Airbag head restraint system

Abstract The function of a head restraint system is to prevent injurious hyperextension of the occupant's neck in the event of a road vehicle rear end impact, and thus it must have adequate stiffness to limit the movement of the head relative to the torso. Also, it should absorb the kinetic energy progressively so that the head does not sustain any injury and does not roll on the cushion. Practically, a well-designed head restraint will have an optimum balance of these features and thereby offer adequate protection for both the head and the neck. This paper presents some pioneering thinking on head restraint design and develops criteria for qualifying the systems. It presents an airbag head restraint system that has optimum stiffness and good potential for reducing head and neck injuries suffered through rear end collisions. It also presents the results of experimental tests conducted on this novel airbag head restraint system and on several randomly selected existing head restraints. Furthermore, analysis of energy absorption capabilities, head injury criterion (HIC) values and a new criterion, called the equivalent impact power criterion (EIPC), is developed in order to quantify the relation between the rate at which energy is imparted to the head during the impact cycle and injury severity. Current test results show that, the lower the EIPC, the better is the head restraint system and the less is the risk of whiplash and head injuries. Moreover, the work has quantified a number of variables, including the optimum stiffness, as the factors governing the severity of injury to the occupant in a rear impact scenario.