Propellant Crack Tip Ignition and Propagation under Rapid Pressurization

Two major tasks performed during the report period were investigation of: (1) crack tip ignition phenomena under rapid pressurization and (2) crack propagation. Ignition of AP-based composite solid propellants located at the tip of an inert crack was investigated both experimentally and theoretically. Results indicate that the ignition-delay time decreases and the heat flux to the propellant surface increases as the pressurization rate is increased. In the theoretical investigation of the tip ignition event a comprehensive model for ignition of AP-based composite solid propellants was developed and numerical solutions were obtained. Crack propagation in a burning composite solid propellant subjected to rapid pressurization in the order of 10 GPa/s was investigated experimentally. The effect of pressurization rate on both crack propagation velocity and time variation of crack shape was studied. Experimental results indicated that the crack velocity increases as the pressurization rate is raised.