Mixed mode II + III interlaminar fracture of carbon/epoxy laminates

This paper reports a study of the mixed mode II + III fracture of carbon/epoxy laminates. The specimens used were six-point bending plates with cross-ply lay-up and the standard 0/0 interface. Finite element analyses (FEA) were performed to select specimen geometries suitable for measuring the initiation critical strain energy release rate Gc over a wide range of mode mix ratios. The main difficulties were the non-uniform distributions of GII and GIII and the considerable geometric non-linearity. Nevertheless, experimental results suggested a quasi-linear evolution of Gc with the GIII/G mode mix ratio consistent with previously measured GIIc values and expected GIIIc > GIIc.