Vibration Transmission Loss of Auxetic Lattices

2015 ◽  
Vol 797 ◽  
pp. 282-289
Author(s):  
Eligiusz Idczak ◽  
Tomasz Strek
Keyword(s):  
Dynamic Behavior ◽  
Poisson’S Ratio ◽  
Natural Frequencies ◽  
Transmission Loss ◽  
Dynamic Properties ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Vibration Transmission ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio

The auxetic lattices are structures, which have the negative Poisson’s ratio. When material has negative Poisson’s ratio, has also auxetic properties - during process of stretching, are made wider and during compressing are made narrower. This structures are cellular and negative Poisson’s ratio is depending on the geometry of single auxetic cell. When geometry of the cell is slightly changed also Poisson’s ratio is different. Auxetics have attracted attention of researchers because of their superior dynamic properties. The lattice auxetic structures at one of their natural frequencies exhibit the deformed geometry. It’s can be exploit as resonance to optimization of the power required for the occurrence localized deformations. The dynamic behavior of auxetic and their transmission of the vibration, which is circumscribed by the parameter VTL (Vibration Transmission Loss) will be analyzed in this article.

Design and fabrication of auxetic warp-knitted structures with a rotational hexagonal loop

2016 ◽  
Vol 86 (20) ◽  
pp. 2151-2157 ◽  
Author(s):  
Pibo Ma ◽  
Yuping Chang ◽  
Gaoming Jiang
Keyword(s):  
Poisson’S Ratio ◽  
Rotation Angle ◽  
Hexagonal Structure ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Two Dimensional ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio ◽  
Novel Structures

In this paper, the design, manufacturing and characterization of two-dimensional warp-knitted textiles with auxetic performance is reported. Four warp-knitted structures based on a rotational hexagonal structure are produced, and these structures can lead to a negative Poisson’s ratio mathematically. The testing results have confirmed that the knitting structure of the front bar, as well as let-off values of the front bar’s chain parts, has a great effect, and auxetic properties of the warp-knitted textiles have a complicated relationship with the rotation angle. These novel structures can expand the applied area of auxetic structures.

scholarly journals Review of Mechanics and Applications of Auxetic Structures

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Mariam Mir ◽  
Murtaza Najabat Ali ◽  
Javaria Sami ◽  
Umar Ansari
Keyword(s):  
Poisson’S Ratio ◽  
Deformation Mechanisms ◽  
Poisson's Ratio ◽  
Cellular Solids ◽  
Negative Poisson’S Ratio ◽  
Auxetic Materials ◽  
Different Types ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio ◽  
Properties Of Materials

One of the important mechanical properties of materials is Poisson’s ratio, which is positive for most of the materials. However, certain materials exhibit “auxetic” properties; that is, they have a negative Poisson’s ratio. Thus auxetic and non-auxetic materials exhibit different deformation mechanisms. A specific microscopic structure in the auxetic materials is important for maintaining a negative Poisson’s ratio. Based on their distinct nature auxetic materials execute certain unique properties in contrast to other materials, which are reviewed in this paper. Thus auxetic materials have important applications in the biomedical field which are also a part of this review article. Many auxetic materials have been discovered, fabricated, and synthesized which differ on the basis of structure, scale and deformation mechanism. The different types of auxetic materials such as auxetic cellular solids, microscopic auxetic polymers, molecular auxetic materials, and auxetic composites have been reviewed comprehensively in this paper. Modeling of auxetic structures is of considerable importance and needs appropriate stress strain configurations; thus different aspects of auxetic modeling have also been reviewed. Packing parameters and relative densities are of prime importance in this regard. This review would thus help the researchers in determining and deciding the various aspects of auxetic nature for their products.

Behavior of Soft 3D-Printed Auxetic Structures Under Various Loading Conditions

2018 ◽  
Author(s):  
Mahmoud K. Ardebili ◽  
Kerim Tuna Ikikardaslar ◽  
Erik Chauca ◽  
Feridun Delale
Keyword(s):  
Poisson’S Ratio ◽  
Tensile Load ◽  
Geometric Parameters ◽  
Poisson's Ratio ◽  
Impact Loads ◽  
Negative Poisson’S Ratio ◽  
Auxetic Structures ◽  
Circular Holes ◽  
Negative Poisson's Ratio ◽  
3D Printed

Auxetic structures exhibiting non-linear deformation are a prevalent research topic in the material sciences due to their negative Poisson’s ratio. The auxetic behavior is most efficiently accomplished through buckling or hinging of 3d printed structures created with soft or flexible materials. These structures have been hypothesized to have some unique characteristics and may provide advantages over conventional engineering materials in certain applications. The objective of present study is to gain a better understanding of behavior of auxetic structures subjected to tensile, compressive and impact loads and assess geometric parameters affecting these structures in applications such as impact shielding or biomedicine. Analytical and experimental methods were employed to investigate two different types of auxetic structures which were 3d-printed with TPU (thermoplastic polyurethane). The first was based on symmetric re-entrant angles cells patterned to form sheet-like structure. Rotation of members in opposite directions in a cell induces negative Poisson’s ratio when the structure is subjected to tensile loading. The second structure was based on rectangular lattice of circular holes. This structure exhibited auxeticity due to formation of pattern of alternating mutually orthogonal ellipses when subjected to compressive and impact loads. Parameters of interest in this study included hardness of the plastic used in printing the structures, the fill pattern of 3d-printed solid parts, porosity of cylinders in the lattice structure, angles and thickness of members in the re-entrant structure. Preliminary results indicated that per unit weight of material, the re-entrant structure requires less tensile load to strain than a solid structure. This is advantageous in applications where expansion in lateral direction is required. The lattice of circular holes structure exhibited similar trend in impact and compressive loading. The results indicate that geometric parameters influence auxeticity of the structure a great deal. When the porosity of the lattice is too small, positive Poisson’s ratio is observed. The length to height ratio of the re-entrant cell has similar effect on the structure’s Poisson’s ratio. The main advantage gained by employing such structures is their overall ability to resist buckling and withstand impact load without cracking. This study will help to develop 3D-printing techniques in manufacturing better performing structures under similar conditions.

Free vibration and sound insulation of functionally graded honeycomb sandwich plates

2021 ◽  
pp. 109963622110204
Author(s):  
Fenglian Li ◽  
Wenhao Yuan ◽  
Chuanzeng Zhang
Keyword(s):  
Free Vibration ◽  
Poisson’S Ratio ◽  
Functionally Graded ◽  
Poisson's Ratio ◽  
Dynamic Equations ◽  
Sound Insulation ◽  
Sandwich Plates ◽  
Negative Poisson’S Ratio ◽  
Honeycomb Sandwich ◽  
Negative Poisson's Ratio

Based on the hyperbolic tangent shear deformation theory, free vibration and sound insulation of two different types of functionally graded (FG) honeycomb sandwich plates with negative Poisson’s ratio are studied in this paper. Using Hamilton’s principle, the vibration and vibro-acoustic coupling dynamic equations for FG honeycomb sandwich plates with simply supported edges are established. By applying the Navier’s method and fluid–solid interface conditions, the derived governing dynamic equations are solved. The natural frequencies and the sound insulation of FG honeycomb sandwich plates obtained in this work are compared with the numerical results by the finite element simulation. It is proven that the theoretical models for the free vibration and the sound insulation are accurate and efficient. Moreover, FG sandwich plates with different honeycomb cores are investigated and compared. The corresponding results show that the FG honeycomb core with negative Poisson’s ratio can yield much lower frequencies. Then, the influences of various geometrical and material parameters on the vibration and sound insulation performance are systematically analyzed.

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