Stress Induced Matrix Microcracking in Brittle Matrix Plain Weave Fabric Composites under Uniaxial Tension

Abstract

A stress induced microcracking non-linear model is employed as part of an incremental and iterative hierarchical modeling procedure aiming at studying the evolution of damage in brittle matrix plain weave fabric composites, subjected to uniaxial tension. The study focuses exclusively on matrix micro-damage and its effects on the macroscopic non-linear woven composite response. For a given load increment, the requisite microstresses and associated state of matrix microcracking are updated through an iterative converging procedure that employs the woven microstress analysis model of Kuhn and Charalambides and the discrete microcracking model employed by Charalambides and McMeeking. While matrix microcracking is predicted in regions of high stress concentration at the early stages of loading, its non-linear effects on the macroscopic stress-strain curve were shown to become visible at applied normalized strain ε̂_x≈≈ 1. At about the same level of applied loading, the composite effective elastic in-plane properties in the ding and transverse directions were shown to degrade non-uniformly, thus resulting in damage induced macroscopic elastic anisotropies. The evolution of matrix micro-damage with the applied load was shown to initially take place within well defined, relatively narrow bands in regions of high stress concentration. With applied load increases, the matrix microcracking zones were shown to spread outward from the center of the unit-cell within a confined region thus forming macroscopic damage zones consistent with discrete micro-fracture events such as inter-bundle matrix cracking, bundle mode I cracking, and bundle transverse matrix cracking. The results are compared with experimental results presented by Aubard, Lamon, and Allix for a brittle matrix system with similar matrix and fiber material, but less complex microstructure.