Research On Multi-objective Optimization Of Carbon Fiber/honeycomb Aluminum Sandwich Engine Hood

With the rapid development of China’s economy and automobile industry,the quantity of vehicle is increasing year by year.At the same time,the negative effects of cars are becoming more and more obvious,such as environmental pollution,traffic accidents and so on.Therefore,energy-saving,environmental protection and safety have become the main goal of automotive industry in the future.Honeycomb sandwich structure composites have the advantages of light weight,high strength and good energy absorption.When crash occurs,it has obvious advantages to reduce the head injury of pedestrians and realize the light weight of the vehicle body when it is applied to the launching hood.The finite element model of honeycomb aluminum and honeycomb sandwich structure is established in this paper.The validity of the finite element model is verified by quasi-static compression test and three-point bending test.According to the regulations,the finite element model of pedestrian head impact engine hood is established,and the pedestrian protection performance of engine hood is verified by selecting representative test points above the hood.According to the finite element model of honeycomb sandwich structure and the shape of the original engine hood,the honeycomb sandwich structure engine hood is established.The bending stiffness,lateral bending stiffness,torsional stiffness,first-order mode,mass and pedestrian protection performance of the two kinds of engine hood are compared and analyzed.It is found that the new material has better performance than the original hood.In order to optimize the performance of the new engine hood,the thickness of the upper,middle and lower layers of the honeycomb sandwich structure is taken as the variable.The optimal Latin hypercube experimental design method is used to sample the design space.The response surface and Kriging approximation model are established according to the sample points and the accuracy of the approximate model is verified.The HIC value of head damage and the mass of engine hood are taken as objective function,and the bending stiffness,lateral bending stiffness,torsional stiffness of engine hood and the first order mode are taken as constraint function.The second generation non-dominated sorting genetic algorithm is used for multi-objective deterministic optimization of engine hood.Considering the uncertainty in the actual manufacturing process,the multi-objective reliability optimization design of the engine hood is carried out on the basis of determining the optimization direction,and the credibility of the optimization results is verified.The results show that compared with the original steel plate engine hood,the optimized honeycomb sandwich structure engine hood has been greatly improved in pedestrian protection and lightweight.It shows that honeycomb sandwich structure composite has broad application prospect in improving pedestrian protection performance and promoting whole vehicle lightweight.