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Overview of Mechanical Behavior of Materials
Published in Heather N. Hayenga, Helim Aranda-Espinoza, Biomaterial Mechanics, 2017
Radu Reit, Matthew Di Prima, Walter E. Voit
Poisson’s ratio, named for the nineteenth-century French mathematician, describes the relationship between the deformation in the loading axis and the deformation normal to the load axis. It can also be thought of as the coefficient of expansion on the transverse axes or the negative ratio of transverse to axial strain. Poisson’s ratio varies between −1.0 and 0.5, the theoretical and practical limits for stable, isotropic, linear elastic materials. Perfectly incompressible materials have Poisson’s ratios of 0.5, and include elastic rubbers. A Poisson’s ratio of 0.5 is density and volume preserving. Thus, the transverse deformation is such that the density is not changed during compression. Most materials have a Poisson’s ratio between 0 and 0.5 and show some signs of densification during compression or tension. Materials such as cork and Styrofoam can have Poisson’s ratios of 0, meaning that there is no change in transverse directions during axial deformation. Materials with negative Poisson’s ratios are called auxetic materials and actually get thicker as they are stretched. Materials such as the synthetic biomaterial Gore-Tex and some tendons [9] show auxetic properties. It is recommended that readers who want to gain a deeper understanding of the complex mechanical properties of materials, delve into more in-depth treatments of these topics and learn about tensor notation, compliance matrices, and advanced mechanics of materials from one of many great references in this area [10].
Metallic Armour Materials and Structures
Published in Paul J. Hazell, Armour, 2023
Auxetic structures are structures that exhibit a negative Poisson’s ratio when applied with a load. That is, when under compression a structure would contract inwards, or when under tension the structure would expand outward (see Figure 7.24). This is counterintuitive as usually one would expect the opposite to occur. However, this behaviour is realized simply through the clever design of an architectured system. Nevertheless, there are several natural auxetic materials that have been discovered in single crystals of arsenic and cadmium as well as other materials. Biological auxetic examples also exist in cow teat skin and cat skin, see (Evans and Alderson, 2000).
An analysis of 3D printed textile structures
Published in Gianni Montagna, Cristina Carvalho, Textiles, Identity and Innovation: Design the Future, 2018
“Auxetic behavior is found in materials with a negative Poisson’s ratio, which relates the deformation in one direction when the material is stressed in a perpendicular. When compressed in one direction, auxetic materials contract in the other, and when stretched, they expand” (Thingy verse, 2014).
A horizontal punch on a layered and orthotropic composite system with negative Poisson’s ratio
Published in Mechanics of Advanced Materials and Structures, 2023
The term “auxetic” was first used by Evans et al. [4] to describe the materials with a negative value of Poisson’s ratio [4]. Isotropic porous materials with a negative value of Poisson's ratios were fabricated by Lakes [5] from conventional open-cell polymer foams by using a method of compression-heating process. The negative Poisson’s ratio of auxetic materials are mainly due to the intertwined deformations of inter-connected members of macro structural forms. Thus, the properties of auxetic cellular materials can be altered if the unit cell architectures are changed. The unusual deformation mode of negative Poisson’s ratio materials exhibit superior properties as compared to conventional materials, such as increased indentation resistance [6–8], improved protective properties [9, 10], higher energy absorption capabilities [11], and better fracture toughness [12, 13]. Auxetic materials are very important in future applications in civil engineering, aeronautical engineering, defense equipment, smart sensors and actuators, filter cleaning technology and biomechanics engineering. In recent years, the number of patent applications and paper publications on auxetic materials has increased significantly.
Study on 3D printed auxetic structure-based non-pneumatic tyres (NPT’S)
Published in Materials and Manufacturing Processes, 2022
Narasimhulu Andriya, Varnali Dutta, Vemula Vijaya Vani
of the road. Figure 2 represents the tire Design Flow Chart. Based on our everyday life experiences when a material is stretched it tends to become longer in the direction of stretch while simultaneously getting reduced at cross-section. This behavior of material undergoing deformation is characterized by a fundamental mechanical property parameter called Poisson’s Ratio(ν). Poisson’s ratio (V) of a material is the ratio of the lateral contractile strain to the longitudinal tensile strain for a material undergoing tension in the longitudinal direction. Therefore, most of the materials have a positive (ν). In case of auxetics, it undergoes lateral expansion when stretched longitudinally and becomes thinner when compressed i.e., they have a Negative Poisson’s Ratio (NPR).[18,19]
Design and fabrication of novel auxetic weft-knitted fabrics with Kevlar yarns
Published in The Journal of The Textile Institute, 2019
Wanli Xu, Yaxin Sun, King Rafiu Raji, Pibo Ma
Auxetic materials and structures exhibit negative Poisson’s ratio (NPR), they laterally contract when compressed and laterally expend when stretched (Evans, Nkansah, Hutchinson, & Rogers, 1991). These materials and structures have gained attention over the last several years from textile experts, materials engineers and other researchers (Lakes, 1987). This is because of their extraordinary properties, such as antishearing ability, robust fracture strength, excellent mechanical properties, anticompression, good surface fitting ability and high energy absorption properties. Auxetic materials can be widely applied in various areas, including architecture, civil engineering, sports clothing, protection against explosives, high performance equipment, insulation, filters and so on (Pichandi, Rana, Oliveira, Fangueiro, & Xavier, 2014; Simkins, Alderson, Davies, & Alderson, 2005; Wright et al., 2012).