Research On New Material And Structure Vehicle Bonnet Based On Child Pedestrian Head Protection

Pedestrian is the most vulnerable group in traffic acc idents and its casualt y rate is quite high. Child is one o f the pedestrian accident high-risk groups. Stat ist ics show that children account for only 18% o f the total populat ion, but children's casualt ies account for a third of the total casualt ies. Head is easy to touch the bonnet in vehicle-pedestrian co llisio n, which is most likely to cause death. GTR9 and EC78/2009 have already put forward specific requirements to children pedestrian protect ion. Therefore, it is important to improve the bonnet to better protect child pedestrian.Research about vehicle's lightweight has become the current development trend, many lightweight materials are applied to vehicle body, but ignore the pedestrian protect ion performance o f bonnet. Therefore, it is necessary to study new materials and new structures o f bonnet based on child pedestrian protect ion.Aluminum allo y and co mposite material are co mmo nly used for vehicle's lightweight design. A collision model o f child head against vehicle is established based on the finite element theory, which is proved validly by real test. The abilit y o f bonnets made by lightweight materials to protect child pedestrian are discussed. The structure o f bonnets is also opt imized to improve its pedestrian protect io n performance.Aluminum allo y is a lightweight material, wit h low densit y and good mechanical propert ies, which is widely applied to vehicle body. The bonnet made in carbon steel is replaced by aluminum allo y and co mpared with each other in pedestrian protect ion. The structure o f aluminum allo y bonnet is optimized and t wo new inner panel structures, radiat ion strengthening ribs and sandwich structure, are proposed which absorb energy more fully and have more uniform st iffness. A energy-absorbing structure is also designed around hinge reinforcing plate to further protect pedestrian. The static st iffness o f Aluminum allo y bonnet is also checked.Co mposite material with light qualit y and high strength is gradually applied in the field o f aerospace and auto mobile. Based on the mechanical propert ies o f sandwich structure, the sandwich structure is put forward with PVC foam in the middle and carbon fiber co mposite material in the surface. The corresponding model is established, which is proved validly. The parameters o f sandwich bonnet to influence child head protect ion performance is researched by using child head impact six dangerous po ints adopt ing the method o f simulat ion in accordance wit h regulat ion. The best thickness co mbination of panel and middle layer are defined by Spin lift method. The sandwich bonnet is installed to original vehicle model to research the child pedestrian protect ion performance and co mpared with original carbon steel bonnet. Results show sandwich bonnet can effect ively protect child pedestrian head, and still can reduce qualit y and material consumpt ion of bonnet by structure design. Therefore, the qualit y o f the thickness gradient sandwich bonnet is also proposed. The feasibilit y o f the scheme is proved by simulat ion.The stat ic st iffness of thickness gradient sandwich bonnet is checked. Results show that stat ic st iffness increase. The weight of thickness gradient sandwich bonnet reduce 77.9%,which is advantageous to the vehicle lightweight.