Plasticity in Energetic Molecular Crystal HMX: Physical Aspects and Constitutive Modeling

Plastic deformation plays a key role in the initiation of energetic materials at impact velocities below the hydrodynamic limit. However, the mechanisms of plasticity in low symmetry molecular crystals are much less studied than those governing the plasticity of monatomic crystals. In this work we investigate the physical basis of plastic deformation in HMX and develop mechanism-based constitutive models which are calibrated based on molecular simulations. The talk will outline several aspects of the physics of plastic deformation, including the mechanisms causing strain rate sensitivity, the pressure sensitivity and the mechanism of strain hardening. A constitutive model that accounts for this physics and which can be used in continuum simulations of shock and initiation will be introduced.