Optimization of bonnet thickness with respect to pedestrian safety

Abstract

Head and face injuries in car–pedestrian accidents account for 60 per cent of all pedestrian fatal injuries, whereas 17.3 per cent of head injuries were due to the bonnet. The above values demonstrate the necessity to consider more carefully the role of the bonnet in pedestrian head safety. Redesigning the bonnet structure to improve pedestrian protection has recently received considerable attention by automobile manufacturers and industry institutes. However, there is a lack of research that considers methods of choosing the most effective thicknesses of bonnet skin and bonnet reinforcement with respect to pedestrian safety. This study analyses the effects of the bonnet skin and bonnet reinforcement thicknesses on pedestrian head injury by performing simulations of headform-impactor-to-bonnet tests according to the European Enhanced Vehicle-safety Committee Working Group 17 regulations for different thicknesses. An optimization method of selecting the most effective thicknesses of bonnet skin and bonnet reinforcement will be introduced. Many positions on the bonnet surface are considered to enhance pedestrian friendliness by using this method. Moreover, a bonnet with the optimal thicknesses is not only pedestrian friendly but also as stiff as possible. Based on the proposed method, this study presents steps for optimizing the bonnet skin and bonnet reinforcement thicknesses using a particular automobile model.