Residual Strength and Fatigue Lifetime of ... - Solid Mechanics
Residual Strength and Fatigue Lifetime of ... - Solid Mechanics Residual Strength and Fatigue Lifetime of ... - Solid Mechanics
Figure 5.25: Kinking of the crack into the core during pre-cracking for an MMB specimen with H100 core. Crack kinking into the face Figure 5.26: Kinking of the crack into the face sheet during pre-cracking for an MMB specimen with H100 core. After pre-cracking, fatigue tests were performed on the MMB specimens. Fatigue crack growth paths for the MMB specimens are shown in Figure 5.27. The crack propagates in both specimens just underneath the face/core interface and below the resin-rich cells. 10-12 mm stable crack growth was measured for all MMB specimens where the crack growth eventually seized. 108
Figure 5.27: Fatigue crack growth path for H45 and H100 MMB specimens. The fatigue crack growth rates data are plotted against the energy release rate (G) obtained from the finite element analysis in Figure 5.28. As it was mentioned earlier, due to large-scale fibre bridging in the H250/GFRP interface, linear elastic fracture mechanics is not valid and no measurements were conducted for this interface. In the Paris regime, which corresponds to stable crack growth and exhibits a linear relation between the crack growth rates and the energy release rates, the crack growth rates can be written as a modification of the traditional Paris Law: Crack path underneath the face/core interface for typical H45 MMB specimens Crack path underneath the face/core interface for typical H100 MMB specimens 109 ( 5.5) where m is the slope of the curve and G is the difference between maximum and minimum energy release rates at the crack tip in each cycle. The energy release rate is determined from the finite element analysis of the MMB specimens. Figure 5.28 illustrates the influence of core density on the crack growth rates. As seen in Figure 5.28 the scatter of the results for the H45/GFRP is larger than that for H100/GFRP, which can be attributed to a larger cell size and increased brittleness of the H45 core. Furthermore, the magnitude of m is larger in the H45/GFRP than in the H100/GFRP interface, which indicates a faster crack growth rate due to the lower density and brittleness of the H45 core.
- Page 80 and 81: H130 MMB H130 Panel H250 MMB Interf
- Page 82 and 83: 3.6 Conclusion In this chapter the
- Page 84 and 85: This page is intentionally left bla
- 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
- Page 100 and 101: B 2 1/ 2 ( S44 S55 S45) (4.17) wh
- Page 102 and 103: 75), which illustrates possible ina
- Page 104 and 105: Figure 4.18 (a) presents the deflec
- Page 106 and 107: Debond radius (mm) 100 90 80 70 60
- Page 108 and 109: using the cycle jump method, more t
- Page 110 and 111: Chapter 5 Face/Core Interface Fatig
- Page 112 and 113: of this chapter, sandwich panels wi
- Page 114 and 115: H250 Specimen H100 Specimen H45 Spe
- Page 116 and 117: Figure 5.5: Test setup. Initially,
- Page 118 and 119: H100 Specimen Fibre bridging Figure
- Page 120 and 121: propagation, the crack continues to
- Page 122 and 123: Figure 5.14: Kinking of the crack i
- Page 124 and 125: Crack length [mm] Crack length [mm]
- Page 126 and 127: mode-mixity phase angle was chosen
- Page 128 and 129: should be taken into account for a
- Page 132 and 133: log (da/dN) (mm/cycle) 10 log G (J/
- Page 134 and 135: erroneous extrapolations in the tra
- Page 136 and 137: compared to the 65% efficiency obta
- Page 138 and 139: the case of uneven debond growth, t
- Page 140 and 141: Load (kN) 2 1.5 1 0.5 0 Panel 1 Pan
- Page 142 and 143: Figure 5.42: Zero and ninety degree
- Page 144 and 145: G(J/m 2 ) 180 150 210 120 150 100 5
- Page 146 and 147: 110 q=qG=0.4 Test #1 100 Test #2 Te
- Page 148 and 149: panels were determined for differen
- Page 150 and 151: Chapter 6 Conclusion and Future Wor
- Page 152 and 153: toughness using MMB fracture toughn
- Page 154 and 155: For the specimens with H250 core th
- Page 156 and 157: 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.
- 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: This page is intentionally left bla
- Page 168 and 169: Out-of-plane displacement (mm) 1 0.
- Page 170 and 171: Out-of-plane displacement (mm) 3 2
- Page 172 and 173: A.5 Out-of-plane deflection of Debo
- Page 174 and 175: (a) Figure A.14: Out-of-plane defle
- Page 176 and 177: (a) (b) Figure A.18: Out-of-plane d
- Page 178 and 179: Load (kN) 250 200 150 100 50 250 30
Figure 5.25: Kinking <strong>of</strong> the crack into the core during pre-cracking for an MMB specimen<br />
with H100 core.<br />
Crack kinking into the face<br />
Figure 5.26: Kinking <strong>of</strong> the crack into the face sheet during pre-cracking for an MMB<br />
specimen with H100 core.<br />
After pre-cracking, fatigue tests were performed on the MMB specimens. <strong>Fatigue</strong> crack growth<br />
paths for the MMB specimens are shown in Figure 5.27. The crack propagates in both specimens<br />
just underneath the face/core interface <strong>and</strong> below the resin-rich cells. 10-12 mm stable crack<br />
growth was measured for all MMB specimens where the crack growth eventually seized.<br />
108
Change language