Micromechanical Analysis of Fiber-Reinforced Composites with Interfacial Phenomena. 2nd Report. Evaluation of Mechanical Properties of Discontinuous Fiber-Reinforced Composites.

Abstract

In the previous paper, micromechanical analysis was performed on a discontinuous fiber-reinfor-ced composite material showing interfacial sliding behavior between a fiber and a matrix, and analytical expressions for energy release rate and elastic modulus, etc., were derived. In the present paper, evaluation of mechanical properties of a composite with such an interfacial sliding characteristics, like a ceramic-based composite, is conducted based on the theoretical analysis of the previous paper. As a result, the calculated elastic modulus is in good agreement with the experimental one. Furthermore, fracture toughness of such a composite can be evaluated in terms of the critical size of the crack which travels across the material in an unstable manner. The effect of material parameters such as the volume fraction of the fiber, friction stress between the fiber and matrix, and the magnitude of sliding, on toughness can be explained by the interfacial phenomenon, whose results are consistent with common experimental facts. It should also be particularly emphasized that there exists an optimal value of friction stress between a fiber and a matrix for obtaining a tougher composite