ON THE STRENGTH OF DUCTILE PARTICLE-REINFORCED BRITTLE-MATRIX COMPOSITES

This study examines theoretically the strength characteristics of duct ile particle reinforced brittle materials in which the strength enhanc ement is derived from the crack bridging process. The crack bridging i s characterized by rectilinear and linear softening bridging laws that relate the crack surface traction to the crack opening displacement. The composite strength is expressed in terms of two non-dimensional pa rameters that combine the effects of the flaw size, elastic modulus, m atrix toughness, and the bridging-law parameters. It is shown that suc h composites can be substantially more flaw tolerant than the monolith ic matrices owing to a narrowing of the strength distribution. The rol e of interface debond length is also examined. It is shown that there exists optimal debond lengths of which the composite strength is maxim ized. In contrast, the steady state toughness increases monotonically with debond length. The implications of these results on the design of composite microstructures are briefly described.