The improvement of neck protection in rear impact requires a better understanding of the interactions between occupant, seatback and headrest. In this study a mathematical approach was developed to analyse the interactions, and to quantify the influences of different design parameters on neck responses. The first phase of this development consisted of neck modelling. For the second phase of the development, the interactions of the thorax and the pelvis with the seatback were modelized, as was that of the head and the headrest. Two types of seatback model were constructed: a global seatback modelling, and a more detailed approach. Finally, the influences of the following four design parameters on neck responses were analysed: head to headrest distance, seatback joint stiffness, and upper and lower seatback stiffnesses. Special attention was paid to the interactions between these parameters. The results indicate that softening of the upper seatback allows reduction of all neck injury risk indicators and enhances the headrest performance. Softening of the lower seatback increases the moment force at the C7/T1 joint and the head extension angle. Stiffening of the seatback joint aggravates, for a classical upper seatback structure, the moment loading of the neck and the head extension angle. Only the moment force at the C7/T1 joint is significantly affected by all parameter changes.
Samenvatting