Prediction of microscopic interface crack onset in fiber-reinforced composites by using a multi-scale homogenization procedure

An innovative two-scale method able to predict local failure quantities (fiber/matrix interfacial stresses, energy release and mode mixity for an interface crack) in an arbitrary cell from the results of a macroscopic homogenized analysis, is proposed. Microscopic crack initiation under mixed-mode loading conditions is thus analyzed by using a coupled stress and energy failure criterion in term of these local quantities. Numerical results are obtained for a plane strain model of a locally periodic fiber-reinforced composite material subjected to shear loading and characterized by initially undamaged fiber/matrix interfaces. Predictions for the critical load factor and interface crack length at crack onset obtained by the proposed model are compared with those obtained by means of a direct simulation.