Virtual Modelling of Motorcycle Safety Helmets: Practical Problems

Motorcycle helmets are safety devices that can be optimised to perform better in different impact configurations. It is not easy to determine the mechanical properties of a particular model of helmet which maximise its effectiveness in real impact conditions and it is not surprising that most helmet producers use empirical design procedures and assess the effectiveness of their products by carrying out numerous experimental impact tests. The application of advanced computational techniques (i.e. Finite Element Method) to the study of the mechanical behaviour of helmets has been conducted with a variable degree of success in several cases. The use of virtual methods clearly provides a superior flexibility during the design process due to the simplicity by which the model is modified and retested. This work is an attempt to clarify modelling aspects encountered in helmet virtual testing, such as mesh dependency of the results, the influence of retention system on the response and composite shell modelling. A Finite Element model of a commercially available helmet has been developed and impact tested reproducing the test conditions prescribed by the ECE 22.05 standards. Particular emphasis has been given to the analysis of fibre reinforced plastic helmets, which are currently under further development, due to their superior performance. The results have been compared with experimental data and possible reasons for discrepancies have been analysed.