Mechanical ignition of combustion in condensed phase high explosives

Condensed phased high explosives are metastable materials that release energy when subjected to a range of thermal, mechanical, and electrical stimuli. Recent interest in safety and low order response from these materials has emphasized the importance of the ignition of combustion under low amplitude (<10kbar), long duration (millisec) loads. The major scientific challenge is a physically based understanding of the processes leading to the ignition of combustion which will predict the violence and extent of the reaction based on global characterization of the materials. A model of the process of ignition of combustion has been formulated based on modification to the Frank-Kamenetskii equations for thermal explosions. With the modifications, the model represents a fully coupled thermal/ mechanical/ chemical kinetic global description of the ignition of combustion. The model places emphasis on the low-pressure equation of state parameters, the pressure dependence in the reaction rate kinetics, and the high rate mechanical properties of these materials. The scale of the thermal explosion problem in these materials is discussed and compared to the scale of classical hot spot theory in detonation physics. Literature references to the reaction kinetics resulting from one-dimensional time to explosion experiments and mechanical property data are included in the discussion. New impact experiments are being developed to better understand the relationship between the mechanical properties and the ignition threshold. Current research is focused on tritonal, PBXN109, and other explosives of interest.