Isentropic compression studies of the mesoscale response of energetic composites and constituents

New experimental techniques and computational modeling provide an unprecedented means to enhance our understanding of energetic material behavior at the mesoscale. In this study, ramp quasi-isentropic compression loading tests (ICE) have been conducted using the Sandia National Laboratories Z machine to determine the appropriate constitutive and EOS property data of an energetic composite and constituents. These materials were subjected to a ramp loading history up to 4.5 GPa over 350 ns. At these conditions the effects of reaction are insignificant. Although explosives have been previously studied with the ICE technique, this work uses an experimental configuration with multiple samples of a composite explosive including its constituents. Hence, all materials are subjected to nearly identical loading, and a direct comparison of response is obtained. Various constituents of PBX 9501, including HMX crystals with different orientation, binder, and fine-particulate laden "dirty binder" are subjected to an identical ramp loading to isolate the dominant deformation features of the mechanical response. Particle velocities are measured during ramp loading, and analysis of the response determines appropriate stress/strain relationships. The mechanical response of large HMX crystals and the fine crystallites in the "dirty binder" of PBX9501 has been directly compared to the overall behavior of the composite mixture, and it is observed that much of the deformation is similar to the binder materials that reside at the interstitial locations. Upon a determination of the appropriate constitutive response, detailed mesoscale simulations have been conducted to determine the statistical variations of response that are the prelude to reactive behavior.