Energy Absorption Bionic Structure Design And Additive Manufacturing Research Inspired By Arapaima Scales

From"Chang’e"to the moon,"Zhurong"to the mars and"Xihe"to the sun,China’s space exploration capabilities continue to grow.In the process of planetary exploration,the lander carrying important instruments plays a crucial role in the success of the exploration mission.Legged lander is widely used in the field of planet exploration because of its stable landing attitude,high reliability and strong control.The energy absorption structure of the existing lander cannot simultaneously combine the requirements of simple structure,high energy absorption efficiency,and reversibility after deformation.Therefore,the energy-absorbing structure carried out in this paper has important research value for legged landers and provides a theoretical basis for energy-absorbing buffers in aerospace.In this paper,according to the similarity principle,the scale of Arapaima was selected as the bionic prototype,and its macro and micro structures as well as chemical molecules were observed and tested.At the same time through the experiment to explore the mechanical properties of the scale,analysis of its energy absorption anti impact mechanism.Scanning electron microscopy（SEM）was used to observe the cross sections of the scales and found that the internal layers were rotating.The elastic modulus of the flake is 0.38 GPa and the ultimate tensile strength is 27 MPa.The failure mechanism is mainly the fiber delamination and tensile failure.A new bionic lattice structure（BLS）and bionic lattice center structure（BLCS）were designed by extracting the characteristic structure（BS）of the scales of the Arapaima.Ni_50.8Ti_49.2 alloy material with shape memory performance was selected,and the bionic structure sample was printed and prepared by laser selective melting forming technology.The forming quality of the structure sample was observed by size measurement and defect analysis.The energy absorption and recovery performance of the sample were investigated by quasi-static compression test and cyclic loading and unloading recovery test.It was found that when the compression rate of BLS was 25%,the recovery rate was 98.5%after 5 times of cyclic loading and unloading,indicating excellent recovery performance.The energy and specific energy of BLCS are 2.3 times and 1.85 times stronger than those of BLS,but the compressibility of BLCS is only12%.In order to synthesize the excellent performance of BLS and BLCS,the characteristic structure of BLCS samples was optimized to obtain topological negative Poisson’s ratio structure（TNPR）,which was combined with BS structure to obtain H-BBTT,H-BTBT,H-BTTB and H-TBBT in different arrangement modes.It is found that H-TBBT sample has the best energy absorption and recovery performance.By comparing the experimental results with the finite element results,the accuracy of the simulation is verified by the force-displacement curves,deformation modes and performance errors.The optimal sample H-TBBT was selected,and the influence of structural parameters on load bearing performance,deformation mode and energy absorption performance of the sample was studied by finite element simulation.（1）With the increase of TNPR cell thickness,the densification displacement of the sample decreases,the elastic modulus and yield strength increase,and the EA and SEA increase,but the increase is less and less due to the increase of mass.（2）When the concave Angle of TNPR structure is 30°,the negative Poisson’s ratio effect is the most obvious and the bearing performance is the highest,while the energy absorption performance is the best when the concave Angle is 45°.（3）With the increase of the pitch,the densification displacement of the sample decreases,the yield strength increases,and the spiral deformation of the sample becomes less obvious.EA and SEA basically follow the trend of increasing with the increase of the pitch.