Thermal softening of a particlemodified tungsten-based composite under adiabatic compression

micromechanics study is made of the rate-dependent thermal softening behavior of a tungsten matrix composite containing glassy particles. Under adiabatic compression of the composite, the elastic glassy particles thermally soften at relatively high strains, enhancing the thermal softening of the tungsten-based composite, thus reducing the strain rate sensitivity and fostering shear localization. To guide the microstructural design of the particle-modified tungstenbased composite in penetration applications, systematic predictions are made for the stress-strain behavior of the composite under overall adiabatic compression with different temperature-dependent behaviors, sizes, volume fractions of the particle and different applied strain rates. The temperaturedependent behavior of the particles is characterized by a set of exponential functions using two nondimensional parameters and a reference temperature. The plastic behavior of tungsten is taken to be power-law strain and strain rate hardening. It is found that the radius r of the particles has very little influence on the composite behavior if r Q 10 q. It is also found that both the onset and the rate of thermal softening of the composite depend critically on the applied strain rate. Owing to thermal softening of the glassy particles, the strain-rate sensitivity of the composite is reduced. 0 1997 Elsevier Science Ltd.