MICROMECHANICS PREDICTION OF THE SHEAR-STRENGTH OF CARBON-FIBER EPOXY MATRIX COMPOSITES - THE INFLUENCE OF THE MATRIX AND INTERFACE STRENGTHS

Presently there is great interest in understanding and improving the bonding between the fibers and matrix in high performance composite materials. Indeed, the fiber-matrix adhesion in many recently-developed systems is poor. To improve bonding, various fiber surface treatments have been developed. These treatments are often evaluated by measuring their effect on a composite property sensitive to the interfacial bond strength (e.g., the composite shear strength). Such methods are, however, inferential, and do not provide a direct measure of the strength of the interfacial bond. A method is presented to estimate the influence of the matrix and the interfacial bond strength itself on the composite shear strength for a given fiber/matrix composite. Analytical prediction of these effects has been achieved using a finite element micromechanics model. Numerical results generated using this model have been shown to compare well with experimental data, which suggests that the micromechanics approach to predicting constituent and interface effects on the composite shear strength is a potentially valuable tool.