Investigation of Modified Auxetic Structures from Rigid Rotating Squares (original) (raw)
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Hierarchical Auxetic Mechanical Metamaterials
Scientific Reports, 2015
Auxetic mechanical metamaterials are engineered systems that exhibit the unusual macroscopic property of a negative Poisson's ratio due to sub-unit structure rather than chemical composition. Although their unique behaviour makes them superior to conventional materials in many practical applications, they are limited in availability. Here, we propose a new class of hierarchical auxetics based on the rotating rigid units mechanism. These systems retain the enhanced properties from having a negative Poisson's ratio with the added benefits of being a hierarchical system. Using simulations on typical hierarchical multi-level rotating squares, we show that, through design, one can control the extent of auxeticity, degree of aperture and size of the different pores in the system. This makes the system more versatile than similar non-hierarchical ones, making them promising candidates for industrial and biomedical applications, such as stents and skin grafts.
Auxetic Structures from Rotating Squares
2022
The article deals with auxetic structures made on the basis of suitably connected rigid rotating squares (from Grima and Evans), with axes of rotation on the squares’ surface. The geometric model and the resulting relationships that allow for the determination of Poisson’s ratio are considered in detail. It is demonstrated that changing the rotation axis position does not affect the negative Poisson’s ratio, equal to -1. The models built confirm the initial considerations and can offer new application possibilities.
Two Dimensional Auxetic Metamaterials with Adjustable Values of Poisson's Ratio
IRJET, 2023
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.
Selective hinge removal strategy for architecting hierarchical auxetic metamaterials
Nature Communications Materials , 2022
Mechanical metamaterials are man-made structures capable of achieving different intended mechanical properties through their artificial, structural design. Specifically, metamaterials with negative Poisson's ratio, known as auxetics, have been of widespread interest to scientists. It is well-known that some pivotally interconnected polygons exhibit auxetic behaviour. While some hierarchical variations of these structures have been proposed, generalising such structures presents various complexities depending on the initial configuration of their basic module. Here, we report the development of pivotally interconnected polygons based on even-numbered modules, which, in contrast to odd-numbered ones, are not straightforward to generalize. Particularly, we propose a design method for such assemblies based on the selective removal of rotational hinges, resulting in fully-deployable structures, not achievable with previously known methods. Analytical and numerical analyses are performed to evaluate Poisson's ratio, verified by prototyping and experimentation. We anticipate this work to be a starting point for the further development of such metamaterials.
In-plane mechanical behavior of novel auxetic hybrid metamaterials
Thin-Walled Structures, 2021
We present in this paper two novel concepts of hybrid metamaterials that combine a core unit cell of re-entrant or cross-chiral shape and lateral missing ribs. The first topology is a hybrid between an anti-tetrachiral and a missing rib (cross-chiral) configuration; the second one has a variable cross-chiral layout compared to the classical missing rib square structure. Their in-plane mechanical properties have been investigated from a parametric point of view using finite element (FE) simulations. The two classes of metamaterials have been benchmarked to obtain optimized designs and specific effective properties. Nonlinear simulations and experimental tests of the new re-entrant missing rib metamaterials featuring optimized geometry parameters have been performed to understand the behavior of these architectures under large deformations.
Numerical Analysis of Dynamic Properties of an Auxetic Structure with Rotating Squares with Holes
Materials
In this paper, a novel auxetic structure with rotating squares with holes is investigated. The unit cell of the structure consists of four units in the shape of a square with cut corners and holes. Finally, the structure represents a kind of modified auxetic structure made of rotating squares with holes or sheets of material with regularly arranged diamond and square cuts. Effective and dynamic properties of these structures depend on geometrical properties of the structure. The structures are characterized by an effective Poisson’s ratio from negative to positive values (from about minus one to about plus one). Numerical analysis is made for different geometrical features of the unit cells. The simulations enabled the determination of the dynamic characteristic of the analyzed structures using vibration transmission loss, transmissibility, and mechanical impedance. Numerical calculations were conducted using the finite element method. In the analyzed cases of cellular auxetic struc...
Metamaterial computation and fabrication of auxetic patterns for architecture
The paper investigates the potential of auxetics in architectural applications by means of computational design and additive manufacturing. This class of metamaterials expresses interesting behaviour related to the unusual characteristics of a negative Poisson's ratio. Different patterns have been studied through a design workflow based on parametric software and the use of Particle Spring systems to support the form-finding process of bending-active auxetic structures. An advanced understanding of their bending capacity is explored with the use of variable infill patterns informed by structural analysis. Furthermore, principles for the design and fabrication of auxetic gridshells are discussed.
Normal and shear behaviours of auxetic metamaterials: homogenisation and experimental approaches
Meccanica, 2019
Auxetic metamaterials exhibit attractive mechanical properties, including negative Poisson's ratio and compressional resistance. Although auxetic meta-materials have been extensively investigated using experimental and computational approaches, the consistent estimation of shear properties is unclear. According to Cauchy elasticity, the shear properties of an auxetic structure should be enhanced because of the negative Poisson's ratio. However, this study used homogenisation and experimental approaches to demonstrate that shear elasticity is highly non-linear with respect to the characteristic geometrical parameters of a unit cell and that shear properties are not always improved.
Photonics and Nanostructures - Fundamentals and Applications, 2021
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