Correlation between kinematics and biomechanics of helmeted head under different impact conditions

Abstract

Helmet is the most common and effective means to avoid severe injuries of human head in accidents. Nonetheless, the helmet may not completely protect the head and head injuries can still happen under impacts. To improve the protectability of helmets, this study aims to systematically investigate the impact characteristics (e.g., helmet structural behaviours, head kinematics and biomechanical responses) of a helmeted head under different impact conditions (e.g., anvil shape, impact site, impact velocity and impact angle). The helmeted head model was developed by a representative motorcycle helmet model coupled with a human head FE model, then validated through four helmet experiments under standard drop impact tests. Based upon the validated models, virtual drop impacts were performed on the helmeted head models to explore the helmet impact characteristics and head responses. A parametric study was carried out to investigate the effects of impact conditions on helmeted head responses; correlation analysis was also conducted to understand the relationships between head kinematics and biomechanical responses. It is shown that the impact conditions can significantly influence the helmet protectability and head responses; and the protectability of helmet can be improved by prolonging the compression stage to weaken head impact responses. According to the strong linear relationships between head kinematics and biomechanical responses established, three correlation equations were proposed to predict the head biomechanical responses through the given impact kinematics. This study is anticipated to advance the knowledge on the helmeted head responses under different impact conditions, thereby gaining new insight into the correlation between head impact kinematics and biomechanics, thereby providing technical guidance to the design for helmet protection.