Ballistic Studies with Reactive Material Projectiles

Two important conclusions about the combustion of reactive materials under extreme loading are rooted in their ignition and energy release. From a physical perspective, there is an art to designing experiments that characterize the combustion of a reactive materials as a function of formulation, environment, and loading conditions. Thermodynamics dictates that if an impact induced reaction can be contained in a semi-sealed constant volume chamber, then transient pressure measurements reveal information about thermal energy buildup and release. From an understanding of thermal energy exchange, further conclusions about ignition sensitivity and energy release rates with the environment can be realized. Advances in diagnostics also enable two-dimensional transient temperature measurements of condensed phase materials. Specifically, high-speed cameras are modified to provide a thermal perspective of ballistic impact events. When applied to reactive material projectiles, thermography allows observation of energy transport through a fragmentation field. The role of condensed phase temperatures from reacting fragments on heating the gaseous environment is important. In this presentation, vented chamber calorimetry and thermography experiments reveal information about the ignition sensitivity and energy transport of reactive material projectiles impacting a target plate at velocities up to 1200 m/s. Multiple reactive material formulations will be discussed including projectiles composed of pure metal (aluminum), two metals (intermetallic), and metal and metal oxide (thermite). The projectiles are examined in inert gas (argon) and ambient air environments. The environmental influence on ignition and energy transport is significant. The experimental observations provide a foundation for understanding the influence of varied parameters including formulation, environment, and loading conditions on reactive material performance in terms of ignition and energy generation.