International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 10 Issue: 07 | July 2023
p-ISSN: 2395-0072
www.irjet.net
Two Dimensional Auxetic Metamaterials with Adjustable Values of Poisson’s Ratio Heng Li*, Peng Cheng, Anthony Martin, GeMonye L Glass, Dominic Ross, Salaah J Alston Department of Applied Engineering Technology Virginia State University 1 Hayden St, Petersburg, VA 23806 USA ----------------------------------------------------------------------------***-------------------------------------------------------------------------Abstract In the past decades, mechanical metamaterials have attracted extensive attention due to their unusual mechanical and physical properties with simple structures, as well as their unique potential applications in various fields, including engineering, aerospace, biomedical engineering, robotics, sports equipment, and textiles, etc. Auxetic metamaterials are a class of materials that exhibit negative Poisson’s ratio, meaning they contract in the direction perpendicular to the applied force when compressed. In this work, a group of unit cell structures for two-dimensional auxetic metamaterials was designed and fabricated using 3D modeling and printing technology, with the unique feature of adjustable Poisson’s ratio. The Poisson’s ratios were evaluated experimentally, numerically and analytically, and the results were found to be in agreement each other. Specifically, as the phase shift difference decreased from π to zero, the Poisson’s ratios of the materials increased from -2.8 to -0.19. This study provides insights into the design and fabrication of auxetic materials with tunable Poisson’s ratios, which could have applications in a variety of fields including engineering and medicine.
Keywords: Auxetic metamaterials, 3D printing, Negative Poisson’s Ratio Introduction Mechanical metamaterials are engineered structures that possess unusual mechanical properties and functionalities. The unusual properties include the extraordinary values of familiar mechanical parameters, such as density, Poisson’s ratio, and compressibility [1]. The exotic functionalities include pattern and shape transformations in response to mechanical forces, unidirectional guiding of motion and waves, and reprogrammable stiffness of dissipation [2]. Materials and structures with negative Poisson’s ratio exhibit uncommon mechanical properties that materials either expand or contract in all directions when a force is applied. Resulting from this uncommon behavior, many desired properties are discovered. Auxetic materials have potential applications in the fields of military, biomedical, aerospace, and textiles. However, there are a limited structures in current literature, which possess negative value of Poisson’s ratio, such as re-entrant structure [3], chiral structure, and rigid rotating structure [4]. In addition, there are a few general analytical methods to analyze the relationship of Poisson’s ratio, the parameters of geometry, and base material constants. In this study, we designed a group of 3D modelling of unit cell structures with design software. The specimen of the structures based on the units cells were fabricated using 3D printer. Mechanical properties of these structures were analyzed by finite element methods, COMSOL 5.4, Structural Mechanics Module. The Poisson’s ratios of the structures were measeured by Instron machine. Furthermore, one model of mechanical properties of these structures was created to estimate the Poisson’s ratio of these structures (the details to be published in the other paper). By the comparison of the analytical values of the Poisson ratio with the analytical values from the model, they are found to be in agreement with each other. In particular, the Poisson ratios of the structures are increasing from -2.8 to 0.19 as the phase difference decreasing from π to zero. The insights pave the way for modeling and fabrication of auxetic metamaterials with tunable Poisson’s ratio.
Design, Fabricating and Testing The three two-dimensional cellular structures were designed with TinkerCad and Matlab software. The structures (a), (b), (c) and their unit cells are shown in Fig.1. The shapes of the unit cells are constructed with two straight lines and two curved lines. The sizes of the unit cells are height 11 mm, the width 9 mm, the depth 6 mm, and the thickness 0.5 mm. The two curved lines in each unit cell are sine curve
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