Thermal isolation modeling of aluminized energetic materials for low-cost computational code

Abstract. Aluminum is one of the main additives used to improve energetic materials’ performance. Furthermore, the presence of aluminum in detonating substances increases the non-idealities of the material, creating a mixture that is not in thermodynamic equilibrium once ignited. The non-idealities of aluminum can be described using theories such as the Wood-Kirkwood (WK) theory or Detonation Shock Dynamics (DSD). However, such approaches require algorithms with high computational costs. The purpose of this work is to provide a less computationally expensive alternative that adequately describes the thermodynamic behavior of aluminized explosives both during the reaction and the subsequent expansion. Less computationally expensive models, such as the Chapman-Jouguet (CJ) model and the isentropic expansion model, are based on assumptions of thermal and mechanical equilibrium among the various phases of the product mixture. Mechanical equilibrium operates over very short timescales, shorter than those of chemical kinetics, and remains a valid assumption even for aluminized explosives. However, the assumption of thermal equilibrium among the phases, in the presence of aluminum, is uncertain due to the rapid nature of the phenomenon. Two different hypotheses can be made in this regard: thermal equilibrium and thermal isolation. The latter hypothesis has been introduced into the CJ and isentropic expansion models, and a code capable of implementing the new model has been developed. Finally, the obtained results are compared with those available in the literature, and the isentropic expansion curve is fitted with the Jones-Wilkins-Lee (JWL) equation of state.