Effect of Head-Restraint Rigidity on Whiplash Injury Risk

The present study investigated the effects of the structural stiffness of the head restraint and its attachment rigidity on the biomechanical responses and related injury measures of the neck in a rear impact vehicular collision. A series of simulated rear impacts were conducted using a mid-sized male test dummy seated in a modified late-model front passenger seat on a deceleration crash sled with a FMVSS 202 pulse. Preliminary results demonstrated that a more rigid head restraint in its design and attachment produced lesser values in most biomechanical injury measures such as neck shear force, neck extension bending moment, tension-extension neck injury criterion (Nij), shear-moment neck injury criterion (Nkm), and head-torso relative extension angular displacement. This is true for a wide range of seatback recliner stiffness. This suggests that a more rigid head restraint may have a protective advantage over a more pliant one for the neck in a rear impact. The result of this study underscores the need for dynamic testing to completely evaluate the performance of head restraint system.