Numerical modeling of composite propellant response to drop weight impact

Abstract

Abstract Finite element analysis is used to study the dynamic response of propellant subjected to drop weight impact. The model of the propellant incorporates varying amounts of ammonium perchlorate (AP) particles to account for stress concentrations due to sample inhomogeneity. The intent of this study is to examine locations which may lead to critical initiation shear stresses such as AP sliding on AP or AP sliding on steel. The initial full AP model used a 60% (by weight) solids loading corresponding to a research propellant formulated for a companion experimental program. Due to the unusually high number of slidelines which are needed to model the friction between the AP particles and surrounding media, the code was not capable of compiling the full model. Other models have been run to examine the effects of a few AP particles on the resulting stress state in the propellant. These models show significant increases in the maximum shear stress at locations immediately surrounding the AP particles. Quantitative comparisons are also made between homogeneous propellant and AP–in–propellant models. Two–dimensional geometric constraints of the code are also discussed. In particular, it is shown the default axisymmetric and the alternative plane strain geometries have limitations which do not allow for proper modeling of the particles. Finally, the limitations of using hydrocodes for simulating the effects of particles in propellant are discussed along with recommendation for further work.