Abstract
Viscoelastic polyurea foams with densities of 98, 170, and 230kg/m3 were manufactured and integrated into helmet shells and tested using the NOCSAE and FMVSS 218 standards for football and motorcycle helmets, respectively. For football helmet testing, a Riddell Revolution helmet shell was used. The helmets with a foam liner thickness of 28mm were dropped using a NOCSAE medium headform (4.9kg) from heights ranging from 0.305 to 1.524m. All impact tests were done on the crown of the helmet and dropped on a 12.7mm modular elastomer programmer pad. Use of PU98 foam resulted in a reduction of 22% in peak g's and 25% in Severity Index and Head Injury Criteria values when compared to helmets with the original VN600 foams under ambient conditions. These tests were repeated under varying temperatures along with a reduced liner thickness of 22.2mm. In these tests, PU98 foam reduced the peak g's by 18% at 23°C, 26% at −15°C, and 20% at 50°C when compared to VN600 helmets. The FMVSS motorcycle helmet tests demonstrated the success of using an additional layer of polyurea foam liner on top of the existing expanded polystyrene liner in reducing the peak g's by 17%.
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