The first- and second-impact absorption properties of different commercial polymeric foams were analysed in order to identify possible alternatives to currently used polystyrene foams (EPS) for protective helmets. An appropriate “falling dart” apparatus was built complying with standard regulations to study and compare an expanded polystyrene (EPS) actually used in motorcycle helmets productions, with commercial polypropylene (EPP), polyvinyl-chloride (EPVC) and polyethylene (EPE) foams. Both dynamic cushioning tests in a “free sample” configuration and impact tests using guided hemispherical indenters were performed for each class of material at three different temperatures (-20°C , ambient , 50°C) and at two different bulk densities. Also the residual deformation was measured for each sample. In order to characterise dynamic absorption properties of materials, deceleration peak values obtained from the tests with hemispherical impactors have been plotted versus different static loads in a cushion curve fashion. Expanded polypropylene showed better second-impact absorption properties and lower residual deformation than EPS, suggesting it as a possible alternative material for inner polymeric foam protective shells, particularly in view of matching the two-shock criteria required for official approval of car driving helmets.
Cushioning properties of polymeric foams for impact-protection: comparative evaluation and search for improved resilience
GALLONE, GIUSEPPE CARMINE;LEVITA, GIOVANNI;MARCHETTI, AUGUSTO;ANGUILLESI, IRENE
2006-01-01
Abstract
The first- and second-impact absorption properties of different commercial polymeric foams were analysed in order to identify possible alternatives to currently used polystyrene foams (EPS) for protective helmets. An appropriate “falling dart” apparatus was built complying with standard regulations to study and compare an expanded polystyrene (EPS) actually used in motorcycle helmets productions, with commercial polypropylene (EPP), polyvinyl-chloride (EPVC) and polyethylene (EPE) foams. Both dynamic cushioning tests in a “free sample” configuration and impact tests using guided hemispherical indenters were performed for each class of material at three different temperatures (-20°C , ambient , 50°C) and at two different bulk densities. Also the residual deformation was measured for each sample. In order to characterise dynamic absorption properties of materials, deceleration peak values obtained from the tests with hemispherical impactors have been plotted versus different static loads in a cushion curve fashion. Expanded polypropylene showed better second-impact absorption properties and lower residual deformation than EPS, suggesting it as a possible alternative material for inner polymeric foam protective shells, particularly in view of matching the two-shock criteria required for official approval of car driving helmets.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.