The deformation of discontinuously reinforced MMCs-I. The initial yielding behaviour

A new method of defining the onset of yielding is proposed. This is shown to be physically more appropriate than a conventional proof stress for the comparison of the yield behaviour of inhomogeneous materials such as MMCs. For whisker reinforced materials, the criterion adopted is shown to be sensitive to the localised relief of the inhomogeneous matrix stress. Further, through a comparison with the conventional 0.2% proof stress, it is possible to interpret both the early work hardening behaviour and the initial inhomogeneity of internal stress development in MMCs.