Micromechanical assessment of local failure mechanisms and early-stage ply crack formation in cross-ply laminates

Abstract

Three-dimensional computational micromechanical models are developed to study local failure mechanisms and early-stage ply crack formation in a carbon fiber/epoxy [0/90/0] cross-ply laminate under tensile loading. Pressure-dependent inelastic deformation of the epoxy is captured by a user-defined material model, where brittle cavitation and ductile failure are considered local failure mechanisms. Manufacturing-induced defects, including nonuniform fiber spatial dispersion and resin pockets, are represented in the 90° ply. The effects of ply constraints on the local distortional and dilatational energy densities in the matrix are evaluated. Brittle cavitation is found to be the first and dominating failure mechanism, while local inelastic deformation indirectly influences the number and location of cavitation sites. Inelastic deformation is deemed necessary for predicting the linkage of the microcracks that are induced by brittle cavitation. The study provides important insight into the early-stage formation of ply cracks, which is essential for analyzing the subsequent ply crack formation.