Crashworthiness Mechanism Of Bionic Pentacle Thin-Walled Structure Inspired By Carambola

Thin-walled structures are widely used in transportation,civil engineering and other industrial fields because of their excellent crashworthiness,lightweight and low cost.A research focus is how to optimize the design of thin-walled structures and further improve the energy absorption capacity to satisfy the expanding engineering demands.In this paper,inspired by the observation that the exotic pentacle structure of carambola fruit has high crush resistance,the bionic pentacle thin-walled structure was proposed.The finite element simulation,experiment,and theoretical approaches were used to evaluate the deformation mode and energy absorption mechanism of the pentacle structure,and the optimization design of pentacle thin-walled structures was performed out.The followings are brief summaries of the main contents of this work:(1)The axial compression experiments of fruit tissue and structure were carried out.The deformation and load response of carambola and kiwifruit specimens were analyzed based on the normalization method.The results indicate that,as compared to the circular form,the pentacle structure has improved energy absorption capabilities.The physics of carambola’s distinctive pentacle structure were properly explained.(2)Based on the geometric characteristics of carambola,the bionic pentacle thinwalled structure was designed.The effects of section geometry on load response,deformation mode and energy absorption characteristics were analyzed by finite element simulation.The bionic pentacle thin-walled structure is discovered to be more capable of balancing the relationship between the number of corners and the stability of progressive folding deformation.The crashworthiness of pentacle structure is superior to that of thinwalled tubes with common section shapes such as circle,quadrilateral and hexagon,indicating that it has significant engineering application potential.(3)The influence of section geometric parameters on the structural crashworthiness was discussed,as well as their decisive effect on the progressive folding mode or Euler buckling mode.The theoretical model of mean crushing force of pentacle thin-walled structure was derived by energy balance method.The research realized the regulation of the basic energy absorption characteristics,and verified the feasibility of the theoretical method to describe the load plateau of pentacle thin-walled structures.(4)The optimization design of pentacle structure was performed by three types of design schemes,i.e.multi-cell array,hierarchical stiffener and thin-walled shell.The results show that the friction behavior between adjacent layers and the excellent stiffness distribution of stiffeners connected with concave points can provide additional energy dissipation,which is conducive to the sustainable progressive folding of the pentacle hierarchical structure;The pentacle shell can significantly reduce the peak crushing force and greatly optimize the crushing force efficiency with low initial structural stiffness.The results show that the energy absorption performance of pentacle structure is significantly optimized,which provides valuable guidance for relevant engineering applications,and explores the effective method of optimal design of thin-walled structures.