The Design Of Composite Honeycomb Sandwich Structure Bonnet For Pedestrian Protection

Automobile sales have been increasing year by year with the development of the global economy,and the number of cars is also increasing gradually.As a result,the problem of road traffic safety is becoming more and more severe,among which the collision between pedestrians' heads and engine bonnets is extremely likely to cause serious injuries to pedestrians.In order to reduce the degree of head injury caused by collision between pedestrians and cars,this paper investigated the influence of structural parameters on the mechanical properties of CFRP face sheet-aluminum honeycomb sandwich plate under low-velocity impact through experiments and simulations.Then,a composite honeycomb sandwich structure automobile engine bonnet is designed,and the structural parameter design scheme with the best head protection effect is explored.Firstly,the influence of honeycomb core element size on the impact performance of sandwich plate under low speed impact load was investigated.This model is based on the 3D Hashin damage criteria,continuous damage mechanics model and cohesive element model.In the finite element simulation software ABAQUSA,a refined low-speed impact simulation model of CFRP skin-aluminum honeycomb sandwich plate was established.The simulation results are in good agreement with the experimental results.The effects of structural parameters on the low-velocity impact mechanical properties of honeycomb sandwich plate were further investigated by using the numerical model,such as the height of honeycomb core,the thickness of face sheets and the thickness of honeycomb cell wall.Secondly,based on GB/T 24550-2009 "collision protection of vehicles to pedestrians",an effective child pedestrian head impact model was established,and a simulation model of child pedestrian head impact on the engine cover of a certain vehicle was built.It is found that the steel engine bonnet of the original vehicle does not protect the pedestrian's head well in traffic accidents.Finally,a finite element model of composite honeycomb sandwich structure engine bonnet was established based on the above research.L9(34)orthogonalexperimental design method is adopted to carry out the simulation exploration of four factors and three levels.According to the comparison of the results,a better design scheme for pedestrian head protection is found.The results show that the new engine bonnet designed has a good pedestrian head protection performance,and the damage value of each impact point meets the national standard requirements,and the lightweight effect is significant.The mass of the new honeycomb engine cover is only25.02% of that of the original engine cover.The results of this paper show that the composite honeycomb sandwich structure engine bonnet can effectively absorb impact energy,protect pedestrian's head and reduce personal injury when traffic accident occurs with pedestrians,which has a good potential in engineering application.