Use of load limiting tethers in child restraint systems as a method to mitigate injuries to toddlers in frontal crash

This research focuses on methods to alleviate head and neck injuries sustained by children seated in forward facing child safety seats during a frontal vehicle crash. According to the Federal Motor Vehicle Safety Standard 213, the maximum limit for head excursion of the child dummy is 720 mm and the neck injury criteria should be less than 0.33 beyond the first 30 ms of the impact. A fully deformable finite element model of a child restraint seat has been previously developed which has been validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions. Observations from this previous work have illustrated that despite the head excursion being significantly less than the proposed limit of 720 mm, values of the neck injury criteria exceeded the protection reference values. The main objective of this research was to implement load limiting behavior into the upper and lower tethers of the CRS in order to reduce the neck injury criteria by increasing forward head excursion. Through an analysis of injury criteria, using neck loads and head accelerations, it was observed that load limiting of upper and lower tethers was effective in reducing the head injury criteria and neck injury criteria by approximately 75 per cent and 40 per cent respectively.