Data Analysis Strategies for Characterizing Helmet-Head Performance

Soldiers sometimes experience traumatic brain injury (TBI) during combat. Helmet design research is being conducted to reduce injuries; however, most research is centered on crash worthiness or ballistic impact. The objective of this work is to characterize the dynamic response of helmets to broadband loading for helmets of various materials and designs while the helmet is coupled to a head-neck system. The experimental setup consists of a Denton Hybrid III 50th percentile crash test head and neck attached to an optical isolation table to simulate the human torso. Initial experiments included standard modal impact tests with sensors on the helmet, neck, table, and head to measure the dynamic helmet-head coupling. Impact test results were used to extract the Complex Mode Indicator Function for two helmets. The CMIF results indicated that the first helmet absorbed more energy from a blunt impact than the second helmet resulting in less transfer of energy to the head and neck. Transmissibility function analysis was conducted to confirm this finding that the first helmet attenuated the transmitted force relative to the second helmet. The boundary conditions of the helmet on the head including the chin strap and padding are believed to be the source of these significant differences in dynamic performance of the two helmets.