Hypervelocity Impacts on Thin Metallic and Composite Space Debris Bumper Shields

Abstract

The mechanism of hypervelocity impact crater formation in metallic and composite space debris shields has been investigated. Both normal and oblique impact crater formations have been investigated using 2.2-mm-thick aluminum (At 2017), carbon fiber reinforced plastic (CFRP) and aramid fiber reinforced plastic (AFRP) space debris shields in a two-stage light gas gun. A cylindrical projectile made of high-density polyethylene (14 mm in diameter and length) at a muzzle speed of 5.0 +/- 0.2 km/s is used to create the craters in the debris bumper shields. The microscopic study reveals the formation of adiabatic shear bands near the crater zone, from where the secondary cracks emerge, ultimately resulting in the formation of the craters in thin aluminium plates at impact angles of 90, 51, and 64 deg. On the other hand, surface delamination zones caused by the peeling of surface piles surrounding the impact and exit craters are observed in the case of CFRP and AFRP debris shields at normal impact. To estimate the temperature near the craters, time-integrated spectrum of the light emission during the crater formation is recorded. The measurements are taken in the near-UV region of the spectrum. Based on the CN emission from the projectile material, the temperature of the debris cloud during normal and oblique impacts at 5 km/s are estimated to be between 7300 +/- 300 and 7600 +/- 300 K, respectively.