Study of Chest Injuries to 3YO Child Occupants Seated in Impact Shield and 5-point Harness CRSs

<b>Objective</b>: To investigate whether the 5-point harness or the impact shield CRS or both has the potential to cause chest injuries to children. This is determined by examining whether the loading to the chest reaches the internal organ injury threshold for children. <b>Method</b>: The chest injury risk to a child occupant in a child restraint system (CRS) was investigated using Q3 dummy tests, finite element (FE) simulations (Q3 dummy and human models) and animal tests. The investigation was done for two types of CRSs (i.e., the impact shield CRS and 5-point harness CRS) based on the UN R44 dynamic test specifications. <b>Results</b>: The tests using a Q3 dummy indicated that although the chest deflection of the dummy in the impact shield CRS was large, it was less than the injury threshold (40 mm). Computational biomechanics simulations (using finite element FE analysis) showed that the Q3 dummy's chest is loaded by the shield and deforms substantially under this load. To clarify whether chest injuries due to chest compression can occur with an impact shield or with the 5-point harness CRS, seven experiments were performed using Tibetan miniature pigs with weights ranging from 9.7 kg to 13 kg. Severe chest and abdomen injuries (lung contusion, coronary artery laceration, liver laceration) were found in the tests using the impact shield CRS. No chest injuries were present when using the 5-point harness CRS. <b>Conclusion</b>: When using the impact shield CRS, the chest deformed substantially in dummy tests and FE simulations, and chest and abdominal injuries were observed in pig tests. It is possible that these chest injuries also could occur to child occupants sitting in the impact shield CRS.