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This research investigates the compressive property of a novel composite based on a weft-knitted auxetic tube subjected to a quasi-static compression test. In order to maximize the influence of the fiber content on the compression test, a Kevlar yarn was used in knitting the tubular samples using three different auxetic arrow-head structures (i.e. 4 × 4, 6 × 6 and 8 × 8 structure). A quasi-static compression test was conducted under two different impact loading speeds (i.e. 5 mm/min and 15 mm/min loading speed). The results indicate that the energy absorption (EA) property of the auxetic composite is highly influenced by the auxeticity of the knitted tubular fabric.
Content available Vibration properties of auxetic beam
This study presents vibration analysis for a beam with an auxetic cross-section. In order to verify damping properties of auxetic materials, the numerical results were compared with classical H-beam which has basic geometry. The response of analyzed models was considered with taking into account the Rayleigh damping of the internal material structure. Performed calculations comprise deformation of the certain beam, selected points displacement and vibration transmission loss coefficient. The analysis was carried out by means of Finite Element Method using Comsol Multiphysics software.
The example studies a forced response of plate with viscoelastic auxetic damper located at the free end of the plate. Damping elements consist of the cover layer and layer of viscoelastic material with positive or negative Poisson's ratio. Viscoelastic materials are often used for reduction of vibration (seismic or wind induced vibrations in building structures or other structures). The common feature is that the frequency of the forced vibrations is low. Calculations are made using finite element method with Comsol Multiphysics software.
Content available remote Simulations of the properties of elongated hexagonal dodecahedron systems
This study considers a 3D basic unit-cell proposed for auxetic and non-au xetic foams namely the elongated hexagonal dodecahedron deforming through changes in angle b etween its ligaments (idealised hinging model). This structure was studied in detail for the potential of exhibiting negative Poisson’s ratio and/or negative compressibility b y means of a method based on standard force-field molecular modelling technique, termed as Empiri cal Modelling Using Dummy Atoms ( EMUDA ). The mechanical properties obtained from this method were then compared to a previously published analytical model of this structure [Grima J N, CaruanaGauci R, Attard D, and Gatt R 2012, Proc. Roy. Soc. A 468 3121], and found to be in good agreement with each other. The results showed that this system can ex hibit zero Poisson’s ratios in one of its planes and positive or negative Poisson’s ratios in other plan es, depending on the geometry of the model. It was also shown that under certain conditions, ne gative linear and/or area compressibility was also exhibited.
Content available remote Workings of auxetic nano-materials
The human mind is consistently interested in new materials having unique properties. Recently, a relatively new field is being investigated which exhibits a negative Poisson’s ratio (NPR), and consequently are termed auxetic materials. Design/methodology/approach: One of the main reason for interest in auxetic materials is due to the possibility of enhanced mechanical properties such as shear modulus, plane strain fracture toughness and indentation resistance compared to non auxetic material. Findings: Auxetic materials were described concerning their classification, characteristic, properties and potential applications. Research limitations/implications: The paper is an overview the modelling structure and deformation mechanisms of auxetic nano-materials. Originality/value: The paper shows the possibilities of auxetic materials application resulting from their mechanical properties.
It is found the propagation of longitudinal solitary waves in an elastic rod made of material with negative Poisson’s ratio. It is used the difference scheme to solve the non-linear partial differential equation.
Content available remote Negative Poisson's ratios from rotating rectangles
Materials with a negative Poisson's ratio exhibit the unexpected property of becoming fatter when stretched and narrower when compressed. This counter-intuitive behaviour is known as 'auxetic behaviour' and imparts many beneficial effects on the material’s macroscopic properties. This paper discusses the potential of systems composed of rigid rectangles connected together through flexib1e hinges at their vertices. It will be shown that, on application of uniaxial loads, these rigid rectangles will rotate with respect to each other to form, in some cases, a more open structure hence giving rise to a negative Poisson's ratio.
In this paper the static and dynamic performances of sandwich structures with in-plane negative Poisson's ratio core are investigated from an analytical point of view. The cellular material theory is applied to calculate the orthotropic mechanical properties of re-entrant cell honeycomb cores, which shows negative Poisson's ratio values. This special geometrical layout of the cells allows higher out-of-plane shear modulus, compared to the one of regular honeycombs. The laminate orthotropic plate theory with shear correction factors is applied in order to describe the static and dynamic behaviour of symmetric sandwich plates with different core to sheet thickness ratios. Comparisons are made with analogous structures with regular honeycomb. The maximum deflections due to uniform pressure and buckling loads are enhanced, while the natural frequencies show a slight enhancing for some parameters of the cells.
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