Crack propagation due to brittle and ductile failures in microporous thermoelastoviscoplastic functionally graded materials

Plane strain transient finite thermomechanical deformations of heat-conducting functionally gradient materials comprised of tungsten and nickel–iron matrix are analyzed to delineate brittle/ductile failures by the nodal release technique. Each material is modeled as strain-hardening, strain-rate-hardening and thermally-softening. Effective properties are derived by the rule of mixtures. At nominal strain-rate of 2000 s−1 brittle crack speed approaches Rayleigh’s wave speed in the tungsten-plate, the nickel–iron-plate shatters at strain-rates above 1130 s−1, and the composite plate does not shatter. The maximum speed of a ductile crack in tungsten and nickel–iron is about 1.5 km/s, and that in the composite is about 0.14 km/s.