Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

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H11 bimaterial constant H22 bimaterial constant h characteristic length hc core thickness hf face thickness K complex stress intensity factor KI mode I stress intensity factor KII mode II stress intensity factor k non-dimensional curve fitting parameter L length of the specimen M moment Njump number of jumped cycles Nref total number of cycles P load Pcr buckling load Pmax maximum fatigue load qy control parameter R computational efficiency ratio r radius Sij compliance matrix element S12 discrete slope of the state variable increment between cycle one and two S23 discrete slope of the state variable increment between cycle two and three Sjump estimated slope after a cycle jump T none-singular stress parallel to crack surface t time Ws required energy for creation of new surfaces x distance from crack tip y state variable yjump estimated state variable from the cycle jump analysis estimated state variable from the reference analysis yref Greek Symbols material mismatch parameter potential energy deflection ij Kronecker’s delta max maximum displacement x opening relative displacement of the crack flanks y sliding relative displacement of the crack flanks z out-of- plane relative displacement of the crack flanks tcyc time of each cycle tjump cycle jump time cycle jump time for state variable y ty,ump xvi
oscillatory index ratio between compliance matrix elements Poisson’s ratio elastic foundation modulus parameter stress ij cr wrinkling load angle finite width correction factor Mode-mixity phase load partitioning parameter xvii
Page 1: Residual Strength and Fatigue Lifet
Page 4 and 5: Published in Denmark by Technical U
Page 6 and 7: This page is intentionally left bla
Page 8 and 9: method to accelerate the simulation
Page 10 and 11: Synopsis Sandwich kompositter er i
Page 14 and 15: Contents Preface Executive Summary
Page 16 and 17: 5 Face/core Interface Fatigue Crack
Page 24 and 25: These peculiar damage modes often r
Page 26 and 27: 1.2 Overview of the Thesis In this
Page 28 and 29: Figure 1.3: Fracture modes, from Be
Page 30 and 31: In Equations (1.5) and (1.6) H11, H
Page 32 and 33: Figure 1.6: Schematic illustration
Page 34 and 35: The compact tension specimen (CT) i
Page 36 and 37: A Figure 1.10: CSB, DCB, TSD, DCB-U
Page 38 and 39: Chapter 2 Buckling Driven Face/Core
Page 40 and 41: (DIC) measurement system (ARAMIS 2M
Page 42 and 43: corresponds to the onset of debond
Page 44 and 45: Figure 2.7: Crack kinking into the
Page 46 and 47: (2.2) where and for plane str
Page 48 and 49: A modified version of the tilted sa
Page 50 and 51: previous observations of crack path
Page 52 and 53: of contact elements (CONTACT173 and
Page 54 and 55: the debond opening initially increa
Page 56 and 57: Table 2.4: Instability loads determ
Page 58 and 59: G (J/m2) 600 400 200 0 H100 IMP=0.1
Page 62 and 63: Hayman (2007) has described a damag
Page 64 and 65: Table 3.1: Panel test specimens. La
Page 66 and 67: sheet and the core thickness, respe
Page 68 and 69: Load (N) 250 200 150 100 50 0 H130
Page 70 and 71:
Table 3.4: Parameters in the face/c
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was used to monitor 3D surface disp
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arising due to the junction between
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(a) Debonded face sheet Figure 3.16
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Figure 3.19 shows the determined en
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H130 MMB H130 Panel H250 MMB Interf
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3.6 Conclusion In this chapter the
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This page is intentionally left bla
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composite laminates under thermal c
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S S y( t ) y( t ) ( t ) 2 1 12 2
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listed in Table 4.1. The length and
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The strain energy release rate, G,
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high growth rate of G (see Figure 4
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4.4 Face/Core Fatigue Crack Growth
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Debond 310 mm Symmetry B. C. a Figu
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B 2 1/ 2 ( S44 S55 S45) (4.17) wh
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75), which illustrates possible ina
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Figure 4.18 (a) presents the deflec
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Debond radius (mm) 100 90 80 70 60
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using the cycle jump method, more t
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Chapter 5 Face/Core Interface Fatig
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of this chapter, sandwich panels wi
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H250 Specimen H100 Specimen H45 Spe
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Figure 5.5: Test setup. Initially,
Page 118 and 119:
H100 Specimen Fibre bridging Figure
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propagation, the crack continues to
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Figure 5.14: Kinking of the crack i
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Crack length [mm] Crack length [mm]
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mode-mixity phase angle was chosen
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should be taken into account for a
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Figure 5.25: Kinking of the crack i
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log (da/dN) (mm/cycle) 10 log G (J/
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erroneous extrapolations in the tra
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compared to the 65% efficiency obta
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the case of uneven debond growth, t
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Load (kN) 2 1.5 1 0.5 0 Panel 1 Pan
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Figure 5.42: Zero and ninety degree
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G(J/m 2 ) 180 150 210 120 150 100 5
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110 q=qG=0.4 Test #1 100 Test #2 Te
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panels were determined for differen
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Chapter 6 Conclusion and Future Wor
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toughness using MMB fracture toughn
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For the specimens with H250 core th
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Development of testing methods for
Page 158 and 159:
Page 160 and 161:
Bezazi A., Mahi A. E., Berthelot J.
Page 162 and 163:
Kanny K. and Mahfuz H. (2005), Flex
Page 164 and 165:
Ratcliffe J. and Cantwell W. J. (20
Page 166 and 167:
Page 168 and 169:
Out-of-plane displacement (mm) 1 0.
Page 170 and 171:
Out-of-plane displacement (mm) 3 2
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A.5 Out-of-plane deflection of Debo
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(a) Figure A.14: Out-of-plane defle
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(a) (b) Figure A.18: Out-of-plane d
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Load (kN) 250 200 150 100 50 250 30
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Displacement (mm) 4 3 2 1 0 8 9 (a)
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(a) (b) Figure B.11: Out-of-plane d
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(a) (b) Figure B.15: Out-of-plane d
Page 188:
DTU Mechanical Engineering Section
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