A Longitudinal Study of Ice Hockey Helmet Shelf Life

摘要

After manufacture and before retail, ice hockey helmets must pass safety standard tests based primarily on multiple impacts at several global sites to receive certification. Unknown is the effective "shelf life" of these products; that is, do material and construction properties deteriorate with aging to a point below the impact criteria for certification? To address this question, a prospective 6 year study has been completed to investigate the effects of aging on hockey helmet impact attenuation. A longitudinal study (2001-2007) was performed on five models of ice hockey helmet to investigate the effects of aging on these helmets' impact attenuation characteristics. Helmets were tested on the date of manufacture and years two and six (Y0, Y2, and Y6). The five brands (Nike-Bauer-3000, Nike-Bauer-4000, Nike-Bauer-5000, CCM-HT500, and Jofa-690) were evaluated according to ASTM 1045-99 protocol, impacting four sites: the crown, front, rear, and side. All helmets were stored at ambient temperatures 20±4℃ and relative humidity between 10 and 50%. Helmets in Y2 and Y6 did not have prior impacts before testing. Peak acceleration (PA, g) and severity index (SI) were calculated for third impacts and compared between years. In general, PA and SI measures remained within safety criteria levels for all helmets and sites during all testing intervals (that is, all met certification standards). Though some specific helmet/site differences were noted, no substantial change in impact attenuation was observed. Visual inspection of helmets postimpact showed no conspicuous damage to liner or shell, though in several instances the binding glue had disintegrated allowing liners to shift or fall away from the shell. From these results, contemporary ice hockey helmets retain their robust impact attenuation characteristics even after several years of storage, though adhesive embrittlement needs to be addressed. Further testing should evaluate the viability of used helmets in a similar prospective manner to ensure safe helmet function.