Residual Thermal Stresses in Filamentary Polymer-Matrix Composites Containing an Elastomeric Interphase

Abstract

A three-phase micromechanical model based on the method of cells is for mulated to characterize residual thermal stresses in filamentary composites containing an in terphase between the fiber and the matrix. This is the first such study to incorporate a true three-phase version of the method of cells. The model's performance is critically evaluated using data generated from other micromechanical models. Subsequently, a parametric study is performed to quantify the residual stresses in two hypothetical graphite fiber/epoxy matrix composites: one containing an elastomeric interphase whose Young's modulus is less than that of the fiber and the matrix and one incorporating an interphase whose Young's modulus is intermediate with respect to the fiber and the matrix. The data correlate the residual ther mal stresses in the fiber, interphase and matrix as a function of the interphase thickness and fiber volume fraction within each model composite. The study makes a broad assessment of the stress-attenuating characteristics that each interphase imparts to the graphite/epoxy com posites. Over the range of variables considered, properly dimensioning the elastomer inter phase leads to a more favorable reduction of residual thermal stress.