A model based on the micromechanical mechanism of crack growth resistance in fiber reinforced brittle matrix composites is presented. The formulation of the model is based on a small scale geometry of a macrocrack with a bridging zone, in this case the process zone, which governs the resistance mechanism. The effect of high toughness of the fibers in retardation of the crack advance, and the significance of the fiber pullout mechanism on the crack growth resistance, are reflected in this model. The model allows one to address issues such as influence of the fiber spacing and fiber-matrix friction.
Two specific cases are analyzed. One represents the fracture initiation and concentrates on the development of the first microcrack between fibers. The second case deals with the development of an array of microcracks forming the bridging zone. In both cases a discrete fiber distribution is assumed. The analysis is based on an exact solution of the corresponding. boundary value problem.