Microscale Analysis of Stress Wave Propagation Through Plastic Bonded Explosives Under Micro-Sphere Shock Impact

In this article, material stress during microscale shock wave propagation through hydroxyl-terminated polybutadiene (HTPB) binder and polycrystalline cyclotetramethylene-tetranitramine (HMX) based plastic bonded explosive is analyzed. An elliptical shock wave was created by 250 µm-size zirconia sphere impactors accelerated by a laser-based particle launch setup. Particle velocity and strain rate during shock wave stress rise were measured in the target using photon Doppler velocimetry. Viscous behavior of the HTPB binder was characterized through measurement of shock viscosity at strain rates higher than 106/s. Volumetric stress was measured at the interface region close to polycrystalline HMX particle and HTPB binder using in-situ time-gated Raman spectroscopy. Results show measured shock stress rise at the HTPB-HMX interface region is close to idealized simulation values. In-situ time-gated Raman spectroscopy predicts stress due to shock wave reflection from the HMX phase at the HTPB-HMX interface region. Predicted stress is higher than stress propagated through the binder because of impedance mismatch between HTPB and HMX.