Compressive failure analysis of non-crimp fabric composites with large out-of-plane misalignment of fiber bundles

Failure initiation under compressive loading in non-crimpfabric composites containing bundles with out-of-plane orientation imperfections was analyzed using FEM in plane stress and linear elastic formulation. The bundle orientation imperfection in a composite unit was described by a sine function. Failure initiation strain was determined comparing failure functions corresponding to two alternative failure mechanisms: (a) plastic microbuckling in bundle due to mixed compressive and shear load; (b) plastic matrix yielding according to von Mises criterion. Parameters for compressive failure initiation analysis were bundle misalignment angle, fiber volume fraction inside the bundle and bundle volume fraction inside the composite unit. The support effect of the neighbouring material was analyzed varying boundary conditions and solving cases with particular configuration of surrounding material. Model prepreg tape GF/EP composite with different introduced levels of out-of-plane waviness of layers was used to validate the conclusions from parametric analysis.