Shock absorption performance of full-face rider helmets

Full-face rider helmets are widely used these days, but the shock absorption and safety performance of them have not been discussed yet. So we examined the shock absorption performance and the safety of three full-face rider helmets (samples A, B, and C) of which the laminated constitutions of the FRP shell part were respectively different. The effect of the hybrid lamination, composed of aramid and glass fabrics, on the shock absorption performance has been discussed also. Testing was performed twice for the same impact site of a helmet hit flat and with semi-spherical anvils, according to the JIS-C shock absorption test method. The following results were obtained: The acceleration waveform measured at the forehead part of Helmet-A, which was hit on a semi-spherical anvil, behaved flatly while the part on the left side of the head behaved parabolically. In the case of Helmets-B and -C, which have an aramid fabric layer, they behaved conversely, such that a flat waveform was observed on the part on the left side of the head. All helmets hit on the semi-spherical anvil showed a flat acceleration waveform regardless of the impact site of the helmet, and showed a maximum acceleration of less than 120 g, which is exceedingly small compared to the results from the case with the flat anvil. For all the helmets, the maximum acceleration and the elapsing time of more than 150 g in the second test were higher values than the values in the first test. The values of Helmet-B, in particular, were recognized to change remarkably. The hybrid lamination, composed of aramid and glass fabrics, was not so effective. However, it was remarkable that the maximum acceleration and the elapsing time at the forehead of Helmet-B in the first test were the smallest values in all of the data collected from hitting a flat anvil.