The effect of chin-to-chest contact on upper neck axial force in UN Regulation No. 129 frontal impact tests of child restraint systems.

OBJECTIVE: The objective of this study was to investigate the effect of chin-to-chest contact on upper neck axial force in United Nations (UN) Regulation No. 129 frontal impact tests of child restraint systems. METHODS: Frontal impact pilot experiments were carried out according to the test procedure in UN Regulation No. 129. Q-Series child dummies were seated in a small convenience sample of forward-facing child restraint systems. The timing and duration of chin-to-chest contact were determined using the procedure for calculating external head impact force in SAE J2052. RESULTS: Chin-to-chest contact was observed in all of our experiments and generated a tensile peak in the upper neck axial force of the Q-Series dummies. Prior to chin-to-chest contact, a purely inertial, noncontact peak was observed in the axial tension force. The tensile peak due to chin-to-chest contact was often greater than the inertial, noncontact peak force. CONCLUSIONS: Chin-to-chest contact can increase axial neck tension force beyond the level it would reach under purely inertial loading. Adopting upper neck axial force in regulation, without considering how the force is generated, might encourage child restraint designs that mitigate only chin-to-chest contact, rather than the true inertial neck loading.

Effect of the Q10 dummy upgrade kit in UN Regulation No. 129 front and side impact tests.

Objective: The objective of this study was to compare the kinematics and dummy loadings between the original Q10 and the Cellbond Q10 upgrade kit and determine the effect of the kit on the type approval of booster systems in United Nations (UN) Regulation No. 129.Methods: Front and side impact pilot experiments were carried out according to dynamic test procedures in UN Regulation No. 129. In each case, the original Q10 and Q10 upgrade kit were compared in a booster seat.Results: In front impact, the Q10 and Q10 upgrade kit displayed very similar kinematics and seat belt interaction. The peak dummy loads were also very similar. In side impact, the Q10 and Q10 upgrade kit displayed similar kinematics and interaction with the side structure of the booster seat. Once again, the peak dummy loads were also very similar.Conclusions: The original Q10 and the Q10 upgrade kit generated very similar kinematics and loadings in both front and side impact. Adoption of the kit for UN Regulation No. 129 would be unlikely to have significant effects on the type approval of booster seats. However, it would also appear not to offer any specific benefits. This will be verified in a larger program of experiments with a broader range of booster systems.