A micromechanical model for composites containing multi-layered interphases

This paper addresses the problem of predicting the behaviors of a composite material, which consists of a matrix phase and an ellipsoidal reinforcement coated by a multi-layered interphase, under one or more of the hygral, thermal and mechanical loading conditions and based on the micromechanics principles. The multi-layered interphase, which in general includes different properties for each layer, is modeled by applying the multi-inclusion model. The damage is considered by taking into account the progressive debonding of the reinforcement from the interphase. This damage mode is assumed to be controlled by a critical energy criterion and the Weibull distribution function. The effects of the composite parameters; interphase thickness, number of layers, properties of each layer, progressive debonding damage, reinforcement size and aspect ratio, and elastoplasticity of the matrix on the effective thermo–hygro-mechanical properties and the stress–strain response are presented and discussed. Moreover, by controlling the number of layers and their thermo–hygro-mechanical properties, composites with functionally graded interphases are investigated. To validate the predictions of the proposed microstructure-based model, results are compared to theoretical and experimental findings available in the literature and completely satisfactory agreements are obtained for both the micro-composites and nano-composites.