Real-time visualization and numerical investigation of the dynamic compression response behaviours of single AP/HMX particles embedded in an HTPB binder

An in-depth understanding of the behaviours of solid propellants under low-velocity impact loads is crucial for enhancing their safety in applications such as aerospace propulsion. This study investigated the dynamic responses of single ammonium perchlorate (AP)/octogen (HMX) particles embedded in a hydroxyl-terminated polybutadiene (HTPB) binder under dynamic compression loading via real-time synchrotron-based X-ray phase contrast imaging and a modified split Hopkinson pressure bar (SHPB) system. The compression of the viscoelastic binder and subsequent dynamic fracturing of the AP/HMX particles were captured. During compression, transverse cracks developed within the AP particles, and their propagation led to particle fracturing, resulting in ductile fracturing. Unlike AP, HMX generated numerous short cracks within the internal and edge regions simultaneously, leading to fragmentation and brittle fracturing. Moreover, particle damage reduced the modulus of the sample, shifting its dynamic stress response from nonlinear elasticity to strain softening and further strain hardening as the binder exhibited plastic deformation. A compression simulation incorporating a real particle microscopic structure was established to study the mechanical response of the interface and particles. The simulation results agreed with the experimental observations. These results indicate that the shear stress at the HTPB-AP interface is greater than that at the HTPB-HMX interface, which is a factor influencing the differences in the mesoscale damage mechanisms of the particles.