Interfaces in AlCu-Al₂O₃ Metal Matrix Composites Studied by Mechanical Spectroscopy

Abstract
Mechanical spectroscopy has been used for studying the relaxation of the mechanical and thermal stresses, which are built at the fibre-matrix interfaces in AlCu-Al₂O₃ Metal Matrix Composites (MMCs). The interface strength has been evaluated by the stress dependent damping which exhibits a peak of solid friction. This peak is interpreted as due to interface microcracking. Relaxation of thermal stresses during thermal cycling has been studied by transitory effects which appear at low temperature in the mechanical loss spectrum. It may be concluded from the results that the mechanical performance of MMCs with age hardenable matrix is improved when the fibres are surrounded by a soft shell which is able to relax the interface stresses by local plasticity.