Mechanism of void-debonding synergy mediated hotspot formation in PBXs: A multifield-coupled lattice spring model study

Accurate prediction of shock-to-detonation transition (SDT) in polymer-bonded explosives (PBXs) requires an understanding of multi-mechanism hotspot formation. To address this, we developed a novel mechanical-thermal-chemical coupled lattice-spring model (MTC-LSM) that explicitly integrates damage evolution (interfacial debonding, crystal/binder fracture), localized heat generation (friction, void collapse), and incipient reactions. This framework enables synchronized simulation of damage progression and temperature evolution under impact loading. The model successfully captures the primary PBXs damage characteristics. For non-porous PBXs, simulations show debonding progresses to crystal fracture with increasing impact velocity. At lower impact velocities, damage occurs but temperatures remain subcritical. Higher impact velocities intensify binder-crystal debonding interactions, inducing sharp interfacial temperature rises conducive to hotspot formation. In porous PBX, void collapse alone at moderate impact velocities generates subcritical temperatures. However, at significantly higher impact velocities, synergistic void collapse and debonding enhance void-interface coupling, producing pronounced temperature spikes. This mechanistic understanding of void-debonding synergy provides new insights into hotspot formation physics, offering critical guidance for suppressing ignition risks in PBX design.