Characterizing hypervelocity (>2.5 km/s)-impact-engendered damage in shielding structures using in-situ acoustic emission: Simulation and experiment

Pervasive in outer space, hypervelocity impact (HVI), caused by man-made debris (a.k.a. space junk) and natural micrometeoroids, poses a clear and tremendous threat to the safe operation of orbiting spacecraft, and it will possibly lead to the failure of a space exploration mission. Addressing such an issue, damage in a downscaled two-layer space shielding assembly, engendered by HVI events with an impact velocity up to 4 km/s, was characterized quantitatively, using in-situ measured acoustic emission (AE) induced under HVI. A hybrid model, based on three-dimensional smooth-particle hydrodynamics and finite element, was developed, to achieve insight into the traits of HVI-induced AE waves and HVI-caused damage. Proof-of-concept simulation was accomplished using the hybrid model, in which a projectile, at various impact velocities, impinged a series of shielding assembly of different thicknesses, in a normal or oblique manner. Experimental validation was implemented, and HVI-induced AE waves were in-situ acquired with a built-in piezoelectric sensor network integrated with the shielding assembly. Results from simulation and experiment show qualitative consistency, demonstrating the capability of the hybrid model for depicting HVI-produced shock waves, and the feasibility of in-situ measurement of HVI-induced AE signals. Taking into account the difference and uniqueness of HVI against other ordinary impact cases, an enhanced, delay-and-sum-based imaging algorithm was developed in conjunction with the built-in sensor network, able to “visualize” HVI spots in pixelated images accurately and instantaneously.