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

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(DIC) measurement system (ARAMIS 2M) was used to monitor 3D surface displacements and surface strains during the experiments. Testing of the columns was conducted using ramp displacement control with a piston loading rate of 0.5 mm/min. A sample rate of one image per second was used in the DIC measurements. Three replicate tests were conducted for each specimen configuration. The material properties of the face sheets, assumed to be in-plane isotropic, were determined by tensile tests based on the ASTM standard D3039. The compression strength of the face sheets was measured on laminate specimens cut from the actual sandwich face sheet using the ASTM standard IITRI (D3410) test fixture. Core material properties were obtained from the manufacturer (DIAB, Divinycell H Technical Data, Labholm), see Table 2.1. Symbols E and G represent Young’s and shear moduli, Poisson’s ratio, max the compression strength of the core and the tensile and compression strengths of the face sheets. GIC is the mode I fracture toughness of the core material (Li and Carlsson, 1999). 2.1: Face and core material properties from experiments conducted on samples from the face sheet and fracture toughness, from Li and Carlsson (1999). Material E (MPa) G (MPa) max (MPa) GIc (J/m 2 ) Face: E-glass/epoxy 10360 3816 0.31 168 (T)/ 95.4 (C) N/A Core: H45 50 15 0.33 0.6 (C) 150 Core: H100 135 35 0.33 2 (C) 310 Core: H200 240 85 0.33 4.8 (C) 625 Figure 2.1: A column test specimen with H100 core and 38.1 mm debond. 18
Figure 2.2: (a) Schematic representation of test fixture (b) actual test setup. 2.3 Experimental Results Figure 2.3 shows typical load vs. axial displacement and load vs. out-of-plane displacement curves for columns with a 50.8 mm debond and H45, H100 and H200 cores. The out-of-plane deflection refers to the centre of the debond, for additional results see Apendix A. Load (kN) 10 8 6 4 2 0 (a) H200 H100 H45 (a) 0 0.2 0.4 0.6 0.8 1 Axial displacement (mm) Figure 2.3: (a) Load vs. axial displacement (b) out-of-plane deflection at the debond centre vs. load for columns with a debond length of 50.8 mm. Figure 2.3 (a) shows that the columns respond in a fairly linear fashion after the initial stiffening region until collapse. Figure 2.3 (b) shows that the out-of-plane deflection increases slowly with increasing load until the maximum load. It will later be shown that the point of maximum load 19 3 Out-of-plane deflection (mm) 2 1 0 (b) H200 H100 H45 (b) 0 5 Load (kN) 10
Page 1: Residual Strength and Fatigue Lifet
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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 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 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
Page 72 and 73: was used to monitor 3D surface disp
Page 74 and 75: arising due to the junction between
Page 76 and 77: (a) Debonded face sheet Figure 3.16
Page 78 and 79: Figure 3.19 shows the determined en
Page 80 and 81: H130 MMB H130 Panel H250 MMB Interf
Page 82 and 83: 3.6 Conclusion In this chapter the
Page 86 and 87: composite laminates under thermal c
Page 88 and 89: 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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