Effect of Porosity on the Nonlinear and Time-Dependent Behavior of Ceramic Matrix Composites

The effect of porosity on the non-linear stress-strain response and time-dependent strain response under constant stress has been investigated. The material used in the study is a woven composite of CG-Nicalon™ fiber and SiNC matrix. The composite has been modeled using a model for spheroidal inclusions in a medium in combination with a micromechanics-based progressive damage and constituent inelasticity model for CMCs. Numerical estimates of deformation and failure are shown to compare favorably with experimental measurements. It has also been shown that porosity affects through-thickness properties more as compared to the in-plane properties and that creep rupture strength is significantly degraded by increased porosity in the material.