Statistical analysis of oblique crack evolution in composite laminates

A previously developed statistical model for transverse cracking in cross ply laminates is extended to oblique cracking in multidirectional laminates. The oblique cracks are assumed to form in a ply when the local in-plane tensile stress normal to fibers exceeds the transverse strength of the ply. This strength is assumed to have a statistical distribution given by a two-parameter Weibull function. The model is applied to a glass–epoxy [0/602/0/−602]s laminate in which cracking evolution of the four −60° plies in the middle of the laminate is examined. The local stress field in the cracked −60° plies is calculated by a three-dimensional finite element method based on a unit cell construction developed by Li et al. [1]. The measured crack density is found to agree well with that calculated by the statistical model.