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•The LCF-behaviour of Al-alloys was investigated experimentally and computationally.•A comprehensive statistical approach was proposed to evaluate the experimental results.•An ...elastic–plastic kinematic material model was applied in the computational model.•The strain life approach with Morrow correction was used to obtain the fatigue life.•Comparison between computational and experimental results showed a good agreement.
This study presents the experimental and computational analysis for determining the fatigue life of the auxetic cellular structures made of aluminium alloys. For the fatigue life calculation, the strain life approach was applied in the framework of the ANSYS software. The obtained experimental results were evaluated using the comprehensive statistical analysis, and presented in the form of different fatigue-life curves.
Based on the reasonable agreement between computational and experimental results the proposed computational model was validated and can be used further for the fatigue studies of various auxetic structures made of Al-alloys.
Wearable Haptic Auxetic Fabric
In article number 2304442, Il‐Kwon Oh and co‐workers unveil an easy‐to‐wear, multimodal, wearable haptic auxetic fabric (WHAF) prepared by knotting shape‐memory alloy ...wires into an auxetic‐architectured fabric. Incorporating meta‐design allows the WHAF to seamlessly adapt to skin contours, and surface electrical properties of the WHAF are modulated to deliver zone‐specified tactile feedback to users, bridging between the real and virtual worlds.
Auxetic materials are a group of metamaterials that have a negative Poisson's ratio. The most important advantage of auxetics over conventional materials is higher energy absorption. Consequently, in ...Civil Engineering, a wide range of applications may be considered for auxetic materials including energy absorber structural elements. In this study, two auxetic structures named re-entrant and arrowhead were selected along with the conventional honeycomb structure to investigate the effect of the negative Poisson's ratio on their mechanical behavior. These structures were produced utilizing a fused deposition modeling (FDM) 3D printer. Energy absorption was investigated numerically and experimentally. In order to increase the accuracy of the numerical study, ductile damage for the material was considered. The results showed that the ultimate forces of the re-entrant and arrowhead structures were increased by 125 % and 164 %, respectively, compared to the honeycomb structure. Furthermore, the amount of energy absorption of the re-entrant and arrowhead compared to the honeycomb structure increased by 47.4 % and 176.8 %, respectively. The rate of specific energy absorption in the two mentioned auxetic structures compared to the non-auxetic structure improved by 20.9 % and 53.5 %, respectively.
•Negativity of Poisson's ratio has a significant effect on energy absorption.•Auxetic structures strength would not decrease after yielding.•Considering the material damage in simulation process, increases the accuracy of numerical study.•Arrowhead structure performs better than Re-entrant structure in terms of decreasing the crash intensity.
Gyroid surface lattices of different densities exhibit Young's modulus consistent with stretch‐dominated extremal behavior approaching the Hashin–Shtrikman upper bound. The gyroid lattices exhibit a ...Poisson's ratio of 0.34 ± 0.06 independent of direction, independent of specimen diameter, and independent of chirality. This behavior is in contrast with prior chiral lattices that exhibited pronounced size effects in Poisson's ratio, allowable for chiral elastic solids.
Gyroid lattices (shell lattices with cubic structural symmetry) exhibit a density dependence of Young's modulus consistent with stretch‐dominated behavior. The modulus is extremal and approaches the Hashin–Shtrikman upper bound. The Poisson's ratio exhibits no significant dependence on direction, chirality, or specimen size. This behavior is in contrast with prior chiral lattices that exhibited pronounced size effects in Poisson's ratio.
Numerous applications of DNA origami nanotubes for load-bearing purposes necessitate the improvement of properties and mechanical behavior of these types of structures, as well as the use of ...innovative structures such as metamaterials. To this end, the present study aims to investigate the design, molecular dynamics (MD) simulation, and mechanical behavior of DNA origami nanotube structures consisting of honeycomb and re-entrant auxetic cross-sections. The results revealed both structures kept their structural stability. In addition, DNA origami based-nanotube with auxetic cross-section exhibits negative Poisson's ratio (NPR) under tensile loading. Furthermore, MD simulation results demonstrated that the values of stiffness, specific stiffness, energy absorption, and specific energy absorption in the structure with an auxetic cross-section are higher than that of a honeycomb cross-section, similar to their behavior in macro-scale structures. The finding of this study is to propose re-entrant auxetic structure as the next generation of DNA origami nanotubes. In addition, it can be utilized to aid scientists with the design and fabrication of novel auxetic DNA origami structures.
Communicated by Ramaswamy H. Sarma
The human being has always been looking for optimal use of his surrounding materials and over the years, has managed to invent various structures with special properties. Lattice structures are ...widely used in various applications due to their lower weight and desirable compressive strength. An example of these structures is the honeycomb that is very popular and many studies have been done about it. A new type of lattice structures is auxetic structure that has negative Poisson’s ratio due to its geometry. This characteristic has caused auxetic structures to have unique properties such as high shear strength, indentation resistance and energy absorption. Investigation of energy absorption of auxetic structures is a subject that has not been studied in researches. In this study, the ability of some auxetic structure for absorbing energy is investigated at quasi-static and low velocity impact transverse loading. Specimens with three types of geometries (re-entrant, arrowhead and anti-tetra chiral) are fabricated using additive manufacturing method (3D printing). Discussion about energy absorption and failure mechanisms of all three structures were carried out and compared in both types of loading.
This article examines the compressive behavior of re-entrant auxetic structures to optimize its energy absorption. The unique properties of auxetic structures have made them popular in various ...industries, especially for sports equipment. This study aims to create different types of structures using an FDM 3D printer. First, an appropriate raster angle for 3D printing of tensile test samples is examined for PLA and PLA+ materials. Next, three types of structures are constructed using brittle PLA and ductile PLA+ materials, and their energy absorption is compared. These structures are homogeneous auxetic re-entrant (HAR), unilateral graded thickness (UGT), and bilateral graded thickness (BGT). Changing from brittle (PLA) to soft material (PLA+) increases energy absorption in all structures. Likewise, grading the thickness of the structure, especially on BGT, increases energy absorption. Simulation results are validated by modeling the structures in two ways for brittle and ductile materials using Abaqus software. Finally, based on the simulation results, the most appropriate step of the bilateral graded thickness is recognized as 0.8-1-1.2.
In this study, a new reentrant rhombic auxetic structure is first designed by replacing the reentrant strut of the regular reentrant structure with a rhombic structure. A simulation calculation ...method verified by experimental results is comprehensively developed to reveal the compressive behavior of the proposed structures in terms of deformation pattern, compression strength, Poisson's ratio, and energy absorption (EA). Based on the validated simulation method, the results indicate that compression load can give rise to an “X” deformation pattern of the rhombic auxetic structures. In the structure parametric study, it is further proved that the unit configuration exhibits a significant influence on the compression stress and EA of the structures. Furthermore, the rhombic auxetic structures present diverse Poisson's ratios with the structure parameters and compression global strain, that is, the structures with larger H, smaller D, and θ are found to present more pronounced auxetic effect. The compression direction also exhibits a remarkable effect on the performance of the structure, which accordingly indicates the anisotropic characteristic of the proposed structures. Moreover, compared with the other regular auxetic structures, the rhombic auxetic structures exhibit superior mechanical behavior and EA feature due to the introduction of the rhombic structure.
A new reentrant rhombic auxetic structure is first designed and fabricated through 3D printing combined with molten metal infiltration technology method. In the structure parametric study, it is proved that the unit configuration exhibits a significant influence on the compression stress, Poisson's ratio, and energy absorption (EA) of the structures. Moreover, the new structures exhibit superior mechanical behavior and EA feature compared with the other regular auxetic structures.
Owing to being lightweight and offering excellent properties, the auxetic structures characterized by negative Poisson’s ratio are gaining growing interest from academia and industry. In view of the ...complex nature of these structures, 3D printing owing to offering shape flexibility is gaining increasing attention as a preferred fabrication process. Each cell in these structures consists of multiple ribs printed with different orientations thereby likely to show mechanical anisotropy when loaded. To accurately model their mechanical behavior and thus to reliably assess their performance through numerical modeling, anisotropy should be taken into account. This subject has been merely addressed in numerical modeling of printed auxetic structures, especially for those fabricated through fused deposition modeling (FDM), a 3D printing technique. The present study, therefore, addresses this subject. The ABS polymer is employed as the experimental material. For numerical modeling, the necessary material constants are determined by following the standard printing and testing practices. A variety of auxetic structures are designed and their mechanical behaviors are studied numerically as well as experimentally. The analysis shows that the anisotropic model yields fairly accurate results comparable to the experimental ones, while the isotropic model suffers from an error of 26%. The presented study is the first of its nature and is believed to act as a guideline for accurately assessing the mechanical performance of auxetic structures.
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