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1
Content available Materiały auksetyczne – struktury, potencjalne zastosowanie
Masłowska-Lipowicz Iwona, Wyrębska Łucja, Szałek Beata, Olszewski Piotr, Gajewski Robert
Technologia i Jakość Wyrobów
|
2020
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R. 65
116--128
PL
Dokonano przeglądu literatury pod kątem badań materiałów auksetycznych, które posiadają ujemny współczynnik Poisson’a (NPR) charakteryzujący odpowiedź materiału na naprężenie jednoosiowe. Struktury i materiały auksetyczne zachowują się sprzecznie z intuicją, tzn. przy jednoosiowym rozciąganiu, rozszerzają się poprzecznie, co wynika z ich skomplikowanych struktur geometrycznych. Opisano reprezentatywne modele strukturalne (re-entrant, struktury składające się z tzw. sztywnych lub półsztywnych obracających się jednostek , struktury chiralne, przędze auksetyczne i struktury włókienkowo-zgrubieniowe) oraz zastosowanie materiałów auksetycznych wynikające z ich właściwości. Właściwości materiałów auksetycznych, np. synklastyczna krzywizna zginania, zmienna przepuszczalność, zwiększona odporność na wgniecenia, wysoka odporność na pękanie oraz tłumienie i pochłanianie dźwięku stwarzają szerokie możliwości ich zastosowania, m.in. w materiałach biomedycznych, materiałach amortyzujących, urządzeniach do pozyskiwania energii, wyposażeniu sportowym, filtrach, robotyce, tekstyliach czy materiałach stosowanych w przemyśle lotniczym oraz budownictwie.
EN
The literature was reviewed in terms of research on auxetic materials with a negative Poisson's ratio (NPR) characterizing the material's response to uniaxial stress. Auxetic structures and materials behave counter-intuitively, i.e. when stretched uniaxially, they expand laterally due to their complex geometric structures. Representative structural models are described (re-entrant, structures consisting of so-called rigid or semi-rigid rotating units, chiral structures, auxetic yarns and fibril - noudle structures) and the use of auxetic materials resulting from their properties. Properties of auxetic materials, e.g. synclastic bending curvature, variable permeability, high shear stiffness, increased resistance to indentation, high resistance to cracking and sound attenuation and absorption create a wide range of applications, including in biomedical materials, shock-absorbing materials, energy generation devices, sports equipment, filters, robotics, textiles or materials used in the aerospace industry and construction.
2
Content available remote The impact of technology on Poisson's ratio of auxetic polyurethane foams
Lisiecki J., Nowakowski D.
Aviation Advances & Maintenance
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2018
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Vol. 41, Issue 1
119--140; 141--160
EN
The article presents a method for measuring Poisson’s ratio of the polyurethane foam, including shapes of the auxetic foam. The impact of technology applied in Air Force Institute of Technology, that is a method for processing the selected polyurethane foams, on the value of Poisson’s ratio of the auxetic foam shape was presented. In order to manufacture the auxetic foam shapes, two methods; mechanical-thermal and mechanical-chemical-thermal, were applied.
PL
W artykule przedstawiono sposób pomiaru współczynnika Poissona próbek pianki poliuretanowej, w tym kształtek pianki auksetycznej. Przedstawiono wpływ technologii zastosowanej w ITWL, tzn. sposobu przetwarzania wybranych pianek poliuretanowych na wartość współczynnika Poissona kształtki pianki auksetycznej. Do wytwarzania kształtek pianki auksetycznej zastosowano dwie metody: mechaniczno-termiczną oraz mechaniczno-chemiczno-termiczną.
3
Content available Dynamic analysis of optimized two-phase auxetic structure
Idczak E., Stręk T.
Vibrations in Physical Systems
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2017
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Vol. 28
art. no. 2017003
EN
This paper presents a dynamic analysis of earlier optimized auxetic structure. This optimization based on the distribution of two materials in such way to obtain a minimal value of Poisson’s ratio (PR), which indicates the auxetic properties. The initial optimized shape was so-called star structure, which if is made from one material has the PR close to 0.188. After optimization with the goal function of PR-minimization, the obtained value was equal to -9.5043. Then the eigenfrequencies for the optimized structure were investigated. The calculations were carried out by means of Finite Element Method (FEM). For optimization of the value of Poisson’s ratio was used algorithm MMA (Method of Moving Asymptotes). The computing of single material properties (PR, Young’s modulus, density) for the whole shape was made by means of SIMP method (Solid Isotropic Method with Penalization).
4
Content available Computational modelling of vibrations transmission loss of auxetic lattice structure
Idczak E., Stręk T.
Vibrations in Physical Systems
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2016
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Vol. 27
123--128
EN
In this article dynamical properties of auxetic lattice structures will be analysed. Auxetic structures are materials, which have negative Poisson’s ratio and some of these have got specific dynamic properties. Their dynamic behaviour in the frequency domain will be also shown in this article. The possibility of isolation of auxetics will show the factor VTL – Vibration Transmission Loss.
5
Content available Simulations of the properties of elongated hexagonal dodecahedron systems
Grima J. N., Caruana-Gauci R., Attard D., Gatt R.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2014
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Vol. 18, No 2
117--135
EN
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.
6
Content available Core-shell modelling of auxetic inorganic materials
Zammit V., Gatt R., Attard D., Grima J. N.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2014
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Vol. 18, No 2
137--165
EN
This paper investigates the suitability of the General Utility Latti ce Program ( GULP ) for studying auxetic materials at the molecular level. GULP is a force-field based molecular modelling package which incorporates the ‘core-shell’ model for si mulating polarisability. A validation procedure was performed where the capability of GULP to reproduce the structural and mechanical properties of SOD (a zeolite for which the single crystalline elastic constants have been experimentally measured). It was found that not all GULP libraries (force-fields) could reproduce these properties, although the ‘Catlow 1992’ and ‘Sauer 1997’ libraries were found the produce good results. These libraries were then used t o study the all-silica forms of various ‘presumably auxetic’ zeolites. The simulations generally confi rmed the conclusions reported in earlier studies, and in particular, the fibrous zeolites THO , NAT and EDI where once again shown to be auxetic in the (001) plane. A study was also performed aimed at assessing the effect of interstitial species on the mechanical properties of NAT where it was shown that these species reduce the auxetic effect. This is very significant as once again we have confirmed the potential of these materials as molecular level auxetics, and hopefully, t hese results will result in generating more interest into the fascinating materials which could be used in many practical applications ( e.g. tuneable molecular sieves).
7
Content available remote Workings of auxetic nano-materials
Yao Y. T., Uzun M., Patel I.
Journal of Achievements in Materials and Manufacturing Engineering
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2011
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Vol. 49, nr 2
585--593
EN
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.
8
Content available remote Flexible auxetic foams - fabrication, properties and possible application areas
Lisiecki J., Błażejewicz T., Kłysz S.
Prace Naukowe Instytutu Technicznego Wojsk Lotniczych
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2010
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nr 27
57-75
EN
The paper presents a review of worldwide literature related to auxetic materials manufactured on the basis of the flexible polyurethane foam. Properties of auxetic foams are discussed with account taken of raw materials and fabrication methods applied. Due to their negative value of the Poisson's ratio the properties demonstrated by auxetic foams are totally different from those of polyurethane foam that has been used so far. Application examples of these new foams are specified with account taken of their physical and chemical parameters but the particular attention is paid to possible use as vibration damping materials in automotive industry and transportation systems.
9
Content available Production and study of polyether auxetic foam
Stręk A. M.
Mechanics and Control
|
2010
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Vol. 29, no. 2
78-87
EN
The article describes the experiment consisting in production and study of auxetic open-cell polyether foam. In the introduction I briefly explain what auxetic materials are and list their main properties together with possible application areas. Next, detailed information about the background of the experiment is given: important material characteristics and extensive description of the procedure. Further, discussion of the results is presented, basing on microscopic imagery of the obtained auxetic foam. The article describes also tensile tests performed on the produced material and cites quantitative results in the form of text and graphs illustrating the Poisson ratio dependence on deformation, as well as stress-strain relations (true and engineering values). In the final part of the article conclusions are enclosed.
PL
Artykuł opisuje eksperyment polegający na laboratoryjnym wytworzeniu i badaniu właściwości auksetycznej otwarokomórkowej pianki polieterowej. We wstępie krótko opisane jest, czym są materiały auksetyczne, podane są ich najważniejsze własności oraz możliwe obszary zastosowań. Następnie przedstawione są szczegółowo informacje o samym eksperymencie: scharakteryzowano użyty materiał i przedstawiono sposób wytworzenia pianki. W kolejnej części artykułu znajdują się mikroskopowe obrazy struktury pianki wraz z komentarzem dotyczącym mechanizmów deformacji. Opisany jest także test na rozciąganie otrzymanej pianki auksetycznej; wyniki opatrzone są komentarzem oraz wykresami. Wykresy ilustrują zależności współczynnika Poissona od odkształcenia oraz relację naprężeń i odkształceń (inżynierskich oraz rzeczywistych). W ostatniej części zamieszczono uwagi podsumowujące.
10
Content available Numerical modeling of auxetics in structure strength
Stanisławek S., Morka A., Niezgoda T.
Journal of KONES
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2010
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Vol. 17, No. 4
459-462
EN
The paper deals with computer simulations of mechanical behaviour of a no-void ideal auxetic isotropic material. Current literature offers wide range of models which resemble the manufactured or natural structures. However, it does not answer the question how a change into auxetic no-void state would affect the continuum effective mechanical properties. Auxetic with the Poisson ratio -0.3 has been compared through typical tests to a classic steel elastic material. Most of the engineering software cannot precede Poisson ratio helow zero. Therefore a unique technique was applied using equation of state to overcome this obstacle. All simulations have been done in elastic regime. For the tensile compression tests a 10 mm edge cube was modelled, the bending test used a 5x5x250 mm bar. The loading for initial tests was realized as a kinematic displacement of particular nodes. For bar bending a force was applied in the middle of the beam. The finite element method has been used with explicit time integration algorithm implemented in commercial software with one integration point brick elements. Specific properties have been observed for each test, for tensile test auxetic showed higher strength while for compression material was weaker. Logically the bending test showed no clear influence of negative Poisson to material strength. Further simulations as a shear or impact tests are planned.
11
Content available remote Material design of anisotropic elastic cellular bodies with respect to contact problem
Jasińska D., Janus-Michalska M.
Engineering Transactions
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2008
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Vol. 56, iss. 3
201-225
EN
Two-dimensional contact problem formulated for anisotropic, elastic bodies is considered. As an example of anisotropic medium, the cellular material is taken. The idea of two-scale modeling is adopted for formulation of an equivalent continuum, on the basis of which elastic properties can be obtained. Typical cellular microstructures with various types of symmetries are considered. Special attention is paid to cell structures giving negative Poisson's ratio in some directions (reentrant cells). Application of the energy-based criterion for equivalent continuum gives macroscopic yield condition. Condition for the energy coefficient defined as a sum of weighted energies stored in elastic eigenstates ensures that the material works in elastic state. Unilateral frictional contact problem is analyzed using FK.M. Calculations are performed for rough contact of square block subjected to normal load. Numerical solutions show differences in deformation type and contact stress distributions for different types of microstructures of the analyzed medium. The study enables the optimal choice of material structure topology, which ensures the reduction of peak contact pressure and friction stress, and applicability of anisotropic material to the given problem.
12
Content available remote Molecular auxetics
Wojciechowski K. W.
Vibrations in Physical Systems
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2006
|
Vol. 22
49--52
13
Content available remote Poisson’s ratio of anisotropic systems
Wojciechowski K.
Computational Methods in Science and Technology
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2005
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Vol. 11, nr 1
73-79
EN
The Poisson’s ratio of anisotropic materials depends, in general, both on a “longitudinal” direction along which the stress is changed and on a “transverse” direction in which the transverse deformation is measured. For cubic media there exist “longitudinal” directions, parallel to the 4-fold and 3-fold axes, for which the Poisson’s ratio does not depend on the “transverse” direction. Depending on the tensor of elastic compliances (or elastic constants), crystals of cubic symmetry can exhibit negative Poisson’s ratio in both these directions (they are called strongly auxetics), in one of them (i.e. either along the 4-fold axis or along the 3-fold one; they are called partially auxetic) or in none of them. For crystals exhibiting 3-fold symmetry axis the Poisson’s ratio along this axis does not depend on the “transverse” direction. For other “longitudinal” directions the Poisson’s ratio depends, in general, on the “transverse” direction. The Poisson’s ratio averaged with respect to the “transverse” direction depends only on the “longitudinal” direction and can be conveniently presented graphically. As an example the f.c.c. hard sphere crystal is considered. It is shown that the average (with respect to “transverse” direction) Poisson’s ratio of the hard sphere crystal is positive for all “longitudinal” directions. One should add, however, that there exist directions for which the (not averaged) Poisson’s ratio of hard spheres is negative.
14
Content available remote Negative Poisson's ratios from rotating rectangles
Grima J. N., Alderson A., Evans K. E.
Computational Methods in Science and Technology
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2004
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Vol. 10, nr 2
137-145
EN
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.
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