A novel 3D re-entrant unit cell structure with negative Poisson’s ratio and tunable stiffness

Abstract

In this paper, a novel three-dimensional (3D) unit cell structure with butterfly-like perforations was designed, and negative Poisson's ratio and tunable stiffness were achieved in such a geometry. The Poisson's ratio and strain-stress relationship of structures with different geometric parameters were determined using the finite element method (FEM). Samples with identical geometric variables to those of finite element models were fabricated via 3D printing technique, and their Poisson's ratios and stress-strain relationships were experimentally determined and compared with the FEM results. Results showed that the proposed 3D cellular structures exhibit negative Poisson's ratios, and a minimal value of −0.7091 could be reached. The stress-strain curve of each structure exhibited three distinct stages (elastic response, rib buckling and selfcontact), with different elastic moduli being observed at each stage, and demonstrated a tunable range of the compressive stiffness ratio between stages varying from 0.1866 to 1.4006(tunable stiffness), as determined by FEM analysis. Good agreement was found between the experimental results and FEM predictions. The design concept can be implemented and optimized for specific applications via geometric parameters manipulation.

Study on a Chiral Structure with Tunable Poisson’s Ratio

“…For isotropic auxetics, the Poisson's ratio is in the range of −1 to 1 for two-dimensional structures and −1 to 0.5 for three-dimensional structures [1,[11][12][13][14]. Auxetics include many classical structures, such as chiral structures, concave structures, missing rib models, and star structures [13,[15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Research on auxetics is still in the experimental stage, and there has been little practical application [29].…”

Negative Poisson’s Ratio-Spacer Design and Its Thermo-Mechanical Coupling Analysis Considering Specific Force Output

“…These units can be classified into seven categories based on their structural features and deformation mechanisms: chiral structures, re-entrant structures, rotating rigid structures, origami-based and kirigami-based metamaterials, perforation structures, and auxetic foams [ 11 ]. Among them, chiral structures [ 12 , 13 ], re-entrant structures [ 14 , 15 , 16 , 17 ], and rotating rigid structures [ 17 ] are high-porosity structures used in seismic isolation, buffering, and noise reduction [ 17 , 18 ]. The origami-based and kirigami-based metamaterial patterns possess interesting mechanical features—one degree of freedom-mobility, auxetic in-plane behavior, and energy absorption capability—for applications such as core to sandwich structures, shock absorbers, and airless tires [ 19 , 20 ].…”

“…Therefore, it was necessary to develop a three-dimensional (3D) annular NPR structure to achieve axial positioning and preload adjustments of the inner ring of the bearings (see Section 2 for a description of the principle). At present, the research on the design and application of negative Poisson’s ratio three-dimensional structures mainly focuses on high porosity [ 12 , 13 , 14 , 15 , 16 ] and the research on the design and application of low-porosity three-dimensional structures, especially on the deformation capacity and force output characteristics of such circular structures under centrifugal force and boundary constraints, has not been reported. Simultaneously, owing to the large variation in the internal temperature range of a spindle in the full operating range [ 25 , 26 ], the influence of temperature on the geometric and mechanical properties of an NPR spacer is nonnegligible.…”

A New Polymer-Based Mechanical Metamaterial with Tailorable Large Negative Poisson’s Ratios

“…Alternatively, the rhombic configuration was placed in the re-entrant honeycomb to improve in-plane stiffness while maintaining the negative Poisson's ratio of the original re-entrant structure [26]. Combining pore-embedded unit and re-entrant structure, Li et al [27] proposed a butterfly-like perforated 3D structure, and its soft structure could achieve a negative Poisson's ratio by squeezing the pores inside the unit. Different stiffness ratios could be adjusted by varying the geometry parameters.…”