Lorenzo Leonetti

Prediction of Microscopic Interface Crack Onset in Fiber-Reinforced Composites by Using a Multi-Scale Homogenization Procedure

A two-scale method able to carry out a macroscopic failure analysis of a composite structure in presence of microscopic mixed mode interface crack initiation, is proposed. The method is able to accurately 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. Microscopic crack initiation 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.

A Concurrent Multiscale Model for Crack Propagation Analysis in Composite Materials

An innovative concurrent multiscale model is proposed for simulating transverse crack propagation in fiber-reinforced composite materials, based on a domain decomposition technique equipped with an adaptive zooming-in strategy. Under general loading, the crack path is not a priori known, as both fiber/matrix interface debonding and matrix cracking are involved. Therefore, a suitable crack path tracking strategy is proposed, based a moving mesh approach coupled with a shape optimization method. A number of numerical experiments have been carried out for assessing the validity of the proposed model, with reference to the complete failure analysis of a single notched fiber-reinforced composite beam subjected to both mode-I and mixed-mode crack propagation conditions.