The role of tension-compression asymmetrical microcrack evolution in the ignition of polymer-bonded explosives under low-velocity impact

The influence of microcrack on the ignition of polymer-bonded explosives is missing a comprehensive description of the cracking microstructure characteristics. In this article, the mechanical-thermal-chemical response of octahydro-1,3,5,7-tetranitro-tetrazocine (HMX)-based polymer-bonded explosives (PBXs) under low-velocity impact is investigated by a dynamic damage viscoelastic model with tension-compression asymmetrical microcrack evolution and a friction-based hotspot formation mechanism. The microcrack evolution fully considers cracking nucleation and growth, where the nucleation depends on tension or compression condition and the growth follows the law of the energy-release rate. The simulation concerns the mechanical and ignition response of HMX-based PBX in the Steven test. The cracking formation from tension or compression is captured, and the damage morphology is well simulated. The simulation on the ignition response reveals the effect of the cracking microstructure characteristics, including the initial microcrack density number and the tension-compression asymmetrical nucleation rate. In addition, heterogeneous microcrack density number is constructed by unimodal normal distribution and bimodal normal distribution, corresponding to pristine and damaged scenarios, respectively. The uncertainties in the microcrack density number are propagated and quantities in the mechanical-thermal-chemical-coupled model and further, the effect on the ignition, are obtained.