A High-Throughput LIPIT System for V50 Testing

Traditional laser-induced particle impact test (LIPIT) methods incorporate a “pusher” layer: an elastic material that captures the ablation gasses, expands, and drives a microsphere. While most groups currently launch projectiles with diameters less than 100 µm, fabrication of typical protection materials in that size regime can be difficult since the thickness of the target material needs to scale with the projectile diameter. Thus, the focus of this work was to develop a high throughput system that could launch 300 µm projectiles at speeds up to 500 m/s, which would allow for V50 testing of metallic targets greater than 50 µm thick. The LIPIT system developed in this work incorporated a custom fixture designed to hold 25 projectiles at a time. Each projectile had an individual barrel, which allowed the ablation gasses to accelerate the projectile over a longer distance than the traditional “pusher” layer method. Two experiments were conducted to evaluate the scalability of V50 results across a 10X size scale. The first experiment used a LIPIT system, which launched 300 µm SS304 sphere projectiles at 50 µm thick Al-6061-T6 targets. The second experiment used a compressed gas gun, which launched 3,000 µm SS304 sphere projectiles at 610 µm thick Al-6061-T6 targets. The novel barrel fixture used in this study increased velocities by a factor of 6.5 compared to the traditional pusher layer method. The ballistic limit determined during the LIPIT experiments was within 13% of the ballistic limit determined during the compressed gas gun experiments. These results indicate that the ballistic performance at a sub-millimeter scale translates to macroscale ballistic testing for this material. Additionally, the rate of LIPIT testing was six times faster than the rate of compressed gas gun testing. Thus, the results and developments from this study strengthen the case for using LIPIT as an economical and effective method for evaluating the ballistic performance of materials.