Shape effect of non-spherical projectiles on CFRP spacecraft structures

The vast majority of hypervelocity impact experiments that provide the underlying database for ballistic limit equations have been performed using projectiles with spherical shapes only. This, despite the fact that researchers have shown that a sphere is an unlikely shape for space debris and is a non-conservative assumption for shield perforation. In this paper, we investigate the effect of impactor shape on the shielding performance of carbon fiber reinforced polymer sandwich panels typical of spacecraft structures. We present five hypervelocity impact experiments involving disk, rod, and nugget shaped impactors and analyze the damage on aluminum witness plates placed behind the sandwich panel. Impactor orientation is accurately measured via two high-speed cameras, while the fragment cloud is recorded by a further two high-speed cameras. Experimental data is used to calibrate and validate a two-part numerical simulation. The first part of the simulation is performed with a discrete element simulation that is adept at capturing the fragmentation. The second part is performed with a finite element simulation to model the cratering and perforations in the aluminum witness plate. Experimental and numerical results are in good accordance allowing the numerical model to be used in future work to efficiently cover the wide parameter space opened up by the introduction of shape and orientation.