Soft material layers influence on the torsional stiffness of alpine skis

Engineering of Sport 15 - Proceedings from the 15th International Conference on the Engineering of Sport (ISEA 2024)

Ski manufacturers constantly develop new laminates using different materials in order to achieve various goals, like improving stiffness-to-weight ratio and durability, or reducing their environmental impact. Some manufacturers have shown a recent interest in replacing the composite fibre reinforcement layers with recycled/recyclable metallic materials such as aluminum for sustainability reasons, such as the Essential ski by Rossignol Group or Ferreol’s Scalium alloy. However, doing so brings challenges. For example, skis designed with aluminum sheets tend to have elevated torsional stiffness (𝐺𝐽) due to the isotropy of the aluminum. This can be suitable for expert skiers, but it is not ideal for most skiers of lower skills [4] and for skiers looking for a more relaxed or playful ride. It is known from structural mechanics that soft material layers reduce the torsional stiffness of composite beams. However, the common skiing knowledge is that soft material layers like VDS foil (i.e. vulcanized rubber) are used mainly to improve bonding and vibration damping. This work thus explores the effect of VDS foil on the stiffness properties of ski-like laminates and demonstrates that their torsional stiffness can be reduced by more than 50%. This technique could be used as an additional design parameter to obtain any desirable level of torsional stiffness, including when using metallic reinforcement layers, and to also better understand the true effects of soft material layers on the on-snow feel of alpine skis.