Design And Mechanical Properties Of A New Star-shaped Negative Poisson’s Ratio Honeycomb Metamaterial

Metamaterials with negative Poisson’s ratio have the advantages of light weight,strong impact resistance,unconventional overall deformation behavior(materials expand laterally under tension and contract laterally under pressure),easy adjustment of structural parameters and stable mechanical properties.Its mechanical and mechanical properties are better than traditional materials.It has great application prospects in the fields of civil engineering,energy and chemical industry and aerospace.On the premise of ensuring structural stress constraints,the space utilization,stability and reliability of metamaterials with negative Poisson’s ratio are improved,and the safety of facilities such as piers is further improved.Therefore,it is of great significance to design negative Poisson’s ratio metamaterials with better performance.In this paper,based on the star-shaped negative Poisson cell structure,a new star-shaped cell structure model is designed and its structural performance is analyzed.The main contents are as follows:On the basis of the traditional negative Poisson’s ratio star structure,a new star cell structure is designed by breaking and reconnecting the ribs of the star structure.The shape of the new star cell structure is controlled by changing the included angle θand the side length A.The equivalent mechanical analysis of the new star cell structure is carried out.Based on the force method of structural mechanics,the internal force diagram of the bar is obtained,and then the lateral displacement and longitudinal displacement of the bar are obtained,and finally the effective Young’s modulus and initial Young’s modulus ratio and Poisson’s ratio of the cell are obtained.Using Matlab to draw the binary function image of Poisson’s ratio about included angle θ and side length a,it is concluded that side length a has great influence on the mechanical properties of the new star cell structure.The angle θ is expressed by the side length a,and the univariate function of the side length A about Poisson’s ratio is obtained.The univariate function image of the side length a about Poisson’s ratio is drawn.The cell structure with stronger negative Poisson ratio effect is obtained,which reveals the necessity of structural parameter optimization.The finite element analysis software ANSYS is used to simulate the deformation of the new star-shaped cell structure under uniaxial compression load.By changing the side length A to control the shape of the new star cell structure,the displacement nephogram changing with the side length A is obtained.According to the formula of Poisson’s ratio about transverse strain and longitudinal strain,the numerical solution of Poisson’s ratio of the structure under uniaxial compression load is obtained.Comparing the numerical solution of Poisson’s ratio with the analytical solution,it is concluded that the error between them is less than 2% and the numerical solution is small.The numerical solution is too small because the inner and outer lengths of the finite element model are not completely consistent.By arranging the cell structures periodically,a new honeycomb structure with star cell structure is obtained,and the structure is introduced from micro to macro.The deformation of the new star-shaped honeycomb structure under uniaxial compression load is simulated by finite element analysis software ANSYS.The equivalent Poisson’s ratio of the new star honeycomb structure is calculated and compared with the case of a=0.The results show that with the increase of side length a,Poisson’s ratio first decreases and then increases.The negative Poisson’s ratio effect is the strongest when a is greater than 0.15 mm and less than 0.2mm,and the new star honeycomb structure has the strongest negative Poisson’s ratio effect at this time.At present,the research on the impact resistance of negative Poisson metamaterials basically stays in two-dimensional plane,and rarely designs in three-dimensional space.Compared with the two-dimensional plane,the negative Poisson designed based on the three-dimensional space structure has higher material utilization rate and stronger practicability than metamaterials.The three-dimensional finite element model of the new star-shaped cell structure is generated by the center symmetry of the new star-shaped structure established above about the upper plane center point of the upper connecting rod.By changing the side length a to control the shape of three-dimensional space structure,the impact dynamics numerical simulation of eight design side length models with different impact speeds is carried out by using LS-DYNA software.The deformation mode and stress nephogram distribution of the new star honeycomb structure model with different impact velocities are obtained.Therefore,reasonable setting of cell size parameters provides a new idea for material performance optimization,and negative Poisson’s ratio metamaterials have a very broad application prospect in impact resistance.Figure [68] Table [2] Reference [81]...