Research On Design And Mechanical Properties Of Composite Structures With Negative Poisson's Ratio

As a new type of structural material,negative Poisson's ratio material has more special and superior mechanical properties than traditional materials,such as large shear modulus,high energy absorption efficiency and strong pressure resistance.It is used in aerospace and automobile manufacturing.Other fields have broad application prospects.As a special structure widely existed in nature,hierarchical structure has been widely concerned in engineering manufacturing and scientific research.With the advancement of 3D printing and other industrial technologies,the theoretical and experimental research of negative Poisson's ratio materials has gradually become the focus of material scientists.The concept of band gap and passband of band gap structure was originally derived from the study of crystal lattice characteristics in solid state physics,and was later used in the study of phononic crystals.In recent years,it has been found that the lattice structure also has a stop band characteristic.By adjusting the geometric parameters,good performance of low-frequency vibration isolation can be obtained,so the study of the band characteristics of the lattice structure has attracted much attention.In this paper,some models are designed,which are the hierarchical structure with negative Poisson's ratio and the re-entrant structure model with variable stiffness effect.The finite element method is used to study the mechanical properties of different structures.At the same time,the band characteristics of two-dimensional and three-dimensional hierarchical structures with negative Poisson's ratio are studied.Research has been carried out to make a useful exploration for the study of hierarchical structures and negative Poisson materials.The research contents are showed as follows in details:(1)Based on the finite element method,the Poisson's ratio of two-dimensional hierarchy with negative Poisson's ratio structure is calculated by using the APDL parametric modeling method of ANSYS,and the deformation behavior and energy absorption capacity of the structure are studied at quasi-static compression and different velocity compression.The results show that the structure can change from positive Poisson's ratio to negative Poisson's ratio by adjusting the structural geometry parameters.Compared with the traditional concave hexagonal structure,the hierarchical negative Poisson's ratio structure has better energy absorption capacity.(2)Based on Floquet-Bloch theory,the band characteristics of two-dimensional and three-dimensional hierarchical structures are analyzed by COMSOL/Multiphysics and ANSYS software.The band structure of the structure is calculated by using Floquet periodic boundary condition and related theory.Through harmonic response analysis,the transmission coefficient of the structure is calculated and the transmission spectrum is drawn.The results show that the hierarchy structure with negative Poisson's ratio has better energy band characteristics and vibration isolation effect by adjusting the geometric parameters of the structure.(3)A three-dimensional variable stiffness structure is designed and its deformation behavior is simulated by ANSYS/LS-DYNA at quasi-static compression.The relationship between relative stiffness and strain is analyzed.The results show that the three-dimensional variable stiffness structure has a significant negative Poisson's ratio effect,and its relative stiffness shows the characteristics of gradual rise.