The Mechanical Design And Analysis Of The Intelligent Flexible Metamaterial With Negative Poisson's Rate

Metamaterials exhibit amazing physical and mechanical properties due to their unique microstructure,among which negative Poisson's ratio mechanical metamaterials have received extensive attention because of their special deformation mode and excellent mechanical properties.Intelligent materials are a new type of functional materials that can sense and respond to external stimulation.They have many special functions that ordinary materials do not have.Intelligent metamaterials with selfsensing and self-driving functions can be prepared by combining metamaterials with intelligent materials to realize the integration of structure and function.Based on the negative Poisson's ratio metamaterials and the intelligent flexible materials of shape memory polymer(SMP)and hydrogels,we explore the deformation mode and band gap characteristics of intelligent flexible metamaterials.The main research contents are as follows.(1)A three-dimensional negative Poisson's ratio metamaterial is proposed based on the two-dimensional anti-tetrachiral structure.In the case of small deformation,the deformation behavior of the structure is studied.The analytical solutions of Poisson's ratios and elastic modulus are all obtained using the beam theory and energy method,and compared with the finite element results.In addition,the influence of geometric parameters on Poisson's ratios and elastic modulus of the metamaterial is explored in detail.This work lays a foundation for the design and deformation analysis of intelligent flexiable metamaterials in the next works.(2)The intelligent flexiable negative Poisson's ratio metamaterial is designed and prepared using SMP material with shape programmable and variable stiffness functions.Firstly,the relationship between mechanical properties and geometrical parameters of the metamaterial is established.Then the temperature and loading mode are controlled artificially,to realize the programming control of the shape of metamaterial.Then the relationship between band gap and lattice parameters and the evolution law of band gap with strain of metamaterial are explored systematically.Finally,the effective stiffness of the metamaterial is adjusted by changing the temperature to realize the control of the temperature on band gap,realizing the intelligent regulation of elastic wave.(3)Based on the deformation pattern of the re-entrant negative Poisson's ratio structure and the property of swelling after absorbing water for hydrogel,we develope a 2D/3D composite intelligent flexiable metamaterial with negative expansion function and analyze its band gap characteristics.Taking the swelling of hydrogel as the driving force of deformation,we arrange the position of hydrogel in the negative Poisson's ratio structure reasonably and then prepare it using the multi-materials 3D printing technology.Then the deformation behavior of the metamaterial is verified with experiment and simulation.Finally,the vibration response ability of the metamaterial with different strain is analyzed.