On the Role of Interphases in the Transverse Failure of Fiber Composites

A numerical investigation into the effect of interphase properties on the transverse strength of unidirectional fiber-reinforced composites is carried out in the con text of plane strain linear elasticity. The phase geometry of the composite is modeled by a regular hexagonal array of fibers in a matrix, and the interphase behavior is represented by a constrained spring layer model. A variationally coupled finite element-boundary ele ment method is used to obtain the mechanical response of a cell containing a center fiber and parts of surrounding fibers. We assume matrix cracking to be the predominant mode of failure. It is demonstrated that the interphase properties significantly affect the overall cracking patterns. Issues regarding the strength and integrity of the composite are dis cussed.