A new motorcycle helmet liner material: The finite element simulation and design of experiment optimization

This paper is devoted to study and verify the suitability of the expanded polypropylene (EPP) foam as a liner for motorcycle helmet and to perform helmet design optimization. This EPP foam has a multi-impact protection performance and also has a potential for ventilation system improvement due to its resiliency. This resiliency allows for the ease of ventilation holes and channels molding without the foam breakage at the stage of mold extraction. The large scale, non-linear, dynamic finite element package LS-DYNA3D is used as a verification tool for motorcycle helmet design. Then the simulation work is carried further to provide data for helmet design analysis and optimization using the response surface methodology (RSM). The foam thickness, the foam density, and shell thickness being selected as the design factors for the response surface generation and design optimization. The results showed that the EPP satisfies the 300g headform center of gravity acceleration limit required by most of the international standards. The extended simulation output data is then used to create the response surface and determine the optimum design points. Therefore, two main contributions on motorcycle helmet design are achieved. The first is on the use of the EPP as a helmet energy absorption liner for the motorcycle helmet application, and the second is that by combining the simulation output with the design of experiment (DOE) method to study the effects of the various factors on helmet design optimization.