Use of Rigid and Deformable Child Restraint Seats in Finite Element Simulations of Frontal Crashes

This research focuses on the injury potential of children seated in forward facing child restraint seats during frontal vehicle crashes. Experimental sled tests were completed in accordance to the Federal Motor Vehicle Safety Standard 213 using a Hybrid III three-year-old dummy in a five point child restraint system. A full vehicle crash test was completed in accordance to the Canadian Motor Vehicle Safety Standard 208 with the addition of a three-year-old Hybrid III crash test dummy, seated behind the passenger seat, restrained in the identical five-point child safety seat. Different child restraint finite element models were developed incorporating a subset of the apparatus used in the two experimental tests and simulated using LS-DYNA. Three different finite element models utilizing (i) an assumed rigid CRS seat model containing only pertinent surfaces which come into contact with the Hybrid III dummy, (ii) a completely deformable CRS model incorporating material nonlinearities determined through standardized tensile tests completed on specimens extracted from various portions and parts of the CRS with complete use of CAD data for the spatial discretization, and (iii) a rigid model implementation of the deformable seat incorporating material nonlinearities of the seat belt webbing. Observations from the numerical simulations were compared to experimental values of the head and chest accelerations with a reasonable correlation observed. Values of the head injury criteria, calculated using a 15 ms window ranged from 50 to 100 for FMVSS 213 pulse, and 300 to 400 for CMVSS 208 pulse. For all three child restraint models, the child dummy exhibited substantially higher values for the neck injury criteria as compared to the experimental tests.