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

The behavior of fiber-reinforced composites is governed by the crack-bridging force provided by the fibers, which can be obtained by the analysis 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 literature, the present work focuses on the component of crack-bridging force due to fiber bending, which is obtained by analyzing the bending of an elastoplastic beam on an elastic foundation with variable stiffness along the fiber. The possibility of matrix spalling below the fiber is also considered. Some of the assumptions made in the model are verified with more accurate analyses. Model prediction of the maximum crack-bridging force in metallic fiber-reinforced brittle matrix composites is found to be in reasonably good agreement with experimental results. A parametric study of the model reveals the existence of an optimal range of fiber yield strength that can provide the most desirable crack-bridging behavior.