Internal stress measurements in a model Cu-sapphire composite

Abstract

MMCs (metal-matrix composites) have potential for structural applications, but their introduction as engineering components is limited by their tendency to sustain damage at modest plastic strains. Various methods have been used for the measurement of internal stresses in the reinforcement of MMCs, including dispersive x-ray diffractometry, x-ray diffraction, neutron diffraction and exploiting the birefringent properties of photoelastic materials. A new method has emerged which uses the piezospectroscopic effect, the observed stress dependence of electronic transitions in some optically transparent crystals. The present work exploits this method to gain information on the load transfer process in a model Cu-sapphire composite by measuring the residual internal stresses in a sapphire fiber subsequent to plastic straining of the composite in plane strain compression.