scholarly journals Investigating the influence of the core material on the mechanical performance of a nitinol wire wrapped helical auxetic yarn

2021 ◽  
pp. 030932472110270
Author(s):  
Nadimul Haque Faisal ◽  
Andrew Fowlie ◽  
Joe Connell ◽  
Sean Mackenzie ◽  
Ryan Noble ◽  
...  
Keyword(s):  
Analytical Model ◽  
Mechanical Performance ◽  
Poisson Ratio ◽  
Axial Strain ◽  
Impact Resistance ◽  
Tensile Tests ◽  
Core Material ◽  
The Core ◽  
Nitinol Wire ◽  
Theoretical Predictions

Helical Auxetic Yarns (HAYs) can be used in a variety of applications from healthcare to blast and impact resistance. This work focuses on the effect of the use of different core materials (e.g. rubber, polyurethane, polytetrafluoroethylene/teflon, polypropylene, polyetheretherketone, polycarbonate, acetal) with a nitinol wire wrap component on the maximum Negative Poisson Ratio (NPR) produced and thus the auxetic performance of Helical Auxetic Yarns (HAYs). From the analytical model, it was found that an acetal core produced the largest NPR when compared to the other six materials. The trend obtained from the experimental tensile tests (validation) correlated closely with the theoretical predictions of the NPR as axial strain was increased. The experimental method presented a maximum NPR at an average axial strain of 0.148 which was close to the strain of 0.155 predicted by theory. However, the maximum experimental NPR was significantly lower than that predicted by the analytical model.

scholarly journals Moisture Absorption Effects on the Mechanical Properties of Sandwich Biocomposites with Cork Core and Flax/PLA Face Sheets

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7295
Author(s):  
Hom Nath Dhakal ◽  
Chulin Jiang ◽  
Moumita Sit ◽  
Zhongyi Zhang ◽  
Moussa Khalfallah ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Moisture Absorption ◽  
Mechanical Performance ◽  
Core Sample ◽  
Environmental Benefits ◽  
Matrix Cracking ◽  
Core Material ◽  
Poly Lactic Acid ◽  
The Core

The aim of this study was to evaluate the moisture absorption behaviour and its influence on the mechanical properties of newly developed sandwich biocomposites with flax fibre-reinforced poly-lactic acid (PLA) face sheets and soft cork as the core material. Three different types of sandwich biocomposite laminates comprised of different layup configurations, namely, non-woven flax/PLA (Sample A), non-woven flax/PLA and cork as core (Sample B) and non-woven flax/paper backing/PLA, cork as core (Sample C), were fabricated. In order to evaluate the influence of moisture ingress on the mechanical properties, the biocomposites were immersed in seawater for a period of 1200 h. The biocomposites (both dry and water immersed) were then subjected to tensile, flexural and low-velocity falling weight impact tests. It was observed from the experimental results that the moisture uptake significantly influenced the mechanical properties of the biocomposites. The presence of the cork and paper in sample C made it more susceptible to water absorption, reaching a value of 34.33%. The presence of cork in the core also has a considerable effect on the mechanical, as well as energy dissipation, behaviours. The results of sample A exhibited improved mechanical performance in both dry and wet conditions compared to samples B and C. Sample A exhibits 32.6% more tensile strength and 81.4% more flexural strength in dry conditions than that in sample C. The scanning electron microscopy (SEM) and X-ray micro-CT images revealed that the failure modes observed are a combination of matrix cracking, core crushing and face core debonding. The results from this study suggest that flax/PLA sandwich biocomposites can be used in various lightweight applications with improved environmental benefits.

scholarly journals Delamination Testing of Additive Manufactured Sandwich Structures with Lattice Truss Core

2021 ◽  
Author(s):  
Miguel Nuño ◽  
Jannik Bühring ◽  
Narasimha Rao Mekala ◽  
Kai-Uwe Schröder
Keyword(s):  
Adhesive Bonding ◽  
Sandwich Structures ◽  
Sheet Thickness ◽  
Tensile Tests ◽  
Design Guidelines ◽  
Core Material ◽  
The Core ◽  
Truss Core ◽  
Out Of Plane ◽  
Peel Tests

Abstract Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight. This makes them very suitable for lightweight applications where high stiffness to weight ratios are needed. Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets. However, adhesive bonding is prone to delamination, a failure mode which is often difficult to detect. In this paper, the results of delamination testing of fully additive manufactured (AM) AlSi10Mg sandwich structures with pyramidal lattice truss core are presented. To characterise the bonding strength, climbing drum peel tests and out-of-plane tensile tests are done. The thickness of the faces and the diameter of the struts is 0.5 mm, while the core is 2 mm thick. The inclination of the struts is 45°. To predict the expected failure loads and modes, analytical formulas are derived. The analytics and tests are supported by finite element (FE) calculations. From the analytic approaches, design guidelines to avoid delamination in AM sandwich structures can be followed. The study shows, that critical ratios for face sheet thickness to strut diameter can be determined, to define if the structure tends to delaminate under certain loads. Those ratios are mainly influenced by the strut inclination. The peel tests resulted in face yielding, which can also be followed from the analytics and numerics. The out-of-plane tensile tests didn't damage the structure.

The Process of Co-Extrusion – An Analysis

2011 ◽  
Vol 491 ◽  
pp. 81-88 ◽  
Author(s):  
Kai Kittner ◽  
Birgit Awiszus
Keyword(s):  
Numerical Simulation ◽  
Axial Strain ◽  
Strain Difference ◽  
Stable Process ◽  
Quality Criterion ◽  
Extrusion Process ◽  
Core Material ◽  
Process Window ◽  
The Core ◽  
Adequate Quality

This paper provides an analysis of a co-extrusion process. The compound consists of the sleeve material, aluminum, and the core material, magnesium. It is imperative to produce impeccable compounds without cracks in the interface. Therefore, a simple indicating value for damaging effects during the process is necessary. In the numerical simulation the compound quality is noticeable by the current macro mechanical criterion of axial strain difference. A statistical analysis verifies this criterion as an adequate quality criterion. By means of this criterion it is possible to define a stable process window for the co-extrusion process.

An Experimental Analysis of Bending Behavior of Sandwich Constructions for Transport Industry

2016 ◽  
Vol 827 ◽  
pp. 61-64
Author(s):  
Ladislav Fojtl ◽  
Soňa Rusnáková ◽  
Milan Žaludek ◽  
Vladimír Rusnák
Keyword(s):  
Experimental Analysis ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Core Material ◽  
The Core ◽  
Transport Industry ◽  
Bending Behavior ◽  
The Impact ◽  
Environmental Temperatures ◽  
Sandwich Constructions

In this work the mechanical performance of various sandwich constructions with respect to core material were experimentally evaluated. Sandwich structures were made of glass prepreg and three types of plastic core using vacuum bagging, technology traditionally used for production of parts for transport industry. The aim of this study is to analyze the impact of the core material type and its thickness on bending behavior at different environmental temperatures. Moreover, the effect of core layers compared to one layer core of same thickness was determined. Conducted research provided useful information of bending behavior and showed specific failure modes of individual sandwich constructions.

An Analysis of Viscoelastic Damping Characteristics of a Simply-Supported Sandwich Beam

1971 ◽  
Vol 93 (4) ◽  
pp. 1239-1244 ◽  
Author(s):  
A. Chatterjee ◽  
J. R. Baumgarten
Keyword(s):  
Energy Method ◽  
Sandwich Beam ◽  
Core Material ◽  
Viscoelastic Damping ◽  
Experimental Measurements ◽  
Simply Supported ◽  
The Core ◽  
Damping Characteristics ◽  
Viscoelastic Core ◽  
Theoretical Predictions

An energy method is employed to analyze the damping in the fundamental mode of a simply-supported sandwich beam with viscoelastic core material sandwiched between two elastic metallic layers called the facings. The theory developed herein enables one to predict the damped natural frequency and the damping (in terms of logarithmic decrement) of the transverse vibration of a beam of known dimensions, provided the moduli-frequency characteristics of the core material are known. Experimental measurements bear out the accuracy of the theoretical predictions. The theory can very easily be extended for the analysis of higher discrete modes.

scholarly journals Effect of MF-Coated Epoxy Resin Microcapsules on Properties of Waterborne Wood Coating on Basswood

Coatings ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 785 ◽  
Author(s):  
Xiaoxing Yan ◽  
Yijuan Chang
Keyword(s):  
Epoxy Resin ◽  
Mass Fraction ◽  
High Performance ◽  
Impact Resistance ◽  
Color Difference ◽  
Core Material ◽  
Wall Material ◽  
The Core ◽  
Mass Fractions ◽  
The Stability

In this paper, melamine–formaldehyde (MF) was used as the wall material, and epoxy resin was used as the core material to prepare microcapsules. The optical properties, mechanical properties and ageing resistance of waterborne topcoat were investigated by adding different mass fractions of microcapsules into the waterborne topcoat. Through scanning electron microscopy and infrared spectroscopy analysis, the prepared microcapsules of core-wall ratio of 0.50 were more uniform. It was found that when the mass fraction of microcapsules is less than 10.0% and the core–wall ratio is 0.50, the original color difference of the coating can be maintained. With the increase in microcapsule mass fraction, the gloss of the topcoat film gradually decreases. The mass fraction of the microcapsule of 4.0% with the core–wall ratio of 0.50 can maintain the original gloss of 30.0 GU. The topcoat film with the MF-coated epoxy resin microcapsules of the core–wall ratio of 0.50 has high impact resistance, adhesion and hardness. The results showed that the gloss loss and color difference of the coating with the MF-coated epoxy microcapsules were the lowest when the mass fraction of microcapsules was 4.0%, indicating that microcapsules can improve the stability of coating. These results lay a technical foundation for the development and application of high-performance wood coatings.

scholarly journals Effect of Microcapsules of a Waterborne Core Material on the Properties of a Waterborne Primer Coating on a Wooden Surface

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 657 ◽  
Author(s):  
Xiaoxing Yan ◽  
Wenwen Peng
Keyword(s):  
Mass Fraction ◽  
Impact Resistance ◽  
Chromatic Aberration ◽  
Core Material ◽  
Core Shell ◽  
The Core ◽  
Mass Fractions ◽  
Wooden Surface ◽  
The Impact ◽  
Wooden Products

Microcapsules of a waterborne core material were prepared using a waterborne primer. The microcapsules of the waterborne core material were added to the waterborne primer to explore the effects of different core–shell ratios and mass fractions of the microcapsules on the property of the waterborne primer coating on the wooden surface. The results show that as the mass fraction of the microcapsules increased, the chromatic aberration increased by degrees, the glossiness decreased gradually, and the hardness increased by degrees, whilst—except for the coating with 0.50:1 microcapsules—the adhesion decreased gradually. When the mass fraction of the microcapsules increased, the impact resistance increased first and decreased later, or remained unchanged after reaching a certain value. When the mass fraction of the microcapsules increased, the elongation at the break increased first and decreased later. When the core–shell ratio was small and the mass fraction was between 5.0% and 15.0%, the coating had better liquid resistance. When the core–shell ratio was 0.67:1 and the mass fraction was 10.0%, the overall property of the coating on the Basswood was the best. The technology of microencapsulation provides a technical reference for the waterborne primer with self-repair qualities on the surface of wooden products.

Strengthening of Thin Masonry Arches

2014 ◽  
Vol 624 ◽  
pp. 51-58 ◽  
Author(s):  
Antonio Borri ◽  
Giulio Castori ◽  
Marco Corradi
Keyword(s):  
Structural Unit ◽  
Mechanical Performance ◽  
Axial Stress ◽  
Axial Strain ◽  
Vertical Load ◽  
The Core ◽  
Number Of Layers ◽  
Reinforced Masonry ◽  
Masonry Vaults ◽  
Modern Technologies

The innovative technique here illustrated is the result of historical evolution of an ancient system of reinforcing tiled vaults belonging to the constructive Spanish tradition. Such a traditional technique consists in the lamination of flat rectangular tiles or thin bricks into thin vaults known as boveda tabicada. Since the use of modern technologies may improve the mechanical performance of the traditional materials, the core of the proposed strengthening system is based on the idea of combining the peculiar features of tabicada technique with the good tensile properties of composite materials. More in detail, it is possible to obtain reinforced masonry vaults or arches by overlapping different layers of tiles or thin bricks and laminates, embedded within an hydraulic mortar, so that the entire assembly may act as a single structural unit. Eighteen prototypes of tiled arches were tested under a monotonic vertical load applied at the keystone. The influence of the types of reinforcement, number of layers and properties of hydraulic mortar has been investigated. Laboratory outcomes are presented and discussed in the paper considering mechanical behavior of specimens and axial stress-axial strain relationships.

Mechanical Performance of a New Coir Fiber Laminated Composites

2011 ◽  
Vol 217-218 ◽  
pp. 852-855 ◽  
Author(s):  
Jia Yao ◽  
Ying Cheng Hu ◽  
Wei Lu ◽  
Jin Li
Keyword(s):  
Mechanical Performance ◽  
Laminated Composites ◽  
Performance Testing ◽  
Sem Analysis ◽  
Core Material ◽  
Coir Fiber ◽  
Excellent Performance ◽  
Fiber Density ◽  
The Core ◽  
New Type

In order to overcome the uneven distribution of coir fiber density in the materials and the poor forming of the outer surface, a new type of coir fiber hybrid laminated composites has been developed. The non-woven needle felts of coir fiber are added as the core material, wood veneers are as the surface material, and E-type glass fiber felts are as the reinforcement material, the preparation of hybrid laminated composites has been carried out. Through the performance testing and scanning electron microscopy (SEM) analysis, a new type of biomass composite with excellent performance has been successfully developed. The application of coir fiber to obtain good impact toughness of composites has been effectively verified.

scholarly journals Experimental and Numerical Analysis of 3D Printed Polymer Tetra-Petal Auxetic Structures under Compression

2021 ◽  
Vol 11 (21) ◽  
pp. 10362
Author(s):  
Demetris Photiou ◽  
Stelios Avraam ◽  
Francesco Sillani ◽  
Fabrizio Verga ◽  
Olivier Jay ◽  
...  
Keyword(s):  
Finite Element ◽  
3D Printing ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Poisson Ratio ◽  
Impact Resistance ◽  
Experimental Tests ◽  
Polymer Materials ◽  
Compression Tests ◽  
Auxetic Structures

Auxetic structures possess a negative Poisson ratio (ν < 0) as a result of their geometrical configuration, which exhibits enhanced indentation resistance, fracture toughness, and impact resistance, as well as exceptional mechanical response advantages for applications in defense, biomedical, automotive, aerospace, sports, consumer goods, and personal protective equipment sectors. With the advent of additive manufacturing, it has become possible to produce complex shapes with auxetic properties, which could not have been possible with traditional manufacturing. Three-dimensional printing enables easy and precise control of the geometry and material composition of the creation of desirable shapes, providing the opportunity to explore different geometric aspects of auxetic structures with a variety of different materials. This study investigated the geometrical and material combinations that can be jointly tailored to optimize the auxetic effects of 2D and 3D complex structures by integrating design, modelling approaches, 3D printing, and mechanical testing. The simulation-driven design methodology allowed for the identification and creation of optimum auxetic prototype samples manufactured by 3D printing with different polymer materials. Compression tests were performed to characterize the auxetic behavior of the different system configurations. The experimental investigation demonstrated a Poisson’s ration reaching a value of ν = −0.6 for certain shape and material combinations, thus providing support for preliminary finite element studies on unit cells. Finally, based on the experimental tests, 3D finite element models with elastic material formulations were generated to replicate the mechanical performance of the auxetic structures by means of simulations. The findings showed a coherent deformation behavior with experimental measurements and image analysis.

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