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

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5 Face/core Interface Fatigue Crack Propagation in Sandwich Structures 88 5.1 Background …………………………………………………………………. 88 5.2 Face/Core Fatigue Crack Growth in Sandwich X-Joints …………………… 90 5.2.1 Experimental Study of the STT Specimens …………………………….. 91 5.2.2 Fatigue Characterization of the Face/Core Interface …………………… 102 5.2.3 Finite Element Modeling of the STT Specimen ……………………….. 110 5.3 Fatigue Crack Growth in the Face/Core Interface of Sandwich Panels ……. 114 5.3.1 Fatigue Experiments on Sandwich Panels ……………………………… 114 5.3.2 Finite Element Modeling of the Debonded Panels ……………………... 120 5.4 Conclusion …………………………………………………………………. 124 6 Conclusions and Future Work 128 6.1 Buckling Driven Face/Core Debond Propagation in Sandwich Structures … 128 6.2 Fatigue Crack Growth in Bimaterial Interfaces …………………………….. 130 6.3 Face/Core Interface Fatigue Crack Growth in Sandwich Structures ……….. 131 6.4 Future Works ……………………………………………………………….. 133 References 137 A Additional Results from the Column Compression Tests 145 A.1 Debonded Columns with H45 Core ……………………………………………. 145 xii
A.2 Debonded Columns with H100 Core …………………………………………. 146 A.3 Debonded Columns with H200 Core …………………………………………. 147 A.4 Initial Imperfections in Debonded Columns …………………………………. 148 A.5 Out-of-plane deflection of Debonded Columns ………………………………. 150 B Additional Results from the Panel Compression Tests 155 B.1 Load vs. In-plane Displacement Curves ………………………………………. 155 B.2 Out-of-plane Deflection vs. Load Curves ……………………………………. 157 B.3 Out-of-plane Deflection of the Debonded Panels ……………………………. 159 C Additional Results from the Tests on the STT Specimens 163 B.1 Axial Displacement vs. Force Curves from the Static Tests …………………. 163 xiii
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 20 and 21: H11 bimaterial constant H22 bimater
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
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sheet and the core thickness, respe
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Load (N) 250 200 150 100 50 0 H130
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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,
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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
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Bezazi A., Mahi A. E., Berthelot J.
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Kanny K. and Mahfuz H. (2005), Flex
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Ratcliffe J. and Cantwell W. J. (20
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Out-of-plane displacement (mm) 1 0.
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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
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DTU Mechanical Engineering Section
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Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

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