Статті в журналах: "Non-auxetic"

1

de Jonge, Christa, Helena Kolken, and Amir Zadpoor. "Non-Auxetic Mechanical Metamaterials." Materials 12, no. 4 (February 20, 2019): 635. http://dx.doi.org/10.3390/ma12040635.

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The concept of “mechanical metamaterials” has become increasingly popular, since their macro-scale characteristics can be designed to exhibit unusual combinations of mechanical properties on the micro-scale. The advances in additive manufacturing (AM, three-dimensional printing) techniques have boosted the fabrication of these mechanical metamaterials by facilitating a precise control over their micro-architecture. Although mechanical metamaterials with negative Poisson’s ratios (i.e., auxetic metamaterials) have received much attention before and have been reviewed multiple times, no comparable review exists for architected materials with positive Poisson’s ratios. Therefore, this review will focus on the topology-property relationships of non-auxetic mechanical metamaterials in general and five topological designs in particular. These include the designs based on the diamond, cube, truncated cube, rhombic dodecahedron, and the truncated cuboctahedron unit cells. We reviewed the mechanical properties and fatigue behavior of these architected materials, while considering the effects of other factors such as those of the AM process. In addition, we systematically analyzed the experimental, computational, and analytical data and solutions available in the literature for the titanium alloy Ti-6Al-4V. Compression dominated lattices, such as the (truncated) cube, showed the highest mechanical properties. All of the proposed unit cells showed a normalized fatigue strength below that of solid titanium (i.e., 40% of the yield stress), in the range of 12–36% of their yield stress. The unit cells discussed in this review could potentially be applied in bone-mimicking porous structures.

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El Dhaba, A. R., and M. Shaat. "Modeling deformation of auxetic and non-auxetic polymer gels." Applied Mathematical Modelling 74 (October 2019): 320–36. http://dx.doi.org/10.1016/j.apm.2019.04.050.

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Hu, L. L., M. Zh Zhou, and H. Deng. "Dynamic indentation of auxetic and non-auxetic honeycombs under large deformation." Composite Structures 207 (January 2019): 323–30. http://dx.doi.org/10.1016/j.compstruct.2018.09.066.

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Mir, Mariam, Murtaza Najabat Ali, Javaria Sami, and Umar Ansari. "Review of Mechanics and Applications of Auxetic Structures." Advances in Materials Science and Engineering 2014 (2014): 1–17. http://dx.doi.org/10.1155/2014/753496.

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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.

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5

Zulifqar, Adeel, Tao Hua, and Hong Hu. "Development of uni-stretch woven fabrics with zero and negative Poisson’s ratio." Textile Research Journal 88, no. 18 (June 17, 2017): 2076–92. http://dx.doi.org/10.1177/0040517517715095.

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Fabrics with zero or negative Poisson’s ratio are referred as auxetic fabrics, which have the unusual property of lateral expansion or zero expansion upon stretch. The use of conventional materials and machinery to produce auxetic fabrics has gained the interest of researchers in recent years. However, this approach is limited to knitted fabrics only. The development of auxetic fabric using conventional yarns and weaving technology is a research area that is still unaddressed. This paper reports a study on the development of a novel class of stretchable auxetic woven fabrics by using conventional yarns and weaving machinery. The phenomenon of differential shrinkage was successfully employed to realize auxetic geometries capable of inducing auxetic behavior in woven fabrics, and a series of auxetic woven fabrics were fabricated with elastic and non-elastic yarns and a dobby machine. The uni-axial tensile tests showed that auxetic woven fabrics developed exhibited zero or negative Poisson’s ratio over a wide range of longitudinal strain.

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6

Kasal, Ali, Tolga Kuşkun, and Jerzy Smardzewski. "Experimental and Numerical Study on Withdrawal Strength of Different Types of Auxetic Dowels for Furniture Joints." Materials 13, no. 19 (September 24, 2020): 4252. http://dx.doi.org/10.3390/ma13194252.

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Studies on the application of auxetic metamaterials and structures in furniture joints are very limited. However, they have huge potential for use in ready-to-assemble furniture. This study aimed to design and produce different types of auxetic dowels in 3D printing technology, and experimentally and numerically analyze the withdrawal strength of these dowels. In the scope of the study, 24 auxetic dowels with different types and size of inclusions, different diameter of holes, and a non-auxetic reference dowel were designed and produced with appropriate muffs. Dowels were 3D printed from polyamide (PA12). Poisson’s ratios, withdrawal strength, contact pressures, and friction coefficients of dowels were determined theoretically by means of numerical analyses and real static compression tests. After the pre-production of dowels, the dowels with triangular inclusions have not been found to have sufficient strength and stiffness. Withdrawal strength of dowels decreased as the size of inclusions is decreased, or dowel hole diameter is increased. Furthermore, contact pressures and stresses in auxetic dowels were considerably lower than non-auxetic dowels under the withdrawal force.

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7

Rapaka, Sri Datta, Manoj Pandey, and Ratna Kumar Annabattula. "Dynamic compressive behaviour of auxetic and non-auxetic hexagonal honeycombs with entrapped gas." International Journal of Impact Engineering 146 (December 2020): 103718. http://dx.doi.org/10.1016/j.ijimpeng.2020.103718.

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8

Xue, Yingying, Peixin Gao, Li Zhou, and Fusheng Han. "An Enhanced Three-Dimensional Auxetic Lattice Structure with Improved Property." Materials 13, no. 4 (February 24, 2020): 1008. http://dx.doi.org/10.3390/ma13041008.

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In order to enhance the mechanical property of auxetic lattice structures, a new enhanced auxetic lattice structure was designed by embedding narrow struts into a three-dimensional (3D) re-entrant lattice structure. A series of enhanced lattice structures with varied parameters were fabricated by 3D printing combined with the molten metal infiltration technique. Based on the method, parameter studies were performed. The enhanced auxetic lattice structure was found to exhibit superior mechanical behaviors compared to the 3D re-entrant lattice structure. An interesting phenomenon showed that increasing the diameter of connecting struts led to less auxetic and non-auxetic structures. Moreover, the compressive property of the enhanced structure also exhibited obvious dependence on the base material and compression directions. The present study can provide useful information for the design, fabrication and application of new auxetic structures with enhanced properties.

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9

Sakai, Yusuke, and Makoto Ohsaki. "Parametric Study of Non-periodic and Hybrid Auxetic Bending-Active Gridshells." Journal of the International Association for Shell and Spatial Structures 61, no. 4 (December 1, 2020): 275–84. http://dx.doi.org/10.20898/j.iass.2020.010.

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This paper presents a design method of Auxetic Bending-Active Gridshells (ABAGs), which are curved surfaces generated from the initial flat grid with 2-dimensional auxetic patterns. One of the mechanical properties of ABAGs is that a dome-like shape of a curved surface can be easily obtained by bending a grid due to negative Poisson's ratio for in-plane deformation. Shapes of auxetic patterns are relevant to Poisson's ratio. Non-periodic and/or hybrid 2-dimensional auxetic patterns are developed for designing the initial flat grid of ABAGs. Shape parameters are the sizes of each plane unit for tuning its reentrant pattern, and two types of reentrant shapes are mixed on an initial flat grid. Using the non-uniform patterns, we can obtain an asymmetric and more complex free-form surface of ABAGs than those composed of a uniform reentrant pattern. Discrete Gaussian curvature at each node on a curved surface is computed for quantitatively evaluating the properties of shapes of the obtained surfaces. Possibility of ABAGs as a new design tool is demonstrated by showing that various shapes are generated through large deformation analysis with the forced displacements at the supports.

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10

Ferreiro-Vila, Elias, Lucia Iglesias, Irene Lucas del Pozo, Noa Varela-Dominguez, Cong Tinh Bui, Beatriz Rivas-Murias, Jose M. Vila-Fungueiriño, et al. "Apparent auxetic to non-auxetic crossover driven by Co2+ redistribution in CoFe2O4 thin films." APL Materials 7, no. 3 (March 2019): 031109. http://dx.doi.org/10.1063/1.5087559.

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11

Martin, E., F. Roulland, S. Grenier, F. Appert, J. Juraszek, M. Trassin, C. Bouillet, et al. "Non-auxetic/auxetic transitions inducing modifications of the magnetic anisotropy in CoFe2O4 thin films." Journal of Alloys and Compounds 836 (September 2020): 155425. http://dx.doi.org/10.1016/j.jallcom.2020.155425.

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12

Bilski, Mikołaj, Krzysztof W. Wojciechowski, Tomasz Stręk, Przemysław Kędziora, James N. Grima-Cornish, and Mirosław R. Dudek. "Extremely Non-Auxetic Behavior of a Typical Auxetic Microstructure Due to Its Material Properties." Materials 14, no. 24 (December 17, 2021): 7837. http://dx.doi.org/10.3390/ma14247837.

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The re-entrant honeycomb microstructure is one of the most famous, typical examples of an auxetic structure. The re-entrant geometries also include other members as, among others, the star re-entrant geometries with various symmetries. In this paper, we focus on one of them, having a 6-fold symmetry axis. The investigated systems consist of binary hard discs (two-dimensional particles with two slightly different sizes, interacting through infinitely repulsive pairwise potential), from which different structures, based on the mentioned geometry, were formed. To study the elastic properties of the systems, computer simulations using the Monte Carlo method in isobaric-isothermal ensemble with varying shape of the periodic box were performed. The results show that all the considered systems are isotropic and not auxetic—their Poisson’s ratio is positive in each case. Moreover, Poisson’s ratios of the majority of examined structures tend to +1 with increasing pressure, which is the upper limit for two-dimensional isotropic media, thus they can be recognized as the ideal non-auxetics in appropriate thermodynamic conditions. The results obtained contradict the common belief that the unique properties of metamaterials result solely from their microstructure and indicate that the material itself can be crucial.

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13

Xue, Ying Ying, Xing Fu Wang, Xin Fu Wang, and Fu Sheng Han. "Compressive Behavior and Deformation Characteristic of Al-Based Auxetic Lattice Structure Filled with Silicate Rubber." Materials Science Forum 933 (October 2018): 240–45. http://dx.doi.org/10.4028/www.scientific.net/msf.933.240.

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The composites composed of Al-based auxetic lattice structures and silicate rubbers were fabricated by pressure infiltration technology. The compressive behavior and deformation characteristic of the composites were investigated related with the relative densities of the auxetic lattice structures. We found that the composites exhibit a longer plateau region than the non-filled Al-based auxetic lattice structures, and the relative density of the auxetic lattice structures play an important role in the compressive mechanical properties, the higher the relative density, the higher flow stress. It is also noticing that, the composite structures show different deformation and damage mechanism due to the filled incompressible silicate rubber. It is expected that the study may provide useful information for the applications of composite structure.

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14

Al-Rifaie, Hasan, and Wojciech Sumelka. "The Development of a New Shock Absorbing Uniaxial Graded Auxetic Damper (UGAD)." Materials 12, no. 16 (August 12, 2019): 2573. http://dx.doi.org/10.3390/ma12162573.

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Auxetic structures are efficient cellular materials that can absorb blast/impact energy through plastic deformation, thus protecting the structure. They are developing sacrificial solutions with light weight, high specific strength, high specific toughness and excellent energy dissipating properties, due to its negative Poison’s ratio nature. The use of auxetic and non-auxetic panels in blast resistant structures had been relatively perceived by researchers. Nonetheless, implementation of those energy dissipaters, explicitly as a uni-axial passive damper is restrained to limited studies, which highlight the potential need for further explorations. The aim of this paper is the design of a new uniaxial graded auxetic damper (UGAD) that can be used as a blast/impact/shock absorber in different scales for different structural applications. First, the geometry, material, numerical model and loading are introduced. Then, a detailed parametric study is conducted to achieve the most efficient graded auxetic system. Moreover, the designed auxetic damper is numerically tested and its static and dynamic constitutive relations are derived and validated analytically. The selection of optimum parameters was based on the ratio of the reaction force to the applied load (RFd/P) and plastic dissipation energy (PDE). The final designed UGAD contains three auxetic cores that have the same geometry, material grade (6063-T4), size and number of layers equal to eight. The cell-wall thickness t of the three auxetic cores is 1.4 mm, 1.8 mm and 2.2 mm, respectively; composing a graded auxetic system. The performance of the three auxetic cores together have led to a wide plateau region (80% of total crushing strain) and variant strength range (1–10 MPa), which in return, can justify the superior performance of the UGAD under different blast levels. Finally, the 3D printed prototype of the UGAD is presented and the possible applications are covered.

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15

Jiang, Ning, and Hong Hu. "A study of tubular braided structure with negative Poisson’s ratio behavior." Textile Research Journal 88, no. 24 (September 28, 2017): 2810–24. http://dx.doi.org/10.1177/0040517517732086.

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Textile structures with negative Poisson’s ratio (PR) behavior are called auxetic textile structures. They have received increasing attention in recent years and have been designed and fabricated through spinning, knitting, weaving and non-woven methods. However, auxetic textile structures fabricated using braiding method have not been reported so far. This paper reported a novel type of auxetic braided structure based on a helical structural arrangement. The geometry of the structure and its deformation mechanism were first introduced and described. Then a special manufacturing process was developed by the modification of commonly used tubular braiding technology. Various auxetic braids were fabricated with different structural parameters and yarns and tested under uniaxial extension conditions. The results showed that all manufactured braids exhibited high negative PR behavior and maintained this behavior until the fracture of the component wrap yarn. Among three structural parameters discussed, namely wrap angle, braiding angle and braiding yarn diameter, the wrap angle had more effects on the tensile properties of auxetic braided structure than the other two parameters. The success of fabricating auxetic braids with commercially available yarns in this study provides an alternative way to manufacture auxetics from positive PR materials.

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16

Kamrul, Hasan, Adeel Zulifqar, and Hong Hu. "Deformation behavior of auxetic woven fabric based on re-entrant hexagonal geometry in different tensile directions." Textile Research Journal 90, no. 3-4 (August 13, 2019): 410–21. http://dx.doi.org/10.1177/0040517519869391.

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Auxetic woven fabrics made of non-auxetic yarns have gained the interest of textile scientists in recent times. Such fabrics have already been produced and investigated for their negative Poisson's ratio (NPR) effect in two principle directions. However, the NPR effect of these fabrics in different biased tensile directions has not been studied. In particular, the influence of repeated tensile loading on the NPR effect retention ability of fabric has not been explored yet. Therefore, this paper aims to report the NPR effect of auxetic woven fabric in different tensile directions and the influence of repeating tensile cycle tests on its NPR effect retention ability. The auxetic woven fabric is firstly fabricated based on a re-entrant hexagonal geometrical structure by using elastic and non-elastic yarns, and then subjected to single and repeating tensile tests in five different tensile directions, which include two principle directions and three biased directions. It is found that the NPR effect is largely dependent upon the tensile direction and the number of repeating tensile cycles.

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17

Bhullar, Sukhwinder K. "Characterization of auxetic polyurethanes foam for biomedical implants." e-Polymers 14, no. 6 (November 1, 2014): 441–47. http://dx.doi.org/10.1515/epoly-2014-0137.

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AbstractAging, accidents and diseases are the leading causes of disability in today’s world. Therefore, implants and prostheses for hard and soft tissues are becoming increasingly common to restore daily activity and improve the quality of life of patients. Although implants have been extensively developed and are in the clinical use, deformation mechanism, inflexibility and mismatch of the elastic and mechanical behavior of the implants with native tissues are challenges for tissue engineering. The objective of this study was to characterize auxetic polyurethane foam as an auxetic soft tissue implant based on mathematical modeling using a nonlinear elasticity theory. The compressibility effects on auxetic soft tissue implants due to equibiaxial loading were studied. Numerical results were computed using experimentally obtained data and compared with the non-auxetic behavior of a soft tissue.

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18

Davini, Cesare, Antonino Favata, Andrea Micheletti, and Roberto Paroni. "A 2D microstructure with auxetic out-of-plane behavior and non-auxetic in-plane behavior." Smart Materials and Structures 26, no. 12 (November 1, 2017): 125007. http://dx.doi.org/10.1088/1361-665x/aa9091.

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Afshar, Arash, and Hamed Rezvanpour. "Computational Study of Non-Porous Auxetic Plates with Diamond Shape Inclusions." Journal of Composites Science 6, no. 7 (July 1, 2022): 192. http://dx.doi.org/10.3390/jcs6070192.

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Creating non-porous structures that offer auxetic behavior can have a variety of industrial applications, especially when the porosity impairs the functionality of the auxetic structures. This study presents the design and finite element analysis of architected bi-material auxetic plates consisting of repeating unit cells that comprise rigid rotary units and soft inclusions. The change in the design parameters of unit cells produces a variety of mechanical properties, such as different levels of Poisson’s ratio and stiffness for the architected plates that can result in specific static or dynamic responses. The natural frequencies and deflection under uniform lateral loading of the architected plates with clamped boundary conditions were investigated. Furthermore, the effectiveness of the homogenization technique based on the mechanical properties obtained from finite element analysis in predicting the dynamic and static response of the architected plate was also studied.

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20

Shokri Rad, M., Hossein Hatami, R. Alipouri, A. Farokhi Nejad, and F. Omidinasab. "Determination of energy absorption in different cellular auxetic structures." Mechanics & Industry 20, no. 3 (2019): 302. http://dx.doi.org/10.1051/meca/2019019.

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This paper deals with the effect of unit cell configuration on the energy absorption response of different cellular auxetic structures subjected to quasi-static and dynamic loadings through the experimental and numerical methods. Among the various structures, a re-entrant structure was selected due to its fundamental properties underlying the main characteristics of an auxetic material. Computer simulation techniques using ABAQUS software validated by experimental testing were used to conduct the evaluation of such devices. Several re-entrant structures with different geometrical parameters were modeled and compared with the conventional ones. Standard compression tests were carried out on the different structures produced by the 3D printing machine to evaluate the influence of auxeticity phenomenon in the energy absorption capability. It is discovered that the auxetic structures are superior to non-auxetic structures in terms of all studied impact resistance and energy absorption indicators due to their ability to withstand quasi-static axial impact loads. The primary outcome of this research is to extract design information for the use of auxetic materials as energy absorbers where quasi-static loading is expected.

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Hunt, G. W., and T. J. Dodwell. "Complexity in phase transforming pin-jointed auxetic lattices." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2224 (April 2019): 20180720. http://dx.doi.org/10.1098/rspa.2018.0720.

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We demonstrate the complexity that can exist in the modelling of auxetic lattices. By introducing pin-jointed members and large deformations to the analysis of a re-entrant structure, we create a material which has both auxetic and non-auxetic phases. Such lattices exhibit complex equilibrium behaviour during the highly nonlinear transition between these two states. The local response is seen to switch many times between stable and unstable states, exhibiting both positive and negative stiffnesses. However, there is shown to exist an underlying emergent modulus over the transitional phase, to describe the average axial stiffness of a system comprising a large number of cells.

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McDonald, Samuel A., Ghislain Dedreuil-Monet, Yong Tao Yao, Andrew Alderson, and Philip J. Withers. "In situ 3D X-ray microtomography study comparing auxetic and non-auxetic polymeric foams under tension." physica status solidi (b) 248, no. 1 (August 16, 2010): 45–51. http://dx.doi.org/10.1002/pssb.201083975.

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Mitschke, Holger, Vanessa Robins, Klaus Mecke, and Gerd E. Schröder-Turk. "Finite auxetic deformations of plane tessellations." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2149 (January 8, 2013): 20120465. http://dx.doi.org/10.1098/rspa.2012.0465.

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We systematically analyse the mechanical deformation behaviour, in particular Poisson's ratio, of floppy bar-and-joint frameworks based on periodic tessellations of the plane. For frameworks with more than one deformation mode, crystallographic symmetry constraints or minimization of an angular vertex energy functional are used to lift this ambiguity. Our analysis allows for systematic searches for auxetic mechanisms in archives of tessellations; applied to the class of one- or two-uniform tessellations by regular or star polygons, we find two auxetic structures of hexagonal symmetry and demonstrate that several other tessellations become auxetic when retaining symmetries during the deformation, in some cases with large negative Poisson ratios ν <−1 for a specific lattice direction. We often find a transition to negative Poisson ratios at finite deformations for several tessellations, even if the undeformed tessellation is infinitesimally non-auxetic. Our numerical scheme is based on a solution of the quadratic equations enforcing constant edge lengths by a Newton method, with periodicity enforced by boundary conditions.

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Ciambella, J., and G. Saccomandi. "A continuum hyperelastic model for auxetic materials." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2163 (March 8, 2014): 20130691. http://dx.doi.org/10.1098/rspa.2013.0691.

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We propose a simple mathematical model to describe isotropic auxetic materials in the framework of the classical theory of nonlinear elasticity. The model is derived from the Blatz–Ko constitutive equation for compressible foams and makes use of a non-monotonic Poisson function. An application to the modelling of auxetic foams is considered and it is shown that the material behaviour is adequately described with only three constitutive parameters.

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De, Rohit. "Impact Analysis of Auxetic Structures for Military Applications." International Journal for Research in Applied Science and Engineering Technology 9, no. 9 (September 30, 2021): 2238–49. http://dx.doi.org/10.22214/ijraset.2021.38359.

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Abstract: Auxetic structures are special structures which tend to become wider when subjected to longitudinal tension instead of getting compressed, which implies structures having a negative poisson’s ratio. These structures are used in impact pads due to this unique property. In this comparative study were done on different types of materials and structures which are recognized for 3D printing the auxetic structures. The three stages of explicit dynamic analysis involves firstly selecting the most appropriate structures from chiral truss, re-entrant hexagon, arrow head and one non- auxetic structure which is hexagon structure. From this the structure having the least deformation at the impact point is selected which is re-entrant hexagon. Following this, keeping re-entrant hexagon as the structure, the next set of analysis is performed by varying the structure materials. Polycarbonate, polystyrene, polyvinyl chloride and high density polyethylene were studied and the analysis results showed, polyvinyl chloride as the suitable material. Lastly the limiting velocity for the impact is calculated by varying the impact velocity from 800m/s, 1000m/s and 1200m/s beyond which the structure experienced fracture. This study proposes the selection of suitable auxetic structure and material for manufacturing impact pads. Keywords: Auxetic structures, impact pads, indentation resistance, explicit dynamics, 3D printing, FDM, Poisson’s ratio

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Kim, Kwang-Won, and Doo-Man Kim. "Contact Pressure of Non-Pneumatic Tires with Auxetic spokes." Journal of the Korean Society for Aeronautical & Space Sciences 39, no. 8 (August 1, 2011): 719–24. http://dx.doi.org/10.5139/jksas.2011.39.8.719.

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Vyavahare, Swapnil, Soham Teraiya, and Shailendra Kumar. "Auxetic structures fabricated by material extrusion: an experimental investigation of gradient parameters." Rapid Prototyping Journal 27, no. 5 (June 8, 2021): 1041–58. http://dx.doi.org/10.1108/rpj-05-2020-0107.

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Purpose This paper aims to focus on studying the influence of gradient parameters, namely, thickness coefficient, length coefficient and height ratio of auxetic structure on responses such as strength, stiffness and specific energy absorption (SEA) under compressive loading. Optimization of significant parameters is also performed to maximize responses. Further, efforts have also been made to develop regression models for strength, stiffness and SEA of auxetic structure. Design/methodology/approach Central composite design of response surface methodology is used for planning experiments. Auxetic structures of acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) materials are fabricated by the material extrusion (ME) technique of additive manufacturing. Fabricated structures are tested under in-plane uniaxial compressive loading. Grey relational analysis is used for the optimization of gradient parameters of the unit cell of auxetic structure to maximize responses and minimize weight and time of fabrication. Findings From the analysis of variance of experimental data, it is found that the compressive strength of auxetic structures increases with a decrease in length coefficient and height ratio. In the case of ABS structures, stiffness increases with a decrease in thickness coefficient and length coefficient, while in the case of PLA structures, stiffness increases with a decrease in length coefficient and height ratio. SEA is influenced by length coefficient and thickness coefficient in ABS and PLA structures, respectively. Based on the analysis, statistical non-linear quadratic models are developed to predict strength, stiffness and SEA. Optimal configuration of auxetic structure is determined to maximize strength, stiffness, SEA and minimize weight and time of fabrication. Research limitations/implications The present study is limited to re-entrant type of auxetic structures made of ABS and PLA materials only under compressive loading. Also, results from the current study are valid within a selected range of gradient parameters. The findings of the present study are useful in the optimal selection of gradient parameters for the fabrication of auxetic structures of maximum strength, stiffness and SEA with minimum weight and time of fabrication. These outcomes have wide applications in domains such as automotive, aerospace, sports and marine sectors. Originality/value Limited literature is available on studying the influence of gradient parameters of ME manufactured auxetic structure of ABS and PLA materials on responses, namely, strength, stiffness and SEA under compressive loading. Also, no work has been reported on studying the influence of gradient parameters on mechanical properties, weight and time of fabrication of auxetic structures. The present study is an attempt to fulfil the above research gaps.

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Dobnik Dubrovski, Polona, Nejc Novak, Matej Borovinšek, Matej Vesenjak, and Zoran Ren. "In-Plane Behavior of Auxetic Non-Woven Fabric Based on Rotating Square Unit Geometry under Tensile Load." Polymers 11, no. 6 (June 12, 2019): 1040. http://dx.doi.org/10.3390/polym11061040.

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This paper reports the auxetic behavior of modified conventional non-woven fabric. The auxetic behavior of fabric was achieved by forming rotating square unit geometry with a highly ordered pattern of slits by laser cutting. Two commercial needle-punched non-woven fabric used as lining and the reinforcement fabric for the footwear industry were investigated. The influence of two rotating square unit sizes was analyzed for each fabric. The original and modified fabric samples were subjected to quasi-static tensile load by using the Tinius Olsen testing machine to observe the in-plane mechanical properties and deformation behavior of tested samples. The tests were recorded with a full high-definition (HD) digital camera and the video recognition technique was applied to determine the Poisson’s ratio evolution during testing. The results show that the modified samples exhibit a much lower breaking force due to induced slits, which in turn limits the application of such modified fabric to low tensile loads. The samples with smaller rotating cell sizes exhibit the highest negative Poisson’s ratio during tensile loading through the entire longitudinal strain range until rupture. Non-woven fabric with equal distribution and orientation of fibers in both directions offer better auxetic response with a smaller out-of-plane rotation of rotating unit cells. The out-of-plane rotation of unit cells in non-homogenous samples is higher in machine direction.

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29

Bhullar, Sukhwinder K. "Three decades of auxetic polymers: a review." e-Polymers 15, no. 4 (July 1, 2015): 205–15. http://dx.doi.org/10.1515/epoly-2014-0193.

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AbstractDevelopments in design and technology in the engineering and medical fields necessitate the use of smart and high-performance materials to meet higher engineering specifications. The general requirements of such materials include a combination of high stiffness and strength with significant weight savings, resistance to corrosion, chemical resistance, low maintenance, and reduced costs. Over the last three decades, it has been demonstrated that auxetic materials offer a huge potential for the fields of engineering, natural sciences, and biomedical engineering, and for many other industries, including the aerospace and defense industries, through their unique deformation mechanism and measured enhancements in mechanical properties. To meet future engineering challenges, auxetic materials are increasingly being recognized as integral components of smart and advanced materials. Although materials with a negative Poisson’s ratio have been known since the early 1900s, they did not capture researchers’ attention until the late 1980s. Since 1991, these materials have been known as auxetic materials. Since then, their benefits and applications have been expanded to all major classes of materials such as metals, ceramics, polymers, and composites, and they are also now being used in engineering applications. The goal of this review was to present the development of auxetic polymers, which were first fabricated in the form of polyurethane foam approximately three decades ago and are now used in the fabrication of non-woven nano/micropolymeric structures. This review could provide useful information for the future development of auxetic polymers.

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30

Hou, Shaoyu, Tiantian Li, Zian Jia, and Lifeng Wang. "Mechanical properties of sandwich composites with 3d-printed auxetic and non-auxetic lattice cores under low velocity impact." Materials & Design 160 (December 2018): 1305–21. http://dx.doi.org/10.1016/j.matdes.2018.11.002.

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31

Usta, Fatih, Halit S. Türkmen, and Fabrizio Scarpa. "Low-velocity impact resistance of composite sandwich panels with various types of auxetic and non-auxetic core structures." Thin-Walled Structures 163 (June 2021): 107738. http://dx.doi.org/10.1016/j.tws.2021.107738.

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32

Yang, Weizhu, Zongzhan Gao, Zhufeng Yue, Xiaodong Li, and Baoxing Xu. "Hard-particle rotation enabled soft–hard integrated auxetic mechanical metamaterials." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2228 (August 2019): 20190234. http://dx.doi.org/10.1098/rspa.2019.0234.

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An auxetic design is proposed by soft–hard material integration and demonstrate negative Poisson's ratio (NPR) can be achieved by leveraging unique rotation features of non-connected hard particles in a soft matrix. A theoretical mechanics framework that describes rotation of hard particles in a soft matrix under a mechanical loading is incorporated with overall Poisson's ratio of the soft–hard integrated metamaterials. The theoretical analysis shows that the auxetic behaviour of the soft–hard integrated structures not only relies critically on geometry of particles, but also depends on their periodic arrangements in the soft matrix. Extensive finite-element analyses (FEA) are performed and validate the theoretical predictions of hard-particle rotation and overall Poisson's ratio of soft–hard integrated structures. Furthermore, uniaxial tensile tests are carried out on three-dimensional printed soft–hard integrated structures and confirm auxetic behaviour of soft–hard integrated structures enabled by the rotation of hard particles. Besides, Poisson's ratio varies nonlinearly with the thickness of specimens and reaches a maximum NPR far out of the bounds of plane stress and plane strain situations, which agrees well with FEA. This work provides a theoretical foundation for the design of mechanical metamaterials enabled by soft–hard material integration with auxetic deformation behaviour.

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33

Pais, Vânia, Pedro Silva, João Bessa, Hernâni Dias, Maria Helena Duarte, Fernando Cunha, and Raul Fangueiro. "Low-Velocity Impact Response of Auxetic Seamless Knits Combined with Non-Newtonian Fluids." Polymers 14, no. 10 (May 19, 2022): 2065. http://dx.doi.org/10.3390/polym14102065.

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Low-velocity impact can cause serious damage to the person or structure that is hit. The development of barriers that can absorb the energy of the impact and, therefore, protect the other side of the impact is the ideal solution for the pointed situation. Auxetic materials and shear thickening fluids are two types of technologies that have great capabilities to absorb high levels of energy when an impact happens. Accordingly, within this study, the combination of auxetic knits with shear thickening fluids by the pad-dry-cure process was investigated. It was observed that, by applying knits with auxetic patterns produced with denser materials and combined with the shear thickening fluids, high performance in terms of absorbed energy from puncture impact is obtained. The increment rates obtained are higher than 100% when comparing the structures with and without shear thickening fluids.

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34

Walkowiak, Marcel, Ulf Reinicke, and Denis Anders. "Numerical Investigation of Different Core Topologies in Sandwich-Structured Composites Subjected to Air-Blast Impact." Applied Sciences 12, no. 18 (September 8, 2022): 9012. http://dx.doi.org/10.3390/app12189012.

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Air-blast loading is a serious threat to military and civil vehicles, buildings, containers, and cargo. Applications of sandwich-structured composites have attracted increasing interest in modern lightweight design and in the construction of dynamic loading regimes due to their high resistance against blast and ballistic impacts. The functional properties of such composites are determined by the interplay of their face sheet material and the employed core topology. The core topology is the most important parameter affecting the structural behavior of sandwich composites. Therefore, this contribution presents a thorough numerical investigation of different core topologies in sandwich-structured composites subjected to blast loading. Special emphasis is put on prismatic and lattice core topologies displaying auxetic and classical non-auxetic deformation characteristics in order to illustrate the beneficial properties of auxetic core topologies. Their dynamic responses, elastic and plastic deformations, failure mechanisms, and energy absorption capabilities are numerically analyzed and compared. The numerical studies are performed by means of the commercial finite element code ABAQUS/Explicit, including a model for structural failure.

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35

Biharta, Michael Alfred Stephenson, Sigit Puji Santosa, Djarot Widagdo, and Leonardo Gunawan. "Design and Optimization of Lightweight Lithium-Ion Battery Protector with 3D Auxetic Meta Structures." World Electric Vehicle Journal 13, no. 7 (July 1, 2022): 118. http://dx.doi.org/10.3390/wevj13070118.

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This research study involves designing and optimizing a sandwich structure based on an auxetic structure to protect the pouch battery system for electric vehicles undergoing ground impact load. The core of the sandwich structure is filled with the auxetic structure that has gone through optimization to maximize the specific energy absorbed. Its performance is analyzed with the non-linear finite element method. Five geometrical variables of the auxetic structures are analyzed using the analysis of variance and optimized using Taguchi’s method. The optimum control variables are double-U hierarchal (DUH), the cross-section’s thickness = 2 mm, the length of the cell = 10 mm, the width of the cell = 17 mm, and the bending height = 3 mm. The optimized geometries are then arranged into three different sandwich structure configurations. The core is filled with optimized DUH cells that have been enlarged to 200% in length, arranged in 11 × 11 × 1 cells, resulting in a total dimension and mass of 189 × 189 × 12 mm and 0.75 Kg. The optimized sandwich structure shows that the pouch battery cells can be protected very well from ground impact load with a maximum deformation of 1.92 mm, below the deformation threshold for battery failure.

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36

Grima, Joseph N., Ruben Gatt, Brian Ellul, and Elaine Chetcuti. "Auxetic behaviour in non-crystalline materials having star or triangular shaped perforations." Journal of Non-Crystalline Solids 356, no. 37-40 (August 2010): 1980–87. http://dx.doi.org/10.1016/j.jnoncrysol.2010.05.074.

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37

Usta, Fatih, Osman F. Ertaş, Altuğ Ataalp, Halit S. Türkmen, Zafer Kazancı, and Fabrizio Scarpa. "Impact behavior of triggered and non-triggered crash tubes with auxetic lattices." Multiscale and Multidisciplinary Modeling, Experiments and Design 2, no. 2 (December 18, 2018): 119–27. http://dx.doi.org/10.1007/s41939-018-00040-z.

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38

Biswas, Ankan Narayan, Nunna Mahesh, Shanmukha Ram Peri, Bharath R Krishnan, and P. S. Rama Sreekanth. "Hybrid auxetic materials implemented in crates & non-pneumatic wheels for shock absorption." Materials Today: Proceedings 56 (2022): 1327–34. http://dx.doi.org/10.1016/j.matpr.2021.11.326.

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39

Abel, Johannes, Anne Mannschatz, Robert Teuber, Bernhard Müller, Omar Al Noaimy, Sebastian Riecker, Juliane Thielsch, Björn Matthey, and Thomas Weißgärber. "Fused Filament Fabrication of NiTi Components and Hybridization with Laser Powder Bed Fusion for Filigree Structures." Materials 14, no. 16 (August 6, 2021): 4399. http://dx.doi.org/10.3390/ma14164399.

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The present study introduces an approach to the powder metallurgical shaping of a pseudo-elastic nickel–titanium (NiTi 44 alloy) combining two different Additive Manufacturing (AM) processes, namely fused filament fabrication (FFF) and Laser Powder Bed Fusion (LPBF), by manufacturing filigree structures on top of sintered FFF parts. Both processes start with commercial gas atomized NiTi powder, which is fractionated into two classes. Using the fine fraction with particle sizes <15 µm, robust thermoplastic filaments based on a non-commercial binder system were produced and processed to different auxetic and non-auxetic geometries employing a commercial standard printer. FTIR analysis for thermal decomposition products was used to develop a debinding regime. After sintering, the phase transformation austenite/martensite was characterized by DSC in as sintered and annealed state. Precipitates resulting from residual impurities were detected by micrographs and XRD. They led to an increased transformation temperature. Adjusting the oxygen and carbon content in the alloy remains a challenging issue for powder metallurgical processed NiTi alloys. Filigree lattice structures were built onto the surfaces of the sintered FFF parts by LPBF using the coarser powder fraction (15–45 µm). A good material bond was formed, resulting in the first known NiTi hybrid, which introduces new production and design options for future applications.

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40

Asad, Mohammad, Tatheer Zahra, and Julian Thamboo. "The Effectiveness of CFRP- and Auxetic Fabric-Strengthened Brick Masonry under Axial Compression: A Numerical Investigation." Polymers 14, no. 9 (April 28, 2022): 1800. http://dx.doi.org/10.3390/polym14091800.

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Bonded brickwork used for loadbearing walls is widely found in heritage structures worldwide. The evaluation of bonded masonry structures and their strengthening strategies against dynamic actions require appropriate understanding under cyclic loading. Subsequently, a simplified 3D microscale numerical model is developed in this paper to analyse bonded brickwork under cyclic compression. A plasticity-based damage constitutive model to represent damage in masonry bricks under cyclic compression loading was employed, and zero-thickness interfaces were considered with non-linear damage properties to simulate the mechanical behaviour of masonry. A threshold strain level was used to enact the element deletion technique for initiating brittle crack opening in the masonry units. The developed model was validated against the experimental results published by the authors in the past. The models were able to accurately predict the experimental results with an error limit of 10% maximum. Mainly, two types of strengthening materials, possessing (1) high energy absorption characteristics (auxetic fabric) and (2) high strength properties (carbon fibre reinforced polymer composites/CFRP) were employed for damage mitigation under cyclic compression. Results show that the CFRP-strengthened masonry failure was mainly attributed to de-bonding of the CFRP and crushing under compression. However, the auxetic strengthening is shown to significantly minimise the de-bonding phenomenon. Enhanced energy dissipation characteristics with relatively higher ductility (up to ~50%) and reduced damages on the bonded brickwork were observed as compared to the CFRP-strengthened brickwork under cyclic compression loading. Additionally, the auxetic fabric application also increased the compressive resistance of brickwork by 38–60% under monotonic loading, which is comparably higher than with the CFRP strengthening technique.

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41

Huang, Xu-hao, Jian Yang, Iftikhar Azim, Xing-er Wang, and Xin Ren. "Geometric Non-Linear Analysis of Auxetic Hybrid Laminated Beams Containing CNT Reinforced Composite Materials." Materials 13, no. 17 (August 22, 2020): 3718. http://dx.doi.org/10.3390/ma13173718.

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In the current work, a novel hybrid laminate with negative Poisson’s ratio (NPR) is developed by considering auxetic laminate which is composed of carbon nanotube-reinforced composite (CNTRC) and fiber-reinforced composite (FRC) materials. The maximum magnitude of out-of-plane NPR is identified in the case of (20 F/20 C/−20 C/20 C) S laminate as well. Meanwhile, a method for the geometric non-linear analysis of hybrid laminated beam with NPR including the non-linear bending, free, and forced vibrations is proposed. The beam deformation is modeled by combining higher-order shear-deformation theory (HSDT) and large deflection theory. Based on a two-step perturbation approach, the asymptotic solutions of the governing equations are obtained to capture the linear and non-linear frequencies and load-deflection curves. Moreover, a two-step perturbation methodology in conjunction with fourth-order Runge–Kutta method is employed to solve the forced-vibration problem. Several key factors, such as CNT distribution, variations in the elastic foundation, and thermal stress, are considered in the exhaustive analysis. Theoretical results for some particular cases are given to examine the geometric non-linearity behavior of hybrid beam with NPR as well as positive Poisson’s ratio (PPR).

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42

Zhang, Zhengyang, Hanxing Zhu, Ru Yuan, Sanmin Wang, Tongxiang Fan, Yacine Rezgui, and Di Zhang. "Auxetic interpenetrating composites: A new approach to non-porous materials with a negative or zero Poisson’s ratio." Composite Structures 243 (July 2020): 112195. http://dx.doi.org/10.1016/j.compstruct.2020.112195.

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43

Ulissi, Zachary W., Ananth Govind Rajan, and Michael S. Strano. "Persistently Auxetic Materials: Engineering the Poisson Ratio of 2D Self-Avoiding Membranes under Conditions of Non-Zero Anisotropic Strain." ACS Nano 10, no. 8 (July 18, 2016): 7542–49. http://dx.doi.org/10.1021/acsnano.6b02512.

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44

Köllner, David, Bastien Tolve-Granier, Swantje Simon, Ken-ichi Kakimoto, and Tobias Fey. "Advanced Estimation of Compressive Strength and Fracture Behavior in Ceramic Honeycombs by Polarimetry Measurements of Similar Epoxy Resin Honeycombs." Materials 15, no. 7 (March 22, 2022): 2361. http://dx.doi.org/10.3390/ma15072361.

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Finding a non-destructive characterization method for cellular ceramics’ compressive strength and fracture behavior has been a challenge for material scientists for years. However, for transparent materials, internal stresses can be determined by the non-destructive photoelastic measurements. We propose a novel approach to correlate the photoelastic stresses of polymer (epoxy resin) prototypes with the mechanical properties of ceramics (alumina). Regular and inverse epoxy honeycombs were 3D-printed via stereolithography with varying structure angles from −35° to 35°, with negative angles forming an auxetic and positive hexagonal lattice. Photoelastic measurements under mechanical loading revealed regions of excess stress, which directly corresponded to the initial fracture points of the ceramic honeycombs. These honeycombs were made by a combination of 3D printing and transfer molding from alumina. The photoelastic stress distribution was much more homogeneous for angles of a smaller magnitude, which led to highly increased compressive strengths of up to 446 ± 156 MPa at 0°. By adapting the geometric structural model from Gibson and Ashby, we showed that we could use a non-destructive technique to determine the compressive strength of alumina honeycombs from the median photoelastic stress measured on similar epoxy honeycomb structures.

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45

Sulym, Heorhiy, Olena Mikulich, and Vasyl’ Shvabyuk. "Modelling of Impulse Load Influence on the Stress State of Foam Materials with Positive and Negative Poisson’s Ratio." Acta Mechanica et Automatica 14, no. 2 (June 1, 2020): 79–83. http://dx.doi.org/10.2478/ama-2020-0011.

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AbstractThe influence of impulse load applied for different duration on the distribution of normalised dynamic radial stresses in positive and negative Poisson’s ratio medium was investigated in this study. For solving the non-stationary problem in the case of plane deformation for structurally inhomogeneous materials, the model of Cosserat continuum was applied. This model enables accounting for the influence of shear-rotation deformation of micro-particles of the medium. In the framework of Cosserat elasticity, on applying the Fourier transforms for time variable and developing the boundary integral equation method, solving of the non-stationary problem reduces to the system of singular integral equations, where the components that determine the influence of shear-rotation deformations are selected. The numerical calculations were performed for the foam medium with positive and negative Poisson’s ratio for different values of time duration of impulse. Developed approach can be used to predict the mechanical behaviour of foam auxetic materials obtained at different values of a volumetric compression ratio under the action of time variable load based on analysis of the distribution of radial stresses in foam medium.

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46

Ghaznavi, A., and M. Shariyat. "Non-linear layerwise dynamic response analysis of sandwich plates with soft auxetic cores and embedded SMA wires experiencing cyclic loadings." Composite Structures 171 (July 2017): 185–97. http://dx.doi.org/10.1016/j.compstruct.2017.03.012.

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47

Gunaydin, Kadir, Halit Süleyman Türkmen, Alessandro Airoldi, Marco Grasso, Giuseppe Sala, and Antonio Mattia Grande. "Compression Behavior of EBM Printed Auxetic Chiral Structures." Materials 15, no. 4 (February 17, 2022): 1520. http://dx.doi.org/10.3390/ma15041520.

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In this study, the cyclic compression and crush behavior of chiral auxetic lattice structures produced from titanium alloy (Ti6Al4V) metallic powder using electron beam melting (EBM) additive manufacturing technology is investigated numerically and experimentally. For material characterization and understanding the material behavior of EBM printed parts, tensile and three-point flexural tests were conducted. Log signals produced during the EBM process were investigated to confirm the stability of process and the health of the produced parts. Furthermore, a compressive cyclic load profile was applied to the EBM printed chiral units having two different thicknesses to track their Poisson’s ratios and displacement limits under large displacements in the absence of degradation, permanent deformations and failures. Chiral units were also crushed to investigate the effect of failure and deformation mechanisms on the energy absorption characteristics. Moreover, a surface roughness study was conducted due to high surface roughness of EBM printed parts, and an equation is offered to define load-carrying effective areas to prevent misleading cross-section measurements. In compliance with the equation and tensile test results, a constitutive equation was formed and used after a selection and calibration process to verify the numerical model for optimum topology design and mechanical performance forecasting using a non-linear computational model with failure analysis. As a result, the cyclic compression and crush numerical analyses of EBM printed Ti6Al4V chiral cells were validated with the experimental results. It was shown that the constitutive equation of EBM printed as-built parts was extracted accurately considering the build orientation and surface roughness profile. Besides, the cyclic compressive and crush behavior of chiral units were investigated. The regions of the chiral units prone to prematurely fail under crush loads were determined, and deformation modes were investigated to increase the energy absorption abilities.

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48

Castaldo, Anna, Emilia Gambale, and Giuseppe Vitiello. "Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings." Energies 14, no. 20 (October 14, 2021): 6668. http://dx.doi.org/10.3390/en14206668.

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Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability.

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49

Zhang, Wenjiao, Shuyuan Zhao, Rujie Sun, Fabrizio Scarpa, and Jinwu Wang. "In-Plane Mechanical Behavior of a New Star-Re-Entrant Hierarchical Metamaterial." Polymers 11, no. 7 (July 3, 2019): 1132. http://dx.doi.org/10.3390/polym11071132.

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A novel hierarchical metamaterial with tunable negative Poisson’s ratio is designed by a re-entrant representative unit cell (RUC), which consists of star-shaped subordinate cells. The in-plane mechanical behaviors of star-re-entrant hierarchical metamaterial are studied thoroughly by finite element method, non-dimensional effective moduli and effective Poisson’s ratios (PR) are obtained, then parameters of cell length, inclined angle, thickness for star subordinate cell as well as the amount of subordinate cell along x, y directions for re-entrant RUC are applied as adjustable design variables to explore structure-property relations. Finally, the effects of the design parameters on mechanical behavior and relative density are systematically investigated, which indicate that high specific stiffness and large auxetic deformation can be remarkably enhanced and manipulated through combining parameters of both subordinate cell and parent RUC. It is believed that the new hierarchical metamaterial reported here will provide more opportunities to design multifunctional lightweight materials that are promising for various engineering applications.

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50

Behravan Rad, A. "Static analysis of non-uniform 2D functionally graded auxetic-porous circular plates interacting with the gradient elastic foundations involving friction force." Aerospace Science and Technology 76 (May 2018): 315–39. http://dx.doi.org/10.1016/j.ast.2018.01.036.

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