scholarly journals Non-Auxetic Mechanical Metamaterials

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 635 ◽  
Author(s):  
Christa de Jonge ◽  
Helena Kolken ◽  
Amir Zadpoor
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Fatigue Behavior ◽  
Analytical Data ◽  
Three Dimensional ◽  
Mechanical Metamaterials ◽  
Macro Scale ◽  
Unit Cells ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

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.

scholarly journals Regularly configured structures with polygonal prisms for three-dimensional auxetic behaviour

2017 ◽  
Vol 473 (2202) ◽  
pp. 20160926 ◽  
Author(s):  
Junhyun Kim ◽  
Dongheok Shin ◽  
Do-Sik Yoo ◽  
Kyoungsik Kim
Keyword(s):  
Poisson’S Ratio ◽  
Three Dimensional ◽  
Unit Cell ◽  
Poisson's Ratio ◽  
Numerical Verification ◽  
Geometric Conditions ◽  
Unit Cells ◽  
Negative Poisson's Ratio ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

We report here structures, constructed with regular polygonal prisms, that exhibit negative Poisson’s ratios. In particular, we show how we can construct such a structure with regular n -gonal prism-shaped unit cells that are again built with regular n -gonal component prisms. First, we show that the only three possible values for n are 3, 4 and 6 and then discuss how we construct the unit cell again with regular n -gonal component prisms. Then, we derive Poisson’s ratio formula for each of the three structures and show, by analysis and numerical verification, that the structures possess negative Poisson’s ratio under certain geometric conditions.

scholarly journals A New Polymer-Based Mechanical Metamaterial with Tailorable Large Negative Poisson’s Ratios

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1492 ◽  
Author(s):  
Shanshi Gao ◽  
Weidong Liu ◽  
Liangchi Zhang ◽  
Asit Kumar Gain
Keyword(s):  
Mechanical Properties ◽  
Cylindrical Shell ◽  
Stress Concentration ◽  
3D Printing ◽  
Mechanical Metamaterials ◽  
Printing Technique ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
3D Printing Technique ◽  
Significant Attention

Mechanical metamaterials have attracted significant attention due to their programmable internal structure and extraordinary mechanical properties. However, most of them are still in their prototype stage without direct applications. This research developed an easy-to-use mechanical metamaterial with tailorable large negative Poisson’s ratios. This metamaterial was microstructural, with cylindrical-shell-based units and was manufactured by the 3D-printing technique. It was found numerically that the present metamaterial could achieve large negative Poisson’s ratios up to −1.618 under uniaxial tension and −1.657 under uniaxial compression, and the results of the following verification tests agreed with simulation findings. Moreover, stress concentration in this new metamaterial is much smaller than that in most of existing re-entrance metamaterials.

scholarly journals Development of PLA Fibers as an Antimicrobial Agent with Enhanced Infection Resistance using Electrospinning/Plasma Technology

2020 ◽  
Author(s):  
Abdelrahman Mahmoud ◽  
Mohammed Naser ◽  
Mahmoud Abdelrasool ◽  
Khalid Jama ◽  
Mohamed Hussein ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Three Dimensional ◽  
Plasma Technology ◽  
Energy Increase ◽  
The Past ◽  
Unit Cells ◽  
Infection Resistance ◽  
Dimensional Shape ◽  
Fiber Dimensions ◽  
Three Dimensional Shape

Humans are vulnerable and easily prone to all kind of injuries, diseases, and traumas that can be damaging to their tissues (including its building unit, cells), bones, or even organs. Therefore, they would need assistance in healing or re-growing once again. Medical scaffolds have emerged over the past decades as one of the most important concepts in the tissue-engineering field as they enable and aide the re-growth of tissues and their successors. An optimal medical scaffold should be addressing the following factors: biocompatibility, biodegradability, mechanical properties, scaffold architecture/porosity, precise three-dimensional shape and manufacturing technology. There are several materials utilized in the fabrication of medical scaffolds, but one of the most extensively studied polymers is polylactic acid (PLA). PLA is biodegradable thermoplastic aliphatic polyester that is derived from naturally produced lactic acid. PLA is characterized with its excellent mechanical properties, biodegradability, promising eco-friendly, and excellent biocompatibility. PLA can be fabricated into nanofibers for medical scaffolds used through many techniques; electrospinning is one of the widely used methods for such fabrication. Electrospinning is a favorable technique because in the preparation of scaffolds, some parameters such as fiber dimensions, morphology, and porosity are easily controlled. A problem that is associated with medical scaffolds, such as inflammation and infection, was reported in many cases resulting in a degradation of tissues. Therefore, a surface modification was thought of as a needed solution which mostly focuses on an incorporation of extra functionalities responsible for the surface free energy increase (wettability). Therefore, plasma technique was a favorable solution for the surface treatment and modification. Plasma treatment enables the formation of free radicals. These radicals can be easily utilized for grafting process. Subsequently, ascorbic acid (ASA) could be incorporated as anti-inflammatory and anti-infection agent on the plasma pretreated surface of scaffolds.

scholarly journals Divergent Design of Mechanical Metamaterials Clan Deducted from Arc-serpentine Curve

2021 ◽  
Author(s):  
Shengli Mi ◽  
Hongyi Yao ◽  
Xiaoyu Zhao ◽  
Wei Sun
Keyword(s):  
Thick Plate ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Design Strategies ◽  
Shape Morphing ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Combinatorial Principles ◽  
Composite Curve ◽  
Typical Design

Abstract The exotic properties of mechanical metamaterials are determined by their unit-cells' structure and spatial arrangement, in analogy with the atoms of conventional materials. Companioned with the mechanism of structural or cellular materials1–5, the ancient wisdom of origami6–11 and kirigami12–16 and the involvement of multiphysics interaction2,17,18 enrich the programable mechanical behaviors of metamaterials, including shape-morphing8,12,14,16,19, compliance4,5,8,17,20, texture2,18,21, and topology11,18,22−25. However, typical design strategies are mainly convergent, which transfers various structures into one family of metamaterials that are relatively incompatible with the others and do not fully bring combinatorial principles3,10,26 into play. Here, we report a divergent strategy that designs a clan of mechanical metamaterials with diverse properties derived from a symmetric curve consisting of serpentines and arcs. We derived this composite curve into planar and cubic unit-cells and modularized them by attaching magnetics. Moreover, stacking each of them yields two- and three-dimensional auxetic metamaterials, respectively. Assembling with both modules, we achieved three thick plate-like metamaterials separately with flexibility, in-plane buckling, and foldability. Furthermore, we demonstrated that the hybrid of paradox properties is possible by combining two of the above assembles. We anticipate that this divergent strategy paves the path of building a hierarchical library of diverse combinable mechanical metamaterials and making conventional convergent strategies more efficient to various requests. Main

scholarly journals Mechanical properties and fracture dynamics of silicene membranes

2014 ◽  
Vol 16 (36) ◽  
pp. 19417-19423 ◽  
Author(s):  
T. Botari ◽  
E. Perim ◽  
P. A. S. Autreto ◽  
A. C. T. van Duin ◽  
R. Paupitz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Temperature Dependence ◽  
Young’S Modulus ◽  
Edge Effects ◽  
Critical Strain ◽  
Young's Modulus ◽  
Stress Distributions ◽  
Fracture Dynamics ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

A thorough study on the mechanical properties of silicene membranes. Young's modulus, Poisson's ratios, critical strain values, edge effects, dynamics of edge reconstructions, temperature dependence and stress distributions were investigated.

Effect of Continuous Direct Current on the Yield Stress of Stainless Steel 304 Micro Tubes During Hydroforming Operations

2012 ◽  
Author(s):  
Scott W. Wagner ◽  
Kenny Ng ◽  
William J. Emblom ◽  
Jaime A. Camelio
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
High Pressures ◽  
Tube Hydroforming ◽  
Process Equipment ◽  
Traditional Methods ◽  
Macro Scale ◽  
Hydroforming Process ◽  
Superior Mechanical Properties ◽  
Electrically Assisted Manufacturing

Hydroforming at the macro scale offers the opportunity to create products that have superior mechanical properties and intricate complex geometries. Micro tube hydroforming is a process that is gaining popularity for similar reasons. At the same time, due to the physical size of the operations, there are many challenges including working with extremely high pressures and available materials that are typically difficult to form. Increasing the formability of micro tubes during the hydroforming process is desired. Being able to increase the formability is essential because as the tube diameters decrease in size, the required forming pressure increases. As a result, it is important to explore methods to decrease the yield stress during forming operations. Traditional methods for decreasing the materials yield stress typically involve heating either the sample or the process equipment. Using traditional methods typically sacrifice dimensional quality of the part, alter the mechanical properties and also raise the costs of the operations. Electrically Assisted Manufacturing (EAM) is a non-traditional method that is gaining popularity by reducing the necessary forces and pressures required in metal forming operations.

Poisson’s Ratios for Wood Species for Structural Purposes

2015 ◽  
Vol 1088 ◽  
pp. 690-693
Author(s):  
Francisco Antonio Rocco Lahr ◽  
André Luis Christoforo ◽  
Eduardo Chahud ◽  
Luiz A. Melgaço N. Branco ◽  
Rosane A.G. Battistelle ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Confidence Intervals ◽  
Wood Species ◽  
Physical And Mechanical Properties ◽  
Timber Structures ◽  
Structural Elements ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

The broader knowledge about physical and mechanical properties of wood allows reliable timber structures design. Even little addressed in the literature, in several situations Poisson's ratios are required for the evaluation of stresses acting on structural elements. This study aimed to obtain values of Poisson's ratios (ν), plans Longitudinal-Radial (νLR) and Longitudinal-Tangential (νLT), for species Peroba Rosa (Aspidosperma polyneuron) and Jatobá (Hymenaea courbarilL.). For this purpose, forty samples Peroba Rosa and eight samples of Jatobá were prepared for testing in compression parallel to the grain, following the recommendations of ABNT NBR 7190 standard. The results of means confidence intervals, considered at the level of 5% significance, revealed that the Poisson's ratios νLR e νLT to Peroba Rosa are 0.27 and 0.42, respectively, and 0.25 and 0.43 to Jatobá.

scholarly journals Moisture-dependent orthotropic tension-compression asymmetry of wood

Holzforschung ◽  
2013 ◽  
Vol 67 (4) ◽  
pp. 395-404 ◽  
Author(s):  
Tomasz Ozyhar ◽  
Stefan Hering ◽  
Peter Niemz
Keyword(s):  
Yield Stress ◽  
Stress Ratio ◽  
Beech Wood ◽  
Strength Parameters ◽  
Young’S Moduli ◽  
Strength Asymmetry ◽  
Poisson's Ratios ◽  
Tension Compression Asymmetry ◽  
Poisson’S Ratios ◽  
Tangential Directions

Abstract The influence of moisture content (MC) on the tension-compression (Te-Co) asymmetry of beech wood has been examined. The elastic and strength parameters, including Te and Co Young’s moduli, Poisson’s ratios, and ultimate and yield stress values, were determined and compared in terms of different MCs for all orthotropic directions. The results reveal a distinctive Te-Co strength asymmetry with a moisture dependency that is visualized clearly by the Te to Co yield stress ratio. The Te-Co asymmetry is further shown by the inequality of the elastic properties, known as the “bimodular behavior”. The latter is proven for the Young’s moduli values in the radial and tangential directions and for individual Poisson’s ratios. Although the bimodularity of the Young’s moduli is significant at low MC levels, there is no evidence of moisture dependency on the Te-Co asymmetry of the Poisson’s ratios.

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