Multiscale Investigation of Micro-Cracking at Composite Laminate Free Edge

Abstract

To investigate the effect of microscopic features on initial micro-cracking at the laminate free edge, a two-scale finite element (FE) modelling approach is proposed. It consists of a meso-scale model to capture the laminate stacking sequence and the global stress field under a given loading condition, and a micro-scale model to predict the local constituent level stresses at the free edge. The two models are coupled oneway through a strain localization rule. A procedure to determine the boundary conditions for micro-scale FE models containing a free edge has been developed. The model developed this way was used to examine the 90/90 interface in [25N/-25N/90N]S composite laminates. The effects of thermal and tensile loading were investigated separately to understand the influence of interlaminar microstructure on micro-scale stresses at laminate free edges during manufacture and under mechanical loading. The results agreed with the trend of free edge pre-cracks and progressive damage observed in experiments.