Biomechanical analysis of pediatric injuries and child restraint system

Airbag related injuries to infants in rear facing child seats are common in frontal crashes. Several vehicular modifications such as deactivated passenger airbags, manual cut-off switches, depowered airbags and smart airbags have been advanced to mitigate the effect of airbag deployment on child seats. However, there is limited research effort to address the biomechanics of airbag injuries due to modification in child restraint systems. The purpose of this research is to evaluate the biomechanical effects of a protective barrier between the rear facing child restraint and the frontal passenger airbag of the vehicle. An experimental study was conducted using an Anthropometric Test Dummy (ATD) in a vehicular partial structure (buck). The rear facing child seat was placed in the right front passenger seat of the vehicle. The child seat was restrained using the three-point restraint in the vehicle. The six-month-old instrumented ATD was restrained in the child seat. The ATD was instrumented with the head tri-axial and two uni-axial linear accelerometers. The uni-axial linear acceleration was used to calculate the angular acceleration. Two different rear facing child seats, the standard rear facing infant seat and the rear facing infant seat inside the protective barrier structure were tested. In each test, the Head Injury Criteria (HIC) and angular head acceleration were measured. Results show that the HIC was reduced by 95% and the angular head acceleration was reduced by 85% by the protective barrier. The head injury values were well below the tolerance limit for the child with the barrier. The protective barrier deflected the airbag away from the ATD’s head and also acted as a shield to minimize airbag force on the child seat. In the typical infant seat, the airbag contacted the ATD’s head and exerted significant force on the child seat which rotated the seat rearward. These kinematic responses may explain the clinical observation of severe head injuries by infants in rear facing seats due to forces transmitted through the child seat and downward force from the top of the head. The present study is a first step in better understanding the injury mitigating aspects of the safety protective structure in child restraints.