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Affiliation
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Defence Science and Technology Group (DST Group) , 506 Lorimer St, Fisherman's Bend , Melbourne , Victoria , Australia , 3207. |
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Abstract
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OBJECTIVE: Soldiers in military vehicles subjected to underbelly blasts can sustain traumatic head and neck injuries due to a head impact with the roof. The severity of head and neck trauma can be influenced by the amount of head clearance available to the occupant, but also by other factors such as wearing a military helmet or the presence of padding on the interior roof. The aim of the current study was to examine the interaction between a Hybrid III headform, the helmet system and the interior roof of the vehicle under vertical loading.
METHODS: Using a head impact machine and a Hybrid III headform, tests were conducted on a rigid steel plate in a number of different configurations and velocities to assess helmet shell and padding performance, to evaluate different vehicle roof padding materials, and to determine the relative injury mitigating contributions of both the helmet and the roof padding. The resultant translational head acceleration was measured and the Head Injury Criterion (HIC) was calculated for each impact.
RESULTS: For impacts with a helmeted headform hitting the steel plate only, which represented a common scenario in an underbelly blast event, velocities of ≤ 6 m/s resulted in HIC values below the Federal Motor Vehicle Safety Standard (FMVSS) 201U threshold of 1000, while a velocity of 7 m/s resulted in HIC values well over threshold. Roof padding was found to reduce the peak translational head acceleration and the HIC, with rigid IMPAXX™ foams performing better than semi-rigid EVA foam. However, the head injury potential was reduced considerably more by wearing a helmet than by the addition of roof padding.
CONCLUSIONS: The results of this study provide initial quantitative findings which provide a better understanding of helmet-roof interactions in vertical impacts and the contributions of the military helmet and roof padding to mitigating head injury potential.
FINDINGS from this study will be used to inform further testing with the future aim of developing a new minimum head clearance standard for occupants of light armoured vehicles.
Language: en |