Modeling of Interphases in Fiber-Reinforced Composites Under Transverse Loading Using the Boundary Element Method

In this paper, interphases in unidirectional fiber-reinforced composites under transverse loading are modeled by an advanced boundary element method based on the elasticity theory. The interphases are regarded as elastic layers between the fiber and matrix, as opposed to the spring-like models in the boundary element method literature. Both cylinder and square unit cell models of the fiber-interphase-matrix systems are considered. The effects of varying the modulus and thickness (including nonuniform thickness) of the interphases with different fiber volume fractions are investigated. Numerical results demonstrate that the developed boundary element method is very accurate and efficient in determining interface stresses and effective elastic moduli of fiber-reinforced composites with the presence of interphases of arbitrarily small thickness. Results also show that the interphase properties have significant effect on the micromechanical behaviors of the fiber-reinforced composites when the fiber volume fractions are large. @S0021-8936~00!02501-0#