• Journal of Powder Materials
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• v.25 no.6
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• pp.507-513
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• 2018

This study investigates the viability of using a Na-ion battery with a tin(Sn) anode to mitigate the vulnerability caused by volume changes during discharge and charge cycling. In general, the volume changes of carbon material do not cause any instability during intercalation into its layer structure. Sn has a high theoretical capacity of $847mAh\;g^{-1}$. However, it expands dramatically in the discharge process by alloying Na-Sn, placing the electrode under massive internal stress, and particularly straining the binder over the elastic limit. The repeating strain results in loss of active material and its electric contact, as well as capacity decrease. This paper expands the scope of fabrication of Na-ion batteries with Sn by fabricating the binder as an auxetic structure with a unique feature: a negative Poisson ratio (NPR), which increases the resistance to internal stress in the Na-Sn alloying/de-alloying processes. Electrochemical tests and micrograph images of auxetic and common binders are used to compare dimensional and structural differences. Results show that the capacity of an auxetic-structured Sn electrode is much larger than that of a Sn electrode with a common-structured binder. Furthermore, using an auxetic structured Sn electrode, stability in discharge and charge cycling is obtained.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.192-197
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• 2017

Typical materials including concrete behaves with positive poisson's ratio when external force is applied. However, it is also available to manufacture a grating system which has negative poisson's ratio(Auxetic). In this study, double arrow type 2-D auxetic mesh was manufactured and mechanical behaviors were observed. Also, direct tensile tests of cementitious composites reinforced by auxetic mesh were performed and the results were compared with composites reinforced by typical mesh. The results showed that auxetic mesh more effectively restrained the deformation(shortening) of cementitious composites perpendicular to the load direction comparing with typical mesh.

• Composites Research
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• v.37 no.4
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• pp.310-315
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• 2024

An auxetic structure with negative Poisson's ratio exhibits distinctive mechanical properties in contrast to conventional structures, garnering interest in various fields. However, current research has predominantly focused on the design and optimization of auxetic structures, with limited exploration of their practical applications. In this study, we utilized 3D printing technology to fabricate a soft auxetic structure with triangular shaped perforations, examining the mechanical properties based on geometric structure. Additionally, by inserting shape memory alloys into the fabricated soft auxetic structure, we achieved active two-dimensional deformations and confirmed its selective object permeability. This technology holds the potential to have far-reaching implications across a broad spectrum of industries.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.317-323
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• 2017

Due to the unique characteristic of auxetic material, negative poisson's ratio, it has a variety of distinctive properties compared to conventional materials. Numerous researches have been conducted on the auxetic material in order to find out how to make auxetics. In this study, we analyzed triangular and rectangular patterned rotating rigid units using finite element method. Our purpose is to investigate the mechanical properties of the rotating rigid units and to show their auxetic behaviors. We studied the Poisson's ratio and the bulk modulus of the rotating rigid units depending on their unit cell sizes. The Poisson's ratio and the bulk modulus decreased as the number of unit cells increased. Also, when the geometry of the unit cell was changed, the tendency of the Poisson's ratio and the bulk modulus was also different from the previous case. The results of the Poisson's ratio and the bulk modulus referred that they were critically affected by the number of unit cells and the shape of unit cell.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.116-123
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• 2017

This study has been investigated the applicability of auxetic mesh for the reinforcement of structural members. Typical materials including concrete behaves with positive poisson's ratio when external force is applied. In this study, it has been theoretically verified that metallic auxetic mesh restrains as such mechanical behaviors of concrete resulting in the stiffness increase. Also, regarding the applicability to construction field, a type of auxetic mesh has been suggested and the mechanical characteristics were numerically analyzed.

• Structural Engineering and Mechanics
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• v.89 no.1
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• pp.93-102
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• 2024

Using negative Poisson's ratio materials, an innovative metallic-yielding damper is introduced for the first time in this study. Through the use of ABAQUS commercial software, a nonlinear finite element analysis is conducted to determine the performance of the proposed system. Mild steel plates with elliptical holes are used for these types of dampers, which dissipate energy through an inelastic deformation of the constitutive material. To assess the capability of the proposed damper, nonlinear quasi-static finite element analyses have been conducted on the damper with a variety of geometric parameters. According to the results, the proposed system is ductile and has a high capacity to dissipate energy. The proposed auxetic damper has a specific energy absorption of 910.8 J/kg and a ductility of 33.6. Therefore, this damper can dissipate a large amount of earthquake input energy without buckling by increasing the buckling load of the brace with its ductile behavior. In addition, it was found that by incorporating auxetic dampers in the steel frame, the frame was made harder, stronger, and ductile and its energy absorption increased by 300%.

• Fashion & Textile Research Journal
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• v.24 no.6
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• pp.667-685
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• 2022

This paper aims to investigate 4D printing materials for soft robots. 4D printing is a targeted evolution of the 3D printed structure in shape, property, and functionality. It is capable of self-assembly, multi-functionality, and self-repair. In addition, it is time-dependent, printer-independent, and predictable. The shape-shifting behaviors considered in 4D printing include folding, bending, twisting, linear or nonlinear expansion/contraction, surface curling, and generating surface topographical features. The shapes can shift from 1D to 1D, 1D to 2D, 2D to 2D, 1D to 3D, 2D to 3D, and 3D to 3D. In the 4D printing auxetic structure, the kinetiX is a cellular-based material design composed of rigid plates and elastic hinges. In pneumatic auxetics based on the kirigami structure, an inverse optimization method for designing and fabricating morphs three-dimensional shapes out of patterns laid out flat. When 4D printing material is molded into a deformable 3D structure, it can be applied to the exoskeleton material of soft robots such as upper and lower limbs, fingers, hands, toes, and feet. Research on 4D printing materials for soft robots is essential in developing smart clothing for healthcare in the textile and fashion industry.

• Advances in nano research
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• v.10 no.5
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• pp.423-435
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• 2021

This paper examines the thermal post-buckling behaviors of graphene-reinforced metal matrix composite (GRMMC) laminated cylindrical panels which possess in-plane negative Poisson's ratio (NPR) and rest on an elastic foundation. A panel consists of GRMMC layers of piece-wise varying graphene volume fractions to obtain functionally graded (FG) patterns. Based on the MD simulation results, the GRMMCs exhibit in-plane NPR as well as temperature-dependent material properties. The governing equations for the thermal post-buckling of panels are based on the Reddy's third order shear deformation shell theory. The von Karman nonlinear strain-displacement relationship and the elastic foundation are also included. The nonlinear partial differential equations for GRMMC laminated cylindrical panels are solved by means of a singular perturbation technique in associate with a two-step perturbation approach and in the solution process the boundary layer effect is considered. The results of numerical investigations reveal that the thermal post-buckling strength for (0/90)_5T GRMMC laminated cylindrical panels can be enhanced with an FG-X pattern. The thermal post-buckling load-deflection curve of 6-layer (0/90/0)_S and (0/90)_3T panels of FG-X pattern are higher than those of 10-layer (0/90/0/90/0)_S and (0/90)_5T panels of FG-X pattern.