Interaction between transverse cracks and edge delamination considering free-edge effects in composite laminates

The high-cycle fatigue characteristics, especially the initiation and propagation of edge delamination, were investigated with quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates with a stacking sequence of [45/0/-45/90]S. To investigate the influence that transverse cracks have on the initiation and propagation of edge delamination, two types of specimens are used. One was a specimen where transverse cracks were arbitrarily introduced by static tensile loading before conducting the fatigue tests. The other was an undamaged specimen as new. As a result, it was found that the single transverse crack introduced before the fatigue test did not seriously affect the initiation of edge delamination. Moreover, the difference of the fatigue damage growth behavior depending on the applied stress level was observed. Under the test conditions of low-applied stress level and high-cyclic loadings, it was observed that the edge delamination grew before, or simultaneously with, the transverse crack propagation.