A visco-elastic foam as head restraint material – experiments and numerical simulations using a biorid model

Abstract

To prevent whiplash injury by appropriate seat design is the goal of various approaches presented in recent publications. In this context, the head restraint plays an important role, because its geometry as well as its dynamic behaviour greatly influences the occupant kinematics. This study focuses on the effect of the head restraint padding material. It was investigated whether the head restraint foam can be tailored to reduce whiplash injury. A novel formulation of a visco-elastic (VE) foam was chosen as padding material and was compared to a polyurethane (PU) foam commonly used today. The newly developed visco-elastic foam is characterised by a broad temperature range over which it keeps its advantageous deformation properties and therefore allows advanced energy dissipation. As such the visco-elastic foam fulfils an important requirement for use in an automotive application concerned with the interior of a vehicle. Applying the new foam as a head restraint padding material, sled tests and numerical simulations were performed to determine its possible beneficial effects. Both the experiments and the computational analysis mimicked conditions of rear-end collisions with delta-v values ranging from 16 km/h to 40 km/h. A BioRID II dummy was used as a human surrogate. The results indicate that the change of the foam become particularly effective at higher delta-v values. The loading of the head and neck in terms of maximal head acceleration and NICmax values can be reduced effectively by using visco-elastic foam. Additional changes of the head restraint geometry were shown to have large beneficial influence on the occupant kinematics.

Keywords:

• Head restraint
• visco-elastic foam
• whiplash
• neck injury
• BIORID