Longitudinal Compression Loads on a Slender Cylinder in Air and Water

Shockwave propagation and the resulting stress wave through axons located in the brain can cause traumatic brain injury. An experimental study was conducted using scaled-up cylinders under a longitudinal impact load in both air and water. The material properties of the axons are modelled by both ballistic gelatin and PDMS molded into slender cylinders. Each cylinder is given an impulse to simulate an arriving shockwave and filmed with a high-speed camera at 14,000 frames per second to capture the soft material deformation. An in-house image-processing code was written in Matlab to measure the profiles of the cylinder’s top and bottom surface waves and to track the displacement of embedded bubbles/particles to understand the internal strain field. Preliminary experiments in air using blunt force impacts suggest that the surface deformation follows a sinusoidal pattern with time dependent amplitude and frequency as does the internal longitudinal and transverse strain fields. These results from experiments performed in air are expected to hold but decrease in amplitude and frequency when performed in water due to damping effects.