Formation of interfacial voids in composites with a weakly bonded viscoplastic matrix

Abstract

The formation and evolution of interfacial voids are investigated in the case of metal matrix composites (MMCs) reinforced by ceramic fibres and subjected to high compressive loads. The resulting compression flows of a viscoplastic aluminum matrix around rigid fibres are described by a nonlinear free-boundary problem. A new finite element model with boundary-fitted mesh motion is introduced to simulate the formation of interfacial voids. The fibre–matrix interface is weak and allows yielding and sliding with separation at a dynamic contact line connecting three phases. The fibre–matrix interaction is simulated via a modified O'Donovan–Tanner constitutive model and a phenomenologically defined interface potential. The shape of the interfacial surface undergoing large deformation is not known a priori and found as a part of the solution. The influence of hydrostatic stress and constitutive characteristics of the matrix on the evolution of interfacial voids and their growth rates are examined. As the transverse strain increases, the evolution of interfacial voids occurs through a sequence of convex profiles. Numerical simulations are carried out for a special case involving small values of the yield stress and the viscosity of yielded matrix in order to compare them with similar results for linear viscous solids. The numerical results are also compared with the experiments involving similar compression flows of viscoplastic model materials.