Scale Effects on the Perforation Resistance of Soft Materials

From animal and insect bites to drug delivery and ballistics, puncture by a fast-moving projectile into soft materials is an event that occurs in everyday life. Although common, the projectile size and incident velocity of the various puncture events can vary by over several orders of magnitude thus making it challenging to relate the puncture resistance of materials to the scale and conditions of the impact test. Using a microprojectile puncture test, we study the relationship between the minimum puncture velocity (V₀), microprojectile size, and impacted material thickness for two different polymer systems (polycarbonate and polymethylacrylate nanocomposite) with significantly different mechanical properties. By applying a Buckingham-Π dimensional analysis to our results, as well as published data on similar materials from macroscale projectile tests, we present a universal scaling relationship that correlates the size-scale of the system and material properties of the impacted materials to V₀ that spans over two decades. Our results have important implications in predicting and understanding fast puncture events on a variety of length scales, velocities, and test methods for different material systems.