Simplified Micromechanical Equations for Thermal Residual Stress Analysis of Coated Fiber Composites

The fabrication of metal matrix composites poses unique problems to the materials engineer. The large thermal expansion coefficient (CTE) mismatch between the fiber and matrix leads to high tensile residual stresses at the fiber/matrix (F/M) interface which could lead to premature matrix cracking during cooldown. Fiber coatings could be used to reduce thermal residual stresses. A simple closed-form analysis, based on a three-phase composite cylinder model, was developed to calculate thermal residual stresses in a fiber/interphase/matrix system. Guidelines, in the form of simple equations, for the selection of appropriate material properties of the fiber coating were also derived to minimize thermal residual stresses in the matrix during fabrication.