Impact analysis of a honeycomb-filled motorcycle helmet based on coupled head-helmet modelling

Human head is most vulnerable in road traffic accidents involving motorcyclists where the helmet is commonly used to protect human head and reduce head injuries. This study aims to develop a methodology for the analysis of a novel motorcycle helmet based on coupled head-helmet modelling and the kinematic and biomechanical head injure criteria. A representative full-face motorcycle helmet finite element (FE) model was established and validated by the standard drop tests. The validated helmet model was coupled with two types of human head models to obtain the acceleration histories transmitted to the head (e.g. peak acceleration (A_max) and Head Injury Criterion (HIC)) and the biomechanical responses of the head (e.g. intracranial pressure (ICP) and von Mises stress (σ_v)) under external impact load. Analyses were further conducted to investigate the use of honeycomb filler in helmets to improve their protective performance. An optimization study was implemented to find the feasibly optimised geometries of honeycomb filler and densities of liner foam for the helmet, which can significantly enhance helmet's protection performance and reduce head injury from impact scenarios. In comparison with the head responses (A_max = 215.1 g, HIC = 1985, ICP = 228.8 kPa and σ_v = 33.6 kPa) in conventional helmet design, the protective performance of the optimum helmet is considerably improved with a large reduction of the head responses (A_max = 137 g, HIC = 918, ICP = 146.9 kPa and σ_v = 18.1 kPa), representing their respective reductions of 36.3%, 53.8%, 35.8%, and 46.1%. The proposed method and procedure could be used in structural crashworthiness studies when human-structure interaction is important.