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

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(2.2) where and for plane stress and plane strain, respectively. E and are Young’s modulus and Poisson’s ratio, respectively. Normal force and moment in the TSD specimen can be determined from the vertical force P and the tilt angle by (2.3) (2.4) For the reduced formulation where ==0 Finally, the energy release rate can be calculated by Regarding the mode-mixity it was revealed that the mode-mixity for a conventional TSD specimen remains quite unaffected by the tilt angle (Li and Carlsson, 2001). Furthermore, it was discovered that the unreinforced TSD specimens display positive mode-mixity phase angles for tilt angles up to around 80 for all analysed PVC core materials, thus provoking the crack to kink into the core (Berggreen and Carlsson, 2010). To increase the range of achieved mode-mixities by the TSD specimen, two modified designs of the TSD specimen were proposed by Berggreen and Carlsson (2010). In the first modified design the upper face sheet of the TSD specimen is reinforced by a thick stiff steel plate to increase the stiffness of the loaded face sheet as shown in Figure 2.10. It was shown that by reinforcing the upper face sheet with a stiff steel plate the range of phase angles is expanded because of increasing shear loading and crack tip root rotation in the specimen. 24 (2.5) (2.6) (2.7)
Figure 2.10: Schematic presentation of the first modified TSD specimen. Further modifications were made by reducing the global shear deformation of the core by reinforcing the left edge of the TSD specimen by placing a metal block, see Figure 2.11. To avoid compression failure of the core at the right end of the reinforced TSD specimen due to rotation of the reinforced face sheet, a short link is pin-attached between the rigid base of the test rig and the centre of the steel reinforcement bar on both sides of the TSD specimen, see Figure 2.11. Figure 2.11: Schematic presentation of the second modified TSD specimen. 25
Page 1: Residual Strength and Fatigue Lifet
Page 4 and 5: Published in Denmark by Technical U
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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 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 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
Page 90 and 91: listed in Table 4.1. The length and
Page 92 and 93: The strain energy release rate, G,
Page 94 and 95: high growth rate of G (see Figure 4
Page 96 and 97:
4.4 Face/Core Fatigue Crack Growth
Page 98 and 99:
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
Page 130 and 131:
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:
This page is intentionally left bla
Page 160 and 161:
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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This page is intentionally left bla
Page 168 and 169:
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
Page 188:
DTU Mechanical Engineering Section
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Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

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