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Headform durability is a problem for standards bodies evaluating hockey helmets. Presently the Canadian Standards Association (CSA) uses a skull form fashioned from an epoxy-metal alloy, but because this headform is susceptible to cracks and because it is difficult to obtain replacements from suppliers, the CSA is considering a change to the use of a machined magnesium headform. Before doing so, a comparative study of the performance capabilities of the magnesium and epoxy headforms was undertaken at two separate laboratories. The headforms were evaluated on a uniaxial monorail system at velocities that produced energy levels of 10, 20 and 30 joules. Each headform was tested against a modular elastomer programmer (MEP) pad which covered the impact pedestal. Five impacts to each of 6 locations (Front, Front Boss, Side, Rear, Rear Boss and Crown) on both headforms were conducted. Peak headform acceleration was the impact criterion measure. Overall the peak headform acceleration was 165g for the magnesium headform and 151g for the epoxy headform, a difference of 9%. As expected, the magnitude of peak acceleration varied according to location with the side and rear boss showing the largest difference between headforms. When the results of all tests were combined the correlation in peak acceleration between the two headforms was, 92. Based on a linear regression model, a 275g acceleration criterion for the epoxy headform would be equivalent to 272g for the magnesium headform. These results suggest that the magnesium headform performs in a manner similar to that of the epoxy headform.
headforms, epoxy, magnesium, headform performance, headform testing
Professor, University of Waterloo, Waterloo, Ontario