Enhanced Mechanical Behaviors Of Bio-inspired Hierarchical Honeycomb With Variable-thickness Configuration

At present,it is the mainstream method to reduce the energy consumption of the automobile by reducing the quality of the automobile.While realizing the lightweight of the automobile,how to ensure the safety performance of the automobile in the process of driving is a hot topic that people pay close attention to.Traditional automotive safety parts are with a thin wall thickness structure,this design not only reduce the quality of the car,but also improve the crashworthiness of the car,but with the increasingly strict national design standard come on stage,and the use of cars to the people’s attention to the car security,many of the existing automotive safety parts design also has the very big improvement space.Such as filling the automotive safety parts or change the structure of automotive safety parts to improve the ability of impact resistance in the process of moving vehicle,in this paper,based on the advantage of the bio-inspired structure in the nature,bio-inspired hierarchica and bio-inspired variable thickness is put forward to enhance the absorption effect of cellular structure,in order to improve the safety performance of the car.It is well known that cellular structures are widely used in engineering applications due to their lightweight properties and excellent crashworthiness.In nature,there are many hierarchical structures and variable thickness structures that exhibit excellent energy absorption characteristics,and the variable thickness hierarchical honeycomb（VTHH） combined with these two structures can further improve its crashworthiness and energy absorption.This study mainly explored the energy absorption of hierarchical honeycomb variable thickness that based on vertex in the out-of-plane direction.The quasi-static experiments show that regular honeycomb with variable thickness have higher energy absorption than regular honeycomb with uniform thickness,and research result shows that the energy absorption of the honeycomb with variable thickness was 31.14% high er than that of the honeycomb with uniform thickness.Then,the hierarchical honeycomb with variable thickness can further improve its energy absorption capacity by means of simulation.And the results from numerical simulation indicate that the specific e nergy absorption of variable thickness hierarchical honeycomb（VTHH） is improved 11.19% and 26.19% compared to uniform thickness hierarchical honeycomb（UTHH）and variable thickness honeycomb（VTH）respectively.Additionally,by means of finite element numerical model for the parametric study of honeycomb structure,the parameter η₁ was introduced（the ratio of the new hexagonal side length in bio-inspired first-order hierarchical honeycomb and the side length of regular honeycomb）,was used to represent the different size of bio-inspired first-order hierarchical honeycomb,found that when the parameters of the η₁=0.2,the specific energy absorption of bio-inspired first-order hierarchical honeycomb is the best.The effects of Relative density（（?）） and thickness gradient（k₁） on the peak crushing force（PCF） and the energy absorption（EA）performance of the honeycomb structure per unit mass were investigated.With the increase of Relative density and thickness gradient,the specific energy absorption of the bio-inspired variable thickness hierarchical honeycomb structure also increases in different degrees.Finally,the mean crushing force（MCF） of self-similar bio-inspired hierarchical honeycomb with variable thickness is predicted by theoretical analysis,which was based on the Super Folding Element（SFE） theory.It is can provide some guidance for practical application.All the findings of this study indicate the proposed variable thickness hierarchical honeycomb（VTHH） exhibit an excellent crashworthiness performance,which is significantly improved compared with some traditional thin-wall structures studied in the past,such as circular tube and square tube,etc,and the specific energy absorption（SEA）enhance gradually with the increases of Relative density（（?））.