High strain rate deformation in particle reinforced metal matrix composites

A micromechanics study is carried out for the high strain rate deformation of ceramic particle reinforced metal matrix composites. The ceramic particles are taken to be elastic, equal-sized, spherical and uniformly distributed in the matrix. The stress-strain behavior of the matrix material is assumed to be elastic-perfectly plastic or power-law strain hardening of the Ramberg-Osgood type, coupled with power-law strain rate hardening. Systematic predictions are made of the composite flow stress as determined by inclusion volume fraction, the applied strain rate and the strain hardening exponent and strain rate sensitivity of the matrix. It is found that the effect of strain rate is coupled with inclusion volume fraction; the strain rate hardening of the composite can be significantly higher than that of the matrix due to the constraining effect of the inclusions. A simple constitutive expression is obtained which allows one to predict readily the rate-dependent plastic flow behavior of the composite. Comparison between the model predictions and experimental measurements for the strain rate dependence of an Al/Al2O3 composite shows good agreement.