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 compression strength of a composite containing coated, circular fibers. The theoretical development is based on the assumption that shear failure in the matrix governs the compression strength of a unidirectional composite material. The stress concentrations in the matrix are dependent upon the geometry of the fiber and the interphase or coating region around the fiber. Analytical results suggest that an optimum interphase might exist to maximize compression strain to failure. However, in general stiffer coatings appear to provide larger compression strength than do compliant coatings. To evaluate the analytical model, composites containing glass fibers coated with 5 different materials were manufactured. Tests on these samples support the trends predicted by the model and the strong dependence of compression strength predictions on coating properties.