AN ANALYSIS OF THE INFLUENCE OF REINFORCEMENT FRACTURE ON THE STRENGTH OF DISCONTINUOUSLY-REINFORCED METAL-MATRIX COMPOSITES

A micromechanical model was developed to study the influence of reinforcement fracture on the tensile strength of discontinuously-reinforced metal-matrix composites. The analyses were carried out within the framework of the shear lag model, which provides simple expressions for the average stresses acting on the reinforcement as a function of the matrix strength and of the reinforcement aspect ratio. The reinforcement strength was assumed to follow the Weibull statistics, and in this way, the fraction of intact and broken reinforcements can be obtained for any combination of matrix and reinforcement properties. The overall composite strength was then calculated by assuming that broken reinforcements do not contribute to the composite strengthening. The model was employed to study the influence of various parameters, such as matrix and reinforcement strength, and reinforcement aspect ratio and size, on the strength of discontinuously-reinforced metal-matrix composites. Finally, the model predictions were compared with experimental results on several high strength Al alloys reinforced with SiC particulates.