Mechanical Properties Analysis And Crashworthiness Research Of Hierarchical Honeycomb Structures

At present,lightweight and crashworthiness have become a key research topic in automotive industry.To meet the design requirements of automobile collision safety without increasing the mass of body,more and more ultra-light materials and ultra-light structures used in vehicle structure.Honeycomb structures are typical ultra-light structures.Among them,hierarchical honeycomb structures have excellent mechanical properties and energy absorption characteristics,and have great application prospect in vehicle structure.In this study,a series of studies have been carried out on the mechanical properties and crashworthiness characteristics of hierarchical honeycomb structures.(1)Quasi-static compression experiment of the first-order honeycomb structure based on the edge is carried out and corresponding FE model is established.The accuracy of the model is verified by comparing the experimental results with the simulation results.Finally,the energy absorption characteristics of first-order honeycomb structures and traditional honeycomb structure were compared.The results show that the first-order honeycomb structures have more advantages and potential in energy absorption.(2)The crashworthiness of hierarchical honeycomb structures based on the vertex under the out-of-plane loading is studied.Firstly,FE model is established and the accuracy of the model is verified by theoretical formula.Then,six crashworthiness evaluation indexes are selected,the effects of relative density and edge length ratio on the crashworthiness are discussed.Finally,the complex proportional assessment method is used to evaluate crashworthiness of hierarchical honeycomb structures.The results show that the structures have better crashworthiness performance at high order and small edge length ratio.(3)In-plane equivalent parameters of bionic hierarchical honeycomb structures are studied.Firstly,relative density formulas of the structures are deduced.Then,based on the exact FE model,the equivalent parameters of four kinds of first-order honeycomb structures are investigated under different edge length ratios,the results show that the small edge length ratio of first-order honeycomb structures have better performance.Finally,the equivalent parameters of four kinds of high-order honeycomb structures are analyzed,the results show that P-P and M-M hierarchical honeycomb structures have better mechanical properties.(4)The equivalent parameters and crashworthiness of iterative first-order honeycomb structures are investigated.Firstly,the relationship between the thickness ratio of first-order honeycomb structures and in-plane equivalent parameters are studied.The results show that the small thickness ratio of structures have better performance.Then,using the explicit dynamic FE method to study the crashworthiness of the iterative first-order honeycomb structures under the out-of-plane loading,and compared with the traditional honeycomb structure.The results show that the high relative density and small thickness ratio of structures have better crashworthiness performance.Finally,the effect of the thickness ratio on the crashworthiness under in-plane loading is studied.