Interfacial Stresses and Void Nucleation in Discontinuously Reinforced Composites

This paper presents the theoretical predictions of the stress state at the inclusion-matrix interface in discontinuous metal matrix composites by the generalized inclusion method. In the author’s previous works, this method had been extended to the elastoplastic deformation in the matrix material. The present analysis of the ellipsoidal inclusion problem indicates that the regions at the pole and the equator of the particle/matrix interface essentially remain elastic regardless of the level of deformation, although the size of the elastic region keeps decreasing as deformation becomes larger. It was also found that, when the composite is undergoing a relatively large plastic deformation (strain), the maximum interfacial normal stress is approximately linearly dependent upon the von Mises stress and the hydrostatic stress. Based on the stress criterion for void nucleation, the author determined the void nucleation loci and nucleation strain for a composite subjected to an axisymmetric macroscopic stress state. The influence of interfacial bonding strength, inclusion shape, and volume fraction on the occurrence of void nucleation have been determined. The interfacial bonding strength in a SiC-aluminum system was re-evaluated by using existing experimental evidence. [S0094-4289(00)01301-3]