Research On The Design And Mechanical Properties Of Novel Negative Poisson’s Ratio Materials

As a new type of material,negative Poisson’s ratio materials have more special and superior mechanical properties than traditional materials,such as large shear modulus,high fracture toughness,high energy absorption efficiency,high specific strength and specific stiffness.Negative Poisson’s ratio materials have broader application prospects.Since the first famous material scientist Lakes professor using industrial thermoplastic open-cell foam fabricate the isotropic foam material with Poisson’s ratio of-0.7,and its mechanical properties had been analyzed,and then the material structure with negative Poisson’s ratio effect attracts many scholars’ concerns and research.In this paper,novel concave structure models with negative Poisson’s ratio effect are designed and the finite element method is used to conduct quasi-static mechanical behavior numerical simulation of structural models.At the same time,analysis and experimental study are conducted to verify the reliability of the numerical simulation results of the finite element method;and based on genetic algorithm to optimize the negative Poisson’s ratio structure,and then the structural parameters of negative Poisson’s ratio material with the best macro-mechanical properties are determined.It provides an important basis for the future optimization of porous materials design and practical applications.This article mainly studies the following aspects:(1)Based on the finite element analysis method,structural models with negative Poisson’s ratio which is composed of two materials with different thermal expansion coefficients were established and the relationship between Poisson’s ratio and temperatures was studied.And then the theoretical and experimental methods are used to verify the numerical results.The results show that the Poisson’s ratio of this kind of bi-material structure can be changed from positive to negative(or vice versa)with the change of temperature.(2)By using ANSYS/APDL parametric modeling method,novel two-dimensional and three-dimensional structure achieved by alternating rectangular surface indents on the vertical ribs of the unit cells were designed and the effect of size parameter of structure surface dimple on equivalent Poisson’s ratio and equivalent elastic modulus of structure were studied.And then the porous structure specimens with the same geometrical parameters were prepared by 3D printing technique and the mechanical properties of the specimens were analyzed experimentally to verify the validity of numerical analysis results.The results show that the negative Poisson’s ratio porous structures with dimples on the two-dimensional and three-dimensional surfaces are stiffer than traditional honeycomb materials.(3)The single-target and multi-objective optimization design of minimum Poisson’s ratio and maximum equivalent elastic modulus of star-shaped porous negative Poisson’s ratio structure were carried out by using ANSYS and MATLAB software.The influence of the size of the star-hole micro-structure cell on the optimization target is discussed to get the negative Poisson’s ratio structure with the best mechanical properties.