Analysis of the interaction between child occupants and deploying frontal passenger airbag in simulated frontal crashes

摘要

Objective: Since the 1990s there has been an emphasis on designing the vehicle airbag system to depower the front passenger airbag to improve the safety of child occupants in the front seat. Recommendations based on first-generation airbag designs varied from switching off PAB to having children less than 13 years of age to be seated in the rear seat. Airbags have evolved over the years and there have been changes to the intensities and deployment characteristics of modern airbags. The aim of the study was to quantify the responses of the 6-year-old ATD installed in child restraint systems seated in the front passenger seating position exposed to a deploying modern front passenger airbag. Methods: Finite element (FE) models of a 2012 Toyota Camry model (National Crash Analysis Center archives), child seat models (developed internally), a tuned modem front passenger airbag (PAB) (Takata Inc., MI), a Q6 anthropomorphic test device (ATD) model (Humanetics Inc., MI), and a tuned 3-point lap-shoulder belt with pretensioner/retractor (developed internally) were used for the simulations. Seating conditions consisted of a convertible seat in forward-facing harness mode (FFC) with and without a top tether, a highback booster (HBB) and a baseline condition without any child restraint system (No-CRS) in normal seating and a misuse condition with seatbelt behind the back. Models were simulated (N = 12) for NCAP frontal test at 35mph. Results: Head contact was observed with the instrument panel (IP) in all misuse conditions without PAB (HBB and No-CRS condition with seatbelt behind the back, and FFC without top tether). This contact was eliminated for HBB and FFC seats by the deployment of a PAB. PAB and no-PAB conditions for HBB in normal seating resulted in HIC15 values of 390 and 359 respectively, and resultant head acceleration of 72G and 71G respectively. For FFC with top tether, deployment of PAB resulted in 24.4% reduction in HIC15 (754 to 570) and 12.9% reduction in resultant head acceleration (93G to 81G) as compared to no-PAB condition. For FFC, utilization of top tether resulted in 15.6% reduction in head excursion in the no-PAB condition (471mm to 397mm) and 5.2% reduction (324mm to 307mm) in the case with PAB. In the No-CRS normal usage condition, there was minimal head interaction with the PAB. The PAB and no-PAB conditions showed similar HIC15 (204 and 188 respectively) and resultant head acceleration values (51G for both). In the misuse condition, the Q6 head slid under the deployed PAB and contacted the IP. Conclusions: In all situations, deployment of PAB provided similar or a relative positive effect as compared to no-PAB condition. There was a clear benefit of using a PAB in all the misuse conditions as it eliminated head contact with the IP. Even in cases where there was no contact with IP (no PAB), usage of PAB resulted in reduced head excursion and comparable or lesser values of HIC. Additional simulation conditions and testing are necessary to explore crash pulses, directions and vehicle/airbag models.