Thermal expansion of metal-matrix composites

The thermal expansion of various fiber- and particle-reinforced metal-matrix composites has been measured and the experimentally obtained values compared with the predictions of various theoretical models. The particulate composites exhibited some residual strain when cooled down from the peak temperature to room temperature. The magnitude of this strain was a function of the peak temperature and number of thermal cycles. The thermal expansion response of the fiber-reinforced composites was significantly different from that of the particulate composites. These composites exhibited very small residual strains when cooled down from the peak temperature to room temperature. In addition, the thermal expansion response was not linear over the test temperature range but exhibited regions of distinctly different slopes. The observed behavior of these particulate and fibrous composites is described on the basis of the thermal stresses developed in such composites as a result of the differences in the coefficient of thermal expansion between the reinforcement and the matrix.