Influence of reinforcement fracture on the cyclic stress-strain curve of metal-matrix composites

The cyclic stress-strain curve of a 2618 Al alloy reinforced with 15 vol.% SiC particulates was measured through the incremental step method in the naturally aged and peak-aged conditions. The mechanical response was also simulated by means of the finite element analysis of a unit cell to determine the average stresses acting on the matrix and on the reinforcements during cyclic deformation. The stresses on the reinforcements were used to calculate the fraction of broken reinforcements by assuming that the reinforcement strength follows the Weibull statistics. Then the cyclic stress-strain curve, including the influence of reinforcement fracture, was obtained by neglecting the load carried by broken reinforcements. Finally, the predictions of the model (the cyclic stress-strain curve and the fraction of broken reinforcements) were compared with the experimental results.