THEORY FOR MECHANICAL PROPERTIES OF METAL-MATRIX COMPOSITES AT ULTIMATE LOADING

A model is presented describing the necking phenomena in metal-matrix composites. The model is based on a simple extension of the theory of necking in monolithic materials. This approach recognizes that brittle failure of necking must occur at elongations for which the force borne by the composite is maximum and explicitly calculates this elongation from the stress-strain curves of the constituents. Numerical solutions of the resulting equations agree well with reported values of necking strain and stress, and work to necking. To facilitate rapid initial evaluations of new composite systems and to illustrate the generality of the numerical results obtained here, a set of approximate analytic expressions for obtaining the variation of composite behavior is presented. Particular emphasis is placed on the dependence of necking strain and stress, and work to necking upon two commonly varied parameters, the matrix volume fraction and yield stress.