Development and validation of a bicycle helmet: assessment of head injury risk under standard impact conditions

Abstract

Although cycling may be attractive for both economic and environmental reasons, cyclists are extremely vulnerable road users and subjected to falls or collisions with cars. This present research attempts to understand the degree of protection offered by a commercial bicycle helmet under standard impact conditions. In accordance with the EN 1078 standard, an experimental progr am has been carried out on an existing helmet by performing 90 normative impacts under three different types of conditionings. In parallel, this helmet has been digitalized and meshed to get a finite element model (FEM) that has been implemented under the LS- DYNA® crash code. The e xperimental tests have been numerically reproduced in order to provide an in-depth validation of the helmet model under each of the 90 experimental impacts. The bicycle helmet model was finally coupled to a detailed human head model in order to compute intra-cranial field parameters and to assess the hea d injury risk. Results show that the calculated intra-cranial parameters were higher than previously published human head tolerance limits in terms of diffuse axonal injuries (DAI) and subdural hematoma (SDH) illustrating thus the critical level of loading under standard helmet test conditions.  Specific mass (kg/m 3 ) E Young's modulus (MPa) unloading E Unloading modulus (MPa)  Poisson's coefficient (-)