13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- tip K values were finally obtained from tip J by LEFM relation in plane stress condition, al tip tip K E J = . They are presented in Table 3. 6. Observations Refer Figure 7a) and 7b). Numerical values of, load line, induced stress in aluminum layer and in fibre layer, al fr y induced σ ) ( , , and f fr y induced σ ) ( , , respectively, of un-cracked Glare, are close to the values available in Table 2 that validates the finite element model. Sample load line stress in aluminum layer and in fibre layer, y total al fr σ ) ( , , and f fr y total σ ) ( , , , of cracked Glare containing 5 mm crack are provided in Figure 7c) and 7d). Since no yielding is observed at the crack tip, LEFM regime is numerically confirmed. In addition, the values of al al fr y total Y σ ) ( , , are less than 0.5 that further support LEFM conditions in cracked aluminum. Laminate No. tip J (N/mm) tip K ( MPa m) 1 1.093 8.85 2 1.947 11.84 3 2.899 14.44 4 1.718 11.123 5 0.799 7.58 Table 3. Numerical values of stress intensity parameter at crack tips in Glare laminates Figure 6. Stress-strain plots of materials Stress (MPa) Stress (MPa) Strain (Strain×100) 2014-T6 aluminum alloy E-glass fibre Epoxy resin Stress (MPa) (Strain×100)
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