Predictions of Helmet Pad Suspension System Performance Using Isolated Pad Impact Results

Abstract. The Advanced Combat Helmet (ACH) pad suspension system is the primary attenuator of low-rate blunt impacts to a Soldier’s head. Quantification of pad suspension system improvements currently requires the costly and time consuming testing of an entire helmet. Two potential methodologies for independently testing pads were assessed using four existing pad designs. One of these methodologies used a flat anvil impact surface, and the other used a modular elastomer pad (MEP) impact surface. Independent pad testing was conducted at three environmental and four impact velocity conditions. These test results were compared to those from complete helmet tests under the same environmental conditions and three of the four impact velocity conditions. This comparison shows that ambient (295 oK) temperature, 3.0 m/s independent pad impacts on a MEP surface account for over 99 % of the variation observed in ambient (295 oK) temperature, 3.0 m/s complete system impacts. Under the same conditions, the flat anvil impact surface results account for 92 % of the variation seen in complete system impacts. Despite positive results under ambient conditions, independent pad impacts are not a useful predictor of pad suspension system performance under extreme high or low temperatures. For example, hot (327 oK) temperature, 3.0 m/s independent pad impacts on a MEP surface account for only 31 % of the variation observed in hot (327 oK) temperature, 3.0 m/s complete system impacts. Under the same conditions, flat anvil impact results account for only 4.4 % of the variation seen in system impacts. At extreme temperature conditions, interactions of the helmet or impact surface with the pad suspension system likel