Sensitivity analysis of NHTSA's side sled design for evaluating CRS performance in side impacts

Side impact crashes are second most fatal type of crashes in United States (U.S.), accounting for 300 children lives every year. The use of Child Restraint Systems (CRS) for restraining the occupants in child seats has been effective in reducing injuries to children involved in crashes. Currently there is no regulation in the U.S that evaluates the performance of CRS in the event of side impacts. The National Traffic Highway Safety Administration (NHTSA) is researching a dynamic side impact sled test procedure for evaluating the CRS performance in side impacts.This research is focused on understanding the sensitivity of side impact sled test parameters. Performance of two types of CRS design have been investigated in the study one with extended wing (deep dish) type design and one without extended wing (shallow dish). Finite Element (FE) models have been developed for the two CRS designs and were validated to FMVSS no 213 compliance test and physical dynamic side impact sled test carried out by NHTSA. The NHTSA Side Sled test was performed using Q3s dummy but the simulation were performed using Q3 dummy since the mathematical model of Q3s was not available as Q3s is still in stage of development. The sensitive parameters investigated are the installation method and the installation location of the CRS. The installation method evaluates the four types of installation systems namely lap-belt, lower anchorage with top tether for children (LATCH), the 3 point belt and the 3 point belt with top-tether. To account for variation in installation locations the CRS was initially placed at 300 mm from the bench seat plate in the NHTSA Side Sled test and was later varied to 288mm, 312mm and 325mm.The results showed that the installation method is sensitive to the CRS design. LATCH belt and 3 point belt with top-tether offers more rigid connection of CRS to the bench seat. Rigid installation was found to be detrimental for CRS without extended wing (shallow dish). For CRS without extended wing (shallow dish) the dummy head rotated out of the CRS and contacted the door impactor resulting in higher resultant head accelerations. The extended wing (deep dish type) CRS design provided better protection to the children by restraining the extension of head within the CRS and thus avoiding direct contact of the head with the door impactor. The small variation in installation locations showed no significant change in the resultant head acceleration and was considered as potentially insensitive.This study also compared the response of Q3s dummy with respect to 3 year old Human Child Model and based on the simulations results it was found that the Q3s dummy chest and neck may need further improvement to be Human like.