Numerical investigation of the effect of shell material and thickness on motorcycle helmets impact mechanics

In motorcycle accidents, the acceleration caused by the collision has a huge risk to the health of the motorcyclists and passengers. In this study, the finite element method was used for dynamic analysis of impact mechanics to predict the effect of the shell material and thickness on the head injury criteria of the helmeted head (including head, shell, foam, comfortable foam and strap). The open-face helmet, including three current market materials, were selected. Head orientation, in the most accidents, at the collision moment is oblique. In the simulated impact model, head is also placed obliquely. The results of this study are validated by the experimental results and valid published data. The simulation results show that there is an optimum thickness for the helmet shell regardless of its material. In order to determine the optimum thickness, there must be compromises between the various parameters such as head injury criteria, shell failure, weight, and price. According to the results obtained for the shell thickness, if the thickness increases, the weight and range of acceleration increase while the probability of shell failure decreases. If the thickness decreases, despite of decreasing the acceleration in the head, the stress in the shell increases that leads to failure.