Multiscale modeling for dynamic compressive behavior of polymer bonded explosives

The impact damage behavior of polymer bonded explosives (PBXs) is critical to ensure the safety of explosive systems. PBX 1314 (60 wt% RDX, 16 wt% aluminum, and 24 wt% HTPB) is a popular propellant owing to its characteristics of high energy density and low sensitivity. In this study, the compressive damage evolution rules and the strain rate effect of PBX 1314 were investigated by using a multiscale method. To acquire damage evolution data during loading, a finite element model based on real crystal morphology, with a cohesive zone model (CZM) for describing the damage, was developed. A novel hybrid/inverse optimization strategy was developed to calibrate the cohesive parameters of PBX 1314, and the accuracy of the parameters was verified basis experimental results. Using an as-developed bilinear model, the shift of damage pattern with the variation of strain rate was observed, and the nonlinearity of the stress-strain curve was presented at the mesoscale. The crack parameters and distribution of damaged elements in each mesoscopic component were acquired to quantitively characterize the strain rate dependence of PBX 1314, and the mechanism of crack propagation and the shift of damage mode under various strain rates was illustrated. The findings of this study provide insights for understanding the nonlinearity of macroscopic mechanical behavior and the influence of strain rate on the mesoscopic damage mode of PBXs with high binder content.