EVALUATING THE INFLUENCE OF FIBER COATINGS ON THE COMPRESSION STRENGTH OF A UNIDIRECTIONAL POLYMER COMPOSITE

In this paper we present an analytical model to predict the compressio n strength of a composite containing coated, circular fibers. The theo retical development is based on the assumption that shear failure in t he matrix governs the compression strength of a unidirectional composi te material. The stress concentrations in the matrix are dependent upo n the geometry of the fiber and the interphase or coating region aroun d the fiber. Analytical results suggest that an optimum interphase mig ht exist to maximize compression strain to failure. However, in genera l stiffer coatings appear to provide larger compression strength than do compliant coatings. To evaluate the analytical model, composites co ntaining glass fibers coated with 5 different materials were manufactu red. Tests on these samples support the trends predicted by the model and the strong dependence of compression strength predictions on coati ng properties.