Numerical investigation of damage and ignition behaviors of PBX under punch loading

The major damage and ignition features of polymer bonded explosive (PBX) subjected to punch loading are captured by developed mechanical-thermal-chemical coupled multiphysics peridynamics (PD) framework. The framework integrates a four-step chemical reaction kinetics model and thermal effect induced by friction due to mechanical damage. The heterogeneous microstructures are explicitly taken into consideration, enabling different fracture modes such as intergranular and trans-granular fractures can be captured. Results show that the dynamic damage is characterized by the formation of a triangular-shaped dead zone, in agreement with Prandtl's prediction. Flow field analysis implies that the changes of flow field in the transition zone are responsible for the temperature rise. The riskiest positions to ignite are the boundaries of the triangular-shaped dead zone and the region inside the dead zone. Furthermore, sliding friction dissipation associated with trans-granular fracture and inter-granular fracture are responsible for the ignition along the boundaries of dead zone and inside the dead zone, respectively. The analyses on mechanical damage and temperature rise reveal that mechanical damage precedes the temperature rise. Simulation results provide novel insight into ignition mechanism of PBX, which can be used to construct more accurate physical model of non-shock ignition of PBX.