresin. Cureis accomplishedas withunsaturatedpolyestersbycopolymerizationwithothervinylmonomers,suchas styrene.viscosity Thepropertyof resistanceto flowexhibitedwithinthebody of a material,expressedin termsof relationshipbetweenappliedshearingstressand resultingrate of strainin shear. Viscosityisusuallytakento meanNewtonianviscosity,inwhichcasethe ratioof shearingstressto therate of shearingslminis constant,In non-Newtonianbehavior,whichis theusualcasewithplastics,the ratiovarieswiththe shearingstress,Suchratiosare oftencalledthe apparentviscositiesat the correspondingshearingstresses. Viscosityismeasuredin termsof flowin Pa. s (P),with water as the base standard(valueof 1.0).Thehigherthenumber,thelessflow.void content Volumepercentageof voids,usuallylessthan 170in a properlycuredcomposite.The experimentaldeterminationis indirect thatis, calculatedfrom the measureddensity of acured laminateand the “theoretical”densityofthestartingmaterial.voids #Jr or gas thathasbemitrappedandcuredintoa laminate.Porosityis an aggregationof microvoids.Voids are essentiallyincapable ofwarp The yarn running lengthwise in a wovenfabric. A group of yarns in long lengths and approximatelyparallel.A changein dimensionof acuredlaminatefrom its originalmoldedshape.water absorption Ratio of the weight ofwater absorbedby a materialto the weight of thedry matmial.weathering The exposure of plastics outdoors.Comparewith artificialweathering.weave The particular manner in which a fabricis formed by interlacingyarns. Usually assigneda style number.wefi The transversethreads or fibers in a wovenfabric, Those running perpndicuhr to the warp.Also calledfill, filling yarn, or woof.wet lay-up A method of making a reinforcedproduct by applying the resin system as a liquidwhenthe reinforcementis put in place.wet-out The conditionof an impregnatedrovingor yam in which substantiallyall voids betweenthe sized strands and fdaments are tilled withresin,wet strength The strengthof an organicmatrixcompositewhen the matrixresk is saturatedwithabsorbed moistare, or is at a defied percentageof absorbedmoisture less than saturation. (Saturationis an equilibrium condition in which thenet rate of absorptionunder prescribedconditionsfalls essentiallyto zero.)woven roving A heavy @ss fiber fabricmadeby weavingroving or yarn bundles.yield point !f’k fust stress in a material, lessthan the maximum attainablestress, at which thestmin increases at a higher rate than the stress.The point at which permanent deformation of astressed specimen begins to take place. Only255

GlossaryMarine Compositesmaterialsthat exhibityielding havea yield point. material is viscous, Often defined as the stressyield strength The stress at the yield point, needed to produce a spwifmd amount of plasticThe stressat which a materialexhibitsa specified deformation(usuallya 0,2% changein length),limiting deviation from the proportionality of Young’s modulus The ratio of normal stressstress to strain. The lowest stress at which a to correspondingstrain for tensileor compressivematerial undergoes plastic deformation, Below stresses less than the proportional limit of thethis stress, the material is elastic; above it, the material, See also modulusof elasticity.256/. .-,,..~”r..

Chapter SevenREFERENCE1-11-21-31-41-51-61-71-81-91-101-111-12“Aerospace Composites Technology is Finding New Applications.” R@forced PlaslimVol. 27 (No. 8), Aug. 1983, p. 243-248, in Engineered ~ , vol. 1, ‘Composites, ASM International, 1987.“GRP Proves Its Worth in Tough-Going Powerboat Race.” mforced P- Vol. 29(No. 4), April 1985, p. 106-107, in Engineering College, “Marine Applications;’ in. .~, Vol. 1, Composites, ASM International, 1987,“Composite Material Study: Maturity of Technology Materials and Fabrication;’ F.I.T.Structural Composites Laboratory technical report prepared for UNISYS Corporation andU.S. Navy, March 1988, Distribution Limited,for Bu . . ~, American Bureau of Shipping,1986, Paramus, New Jersey.Shuttleworth, J. “Spectrum 42 Production Catamaran~’ Mrdtihull Int., Vol. 18 (No. 207),April 1985, p. 91-94, in Enw ~ k, Vol. 1, Composites, ASMInternational, 1987.Doyle, J.F. and L. Hadley-Coates. “Distortion of Thin Shells Due to Rapid TemperatureChanges,” Qcean Eng., Vol. 13 (no. 2), 1986, p. 121-129, in -red MaterialsHandbook, Vol. 1, Composites, ASM International, 1987.Pittman, L,L. “Breaking the C)ldMoulds,” W, Jan. 1985, P. 76-81, in En@neeredMaterials Hand book, Vol. 1, Composites, ASM International, 1987.Florida Tod W, November 7, 1989, article by Catherine Liden.Summerscales, John. Royal Naval Engineering College, “Marine Applications,” in.~, Vol. 1, Composites, ASM International, 1987.Second International Conference on Marine Applications of Composite Materials,1988; Invited Pape~ “The High Speed Passenger Ferry SES Jet Rider.” S. Hellbratt andO. Gullberg, Karlskronavarvet AB, Karlskrona, Sweden.March“Italcraft M78.” Boat InL No. 7, 1985, p. 91, in ~n~ineere d Materials Handb ook, Vol. 1,Composites, ASM International, 1987.“Extensive Use of GRP for Tomorrow’s Undersea Craft.” Reinforced Plastic% Vol. 27,.No. 9 (Sept. 1983), p. 276, in E@neered Matermls Handbo ok, Vol. 1, Composites,ASM International 1987.257

Chapter ReferencesMarine Composites1-131-141-151-161-171-181-191-201-211-221-231-24“Composite Hull Increases Submarine’s Range of Action.” Corn-, Vol. 14, No. 3.(July 1983) p. 314, in ~, Vol. 1, Composites, ASMInternational, 1987.IBID ref. [1-9].Heller, S.R. Jr. “The Use of Composite Materials In Naval Ships.” Mdardcd, Proceedings of the Fifth Symposium on Structural Mechanics, 8-10May, 1967, Phil., PA.Landford, Benjamin W; Jr. and J. Angerer. “Glass Reinforced Plastic Developments forApplication to Minesweeper Construction.” Naval Engineers Journal, (Oct. 1971) p,13-26.Olsson, Karl-Axel. “GRP Sandwich Design and Production in Sweden Development andEvaluation.” The Royal Institute of Technology, Stockholm, Sweden, Report 86-6, 1986.Ellis, R.W. and Sridharan, N.S. General Dynamics Land Systems Division, Troy, MI,“Combat Vehicles for New Design Environment for Composites.” AdvancedCom~osites Conference Proceedings, 2-4 Dec. 1985, Dearborn, MI, 1985.Kariy4 B. and J. Hill, FMC Corporation, San Jose, CA. “Implementation of CompositeMaterials in Ground Combat Vehicles.” Adunced Composites III Ex~andin~ theTechnology , Proceedings, Third Annual Conference on Adv~nced Composites, 15-17September 1987, Detroit, MI.Ostberg, Donald T., U.S. Army Tank Automotive Command, Warren, MI. “MilitaryVehicles Composite Applications.” Advanced Composites III Expanding theTechnology, Proceedings, Third Annual Conference on Advanced Composites, 15-17September 1987, Detroit, MI.Fishman, N, “Structural Composites: a 1995 Outlook.” Modern P1asti (July 1989), p.72-73.Margolis, J.M. “Advanced Thermoset Composites Industrial and CommercialApplications.” Van Nostrand Reinhold Company, N.Y., 1986.Koster, J., MOBIK GmbH, Gerlingen, West Germany. “The Composite Intensive Vehicle- A Third Generation of Automobiles! A Bio-Cybernetical Approach to AutomotiveEngineering?” May, 1989.Eruzineers’ Guide to Composite Materials . American Society for Metals, 1987, Abstractedfrom “Composite Driveshafts - Dream or Reality.” D.R. Sidwell, M. Fisk and D. Oeser.Merlin Technologies, Inc., Campbell, CA. New Compos”te Materials and Technoloq,The American Institute of Chemical Engineers, p. 8-11, ~982.258,“,.. . . ‘),{”.!... .,!%,+ “

Chapter SevenREFERENCE1-251-261-271-281-291-301-311-321-331-341-35ers 3 . .e to Co_te Mated .American Society for Metals, 1987, Abstractedfrom “A Composite Rear Floor Pan.” N.G. Chavka and C*F. Johnson, Ford Motor Co.Proceedings of the 40th Annual Conference, Reinforced Plastics/Composites Institute, 28Jan. -l Feb. 1985, Session 14-D. ~eSociety oftie PIastics hdus~, Inc., p. l-6.~, April 1989, Plastiscope feature article.rnP -, September 1989, various articles.“f ~, American Society for Metals SourceBook, 1986.Dickason, Richard T., Ford Motor Company, Redford, MI. “HSMC Radiator Support.”.lC~, American Society for Metals: MetalsPark, OH, 1986.Johnson, Carl F., et al. Ford Motor Company, Dearborn, MI and Babbington, Dorothy A.,Dow Chwnical Company, Freeport, TX. “Design and Fabrication of a HSRTMCrossmember Module.” Advanced Com~* III Expandiruz the TechndctgyProceedings, Third Annual Conference on Advanced Composites, 15-17 Septehber1987, Detroit, MI.“Materials Substitution in Automotive Exterior Panels (1989- 1994).” Philip TownsendAssociates, Inc., Marblehead, MA.Fsmis, Robert D., Shell Development Center, Houston, TX. “Composite Front.Crossmember for the Chrysler T-115 Mini-Van.” Adyanced Co DOStes m Expandl“ngthe Technolo ~, Proceedings, Third Annual Conference on Adv~cedlComposites, 15-17September 1987, Detroit, MI.Engineers’ Guide to Comr)osite Materials. American Society for Metals, 1987. Abstractedfrom “Design and Development of Composite Elliptic Springs for AutomotiveSuspensions.” P,D. Mallick, University of Michigan-Dearborn, Dearborn, MI.Proceedings of the 40th Annual Conference, Reinforced Plastics/Composites Institute, 28Jan.-1 Feb. 1985, Session 14-c, The ‘Society of the Plastics Industry, Inc., p. 1-5.En~ineers’ Guide to Comnosite Nlaterials. American Society for Metals, 1987. Abstractedfrom “Composite Leaf Springs in Heavy Truck Applications.” L.R. Daugherty, ExxonEnterprises, Greer, SC. ~~ si M ri “Fabricati on. Proceedings of Japan-U.S. Conference, 1981, Tokyo, Japan: The JapanSociety for Composite Materials, p. 529-538, 1981.Engineers’ Guide to Com~osite Materials, American Society for Metals, 1987. Abstractedfrom “Composite Truck Frame Rails.” Gerald L. May, GM Truck and Coach Division,and Curtis Tanner, Convair Division of General Dyn~cs. Automotive Engineering, p.77-79, Nov. 1979.259.,,.+’.,,., ,-...” ,.

Chapter ReferencesMarine Conmosites1-36Sea, M.R., Kutz, J. and Corriveau, G., Vehicle Research Institute, Western WashingtonUniversity, Bellingham, WA. “Development of an Advanced Composite MonocoqueChassis for a limited Production Sports Car.” ~ .Devel~ Proceedings of the Second Conference on Advanced Composites, 18-20Nov. 1986, Dearborn, MI, 1986.1-37Modern Plastics, July 1989, article by A. Stuart Wood.1-38Shook, G.D. ~American Society for Metals, 1986.., Metals Park, OH:2-11987 ed.als, Metals Park, OH American Society for Metals,2-22-32-42-52-62-7Feichtinger, K.A. bkdmds of Fvamon ti Perf~ce of Strucmal Core ~Used in Sandw~ ,Proc. of the 42nd Annual Conference SPI ReinforcedPlastics/Composites Institute. 2-6 Feb., 1987.Joharmsen, Thomas J. One-off Airex Fiberglass Sandwich Construcu“on. Buffalo, NY:Chemacryl, Inc., 1973.Hexcel. HRH-78 Nomex Commerc ial Grade Honevcomb Data Sbeet 4400. Dublin, CA.,1989.Rules for Buw and Classing Reinforced Plastic Vesse1s. By the American Bureau ofShipping. New York, 1978.Guide for Building and Classing Offtie Racing Yachts. By the American Bureau ofShipping. Paramus, New Jersey, 1986.Chammis, C.C. “Mechanics of Composite Materials: Pas~ Present, and Future.” Journal ofs Techrmlwv & Researth, JCTRER, Vol. 11, No. 1 (Spring 1989), pp. 3-14.3-1ties of Naval ~Engineers. New York, 1967.By the Society of Naval Architects and Marine3-2Engineers’ Guide to Comnosite Materia 1s. By the American Society for Metals.Park, OH, 1987.Metals3-33-4Evans, J. Harvey. ship Structural Des im~Concerns. Cambridge, MD: Cornell MaritimePress, 1975.Noonan, Edward F. Shi~ JLbmtim i Desire Guide. Washington, D,C.: Ship StructureCommittee, 1989.3-5Guide for Buildin~ and Classin~ Offshore Racing Yachts.Shipping. Paramus, NJ, 1986.By the American Bureau of260 ,, ,.‘.

Chapter SevenREFERENCE3-63-7Speed and 13is~MotorBy the American Bureau of Shipping. New York, 1989.Heller, S.R. and N.H, Jasper. “OntheS tructuralD esignofP laningC raft.” ~,Royal Institution of Naval Architects, (1960) p.49-65.Yachts .3-83-93-1oSmith, C.S. ``BucWng Roblems kthe Design of Fiberglass-Retiorced Plastic Stips.''Jourrlal of ~, ( S~pt. 1972) p.174-190.Schwartz, Mel M. ~ . New York: McGraw Hill, 1984.Tsai, Stephen W. Co-es J@.@. Third ed. Tokyo: Think Composites, 1987.3“11Owens-Corning Fiberglas Corp. ‘The Hand Lay-Up Spray-Up Guide.”1988.Toledo, OH,3-123-133-143-153-163-173-183-193-20Owens-Corning Fiberglas Corp. “Design Properties of Marine Grade FiberglassLaminates.” Toledo, OH, 1978.Gibbs & Cox, Inc. “Marine Design Manual for Fiberglass Reinforced Plastics,” NewYork: McGraw Hill, 1960.“Guide for Selection of Fiberglass Reinforced Plastics for Marine Structures.” Society ofNaval Architects and Marine Engineers, Hull Structure Committee, Panel HS-6, Bulletin2-12, 1965.Owens-Coming Fiberglas Corp. Repoti “Feasibility Study for Application of ReinforcedPlastic Construction to Minesweepers.” Navy Dept. - Bureau of Ships, ContractNObs-4671 - Materials Test Program - Phase 1.“An Analysis of the Causes of Variability in the Hand Lay-Up Process.” OCF ReportTC/RPL/67/24.“Effect of Fill-Warp Ratio on Woven Roving Laminate Flexural Properties.” OCF ReportTR/RPL/68/22.“optimum Laminate Study of Typical Marine Constructions,” OCF Report TC/lWL/65/11.Laminate property data on panels cut from boat hulls in conjunction with the Survey ofU.S. Navy Glass Reinforced Plastic Small Craft conducted by Gibbs & Cox, Inc.“Woven Roving and Glass Fiber Mat Reinforced Plastic Laminates - Basic StrengthProperties.” V.S Ristic, 26th Annual Conference of the SPI (Canada) June, 1968.261

Chapter ReferenceMarine Composites3-213-223-233-24.Reichard, Ronmd P. ~ “.Proc.of the 17th AIAA/SNAME Symposium on the Aero/Hydronautics of Sailing: TheAncient Interface. Vol. 34. 31 Oct.-1 Nov. 1987.Owens-Corning Fiberglas Corp. “Joint Conilrguration and Surface Preparation Effect onBond Joint Fatigue in Marine Application.” Toledo, OH, 1973.Della Rocca, R.J. & R.J. Scott. “Materials Test program for Application of FiberglassReinforced Plastics to U.S. Navy Minesweepers.” 22nd Annual Technical Conference,The $ocie~ of the Plastics Industry, Inc.USCG NVIC No. 8-87. “Notes on Design, Construction, Inspection and Repair of FiberReinforced Plastic (FRP) Vessels.” 6 Nov. 1987.3-25Shipping. New York, 1978.Vea. By the American Bureau of4-1Hashin, Z. “Fatigue Failure Criteria for Unidirectiomil Fiber Composites.”Applied Mechanics, Vol. 38, (Dec. 1981), p. 846-852.Journal of4-2Kim, R.Y. ‘Tatigue Behavior.” Comp@te DesireThink Composites: Dayton, Ohio, 1986.1986, Section 19, S.W. Tsai, Ed.,4-34-44-54-64-7Goetchius, G.M. “Fatigue of Composite Materials.” Advanced Comnosites III Exmrdinghe T~, Third Anmd Conference on Advanced Composites, Detroit, Michigan,15-17 September 1987, p.289-298.Salkind, M.J. “Fatigue of Composites.” Composite Materials: Testing and Design (SecondConference), ASTM STP 497, 1972, p. 143-169.Chang, F.H., Gordon, D.E., and Gardner, A.H. “A Study of Fatigue Damage inComposites by Nondestructive Testing Techniques.” Etkigue of Filamentary Canpw.tĖIkIataW, ASTM STP 636, K.L. Reifsnider snd K.N. Lauraitis, Eds., American Societyfor Testing and Materials, 1977, p. 57-72.Kasen, M.B., SChramm, RX., and Read, D.T. “Fatigue of Composites at Cryogenic.Temperatures.” F-o f Filamentary Co poslte Maten alq, ASTM STP 636, K.L.Reifsnider and K.N. Lauraitis, Eds., Ameri~a Society for Tesdng and Materials, 1977,p. 141-151.Porter, T.R. “Evaluation of Flawed Composite Structure Under Static and Cyclic Loading.”~os ite Materi~ , ASTM STP 636, K.L. Reifsnider and K.N.Lauraitis, Eds., American Society for Testing and Materials, 1977, p. 152-170.,.”262,. .,,.1*P i .“~. , ,,,,.. .,!’ ‘,,.. .

Cha~ter SevenREFERENCE4-84-94-1o4-114-124-134-144-154-164-174-18Ryder, J.T., and Walker, E.K. “Effects of Compression on Fatigue Properties of a.Quasi-Isotropic Graphite/Epoxy Composite.” ~~, ASTM STP 636, K*L. Reifsnider and K.N. Lauraitis, Eds., American Societyfor Testing and Materials, 1977, p. 3-26.Sendeckyj, G.P., Stalnaker, H.D., and Kleismit, R.A. “Effect of Temperature on FatigueResponse on Surface- Notched [(0/+45/0~]3 Graphite/Epoxy Laminate.” me ofc ~,ASTM STP 636, K.L. Reifsnider and K.N. Lauraitis,Eds., American Society for Testing and Materials, 1977, p. 123-140.Sims, D.F., and Brogdon, V.H. “Fatigue Behavior of Composites Under Different Loading.Modes.” _ of F~ C-site Malwials, ASTM STP 636, K,L. Reifsniderand K.N. Lauraitis, Eds., American Society for Testing and Materials, 1977, p. 185-205.Sun, C.T,, and Roderick, G.L. “Improvements of Fatigue Life of Boror@poxy LaminatesBy Heat Treatment Under Load.” -e of Filame~ Composite MatW, ASTMSTP 636, K.L. Reifsnider and K.N. Lauraitis, Eds., American Society for Testing andMaterials, 1977, p. 89-102.Sun, C.T,, and Chen, J.K. “On the Impact of Initially Stressed Composite Laminates.”Journal of Com~osite Materials, Vol. 19 (Nov. 1985).Roderick, G.L., and Whitcomb, J.D. “Fatigue Damage of Notched Boron/EpoxyLaminates Under Constant-Amplitude Loading.” Fatizne of Filamentm co t)oslte~, ASTM STP 636, K.L. Reifsnider and K.N. Lauraitis, Eds., Ameri~~ Societyfor Testing and Materials, 1977, p. 73-88.Highsmith, A.L., and Reifsnider, K.L. “Internal Load Distribution Effects During FatigueLoading of Composite Laminates.” comnosite Materials: Fatiae and Frac we, ASTMSTP 907, H.T. Hahn, Ed., American Society for Testing and Materials, Philadelphia, PA,1986, p.233-251.Reifsnider, K.L., Stinchcomb, W.W,, and O’Brien, T,K. “Frequency Effects on aStiffness-Based Fatigue Failure Criterion in Flawed Composite Specimens.” ~I?ilamentan Com~wte Materials, ASTM STP 636, K.L. Reifsnider and K.N. Lauraitis,Eds., American Society for Testing and Materials, 1977, p. 171-184.Hahn, H.T. “Fatigue of Composites.” Composites Guide. University of Delaware, 1981.Kundrat, R,J., Joneja, S,K,, and Broutman, L,J. “Fatigue Damage of Hybrid CompositeMaterials.” National Technical Conference On Polymer Alloys, Blends, and Composites,The Society of Plastics Engineering, Bal Harbour, Fl, Oct. 1982.Kim, R.Y. “Fatigue Strength.” Enginee red Materials Handb ook ,Volume 1, Composites,ASM International, Materials Park, Ohio, 1987..s’263.,.,’,.“

Chapter ReferencesMarine Composites4-194-204-214-224-234-244-254-264-274-284-294-30Talreja, R. “Estimation of Weibull Parameters for Composite Material Strength andFatigue Life Data.” IZiit@e of C~, Technomic Publishing :Lancaster, PA, 1987.Sims, D.F., and Brogdon, V.H. “Fatigue Behavior of Composites Under DifferentLoading Modes.” Ea@ue of F~ Co ~, ASTM STP 636, KL.Reifsnider and K.N. Lauraitis, Eds., American Soci~ty for Testing and Materials, 1977,p. 185-205.eers to Comn~ . * By the American Society for Metals. MetalsPark, OH, 1987,Bumel, et al. “Cycle Test Evaluation of Various Polyester Types and a MathematicalModel for Projecting Flexural Fatigue Endurance,” Reprinted from 41st Annual, 1986,SPI Conference, Section Marine I, Session 7-D.Konur, O. and L, Mathews. “Effect of the Properties of the Constituents on the FatiguePerformance of Composites: A Review,” ~, VO1. 20, No. 4 (July, 1989), p.317-328.Jones, David E. “Dynamic Loading Analysis and Advanced Composites.” SNAME SESection, May 1983.O’Brien, T. Kevin. Deltiation Durability of CO Dosite Material s for Rotorcrafl. U.S.Army Research and Technology Activity, Langley,~A. LAR-13753.Springer, (3,S. Environ~ ental Effects on Cornr)osite Mate@, Technomic Publishing:Lancaster, PA, 1984.Leung, C.L. and D.H. Kaelble. Moisture 13iffusion Analvsis for Comnosite Micro-Proc. of the 29th Meeting of the Mechanical Failures Prevention Group. 23-25 May1979, Gaithersburg, MD.Pritchard, G. and S.D, Speake. “The Use of water Absorption Kinetic Data to PredictLaminate Property Changes.” Composites, Vol. 18 No. 3 (July 1987), p. 227-232.Crwmp, Scott. A Study of BlistE r Formation in Gel Coate d LaminaLeS. Proc, of theInternational Conference Marine Applications of Composite Materials. 24-26 Mar. 1986.Melbourne,FL: Florida Institute of Florida.Marine, R., et al. l’he Effect of COatinm on Blister Formation. Proc, of the ~~rnationalConference Marine Applications of Composite Materials. 24-26 Mar. 1986. Melbourne,FL: Florida Institute of Technology..264‘i,,.,-.,,>,.”‘>‘ . ..I,., ...,t’ “:,“.,

ChapterSevenREFERENCE4-314-324-334-344-354-364-375-1. . . .Kokarakis, J. and Taylor, R. lleore~Proc. of the Third International Conference on Marine Application ofComposite Materials. 19-21 Mar. 1990. Melbourne, FL Florida Institute of Technology..Smith, James W. _ of Gel C- Co~ 1. .“ .~=. Proc. Of the 43rd ~u~ Conference of the Composites Institute, The Societyof the Plastics Industry, Inc. 1-5 February, 1988..Blackwell, E., et al. ~. “Proc. of theAtlantic Marine Surveyors, Inc. Blistering and Laminate Failures in Fiberglass BoatHulls. 9-10 Feb. 1988. Miami, FL.USCG NVIC No. 8-87. “Notes on Design, Construction, Inspection and Repair of FiberReinforced Plastic (FRP) Vessels.” 6 Nov. 1987.Owens-Corning Fiberglas. “Fiber Glass Repairability: A Guide and Directory to theRepair of Fiber Glass Commercial Fishing Boats.” No. 5-BO-12658. Toledo, OH, 1984.~~ and other Fiber Glass Reinfti Surfaces . PPG Industries:Pittsburgh, PA.Proc. of Atlantic Marine Surveyors, Inc. Two Day Seminar Blistering and LwminateFailures in Fiberglass Boat Hulls. 9-10 Feb. 1988. Miami, FL.“HOWto Build a Mold.” Marine Resin New. Reichhold Chemicals, Inc. ResearchTriangle Park, NC, 1990.5-25-3Reichard, R. and S. LewiL The Use of Polyeste r Fabric to Reduc e Print-Thro I@.the SNAME Powerboat Symposium. 15 Feb. 1989. Miami, FL.“JIT Delivery Plan Set for RP Fabricators.” ~ “Cs,(1989), p. 18.Proc. of5-45-5Zenkert D. snd Groth H.L. “Sandwich Constructions l.” Proceedings of the 1st Intl.Conference on Sandwich Constructions, edited by K.A. Olsson, et d., EMAS, 1989, p.363-381.Gusmer Ca~ . 5th Ed. KenL WA, 1988.5-6Health. Safety and.J@u“ onmetianualVA, 1989.. FRP Supply. Ashland Chemical, Richmond,5-7Safe Handlin~ of Advanced Comnosite Materials Com~o e ts: Health Information.Suppliers of Advanced Composite Materials Association,n~lington, VA, 1989.5-8“FFA Considers OSHA Proposed Agreement”1989), p. 12-13.Fabrication News, Vol. 11, No. 11 (Nov.265,d’”j, “.’ ; ,,’T~...‘\.

Chapter References Mathe Composites5-9 Madmen, S. and C. Madsen. ~ Develo_ in GRP ~Proc. of the3rd International Conference on Mtie Applications of ComposimMaterials. 19-21 March 1990. Melbourne, FL: Florida Institute of Technology, 1990..5-10 Walewski L. and S. Stockton. %ow-styrene Emission Laminating Resins Prove it in theWorkplace.” ~ (Aug. 1985), p. 78-79.5-11 Seemann, Bill. Letter to Eric Greene. 11 April, 1990. Smnann Composites, Inc.,Gulfport, MS.5-12 Miller B. “Hybrid Process Launches New Wave in Boat-Building.” ~, “ (Feb.1989), p. 40-42.5-13 Gougeon Brothers Inc. GT,-oxy Re~eon J.~ . .Epmy. Bay City, MI, 1987.5-14 Thomas, Ronald and Christopher Cable. “Quality Assessment of Glass Reinforced PlasticShip Hulls In Naval Applications.” Diss. MIT 1985. Alexandria, VA:DefenseTechnical Information Center, 1985.5-15 U.S. Navy. MIL-C-9084C. Military Specificau“on Cloth. Glass. Finished. for ResinLarninateS Engineering Specifications & Standards Department Code 93, Lakehurst, NJ.9 June 19~0..5-16 Proposed Gude for Buildirw and Classinv Il@-St)eed and DisnJacement Motor Yachts.By the American Bureau of Shipping. Paramus, NJ, Nov. 1989 Draft.6-1 Reichard, R.P. and T. Gaspamini. “Structural Analysis of a Power Planing Boat.”SNAME Powerboat Symposium, Miami Beach, FL, Feb. 1984.6-2 Reichard, R.P. “Structural Design of Multihull Sailboats.” First International Conferenceon Marine Applications of Composite Materials. Melbourne, FL Florida kstitLIte ofTechnology, March 1986.6-3 1988Annual Book of ASTM Standards, Vols. 8.01,8.02, 8.03, 15.03, ASTM, 1916 RaceSt., Philadelphia, PA 19103.6-4 Weissman-Berman, D. “A Preliminary Design Method for Sandwich-Cored Panels.”Proceedings 10th Ship Technology and Research (STAR) Symposium, SNAME SY-19,Norfolk, VA, May 1985.6-5 Sponberg, E.W. “Carbon Fiber Sailboat Hulls: How to Optimize the Use of an ExpensiveMat.mial.” J. Marine TeclL, 23(2) (April 1986).266

ChapterSevenREFERENCE6-66-76-86-97-17-27-37-47-5Riley, Craig and F. Isley. “ApplicationofBiasFabricR einforcedH ullPanels.” FirstInternational Conference on Marine Applications of Composite Materials. Melbourne,FL Florida Institute of Technology, March 1986.. . .Naval Sea System Command (NAVSEA). ~ Fue amLlbaclty Tesl. .Qu~ti for ~ms TJsedin ~,.~, MIL-STD-X108(SH).Dept. of the Navy, Washington, D.C. 11, July 1989.Schwartz, M.M. “Nondestructive Composites Tesdng.” ImmatimdaLuct News9(Sept./Ott., 1989), p. 28.~Vol..1, Composites. By the American Society of MetalsInternational. Metals Park, OH, 1987.Watson, James A. and William Hayden. “Ovefiew of Coast Guard Plan Review forHigh-Tech Ship Design.” Marine Teclmolo m, Vol. 27, No. 1 (Jan. 1990) p. 47-55.Curry, Robert. ~. . YProc. of the Third International Conference on Marine Applications of CompositeMaterials. 19-21 March, 1990. Melbourne, FL: Florida Institute of Technology, 1990.Heller, S.R. & Jasper, N.H., “On the Structural Design of Planing Craft.” Transactions,RINA, 1960.Savitsky, D. and Brown, P. W., “Procedures for Hydrodymunic Evaluation of PlaningHulls, in Smooth and Rough Water.” MadnLkQhnolo ~, (October 1976).Allen, R.G. and Jones, RR., “A $implifl~d Method for Deterring StructuralDesign-Limit Pressures on High Performance Marine Vehicles.” AIAA 1987.7-6Spencer, J.S., “Structural Design of Alumminum Crewboats.”~ New York, (1975).pp 267-274, Mari.tE267

IndexMarine Compositesablation....................................................................242ablativeplastic........................................................242absorption................................................................N2acceleratedtest........................................................242acceleratedtesting...................................................211acceleratoṙ........................................................48,242acceptancetest........................................................242acetone....................................................................242acid number............................................................ 192acousticemission............................................225,242xtivamr .....................................8.............................242additive....................................................................242adherend..................................................................242advancedcomposite................................................242fiChIICd tactical fighter (ATT)...............................35advsncedtdmology bomber(B-2).........................36Xrospxe ...................................................................34&g ........................................................................242aircushionvehiclė...................................................11airinhibiteḋ..............................................................47AirRideCraft........................................................... 12air-bubblevoid........................................................242W-inhibitedresin....................................................242Airbus........................................................................35aircrafṫ......................................................................35Arex@.......................................................................51allowable.....................,,.,,,,,,,.,.............................242alternatingstress.....................................................242alternatingstressamplitudė...................................242ambientconditionṡ.................................................242American13ureauof Shipping(ABS)................1.230AnericanSocietyforTestingMaterMs(ASTM).197AMTMar& ...............................................................8anisotropic.........................................................86,242antioxidant. ..............................................................242ararnid.....................................................................242aramidfiber...............................................................41wealweighṫ............................................................242artiilcialweatherinġ...............................................242aspectratio..............................................................M3ASTM~StS.............................................................197autoclave.................................................................243autoclavemoldinġ..................................................182automotive~fications ............................................2lbagging................................................................... 243balancedcmstruction............................................. 243balancedlaminate...................................................243ballistic...................................................................... 19balsa..........................................................................49Barcolhardness.............................................. 193,243Barcolhardnesstest ............................................... 202barrierfilm.............................................................. 243basket weave............................................................ 45&am, sandwich...................................................... 109beam, solid ............................................................. 109beddingcompound................................................. 243BeechStarship.......................................................... 35bendingmomen~still............................................... 75bendingmomen~wave............................................ 76Bertrarn....................................................................... 4bias fabric............................................................... 243biaxialload...........................1................................, 243bidirectionallaminate............................................. 243binder......................................................................243blade,comWtiw....................................................... 18bleedercloth........................................................... 243blister......................................................................243blisters..................................................................... 149blisters,repair......................................................... 164Block Island40 .......................................................... 3blockingload............................................................ 77BlountMarine.......................................................... 11Boeing....................................................................... 35bolts, through-........................................................ 126bond........................................................................ 243bond strength.......................................................... 243bond, iiber/matrix..................................................... 87bondingangles........................................................ 243BostonWhalW......................................................2,10boundaryconditions............................................... 243buckling............................................................82,243bulk moldingcompound(BMC)...........................243bulkheads................................................................ 121buoy ....................................................................,...,. 13burn throughtes~ DTRC.......................................215butt joint ................................................................. 243C-Flex@..................................................................... 52c-scan ..................................................................... 245268,-,. ,,,/ ,-—! ,,, ‘1Iy: -,:-.,. . . t,’., ,$,,,~ ,, ,.

ChapterSevenREFERENCEcanoes..........................................................................5mhn ......8...............................................................M3carbonfiber.......................................................43. 244cargovessel.......................s....................................... 12cargovessels...........................................................229carpetplot .........................................................94,244catalyst..............................................................48,244cell...........................................................................244cell size...................................................................244centerlinejoint ...................................................,,.,,118chain @teS ... .... ..... ... . ... .... .... .... .... .... .... .... ... .. .. . .. .... 244chainplateṣ.............................................................. 130chalking................................................................... 159Charpyimpacttest..................................................244choppedstrand..................................................44,244choppergun ............................................................ 169ChristensenMotorYacht ....................................,,.....4Chrysler.....................................................................23classification,AES .................................................233closedcell fom ......................................................244cloth...........................................................................44Coculing...................................................................M4coin test...................................................................244compaction..............................................................244COMPE~ ................................................................43compliance..............................................................244components............................................................... 18compositem. ..................................................Mcompressionafterimpact testing...........................205compm.ssionmolding......................................180,244compressiontest, sandwich....................................204compressiontest, sandwichcore............................200compressiontesting................................................202compressiontesting,open-hole,.,...........................206compressivepropwtiestesting............................,.,203compressiveslrength..............................................244compressivemess ..................................................244compressivetesting.................................................205computerlaminateanalysis......................................96cone calorimeter.....................................................214constituentmaterials...............................................244construction,cored.................................................. 167construction,singleskin......................................... 166contactmolding......................................................Wcontainer,shipping....................................................27continuousstrand......................................................44conversionfactors...................................................236copolymeT...............................................................244core..........................................................................244corematerial.....................................................49,106core matmialdensity,test method......................... 199core materialwaterabsorption,test method.......... 199core separation........................................................ 157Coremat.................................................................... 52corrosionresistance................................................ 244mum ....................................................................... 245couplingagent........................................................ 245cracking,gel coat................................................... 156crazing.................... .creep........................................................................ 245cross-linking........................................................... 245cure......................................................................... 245curingagent............................................................ 245. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24513aedaluṣ................................................................., 38damagetolerance.................................................... 245damage,wmdwich.................................................. 162damage,single-skin................................................ 161DavidTaylorReseamhCenter (DTRC).................. 18debond.................................................................... 245debonding............................................................... 157debonding,core...................................................... 163deck edge connection............................................. 115delamination................................................... 143,245Delta Marine................................................................8denier......................................................................z5details...................................................................... 114dimensionalstability.............................................. 245dimples................................................................... 245draft angle...............................................................245drape....................................................................... 245driveshaft..................................................................dry Mk ............................................................ zductility................................................................... 245ductwork................................................................... 32dynamicphenomena................................................ 76E-glass..............................................................41. 245elastic constants........................................................ 89elastic deformation................................................. 245elasticlimit............................................................. 245elasticity.................................................................. 245elasticity,modulusof............................................. 249elastomeṛ................................................................ 245elongation............................................................... 245encapsulation.......................................................... 246enginebeds............................................................. 126epoxy........................................................................ 48epOXy Pl=tiC ... .... .... .... .... .... .... .... .... .... ... .... .... ...... .. . 246equipment,manufacturing..................................... 169exothermheat......................................................... 246,,

Index Maine Compositesexotherm,peak........................................................ 193exotherm,test methodfor peak.............................. 198failurecriteria............................................................97failurecriterion.......................................................246failureenvelope......................................................U6f@g ......................................................................M6fakings,periacop ..................................................... 15fairwater,submarine............................................... 155fans............................................................................32fasteners,self-tapping............................................. 126fatigue..............................................................133,246fatiguelife...............................................................246fatiguelimit.............................................................246fatiguestrength.......................................................246fatigue test &ti ....................................................... 137fatiguetheory..........................................................136fatigue,tension-tensiontesting...............................204faying surface..........................................................246felt ...........................................................................246ferry,pmsengm......................................................... 11fiber.........................................................................246fiber content....................................,,,,,,..................246fibercontenttesting................................................203fiber comt ...............................................................M6fiber direction..........................................................246fiber volume..............................................................55fiber volumeratio.....................................................89fiber volumetesting................................................207fiberglass...........................................................41,246fiberglasschoppm...................................................M6fiberglassreinforcedpalstic @W) ........................246fiberglassreinforcement.........................................246Fick’s equation........................................................246Fickiandiffusion..................................................... 146fdament.............................................................U. 246fdarnentwin~g .............................................l8l. 246fill............................................................................247filler.........................................................................u7fflet .........................................................................247fillingyarn ..............................................................247finish........................................................................247finishes,glass.......................................................,,..,41fimiteelementmethod (FEM)................................. 110fire testing...............................................................212fret-ply-failure........................................................247fish eye....................................................................247fishingindustry...........................................................8fittings,through-hulḷ.............................................. 129flameretardants.....................a................................u7flammability............................................................247flexuralfatiguetesting........................................... 202flexural modtius..................................................... 247flexurzdstiffness,sandwichbeam.......................... 108flexuralstiffness,sandwichpanel.......................... 110flexuralstiffness,solidbeam................................. 107flexuralstrength...................................................... 247flexumlstrength,beam.......................................... 109flexuraltesting........................................................ 202flexurecreeptesg sandwich................................... 205flexuretest, sandwich............................................. 204flow......................................................................... 247foam-in-placẹ......................................................... 247Ford........................................................................... 22foundation,composite.............................................. 18fracturetoughness.................................................. 247gel ....................................................,,,,,,.,.,,............ 247gel coat ........................................................... 156,247gel tie ................................................................... 192gel time, test metiti .............................................. 198gelationtime........................................................... 247GeneralMotom......................................................... 23girders.......c............................................................. 126glass finish.............................................................. 247glass transition ...................................................... 247~tik .............................................................43. 247Greenstrength........................................................247Hahn,H.T................................................................. 96hand by.UP ..... ... ....... ..... .... .... .... .... .... .... .... ..... 180,247hardener.................................................................. 248hardware,mounting................................................ 126harnesssatin........................................................... 248Harrier‘~mnpjet?’(AV-88)..................................... 36hatches.................................................................... 129haulingload.............................................................. 77hazard...................................................................... 173healthconsiderations.............................................. 173heatbuild-up........................................................... 248heatresistance........................................................ 248heticopkr .................................................................. 37Holler,S.R................................................................ 79holes, smallnon-penetrating.................................. 163homogenwus.......................................................... 248honeycomb.......................................................51,248hoop StIeSS ... .... .... ... ..... .... .... .... .... .... .... .... . .... ... ... ... . 248hove~ .................................................................. 18hfl ............................................................................ ‘-270., .,,,,.;.i.,,,’. :‘,,,. ,..’“, [,,{ “’,!.. -., ,, . . . . . . .

ChapterSevenREFERENCEhull cetication, ABS............................................235hull response.............................................................81hybrid......................................................................248hydrofoil.................................................................... 18hygrotherrnaleffect.................................................248hysteresis.................................................................248ignitionloss.............................................................248impact...................................................................... 139impactstrength.......................................................248impacttit ...............................................................M8impregnatė..............................................................248impregnator............................................................. 172inclusion.................................................................,248inhibitor...................................................................248injectionmolding....................................................248kmMti .............................................................X8interlaminarshear...................................................M8htimhm .............................................................248isophthalic................................................................,47isotropic...................................................................248Itakraft ...................................................................... 12Izod impacttest.......................................................248J/24..............................................................................3Jasper,N.H................................................................79JY 15....................................................................... 178Karlslmonavawe~AB...............................................11kayaks.........................................................................5keel attachment....................................................... 119kerf..........................................................................249Kevlar@.............................................................41,249kinetic energy......................................................... 139knitted fabrics.........................................................249knittedreinforcemenṭ...............................................46ladder.........................................................................33lamina......................................................................249laminae....................................................................249laminate.............................................................93, M9lap joint ...................................................................249Laser............................................................................3lay-up....................................................................,.249leafspringṣ................................................................ 24Lear Fan 2100.......................................................... 35LeComte................................................................... 10Lequerq........................................................................8lifeboats.......................................................................9liner, hull ................................................................ 248load factor,dynamic................................................. 79load, preSSUE ... .... .... .... .... .... .... ... .. ... .... ... ..... .... .... .... . 79load-deflectioncurve..............................................249loads,hydrodynamic................................................ 79loads,out-of-planẹ................................................... 78loads,point ............................................................... 81loss on ignition....................................................... 249low-pressurelaminates........................................... 249low-profile................................................................ 48macromechanicṡ..............................................86,249mat .......................................................................... 249ma~ choppedstrand.................................................46mat surfacing........................................................... 44matrix......................................................................249matrixcracking....................................................... 135mechanicaladhesion.............................................. 249mechanicalproperties............................................ 249mekperoxide(MEKP)........................................... 249micromechanicṡ...............................................86,249mil........................................................................... 249MIL-STD-224)2(SHj ............................................. 216milledfiber.......................................................44,249mine countermeasure(MCM)vessel..................... 16minesweepeṛ............................................................ 15MOBIK..................................................................... 21moisturecontent..................................................... 146molds...................................................................... 166momentof inertia sandwichbeam ....................... 107momentof inerii%sandwichbeam core ...............107momentof inertia,solid beam............................... 106Navy fighteraimraft(Fi8A) .................................. 37nettinganalysis....................................................... 250Nomex@.................................................................... 51non-airr-inhibitedresin .......................................... 250nondestructiveevaluation(NDE).......................... 250nondestructiveinspection(NIX)............................ 250nondestructivetesting ($J13T)................................ 224nonwovenfabric..................................................... 250nonwovenfabrics..................................................... 44271

.IndexMarine Compositesorientation.................................................................87orthophthalic.............................................................47oscillationforces.......................................................76OSHA......................................................................174osmosis .................................................................,, , 149Osprey tilt rotor (V-22) ....................................,,,,,,,, 37oxygen temperature index ......................................212pressurebag molding............................................. 251pressuretable test Ware................................,,.... 208print through........................................................... 159Pr@ler .................................................................... 15pultrusion........................................................ 181,251PVC foam,cross lioked........................................... 50Pvc foam, lhw ...................................................... 51qualityassuranceprogram(QAP)......................... 188quasi-isotropiclaminate......................................... 252panel........................................................................250panel testing,sandwich...........................................207partial volumes..........................................................88passengervessels....................................................228passengervessels,small.........................................229patrol boats................................................................ 16patrol boats,USCG................................................. 154peel ply....................................................................250peel strength............................................................250permanentset..........................................................250permeability............................................................250permissibleexposurelimit (PEL)..........................174phenolic...................................................................251pilings, formsandjackets for................................... 14pipelines,submarine................................................. 14piping systems..........................................................28pitch.........................................................................251plain weave..........................................,,.,.,,,.,,,.45,251plan approval,ABS ................................................235plasticity..................................................................25lplugs........................................................................ 166ply......................................................................93.251ply density...............................................mm ................89plywood.............................................................53,160Pm foam..................................................................52Poission’smti ........................................................251polyester....................................................................47polyester,unsaturated...............................................47polyetheretherketone(PEEK)...............................251polymer...................................................................251polymerfiber ............................................................4lpolpetiation ........................................................25lpolywtie ............................................................25lporosity....................................................................251portlights................................................................. 129post curing..............................................................179postcure...................................................................251pot life.....................................................................251powerboats,racing...................................................... 1prepreg....................................................................251radiantpanel h test ............................................. 214radiography............................................................. 224ranking.................................................................... 252reactioninjectionmolding (RIM).......................... 252reinforcedplastics.................................................. 252reinforcementmaterial............................................. 41reinforcingmat.........................................................44repair....................................................................... 161resin .................................................................,47,252resin content........................................................... 252resin transfermolding(RTMj.,........lO. 177, 182,252resin volumeratio..................................................... 89resin-richarea......................................................... 252resin-starvedarea ................................................... 252rigginglM& ............................................................. 78risers,drilling ........................................................... 14rotor, helicopter........................................................ 37roving................................................................M. 252rudders.................................................................... 130s-glasṣ..............................................................4l. 252S-N diagram........................................................... 253SACMA material tests........................................... 205sailboats,racing.......................................................... 1sandwichbeam....................................................... 108sandwichcons~ction ............................................ 106sandwichconstructions.......................................... 252sandwichlminate testing...................................... 204satin weave............................................................... 45Scantling.................................................................. 252Schat-IvfarineSafety................................................. 10Scott,Robfi ............................................................. 12screws,machine..................................................... 128screws,self-tapping................................................ 128secondarybonding......................................... 114,252272,“””.-’ ‘“ “-” . ,.,’, ., .’ ,., ,,#!l; ‘\, ,, $.$.‘;,. ,., ,, ,{,., ,5,’..-,,. ,, ““-.,’., ,-,~.~1

ChapterSevenREFERENCEsecondarysmcti .................................................252self-extinguishing resin ..........................................252set ............................................................................252set up...............................................................,.,,,,,,252shaft,propulsion.............................................,.,,,,,...18shear...............................................................,.,,.,,,.252shearfatiguetest, sandwichcore...........................200shearmodulus.........................................................253shearstrain..............................................................253shearstrength..........................................................253shearstrength,interlaminar....................................207shearstrength,parallelfiber interlaminar..............202shearstrength,punch tool ......................................202shearStIeSS..............................................................253shearstress test in-pkme........................................2O6shearstress,in-planetesting...................................204shearteS~sandwichCOIE......................................,.200sheetmoldingcompound(SMC).....................22. 253shelflife ..................................................................253shell.........................................................................252shockloading............................................................ 16shortbeam shear(SBS)..........................................253shroudattachmenṭ.................................................. 130silane...............................................................,.,,,,,.,42size..........................................................................253sizing.........................................................................41ti ................................................................ 252-253skin mti ..................................................................252smokechamber,NBS........................................,.,,.213SOLAS....................................................................219solid laminatetesting..............................................201spec~c gravity.......................................................253specfic#vitY, test method.................................. 197spectra ....................................................................43spraygun, gel coat.................................................. 169spraygun,resin....................................................... 169Sp~y.Up.................................................. 169, 180,253spunroving.......................................................44,253stacks,Ship................................................................ 18starvedarea.............................................................253s~eners .................................................................. 122storagelife ..............................................................253stxain........................................................................253stiain entigy releaserate.................................... 143stress.,.”..,.,,.............................................................253stxessconcentratioṇ................................................253stresscorrosion.......................................................253stresscracking.........................................................253stress-straincurve...................................................253struc~ adhesive..................................................253styrene.....................................................................173submhe .................................................................. 15submersible............................................................... 13Sunf~h.........................................................................2surfaceeffectship.................................................... 11surfacingmat.......................................................... 254symmetricallaminate............................................. 254syntacticfoam.......................................................... 50tack.......................................................................... 254tanks .......................................................................... 32@ .......................................................................... 254temperatureeffects................................................. 158tensileproperties,test method............................... 197tensilestingti ........................................................ 254tensilestrength,ultimate........................................ 254tensiles&ss ............................................................ 254tensiletesting..................................................201,206tensiletesting,open-hole....................................... 206tensiontest, sandwich............................................ 204TextronMarineSystems.......................................... 11thermofornhg ........................................................ 254thermographỵ.........................................................225thermoplastic............................................................ 48thermoplasticpolyesters......................................... 254thermoset................................................................ 254thermosctfoam......................................................... 49tlwrmosettingpolyesters........................................ 254thiclmesstransition................................................. 129tiobpic .........................................................48. 254toolingresin............................................................ 254...............................................................,.,,,., 15torsion..................................................................... 254torsionalstress...............j........................................ 254toughness......................................................,,,,,,.,..254tow...............................................................,,,.,,,,...254tower,aerial.............................................................. 33toxicity.................................................................... 173tracer....................................................................... 254transfermolding..................................................... 254tmnsitiontempertati.u-e ........................................... 254trawlers........................................................................8Treveria@............................................................43,52Tsai, S.W.................................................................. 96U.S. CoastGuard................................................... 227ultrasonicinspection............................................... 224ultrasonictesting...........................................,,.,.,,,, 254ultraviolet rays........................................................ 158uniaxialload........................................................... 255uniaxialstrength,in-plane........................................ 90,.,,.,?..,.273

IndexMarine Compositesuniaxialstrength,through-thickness........................91unidirectional............................................................46unidirectionalfibers................................................255uninspectedvessels.................................................227urethaneplastics.............................................,,,,,,,,255USCG NVICNo. 8-87........................................... 122utility vessels............................................................ 10vacuumbag molding......................................181,255veil...........................................................................255ventilation............................................................... 175vessel,pressure......................................................... 18vinyl ester..........................................................48,255viseometer............................................................... 192viscosity..................................................................255void content............................................................255voida..................................................................,,,,,,255volan@...............................................................,,,,,..42volatilecontent.......................................................255Volatileṣ..................................................................255Voyager.....................................................................38warp........................................................................ 255waterabsorption............................................. 146,255waterabsorption,test method................................ 197WatercraftAmeriea.................................................... 9weathering.............................................................. 255weave...................................................................... 255weft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255WestPortShipyard...................................................... 4wet lay-up........................................................i...... 255wet strength............................................................ 255wet-out.................................................................... 255wovenfabric............................................................. 44wovenroving.................................88i8 ...............44,256yarn........................................................................... 44yieldpoint............................................................... 256yield strength.......................................................... 256YoungBrothers.......................................................... 9Young’smodulus................................................... 256,,,\ i274

.+‘:,/,- .._-...—....~..COMMITTEE ON MARINE STRUCTURESCommission on Engineering and Technical SystemsNational Academy of Sciences - National Research CouncilThe COMMITTEE ON MARINE STRUCTURES has technical cognizance overthe interagency Ship Structure Committee’s research program.Stanley G. Stians@n (Chairman)r Riverh~ad, NYMark Y. Berman, Amoco Production Company, Tulsar OKPeter A. Gale, Webb Institute of Naval Architecture, Glen Cover NYRolf D. Glasfeld, General Dynamics Corporation, Groton, CTWilliam H. Hartt, Florida Atlantic University, Boca RatOn, FLPaul H. Wirsching, University of Arj.zona, Tucson, AZAlexander B. Stavovy, National Research Council, Washington, DCMichael K. parrnelee, secretary, Ship Structure Committee,Washington, DCLOADS WORK GROUPPaul H. Wirsching (Chairman), University of Arizona, Tucson, AZSubrata K. Chakrabarti, Chicago Bridge and Iron Company, Plainfield, ILKeith D. Hjelmstad, University of Illinois, Urbana, ILHsien Yun Jan, Martech Incorporated, Neshanic Station, NJJack Y. K. “Lou, Texas A & M University, College Station, TXNaresh Maniar, M. Rosenblatt ~ Son, Incorporated, New York, NYSOloman C. S. Yim, Oregon State University, Corvallis, ORMATERIALS WORK GROUPWilliam H. Hartt, Florida Atlantic University, Boca Raton, FLFereshteh Ebrahimi, University of Florida, Gainesville, FLSantiago Ibarra, Jr., Amoco Corporation, Nape~ville, ILPaul A. Lagace, Massachusetts Institute of Technology, Cambridge, MAJohn Landes, University of Tennessee, Knoxville, TNMamdouh M. Salama, Conoco Incorporated, Ponca City, OKJames M. Sawhill, Jr., Newport News Shipbuilding, Newport News, VA