Prediction of Nonlinear Specific Heat During Single Crystal HMX Phase Transition

We develop a thermodynamically consistent chemo-thermo-mechanical model for the $\beta\rightarrow\delta$ phase transition of energetic HMX crystals. In contrast to previous models, which either considered specific heat to be a constant or utilized a calibrated function, this model provides novel expressions for the specific heats at constant volume and constant elastic strains derived directly from continuum mechanics. In addition, the model provides a novel prediction for the critical temperature at which the chemical heating rate achieves its extremum for Arrhenius kinetics. The numerical solution predicts highly nonlinear specific heat behavior including order of magnitude changes.