Natural cork and its agglomerates as substitutes for high-density expanded polystyrene foams in sandwich cores

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ramon Miralbes ◽  
David Ranz ◽  
José A. Gómez ◽  
Dimitris Zouzias

Abstract Natural cork (NC) and its agglomerates are renewable materials that could be effective substitutes for non-renewable foams, such as expanded polystyrene (EPS), in the cores of sandwich materials. Although many existing studies have analysed the behaviour of different cork agglomerates under tensile, compression, or shear loads, no studies to date have simultaneously analysed the behaviour of multiple cork materials under all these loads. Therefore, in this study, the behaviour of NC and five cork agglomerates were analysed under tensile, compression and shear loads, and the mechanical and specific properties and the shape of the stress–strain curves were compared with those obtained for five EPS counterparts to analyse the relationship between the mechanical behaviour of the core and the main failure modes of the sandwich. Although EPS exhibited higher specific properties, NC exhibited higher mechanical properties under all the loads. The agglomerates all exhibited lower mechanical properties except for shear strain. Additionally, because no specific standards were available for testing cork products, slightly modified standards for testing other materials were adopted.

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7295
Author(s):  
Hom Nath Dhakal ◽  
Chulin Jiang ◽  
Moumita Sit ◽  
Zhongyi Zhang ◽  
Moussa Khalfallah ◽  
...  

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.


2019 ◽  
Vol 944 ◽  
pp. 351-356
Author(s):  
Sheng Rui Su ◽  
Ren Bo Song ◽  
Chi Chen ◽  
Wen Sheng Ji ◽  
Shi De Li ◽  
...  

The microstructure and mechanics of 15CrNiMo steel with different quenching temperatures (800°C, 825°C, 850°C, 875°C, 900°C) and different quenching holding time (15min, 25min, 35min) were studied for steel 15CrNiMo for roller bit. The relationship between the properties of different quenching parameters and the mechanical properties such as microstructure, impact toughness and hardness was analyzed. The results show that the microstructure of the annealed precursor is mainly ferrite and pearlite. With the increase of quenching temperature, the ferrite is gradually reduced, the lath martensite is gradually increased, and the martensite grains tend to grow. The strength increases first and then decreases, and the plasticity increases slightly. The quenching and holding time has no obvious effect on the test steel, and the austenitization of the core is the best time. The best quenching temperature is 850°C, the best holding time is 25 min, (tempering temperature is 220°C, tempering holding time is 50 min) and the mechanical properties are optimal.


2021 ◽  
pp. 109963622110354
Author(s):  
Minhui Xie ◽  
Liang Gao ◽  
Dong Cao ◽  
Botao Xie ◽  
Kai Li ◽  
...  

Composite lattice cores sandwich structures have shown obvious advantages in specific mechanical property and potential multifunctional integration. 3D-Kagome lattice core is regarded as a classic core configuration with relative optimal theoretical performance. However, it is still unavailable due to preparation problem of the overlap joint-node of composite cores. In this paper, a self-locking mortise-tenon joint method is presented to sucessfully fabricate the integrated 3D-Kagome cores with the expected mechanical properties. The out-of-plane compressive behaviour and energy absorption characteristics are experimentally studied. For the composite structures with various relative densities, three kinds of compressive curves are observed, following by different failure modes. An obvious bearing reinforcement emerges for the lattice cores with high relative density. As the length-to-thickness ratio of the core-rods increases, the initial peak strength and modulus of structures both decrease with a slowing rate. Though the mortises weaken the load-bearing capacity of core-rods, the active constraint of mortise-tenon joint suppresses an obvious degradation. The dominated failure more depends on the core-height than rod-thickness. The composite 3D-Kagome cores show more excellent mechanical properties than other similar structures, especially for the elastic strain before the initial peak stress. The semi-rigid power-wasting mortise-tenon joint and load-bearing characteristics of Kagome core together provide a large deformation tolerance at a relatively high stress level. All suggest that the presented 3D-Kagome lattice cores could be considered as a potential energy absorbing material.


2019 ◽  
pp. 246-256
Author(s):  
A. K. Zholkovsky

In his article, A. Zholkovsky discusses the contemporary detective mini-series Otlichnitsa [A Straight-A Student], which mentions O. Mandelstam’s poem for children A Galosh [Kalosha]: more than a fleeting mention, this poem prompts the characters and viewers alike to solve the mystery of its authorship. According to the show’s plot, the fact that Mandelstam penned the poem surfaces when one of the female characters confesses her involvement in his arrest. Examining this episode, Zholkovsky seeks structural parallels with the show in V. Aksyonov’s Overstocked Packaging Barrels [Zatovarennaya bochkotara] and even in B. Pasternak’s Doctor Zhivago [Doktor Zhivago]: in each of those, a member of the Soviet intelligentsia who has developed a real fascination with some unique but unattainable object is shocked to realize that the establishment have long enjoyed this exotic object without restrictions. We observe, therefore, a typical solution to the core problem of the Soviet, and more broadly, Russian cultural-political situation: the relationship between the intelligentsia and the state, and the resolution is not a confrontation, but reconciliation.


2018 ◽  
Vol 69 (05) ◽  
pp. 381-389
Author(s):  
MENGÜÇ GAMZE SÜPÜREN ◽  
TEMEL EMRAH ◽  
BOZDOĞAN FARUK

This study was designed to explore the relationship between sunlight exposure and the mechanical properties of paragliding fabrics which have different colors, densities, yarn counts, and coating materials. This study exposed 5 different colors of paragliding fabrics (red, turquoise, dark blue, orange, and white) to intense sunlight for 150 hours during the summer from 9:00 a.m. to 3:00 p.m. for 5 days a week for 5 weeks. Before and after the UV radiation aging process, the air permeability, tensile strength, tear strength, and bursting strength tests were performed. Test results were also evaluated using statistical methods. According to the results, the fading of the turquoise fabric was found to be the highest among the studied fabrics. It was determined that there is a significant decrease in the mechanical properties of the fabrics after sunlight exposure. After aging, the fabrics become considerably weaker in the case of mechanical properties due to the degradation in both the dyestuff and macromolecular structure of the fiber


Author(s):  
А.В. Мацук

В статье исследуются события бескоролевья 1733 г. в Речи Посполитой. Согласно «трактату Левенвольде» компромиссным кандидатом на избрание монархом Речи Посполитой был португальский инфант дон Мануэль, которого предложила Австрия. Россия больше склонялась к кандидатуре «пяста». Россия оказалась не подготовленной к началу бескоролевья. Бывшие российские союзники магнаты ВКЛ рассорились с российским послом Фридрихом Казимиром Левенвольде и перешли на сторону Франции. В конце февраля 1733 г. в ВКЛ направили Юрия Ливена, который от имени российской царицы предложил поддержку в получении короны Михаилу Вишневецкому и Павлу Сангушке. Принятое на конвокационном сейме решение об избрании королем «пяста» и католика показало популярность Станислава Лещинского. В результате вслед за Австрией Россия поддержала кандидатом на корону Фридриха Августа. Магнаты ВКЛ до последнего оставались конкурентами о короне. Оппозиция Лещинскому объединилась под лозунгом защиты «вольного выбора» и поэтому в ней остались кандидаты «пясты», которые не могли уступить друг другу, и согласились на компромисс – кандидатуру Фридриха Августа. Для противодействия возможному избранию Лещинского Россия создала в ВКЛ новоградскую конфедерацию. Ее организатором стал новоградский воевода Николай Фаустин Радзивилл. Эта конфедерация становится основой Генеральной Варшавской конфедерации, которая 5 октября 1733 г. избирает королем саксонского курфюрста. The article examines the events of the «kingless» year of 1733 in the Polish-Lithuanian Commonwealth. According to the Levenwolde Treaties the compromise candidate for the Commonwealth’s throne was the Portuguese Infante Don Manuel, who’s candidacy was proposed by Austria. Russia, in turn, leaned towards the «pyasta» candidate. The Russian Empire was clearly unprepared for the start of the kingless period. Russia’s former allies – magnates of the Grand Duchy of Lithuania – came into conflict with the Russian ambassador Frederick Kazimir Levenwolde and sided with France. In late February of 1733, Empress Anna Ioanovna of Russia sent Yuri Liven to the Grand Duchy of Lithuania, who offered official support in the struggle for the crown to Mikhail Vishnevetsky and Pavel Sangushka. The electoral decision made at the Sejm proved the popularity of the «pyast» and Catholic candidates, specifically – Stanislaus Leschinsky. In turn, Russia – following Austria – showed its support for the candidacy of Frederick August. The magnates of the Grand Duchy of Lithuania remained in opposition in the crown issue until the very last. Opposition to Leschinsky was united under the motto of «free choice». For that reason, it was comprised of «pyasta» candidates, who were in a deadlock with one another, and were now ready for the compromise candidacy of Frederick Augustus. In order to counter the possible election of Leschinsky, Russia created the Novograd Confederation in the Grand Duchy of Lithuania. It was organized by the Novograd Voevoda Faustin Radzivill. This confederation became the core of the General Warsaw Confederation that – on October 5th 1733 – elected the Saxon King to the throne of the Polish-Lithuanian Commonwealth.


Author(s):  
Peter Lake ◽  
Michael Questier

This volume revisits the debates and disputes known collectively in the literature on late sixteenth- and early seventeenth-century England as the ‘Archpriest Controversy’. We argue that this was an extraordinary instance of the conduct of contemporary public politics and that, in its apparent strangeness, it is in fact a guide to the ways in which contemporaries negotiated the unstable later Reformation settlement in England. The published texts which form the core of the arguments involved in this debate survive, as do several caches of manuscript material generated by the dispute. Together they tell us a good deal about the aspirations of the writers and the networks that they inhabited. They also allow us to retell the progress of the dispute both as a narrative and as an instance of contemporary public argument about topics such as the increasingly imminent royal succession, late Elizabethan puritanism, and the function of episcopacy. Our contention is that, if one takes this material seriously, it is very hard to sustain standard accounts of the accession of James VI in England as part of an almost seamless continuity of royal government, contextualized by a virtually untroubled and consensus-based Protestant account of the relationship between Church and State. Nor is it possible to maintain that by the end of Elizabeth’s reign the fraction of the national Church, separatist and otherwise, which regarded itself or was regarded by others as Catholic had been driven into irrelevance.


Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2323
Author(s):  
Yubing Du ◽  
Zhiqing Zhao ◽  
Qiang Xiao ◽  
Feiting Shi ◽  
Jianming Yang ◽  
...  

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.


Friction ◽  
2021 ◽  
Author(s):  
Shaoqing Xue ◽  
Hanglin Li ◽  
Yumei Guo ◽  
Baohua Zhang ◽  
Jiusheng Li ◽  
...  

AbstractWater is as an economic, eco-friendly, and efficient lubricant that has gained widespread attention for manufacturing. Using graphene oxide (GO)-based materials can improve the lubricant efficacy of water lubrication due to their outstanding mechanical properties, water dispersibility, and broad application scenarios. In this review, we offer a brief introduction about the background of water lubrication and GO. Subsequently, the synthesis, structure, and lubrication theory of GO are analyzed. Particular attention is focused on the relationship between pH, concentration, and lubrication efficacy when discussing the tribology behaviors of pristine GO. By compounding or reacting GO with various modifiers, amounts of GO-composites are synthesized and applied as lubricant additives or into frictional pairs for different usage scenarios. These various strategies of GO-composite generate interesting effects on the tribology behaviors. Several application cases of GO-based materials are described in water lubrication, including metal processing and bio-lubrication. The advantages and drawbacks of GO-composites are then discussed. The development of GO-based materials for water lubrication is described including some challenges.


2021 ◽  
pp. 109963622199386
Author(s):  
Tianshu Wang ◽  
Licheng Guo

In this paper, a shear stiffness model for corrugated-core sandwich structures is proposed. The bonding area is discussed independently. The core is thought to be hinged on the skins with torsional stiffness. The analytical model was verified by FEM solution. Compared with the previous studies, the new model can predict the valley point of the shear stiffness at which the relationship between the shear stiffness and the angle of the core changes from negative correlation to positive correlation. The valley point increases when the core becomes stronger. For the structure with a angle of the core smaller than counterpart for the valley point, the existing analytical formulations may significantly underestimate the shear stiffness of the structure with strong skins. The results obtained by some previous models may be only 10 persent of that of the present model, which is supported by the FEM model.


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