Role of Added Mass in Defining the Ballistic Limit of Polymer Thin Films

In traditional dynamic impact experiments such as projectile impact testing, a common metric for accessing a material’s ability to withstand such impact is the ballistic limit, which is defined as the maximum projectile velocity a material can sustain without puncture. In this contribution, we quantify the ballistic limit of thin polymer films using a recently developed micro-projectile impact test called laser-induced projectile impact testing (LIPIT). Specifically, we use LIPIT to study the puncture behavior of free-standing polycarbonate thin films with thickness ranging from 60 nm to 500 nm at microprojectile impact velocities ranging from 50 m/s to 200 m/s. We show that the critical film thickness that defines the ballistic limit changes with impact velocity. For a given impact velocity, find that the ballistic resistance is related to the increase in mass of the system, which can be controlled by increasing the thickness of the polymer film. These results have important implications in understanding the length scale-dependent puncture resistance of polymer thin films relevant to dynamic impact applications.