Numerical modelling of impacts on ski safety nets

Safety nets are used to protect skiers during downhill competitions. However, although these nets are now able to retain skiers in almost all cases, the deceleration during such impacts can cause severe harm to skiers including hyperflexion injury or vertebra compaction. Experience showed that the behaviour of the nets is highly dependant on: • the material of which they are made of • the boundary conditions (installation and fastening). The aim of this study was : • to analyse the net constitutive material under dynamic loadings to determine its characteristics. • to analyse well defined impacts to be able to simulate them numerically • to improve the net behaviour during real impacts • to provide some recommendations concerning the geometry of the complete system. This study continues Fayçal Ben Yahia's work which was presented in Paris in June 2001. The whole study was performed under the funding of the French company Dalloz Montagnes and with the technical collaboration of the International Skiing Federation (FIS). As a first step, we used the tests on the net thread to model it in static and dynamic conditions. Then we compared the results from impact tests on small safety systems and simulations with LS-DYNA which led to the validation of the whole model. Finally, simulations of impacts on real size nets were used to study the influence of the boundary configuration on the net behaviour. The model developed during this study makes it possible to optimise the geometry of the whole system in order to increase skier protection.