A Pressure-Dependent Plasticity Model for Polymer Bonded Explosives under Confined Conditions

The safety of explosives is closely related to the stress state of the explosives. Under some stress stimulation, explosives may detonate abnormally. It is of great significance to accurately describe the mechanical response of explosives for the safety evaluation of explosives. The mechanical properties of polymer bonded explosives (PBXs) strongly depend on pressure. In this study, the mechanical behaviour of PBXs under confined conditions was investigated. It was found that the stress-plastic strain response of a PBX under high confining pressures is a combination of the non-linear and linear hardening portions. However, the linear hardening portion has often been neglected in characterizing the mechanical behaviour of a PBX under such pressures. The Karagozian and Case (K&C) model was applied to characterize the mechanical behaviour of PBXs. The numerical results demonstrated that when the confining pressure was high, the K&C model could not adequately match the experimental data due to the limitation of the damage model. Therefore, a new damage model was developed by means of considering intragranular damage and transgranular damage. This modification made it possible to introduce a linear hardening process into the original K&C model. The method proposed to describe the stress-strain results under high confining pressures was to consider the stress-plastic strain curve, including the nonlinear and linear hardening portions. The damage evolution of the original K&C model and a linear hardening model were applied for the nonlinear and linear hardening portions respectively. The influence of the linear hardening model on the damage evolution of the original K&C model was included when describing the nonlinear hardening portion. A comparison between simulation and experiment showed that the modified K&C model could well describe the mechanical response of PBXs under different confining pressures.