Hypervelocity Impact Performance Polymer Coated Ballistic Fabric Back Bumper

This paper discusses an approach to improve the structural performance of the fabric back bumper in a Whipple shield design for space applications using a polymer spray coating, 3M Super 77 adhesive on the fabric layers. The use of a polymer coating protects the fabric layers from extreme environments. The efficiency of the coating in improving the ballistic performance was verified using high-velocity impact using a single-stage light gas gun. For the hypervelocity impact experiments, a triple bumper configuration with a 3 mm Al 6061-T6 plate as the front bumper, pristine and coated fabric as the back bumper, and a 2 mm Al 6061-T6 plate as a witness panel. To match the areal density, 9 layers of coated fabric were compared with 10 layers of pristine fabric in this study. The hypervelocity impact experiments were performed using a two-stage light gas gun (LGG) at speeds of 1.9 to 2.1 km/s using an Aluminum projectile (Al 2017-T4) of 5.56 ϕ mm and 0.25 g weight. The maximum radius of damage was observed to be higher in the case of coated fabrics and the intensity of damage was observed to be lower compared to the pristine fabrics. On evaluating the penetration area on the back side of the witness plate, for all the impact cases the penetration area of the pristine fabrics was higher than the coated fabric back bumper. A 28.8 percent decrease in penetration area was observed as a result of the coating method over pristine fabrics. The increase in friction coefficient due to the coating process increases the area of fabric involved during impact increasing the energy absorption of the fabric system. Moreover, the coated fabrics help to further fragment the projectile than the pristine fabrics, increasing the debris spread and decreasing the concentration of the high energy particles after impact. Experimental results showed that the coating process is a feasible and potential design approach to improve the shielding efficiency of the Whipple shield design.