INTERFACIAL SHEAR AND MATRIX PLASTICITY DURING FIBER PUSH-OUT IN A METAL-MATRIX COMPOSITE

Interfacial shear during thin-slice fiber push-out of sapphire fibers bonded to a niobium matrix has been examined both experimentally and c omputationally. Observations indicate a failure process involving the combination of interfacial crack growth and diffuse matrix deformation at opposite ends of the fibers being displaced. The result is a stage during which 'stable' fiber displacement occurs under increasing axia l loads applied to the fiber. A straightforward analysis of the extent of this stage suggests that it obeys a load instability criterion, de pending on the competition between geometric softening due to interfac ial crack growth and strain-hardening within the matrix near the inter face.