APPLICATION OF A MULTIPHASE MIXTURE THEORY WITH COUPLED DAMAGE AND REACTION TO ENERGETIC MATERIAL RESPONSE

A multiphase continuum mixture theory is presented that couples the mechanical response, damage evolution, and combustion of energetic materials. The model is demonstrated to capture shock-to-detonation transition, deflagration-to-detonation transition and response due to low velocity impact. The modeling approach has also been demonstrated to simulate delayed detonation for rocket propellants and to investigate the violence of reaction in thermal explosion experiments. The model described here is implemented into the Sandia National Laboratories shock physics code CTH. CTH is a multimaterial Eulerian code with tabular and analytic equation of state options and various strength models. Traditional models for shock-to-detonation transition are not appropriate when the processes that lead to initiation are not initiated directly by mechanical shock. Most shock-to-detonation models are empirically based with input parameters fit to POP-plot and other relevant data. Often, the fits are not unique and several sets of reaction rate parameters will yield similar results. These models are often applied in situations that may not be appropriate. One example is low velocity impact. In a low velocity impact, the stress wave from the impact propagates through the material multiple times before a violent reaction occurs. During this early phase of the impact the energetic material response involves mechanical response, damage evolution, and chemical reaction. A key aspect of the multiphase mixture model is that the dynamic damage evolution interacts with combustion and the resulting enhanced surface area burning will accelerate to shock induced reactions if sufficient damage develops. This paper focuses on the implementation of a level set interface tracking model into the multiphase mixture model framework. The level set model is then demonstrated in a series of calculations