Microcrack and microvoid dominated damage behaviors for polymer bonded explosives under different dynamic loading conditions

A damaged viscoelastic-plastic model incorporating with both microcrack and microvoid evolution laws has been developed and implemented in the hydrodynamic code DREXH, to predict overall mechanical behavior and gain insights into possible failure mode of polymer-bonded explosives (PBXs) under complicated dynamic loading conditions. Multiple stress-state loadings will motivate evolution modes of microcracks, i.e., friction-locked, shear with friction, pure shear, mixed shear and open, and normal open, or microvoids, i.e., void collapse, void distortion. The simulated results connected the asymmetry of PBXs under uniaxial tension and compression with the critical stresses for open-crack and shear-crack initiation. Under high-confinement compression, crack growth is inhibited due to friction-locked (stable) state while more voids become collapsed accompanying with a strong plastic flow, corresponding to the occurrence of brittle-to-ductile transition for PBXs. Under simple shear loading, growth of pure-shear crack contributes more on failure rather than void distortion for pressed PBXs. Effects of void distortion on failure become more important for PBXs containing higher-fraction ductile binder. The simulated results agree with experimental observations and contribute to deepening our understanding of underlying microcrack and microvoid mechanisms for dynamic mechanical failure behavior of PBXs.