Sensitivity Testing of Propellants in a Small-scale Experiment

The shock sensitivity and burning behavior of gun propellants are important performance and safety characteristics for developing insensitive munitions (IM) and are one of the key material characteristics determining the IM signature of ammunition. While the burning rate of gun propellants can be determined from standard closed vessel testing the determination of the SDT limit of a gun propellant charge is much more demanding. Investigating the shock sensitivity of energetic materials (EM) in standardized tests such as flyer impact or gap tests is important for identifying suitable energetic formulations. With advanced methods, initiation models for describing and simulating the initiation/detonation behavior of EM are derived from these experiments but the universality of these models is questionable. Generally, these must be tuned for each experiment and depend on the experimental results, from which they are generated. In this work a modified gap test setup is presented for examining the shock sensitivity of a single gun propellant grain. Measuring Time-of-Arrival (ToA) of the shock in the sample with miniaturized equidistant short circuit pins combined with two independent proofs of detonation measurements provides insight in the processes leading to the shock initiation of gun propellant charges during IM testing. This together with the simulation-based burn rate characterization developed at Fraunhofer ICT allows a
precise characterization of the IM relevant gun propellant properties with a minimum amount of sample mass.