The influence of neck compliance and head displacement on impact dynamics of a Hybrid III head

The objective of this study was to determine the influence of impact deflection and neck compliance on peak linear, peak angular accelerations and the Gadd severity index. To replicate direct impacts to the head, a pneumatic linear impactor was used to impact a Hybrid III head and neck attached to a sliding table. The headform was translated 0cm, 3.88cm, 7.75 cm and 11.63cm laterally to identify the effects of impact deflection. The effects of neck compliance were tested using a Hybrid III 50th percentile neck as well as two specially engineered Hybrid III necks. Impacts away from the centre of gravity of the headform recorded lower values for peak linear and angular accelerations and GSI. This means that impact deflection can effectively reduce brain injury risk. Neck compliance had a significant effect on linear acceleration and angular acceleration. An increase in neck compliance caused a decrease in linear acceleration; however, it also resulted in a decrease in angular acceleration. A comparison to published injury thresholds revealed that a decrease in neck compliance could significantly decrease the risk of brain injury. The data collected provided important insight into the importance of impact avoidance and deflection on injury prevention as well as the effect of the neck on the dynamic response of the head during impact.