Effect of foam densification and impact velocity on the performance of a football helmet using computational modeling

Abstract

The NFL recently released validated helmet-impact models to study the performance of currently used helmets. This study used the model of a Riddell Speed Classic helmet to determine the influence of the properties of protective foam padding on acceleration and deformation at two common impact locations to cause concussions. The performance of the helmet was measured before and after manipulating the material properties of the protective foam liner material using FEA software. The densification strain was adjusted by using the scale factor tool in LS-DYNA to create four material categories – soft, standard, stiff, and rigid. The helmet was tested under side and rear impacts using the four material properties at 2.0, 5.5, 7.4, 9.3 and 12.3 m/s impact speeds using the NOCSAE linear impactor model. This study suggests that the standard foam material compresses to a range that could be considered to have “bottomed out” at impact speeds at 5.5 m/s for side impacts. Despite testing a wide range of material properties, the measured accelerations did not vary dramatically across material properties. Rather, impact speed played the dominant role on measured acceleration. This is the first study to demonstrate how open-source impact models can be used to run a design of experiments and investigate the role between different materials used inside a helmet and football helmet performance.

Keywords:

• Football helmet
• concussion
• computational modeling
• materials
• acceleration

Acknowledgements

This project was supported in part by the PAC-12 Confrence's Student Athlete Health and Well Being initiative. the content of this manuscript is soley the responsibility of the authors and does not necessarily represent the official views of the PAC-12 Confrence, or its members.

The authors would also like to thank Montucky Cold Snacks for their continued support of the Smart Materials and Biomechanics Lab at CU Denver.

Disclosure statement

SM, LC, and CY have a potential conflict of interest by owning equity in a company pursuing the development of helmet materials.