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Thursday, January 31, 2019
2:00 PM - 3:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Postdoc Seminar

Thermo-mechanics of Crystalline High Explosives: Insights from Atomistic Simulations

Nithin Mathew

Energetic molecular crystals such as RDX, HMX, and TATB comprise the energetic component of polymer bonded explosives (PBXs) used in conventional and nuclear munitions. Localization of thermal andmechanical energy, commonly referred to as “hot spots”, is the precursor to initiation of chemical reaction in energetic molecular crystals subjected to shock and non-shock stimuli. The precise mechanisms, leading to the formation of hot spots and, affecting their subsequent temporal and spatial evolution is a matter of continuing research. For example, inelastic deformation of the energetic molecular crystal is arguably an important component in the processes leading up to formation of hot spots. Once formed, growth and spreading of hot spots depends on the energy balance between generative and dissipative processes, both of which are strongly affected by the materials phase state(crystalline/amorphous/molten) and the pressure/temperature-dependentproperties of those phases. In this talk, results on the strongly anisotropic, elastic-plastic response of HMX and TATB modeled with classical, non-reactive, molecular dynamics simulations of quasi-static and high-strain rate compression are shown. The pressure-dependent melting of TATB and pressure/temperature-dependent transport properties of liquid TATB are calculated, where the latter are not readily measurable in experiments. The pressure-dependent elasticity tensor of -HMX was evaluated and shown to be important for crystal-plasticity models to capture experimental results. Finally, recent results onsomewhat unexpected dynamical behavior in TATB and -RDX simulations will be presented, suggesting new thoughts on defining inelastic deformation in these materials.

Host: David Metiver