DAMAGING AND EJECTION PROCESSES DURING HVI ON BRITTLE TARGETS: EXPERIMENTAL DATA AND COMPARISON WITH NUMERICAL SIMULATION USING AN SPH METHOD

Hypervelocity impacts on a spacecraft's surfaces result in ejecta or secondary debris production. These ejecta may contribute to a modification of the debris environment. Brittle materials are particularly sensitive to hypervelocity impacts and produce features larger than those observed on ductile targets. CEA faces to the same problem in the Laser MigaJoule project (LMJ), optics of large lasers are exposed to the chamber environment including hypervelocity shrapnel. This paper is devoted to the damaging and ejection processes during hypervelocity impacts on thin brittle targets (2mm thick fused silica targets for 500_m steel projectiles). Numerical simulations using Ls-Dyna SPH method and the JH2 material model were compared to experimental data obtained with CEA's light gas gun with satisfying results. Fragments ejected during the impact were experimentally collected, analysed and compared to the calculations.