Design of an American Football Helmet Liner for Concussion Mitigation

The objective of this research was to develop an optimal design for a polymeric American football helmet liner for concussion prevention utilizing experiments and high performance. Along with well-established injury criteria (HIC, SI, and Peak acceleration), localized brain injury mechanisms were explored by employing Finite Element simulations and experimental validation. Varying strain rate experiments (monotonic and hysteresis) were conducted on modern football helmet (Rush, Rawlings, Riddell, Schutt, and Xenith) liners and new possible polymeric foam liner materials. These experiments were used to characterize each material at low strain rates (0.1/sec; Instron), intermediate strain rates (100-120/sec; NOCSAE drop tower) and high strain rates (600-1000/sec; Split Hopkinson Pressure Bar). Experimental design optimization was performed on a football helmet liner by utilizing an exploratory Design of Experiments by National Operating Committee on Standards for Athletic Equipment (NOCSAE) drop tests. FEA simulations of drop impact tests were conducted on a helmeted NOCSAE headform model and a helmeted human head model. Correlations were made between both models to relate localized brain response to the global acceleration and the dynamic-based injury criteria HIC, SI, and Peak acceleration). FEA simulations were experimentally validated by twin-wire drop tests of the NOCSAE headform using correlations for validation of the human head model. The helmeted human head simulations were used to explore a Mild Traumatic Brain Injury (MTBI) limits based localized brain response (e.g. pressure and impulse). Based on these limits, future FEA simulations will be used to explore these limits as helmet liner design criteria