Experimental analysis and multi-scale simulation of the fracture behavior of polymer-bonded explosives based on the dynamic notched semi-circular bend method

Polymer -bonded explosives (PBXs) are extensively utilized in both military and civilian applications. Therefore, an accurate measurement of their dynamic fracture properties is critical for ensuring the safety and stability in engineering applications. In this study, a split Hopkinson pressure bar (SHPB) loading system is utilized to conduct dynamic fracture tests on a notched semi-circular bend (NSCB) specimen. A crack propagation gauge (CPG) and a strain gauge (SG) are employed for capturing the transient crack propagation velocity, crack initiation, and unstable propagation at a specific moment. The dynamic fracture behavior of PBX-9001 can be categorized into three stages. To acquire the damage evolution data during loading, a finite element model based on the real crystal morphology, with a cohesive zone model (CZM) for describing the damage, is developed. Additionally, a multi-scale simulation model has been established to investigate the microscopic damage and degree of damage in PBX-9001. The microstructure of PBX-9001 exhibits toughening effects, and the initiation toughness and extension toughness are positively correlated with the loading rate. The multi-scale model effectively simulates the expansion behavior and damage evolution of PBX-9001. Overall, the findings of this study provide useful insights on the nonlinear fracture behavior and the influence of loading rate on the mesoscopic fracture mechanisms of PBXs.