Dynamic Finite Element Simulation of the Human Head Under Impact Loading to Compare the Application of Polyvinyl Alcohol Sponge and Expanded Polystyrene Foam as Helmet Materials

The key function of a helmet is to minimize the injuries that a head can experience during an impact. Nowadays, helmets are mostly designed to control the head from deceleration and not optimized to decrease the head injury due to fall or collision with cars. So far, Expanded Polystyrene foam (EPS) has been mostly employed for helmet designing owing to its suitable mechanical strength as well as appropriate kinetic energy absorption capacity. However, finding the safest helmet material is still controversial and further research is required. Very recently, we proposed a novel spongy material that can be used as an alternative reinforcing material to lessen the effect of impact load applied to the head. This study was aimed to perform a dynamic finite element simulation to compare the kinetic energy absorption capacity of Polyvinyl Alcohol sponge (PVA) and EPS in a bicycle helmet under normal impact loading. Digital computed tomography data for the human head were used to establish a three-dimensional finite element model of the human head to construct a helmet based on the detailed anatomical data of the human head. The mechanism by which a helmet protected a bicycle rider head by PVA and EPS was dynamically simulated using the LS-DYNA code under impact loading. Results showed that the resultant displacement induced by the impact load for the PVA helmet was 18% lower than that of the EPS helmet. In addition, the von Mises stress induced in a PVA helmet (232 kPa) was significantly lower than that of the EPS helmet (440 kPa). The findings advise that the PVA sponge can be used as an alternate reinforcing material in the design of helmet to increase the rate of absorbance of the energy of the impact and to minimize the energy of transmitted load and, consequently, diminish the head injury to the bicycle riders.