13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- HS2 glass fiber and TDE-85 epoxy resin. Figure 1. Lay-up of advanced hybrid laminates Centre crack tension (CCT) specimen was selected for this research, as shown in Fig. 2. Two kinds of saw-cut size, 2as=10mm and 15mm, were processed in order to explore influence of saw-cut length on crack opening contour and delamination behavior. 270 135 75 37.5 Figure 2. Centre crack tension (CCT) specimen 1.2 Fatigue Crack Propagation Test Fatigue crack propagation test was finished with constant-amplitude sine wave fatigue loadings, the frequency of 10 Hz and the stress ratio R of 0.1 on 2.5T MTS-858 electohydraulic servocontrolled fatigue testing machine. Crack length was observed by two JDX-B magnification microscopes with scale of 30X. Average crack length am is obtained by averaging the front-left side crack length a1 and back-right side crack length a2. The matrix of the test is shown in Table 1. Table 1. Matrix of fatigue crack propagation test Saw-cut length 2as/mm Stress level σmax/MPa Target average crack length am/mm 10 60 12，17，22 10 85 12，17，22 15 60 12，17，22 Crack opening contours are captured when am reaches nearly 12mm, 17mm and 22mm. Specific measurement method is: take pictures of crack area with a ruler after applying a tension loading which equal to the maximum fatigue loading, then measure the crack opening contour by using image measurement software, and finally obtained the crack opening contour, as shown in Fig. 3. L direction of aluminium alloy sheet and the direction of fiber outer aluminium alloy sheet 2mm 2A12-T4 0.5mm LY12-M adhesive film prepreg inner aluminiumalloy sheet inner aluminiumalloy sheet central aluminium alloy sheet outer aluminium alloy sheet 2mm 2A12-T4 2as
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