Mechanical And Acoustic Properties Of Two-Dimensional Negative Poisson’s Ratio And Negative Thermal Expansion Metamaterials

Different from conventional materials with a single performance or a single function,advanced multifunctional metamaterials can achieve two or more functions at the same time.Therefore,the multifunctional metamaterials have better adaptability to the service environments.Among various multifunctional metamaterials,lightweight multifunctional mechanical metamaterials with negative Poisson’s ratio and negative coefficient of thermal expansion have received widespread attention from researchers and have broad application prospects in the fields of aerospace,civil engineering and precision instruments.However,the current researches on mechanical metamaterials are mostly focused on single mechanical property and rarely deal with other physical properties and functions,and research methods are too monotonous,which limits the development of multifunctional mechanical metamaterials.Therefore,in this paper,based on the study of perforated auxetic metamaterials with peanut-shaped holes,a two-dimensional ultralight multifunctional auxetic metamaterial composed of orthogonal sinusoidal-shaped beams with negative Poisson’s ratio,negative thermal expansion and the acoustic band gap effect is designed.The main contents of this paper are follows:1.The perforated auxetic metamaterial with peanut-shaped holes is improved for lightweight,and auxetic metamaterial with orthogonal sinusoidal-shaped beams is obtained.Accordingly,a distinctive computational homogenization model is constructed.Then,three different configurations of tensile specimens are prepared by 3D printing technology for tensile experiments.The results show that the experimental results agree well with the calculated results,which verifies the correctness of the computational model.Finally,the parametric analysis of the metamaterials is carried out by the computational homogenization model,and the correspondence between the effective elastic constants and the geometric configurations is highlighted.Meanwhile,a dimensionless design criterion of the crucial zero Poisson’s ratio is given,and its validity is verified by finite element simulation.2.Based on the chiral principle,a novel negative thermal expansion auxetic metamaterial with orthogonal sinusoidal-shaped beams is designed.Finite element simulations show that the structure has almost the same negative thermal expansion effect in the transverse and longitudinal directions when the thermal expansion coefficients of the two materials are different.Furthermore,the effect of the relative material properties on the coefficient of thermal expansion was investigated by parametric analyses.3.Based on the finite element simulation method,the phononic crystal models of the auxetic metamaterial with orthogonal sinusoidal-shaped beams are developed.Meantime,based on acoustic transmission theory,the forbidden band generation mechanism and transmission loss of the metamaterial are analyzed.Then,the effects of different geometric parameters and base material properties on the band gap width and frequency range are investigated by parametric analysis.The results show that the metamaterial has a wide acoustic band gap in a certain frequency range,which can effectively prohibit the propagation of elastic waves in this band gap.By adjusting the geometric parameters and base material properties,the width and frequency range of the band gap can be flexibly modulated.In summary,a novel negative Poisson’s ratio and negative thermal expansion structure with orthogonal sinusoidal-shaped beams is designed in this paper,and its mechanical performance,negative thermal expansion performance and acoustic band gap are systematically investigated,which is also valuable for the design and application of new multifunctional metamaterials.