Ballistic impact testing of acrylic and alumina thin-films

High velocity projectiles cause damage to critical structures in space. Many of them travel at speeds of a few km/s to several hundred km/s. Such projectiles can punch through aircraft. In addition, bullets from modern weapons might reach 2.5 km/s. Spherical diamond projectiles are tested against Poly-Methyl-Metha-Acrylate (PMMA) and single-crystal corundum alumina (α-Al<inf>2</inf>O<inf>3</inf>) thin films. PMMA is created from two configurations: random and oriented along impact direction. The penetration velocity (V<inf>50</inf>) of PMMA and α-alumina are found to be near 400 m/s and 4.5 km/s, respectively. This study indicates that PMMA sandwiched between two layers of alumina can be produced, with a thickness that can be calculated using specific penetration energies (E<inf>p</inf>^∗) from the projectile radius, to stop most projectiles effectively.