Modification of residual thermal stress in a metal-matrix composite with the use of a tailored interfacial region

Abstract

A three-component cylinder model of a unidirectional composite is used to evaluate the importance of an interfacial region in the build-up of residual thermal stress. The components consist of the fibre, an interfacial region and the surrounding matrix. Four mismatch of thermal expansion terms are obtained from this analysis. Each is examined for its contribution to the residual stress state by comparing the coefficients of each mismatch term. The residual stress problem is seen as being influenced by more than the mismatch between the fibre and the matrix. When anisotropic fibre expansion exists in the specific metal-matrix composite, the interfacial region has a significant contribution to residual stress build-up. Further, an interfacial region with an elastic modulus of the order of the elastic modulus of the fibre has a larger effect on the residual stress than when it is of the order of that of the matrix. For an aluminium-matrix composite this large contribution is deleterious and a compliant interfacial region is preferred due to the present considerations.