Characterization of the impact mechanics of polymeric foams subjected to quasi-static and dynamic compressive loading of various impact energies

Impact mass and inbound velocity are important parameters defined in helmet standards, which represent the total energy transferred during a hit to the head. The purpose of this study was to determine the influence that impact mass and inbound velocity had on energy attenuation characteristics of polymeric materials used in helmet design. Materials consisted of three densities of expanded polystyrene, expanded polypropylene, and vinyl nitrile foam. Each sample was impacted once at 25 different levels of energy using a monorail drop test. Significant main effects were observed for impact mass, inbound velocity, and material density on peak linear acceleration and impulse (p<0.05). Using peak linear accelerations as the determinant for risk of injury, head mass and inbound velocity played a significant role in helmet material performance.