Influence of particle volume fraction, shape, and aspect ratio on the behavior of particle-reinforced metal-matrix composites at high rates of strain

Compressive plastic deformation of particle-reinforced metal-matrix composites is investigated through numerical modeling at high rates of strain. The numerical modeling is performed using axisymmetric unit cell models, with the particles treated as elastic ellipsoids or cylinders embedded within a viscoplastic matrix. The constitutive behavior of the matrix material uses a power law strain-rate hardening formulation and is obtained from independent experimental results on the matrix. The flow stress of the composites is predicted over a range of strain rates for different particle volume fractions and for varying particle shapes and particle aspect ratios. The results show that both the flow stress and the strain-rate hardening increase with increasing volume fraction of the reinforcement. It is also shown that the rate-dependent flow stress is influenced not only by particle aspect ratio but also by particle shape (spheroidal or cylindrical). A simple analytical model has been constructed that is able to capture the quantitative features of the computational predictions. Both computational and analytical models have been compared with experimental data on two different composites from two different sources in the literature, with excellent quantitative agreement on the rate-dependent stress-strain behavior. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.