Open cell aluminum foam core sandwich panel structures have been proven to be of interest for protecting satellites against micrometeoroids and orbital debris (MMOD). Bumpers containing aluminum foam show outstanding capabilities to induce multiple shocks to small projectiles in the hypervelocity regime. For this work the protective performance of foam cored sandwich panels with cores made from newly developed hybrid metal foams was evaluated. Therefore shots in the hypervelocity regime on the two-stage light gas gun of the French-German Research Institute of Saint-Louis were performed. The tested targets were sandwich panels with aluminum front and rear facesheets and cores of different types of metallic foams: foams with pore densities of 10 pores per inch and 45 pores per inch were tested as pure aluminum and hybrid metallic foams. The projectiles to simulate micrometeoroids and orbital debris were aluminum spheres with a diameter of 4mm. The impact velocity was 6500m/s. It could be shown experimentally that the nickel coating of the aluminum foams leads to a decreased crater depth in the sandwich panels. However, scatter in the coating thickness leads to variations in the foam densities of the hybrid foams, making the evaluation of the increase in the protective performance difficult. Nevertheless, due to the nickel coating the influence of the pore density seems to be more significant than reported before. By reducing the coating thickness and using high performance aluminum alloys as base material for the hybrid foams, further optimization of the protective performance could be reached. Then, the complete evaluation of the ballistic limit over a broad velocity regime should be done to see the variations in the performance of the hybrid foams over the whole velocity range being of interest for MMOD shielding technologies

The present paper is devoted to three-dimensional numerical simulations of reactive two-phase flows in interior and transitional ballistics. The model presented takes a variety of phenomena into account such as mass transfer by the combustion of complex grain geometries, drag force experienced by the propellant bed in the gas flow, and convective and radiative heat transfer between the solid and the gaseous phase to simulate the process of ignition. A multi-dimensional finite volume scheme based on a nonconservative two-velocity one-pressure model is deployed to compute the pressure distribution in a 40mm weapon system, the velocity of the projectile, and the flow field of the muzzle flash. Comparisons between the obtained results and experimental findings, as well as the predictions of state-of-the-art lumped-parameter codes, show good agreement and serve as a validation. Finally, interior ballistics simulations involving novel grain geometries are discussed which exhibit more effective combustion properties as compared to conventional grains and thus lead to enhanced performances.