Multi-scale constitutive modeling of Ceramic Matrix Composites by Continuum Damage Mechanics

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The microscale damage mechanisms in brittle ceramics are investigated in detail and a Continuum Damage Mechanics (CDM) model is developed in this work to study two common failure modes in Ceramic Matrix Composites (CMC), i.e. matrix/interphase fracture and fiber sliding. In order to empower the developed framework for performing crashworthiness studies, the effect of the dynamic energy density content on the microscale fracture modes of CMCs is also considered. The CDM model is developed within a physically consistent framework that includes basic fracture mechanics of CMCs. Also the CDM model is developed in such a way that most of the material parameters are directly obtainable form the experimental data rather than cumbersome and time consuming numerical curve fitting techniques. In order to construct a computationally effective multiscale analysis platform for CMCs, this work aims to provide an asymptotic solution for a microscale representative volume element (RVE) which represents the fiber, interphase and matrix interactions. The developed asymptotic solution can capture the non-linear response of CMCs through CDM model; and it considerably reduces the computational cost of hierarchical multiscale analysis in comparison to the numerical methods, e.g. numerical models that simulate the real microstructure. The CDM model and the RVE asymptotic solution are utilized to study the microscale damage mechanisms in CMC systems. It is shown that the developed scheme performs quite well in capturing available experiments in the literature and provides a comprehensive description of microscale damage mechanisms in CMCs. The developed framework can be utilized in the future developments of the hierarchical multiscale analysis of CMC systems.