Modeling of Diffusion in a Micro-Cracked Composite Laminate Using Approximate Solutions

Abstract

A set of approximate solutions for predicting through-thickness diffusivity and solvent uptake behavior of micro-cracked composite laminates is presented. In order to maintain solution tractability, Fickian diffusion is adapted as the basic framework of the model. Starting with the assumption of a uniform micro-crack array on the exposed faces of the laminate, an RVE (representative volume element) approach is employed to estimate the laminate through-thickness diffusivity as a function of crack depth and crack density. It is also established that, for the Graphite/Epoxy material system under consideration, the rate of moisture ingress into micro-cracks due to capillary imbibition does not have an appreciable long-term influence on the laminate diffusivity and uptake. The approximate solutions are verified by comparison with available test data from moisture uptake experiments and with finite element predictions.