Vented Chamber Calorimetry for Impact-Initiated Energetic Materials

Abstract

Over the past several years, the Naval Surface Warfare Center, Dahlgren Division (NSWC-DD) and its contractors have used vented test chambers to evaluate the performance of impactinitiated energetic materials. These chambers are initially sealed but have a thin steel cover plate through which a test specimen is launched onto a steel anvil on the interior. During this impact process, the test specimen perforates the thin plate and leaves a vent hole through which chamber gases are vented as the reaction takes place on the interior. The test chamber includes a variety of pressure and light measurements to gauge the performance of the test specimen. The quasi-static pressures have been the primary performance metric used to judge the performance of the material; these pressures most directly relate to the material’s ability to damage a target. This paper will derive the fundamental relationships between the peak quasistatic pressure and the total energy deposited into the gas within the chamber, thereby allowing calorimetric measurements using the vented chamber system. Particular attention will be paid to the uncertainties and assumptions associated with this derivation, including assumptions about gas properties, venting from the chamber, and distribution of the energy between kinetic and potential energy in the gas-phase.