The Laser-Induced Particle Impact Test (LIPIT) has become a prevalent method for probing projectile, target, and synergistic projectile-target responses to high strain rate deformation on the microscale. LIPIT’s advantages over other microscale launching techniques include the ability to controllably launch a single microparticle and precisely characterize the projectile momentum and kinetic energy before and after target impact. In addition, a LIPIT apparatus possesses a relatively small laboratory footprint and is suitable for extension to high-throughput testing. For these reasons, LIPIT experiments have been used to study the impact response of many material systems, such as polymers, gels, and metals, in various structural forms. In these previous studies, microscopic high-rate deformation behavior and impact energy absorption were used to suggest potentially promising materials for macroscopic applications. Geometric scale, however, can significantly influence dynamic material behavior through scale-induced changes in strain rate, event time, and projectile/target material homogeneity. Hence, extrapolation of microscopic impact phenomena should be done with extreme caution. In this study, such geometric-scale effects are intentionally investigated. Noncrystalline alumina spheres ranging five orders of magnitude in diameter (D) (1 µm–1 cm) are launched into scaled D/h polycarbonate targets of thickness (h) at normal incidence using either LIPIT or a gas gun, depending on the scale. For all experiments, projectile impact velocity and the ratio of projectile diameter to target thickness are held fixed. Specific impact energy absorption, local plastic deformation, and deformation microstructure are compared across all scales. This study serves towards understanding the influence of geometric scale on material high-rate deformation behavior and impact energy absorption when scales range from the microscale to macroscale.
2025-04-09 09:00:00
