FRACTURE-MECHANICS OF COMPOSITES WITH NONHOMOGENEOUS INTERPHASES AND NONDILUTE FIBER VOLUME FRACTIONS

A linear elastic fracture mechanics model is developed for a periodic composite geometry with a single cracked layer under uniform longitudinal strain. The interface between the fiber and the matrix can be nonhomogeneous, homogeneous or perfect. Four fracture mechanics models are considered: (1) dilute fiber volume fraction composite with nonhomogeneous interphases; (2) periodic composite with nondilute fiber volume fraction; (3) periodic composite with irregular fiber spacing near a matrix layer; (4) hybrid composites with more than one type of fiber. The stress intensity factors at the crack tips and the interface stress fields are studied to understand the fracture mechanics of composites as a function of the relative elastic moduli of the fiber, the matrix and the interphase, and the global and local fiber volume fractions.