HIGHLY OBLIQUE IMPACTS INTO THICK AND THIN TARGETS

Hypervelocity impact (HVI) tests have been conducted at the JSC Hypervelocity Impact Test Facility (HIT-F) with aluminum projectiles impacting semi-infinite (thick) and thin aluminum plates (with plate thickness to projectile diameter ratios of 6.4 and 0.14, respectively) at impact angles ranging from normal to the plate (0-degrees) to highly oblique (88-degrees). The targets were impacted by solid homogeneous aluminum spheres from 1 mm to 3.6 mm diameter. Results of the HVI tests were not unusual up to approximately 65-degrees, where impact damage is characterized as smooth craters and holes that become progressively elliptical and distended along the projectile flight path. Above 65-degrees angles, however, a transition occurs to an irregularly shaped hole in thin materials and rough bottomed crater in thick targets. Above approximately 80-degrees, multiple damage sites in the targets were formed with the damage areas separated by variable distances of undamaged target surface. Analytical and numerical simulations of the impact process at oblique angles above 65-degrees demonstrates that shock compression and release of the projectile into multiple fragments occurs before the projectile fully engages the target. The resulting projectile fragments are then responsible for the multiple impact sites observed on the targets.