CRACK-BRIDGING FORCE - IN RANDOM DUCTILE FIBER BRITTLE-MATRIX COMPOSITES

The behavior of fiber-reinforced composites is governed by the crack-b ridging force provided by the fibers, which can be obtained by the ana lysis of debonding and bending of fibers across a crack. In this paper , a micromechanical model for the analysis of crack-bridging force is developed. As fiber debonding has been extensively studied in the lite rature, the present work focuses on the component of crack-bridging fo rce due to fiber bending, which is obtained by analyzing the bending o f an elastoplastic beam on an elastic foundation with variable stiffne ss along the fiber. The possibility of matrix spalling below the fiber is also considered. Some of the assumptions made in the model are ver ified with more accurate analyses. Model prediction of the maximum cra ck-bridging force in metallic fiber-reinforced brittle matrix composit es is found to be in reasonably good agreement with experimental resul ts. A parametric study of the model reveals the existence of an optima l range of fiber yield strength that can provide the most desirable cr ack-bridging behavior.