Examination of free-edge crack nucleation around an open hole in composite laminates

The present work examines the free-edge crack nucleation around an open hole in composite laminates by applying a cohesive zone (CZ) model. The boundary-value problem of an open hole with interfacial damage and crack in an infinite laminate plate under far-field straining is considered. The problem has been solved numerically by applying a special single-domain dual boundary element method for multilayered composites. While the fundamental solutions (i.e., integral kernels) satisfy the top- and bottom-surface boundary conditions and interfacial continuity conditions, only the hole surface, damaged interface, and cracks, where these conditions are altered, need to be discretized. The numerical examples have shown that the CZ model is capable of predicting the patterns of damage and crack and the critical loading for crack nucleation around the hole free-edge. In addition, the CZ model has been used to examine the dependence of the critical behavior of edge-crack nucleation on ply thickness and hole radius with the cohesive force law being fixed. It was found that the critical amplitude of far-field straining for the edge-crack nucleation does not vary with the ply thickness and varies inversely proportionally to the hole radius in the ranges explored.