Crack Geometry Dependence on Kinetic Energy and Loading Rate in High-Speed Cavitation

Temporary cavitation occurs when a projectile impacts a soft material causing a large radial expansion of the wound tract immediately after the projectile passes. Though cavity size is known to scale with the kinetic energy of the projectile, the fracture-governed damage accompanying this large deformation remains poorly understood. Using a custom designed table-top ballistic cavitation device, we replicate the temporary cavity phenomenon in soft tissue simulants on a small scale by applying a fast, high-pressure pulse of air through a needle. Temporary cavities produced via air pulse (characterized by energy density, loading rate, and needle size) isolate the damage accompanying large and dynamic stretches from that associated with more complicated impact dynamics such as projectile tumble. We find that increasing kinetic energy density and loading rate both result in greater crack area, while transforming the fracture geometry from a single planar crack to multiple radial cracks. As a result, the dependence of accumulated damage, quantified with crack surface area, increases super-linearly with kinetic energy while the temporary cavitation volume is verified to remain approximately linear over the range of energies tested.