Validating thermomechanical models of cyclotetramethylene tetranitramine (HMX) through impulsively stimulated thermal scattering

Anisotropic single crystal effects play a critical role in the mesoscale behavior of energetic materials in response to external stimuli like dynamic loading. Properties like stress, strain, and temperature are strongly influenced by these orientation effects. In particular, anisotropic thermal conductivity effects can lead to phenomena like hot spot generation during impact scenarios, and potentially lead to deflagration or detonation. Models can predict the behavior of energetic materials in response to external stimuli; however, the accuracy of these models depends on the forcefields and inputs used in the simulation. Experimental validation capable of measuring predicted phenomena is a necessity. Impulsively stimulated thermal scattering, a pump-probe technique, can simultaneously measure the crystal orientation dependent sound speed and thermal conductivity. Experimental measurements of the thermal conductivity for HMX crystals suggest that the thermal conductivity varies between 0.39-0.67 W/m-K. Thermal conductivities were measured for (100), (010), and (011) orientations. Models have predicted the thermal conductivity to have values between 0.39-0.5 W/m-K. Experimental results will be used to refine the forcefields present in the models