Articles de revues : « Cork agglomerates »

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Reis, Luís G., P. Carvalho, C. Alves et Manuel de Freitas. « Mechanical Behaviour of Sandwich Beams Manufactured with Glass or Jute Fiber in Facings and Cork Agglomerates as Core ». Materials Science Forum 636-637 (janvier 2010) : 245–52. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.245.

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The environment is a prominent issue today. Designing environmentally sustainable products is an attempt to address this question. In many cases, natural materials are environmentally friendly for product design manufacturing. The goal of this work is to study the mechanical behaviour of NL10 and NL30 cork agglomerates. Compression, shear and bending tests in sandwich specimens made of glass or jute fiber in facings and cork agglomerates as core were carried out. The sandwich specimens were manufactured by Resin Transfer Moulding (RTM) process. Results show that NL30 has a higher compression strength and shear resistance than NL10 agglomerate due to its manufacturing process, which originates superior density, but the NL30 agglomerate superior density is undesirable. Sandwich test specimens that presented failure by rupture of the core in both types of tests, core shear tests and three point bending tests, showed that the failure is mainly adhesive occurring between the adhesively joined cork grains. Since grains are unaffected and remain intact, it is possible to improve these materials by using better agglutinants and new bonding techniques with the intent of getting cork agglomerates with higher shear and flexural strength.

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Le Barbenchon, Louise, Jérémie Girardot, Jean-Benoît Kopp et Philippe Viot. « Strain Rate Effect on the Compressive Behaviour of Reinforced Cork Agglomerates ». EPJ Web of Conferences 183 (2018) : 03018. http://dx.doi.org/10.1051/epjconf/201818303018.

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The demand for bio-sourced materials is currently increasing. Cork material because of its unique properties (fire resistant, energy absorbing, …) is then an excellent candidate for a large set of applications. In order to widen its possible uses, cork agglomerates with reinforcements at a 0.48 density were studied to compare their mechanical performances with classical cork agglomerates. This paper investigates the effect of these foreign reinforcements on the properties of agglomerated cork under a compressive loading. The material behavior has been determined as a function of the average strain rate and the direction of solicitation. The microstructure was first observed through optical and scanning electronic microscopy, spotting charges between each cork bead. The characterisation of cork at different strain rates was then carried out. An electromechanical testing machine was used to apply an uniaxial compression at quasi-static strain rates. Reinforced agglomerated cork was found to be anisotropic and strain-rate dependant. Its micro-structure reveals at complex composite material influencing strongly mechanical properties. Both Young's modulus and absorbed energy density at 0.6 strain increase with the cross-head speed displacement. From 12.7 MPa and 0.77 J.mm-3 when compressed at 0.05 mm·min-1 to 19.9 MPa and 1.44 J·mm-3 at 500mm·min-1 in the Off-plane direction.

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XIAOZHOU, SONG, LIU GUORUI, FENG XUECHUN et ZHANG LI. « PREPARATION AND PROPERTIES OF AGGLOMERATED CORK PANELS BOUND WITH CHITOSAN BINDER ». WOOD RESEARCH 67(4) 2022 67, n^o 4 (11 août 2022) : 648–60. http://dx.doi.org/10.37763/wr.1336-4561/67.4.648660.

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In this paper, acidified chitosan was used as an adhesive to prepare aldehyde-free, environmentally-friendly agglomerated cork panels by hot-pressing. After preparation, thephysical, mechanical, and the finishing properties of the chitosan-glued agglomerated cork panels were investigated. The optimal mass ratio of acetic acid solution (1wt.%) to chitosan was determined to be 30:1. The resulting hot-pressed agglomerated cork panels, which featured adensity of 0.55 g.cm-3and a thickness of 4 mm, exhibited a tensile strength of 1.70 MPa and athermal conductivity of 0.11W.m-1·K-1. The agglomerated cork panels coated with theoil-based polyurethane and water-based, acrylic-modified polyurethane paints exhibited significantly lower lightness and higher glossiness. The total color differences (ΔE*) ofboth agglomerated cork panels increased before and after finishing. The oil-based polyurethane paint coating exhibited high adhesion of paint film, reaching a level-0 adhesion, while thewater-based, acrylic-modified polyurethane paint coating achieved a level-1 adhesion. Theabrasion resistance results showed that the substrates of cork agglomerates coated two types of paint did not expose after undergoing abrasion for 100 revolutions atthe turntable speed of 60 rpm.

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Silva, José M., Tessaleno C. Devezas, A. Silva, L. Gil, C. Nunes et N. Franco. « Exploring the Use of Cork Based Composites for Aerospace Applications ». Materials Science Forum 636-637 (janvier 2010) : 260–65. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.260.

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Aerospace components are characterized by having high strength to weight ratios in order to obtain lightweight structures. Recently, different types of sandwich components using composite materials have been developed with the purpose of combining the effect of reinforced face-sheets with low weight core materials, such as honeycombs and foams. However, these materials must combine damage tolerance characteristics with high resistance under both static and dynamic loads. Cork composites can be considered as an alternative material for sandwich components since cork is a natural material with some remarkable properties, such as high damage tolerance to impact loads, good thermal and acoustic insulation capacities and excellent damping characteristics for the suppression of vibrations. The experiments carried out in this investigation were oriented in order to optimize the specific strength of cork based composites for sandwich components. Static bending tests were performed in order to characterize the mechanical strength of different types of cork agglomerates which were obtained considering distinct production variables. The ability to withstand dynamic loads was also evaluated from a set of impact tests using carbon-cork sandwich specimens. The results from experimental tests showed that cork agglomerates performance depends on the cork granulate size, the type of reinforcing elements and the bonding procedure used for the cohesion with the matrix material.

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Castro, Osvaldo, José M. Silva, Tessaleno Devezas, Arlindo Silva et Luís Gil. « Cork agglomerates as an ideal core material in lightweight structures ». Materials & ; Design 31, n^o 1 (janvier 2010) : 425–32. http://dx.doi.org/10.1016/j.matdes.2009.05.039.

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Macías-García, A., M. A. Díaz-Díez, E. M. Cuerda-Correa, A. Díaz-Parralejo et V. Gómez-Serrano. « Use of cork agglomerates as acoustic absorbents ». Materials Technology 24, n^o 2 (juin 2009) : 114–18. http://dx.doi.org/10.1179/175355509x425766.

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Knapic, Sofia, Carlos Pina dos Santos, Helena Pereira et José S. Machado. « Performance of Expanded High-Density Cork Agglomerates ». Journal of Materials in Civil Engineering 29, n^o 2 (février 2017) : 04016198. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0001718.

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Fernandes, Fábio, Ricardo Alves de Sousa, Mariusz Ptak et Gonçalo Migueis. « Helmet Design Based on the Optimization of Biocomposite Energy-Absorbing Liners under Multi-Impact Loading ». Applied Sciences 9, n^o 4 (20 février 2019) : 735. http://dx.doi.org/10.3390/app9040735.

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Cellular materials have been used in many applications such as insulation, packaging, and protective gear. Expanded polystyrene has been widely used as energy-absorbing liner in helmets due to its excellent cost-benefit relation. This synthetic material can absorb reasonable amounts of energy via permanent deformation. However, in real-world accidents, helmets may be subjected to multi-impact scenarios. Additionally, oil-derived plastic is presently a major source of societal concern regarding pollution and waste. As a sustainable alternative, cork is a natural cellular material with great crashworthiness properties and it has the remarkable capacity to recover after compression, due to its viscoelastic behavior, which is a desired characteristic in multi-impact applications. Therefore, the main goal is to analyze the applicability of agglomerated cork as padding material in safety helmets. First, a finite element model of a motorcycle helmet available on the market was developed to assess its safety performance and to establish a direct comparison between expanded polystyrene and cork agglomerates as liners. Secondly, a new helmet model with a generic geometry was developed to assess the applicability of agglomerated cork as liner for different types of helmets, based on the head injury risk predictions by the finite element head model, YEt Another Head Model (YEAHM), developed by the authors. Several versions of helmet liners were created by varying its thickness and removing sections of material. In other words, this generic helmet was optimized by carrying out a parametric study, and by comparing its performance under double impacts. The results from these tests indicate that agglomerated cork liners are an excellent alternative to the synthetic ones. Thus, agglomerated cork can be employed in protective gear, improving its overall performance and capacity to withstand multi-impacts.

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Ptak, Mariusz, Paweł Kaczyński, Johannes Wilhelm, José M. T. Margarido, Paula A. A. P. Marques, Susana C. Pinto, Ricardo J. Alves de Sousa et Fábio A. O. Fernandes. « Graphene-Enriched Agglomerated Cork Material and Its Behaviour under Quasi-Static and Dynamic Loading ». Materials 12, n^o 1 (4 janvier 2019) : 151. http://dx.doi.org/10.3390/ma12010151.

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The use of cork for a variety of applications has been gaining significance due to environmental concerns and political agendas. Consequently, its range of applications is growing rapidly. In this work, aiming to improve its mechanical response for crashworthiness applications, cork agglomerates were enriched by small quantities of graphene oxide or graphene nanoplates in order to observe a resulting improvement of the mechanical behaviour during quasi-static and dynamic compressive loading cases. To produce homogenous cork agglomerates including graphene, the material was previously dispersed into granulated cork using stirrers to achieve a good distribution. Then, the typical procedure of compression and curing was carried out. Magnified images attest a good dispersion of graphene into the cork matrix. Mechanical testing was performed for a variety of graphene concentrations (0.1, 0.5 and 1.0 weight %), becoming clear that the beneficial effect of including graphene (either oxide or nanoplates) is related to a later densification stage while keeping the same stress plateau levels.

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Pereira, H., et E. Ferreira. « Scanning electron microscopy observations of insulation cork agglomerates ». Materials Science and Engineering : A 111 (mai 1989) : 217–25. http://dx.doi.org/10.1016/0921-5093(89)90215-3.

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Reis, L., et A. Silva. « Mechanical Behavior of Sandwich Structures using Natural Cork Agglomerates as Core Materials ». Journal of Sandwich Structures & ; Materials 11, n^o 6 (5 juin 2009) : 487–500. http://dx.doi.org/10.1177/1099636209104523.

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Jardin, R. T., F. A. O. Fernandes, A. B. Pereira et R. J. Alves de Sousa. « Static and dynamic mechanical response of different cork agglomerates ». Materials & ; Design 68 (mars 2015) : 121–26. http://dx.doi.org/10.1016/j.matdes.2014.12.016.

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Dı́az-Parralejo, A., M. A. Dı́az-Dı́ez, A. Macı́as-Garcı́a, P. de la Rosa-Blanco et V. Gómez Serrano. « Bending strength of black and composite agglomerates of cork ». Materials Letters 57, n^o 24-25 (août 2003) : 4004–8. http://dx.doi.org/10.1016/s0167-577x(03)00255-6.

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Antunes e Sousa, Guilherme José, Ana Rita Santos Rocha, Gabriel Ferreira Serra, Fábio António Oliveira Fernandes et Ricardo José Alves de Sousa. « Shear Thickening Fluids in Cork Agglomerates : An Exploration of Advantages and Drawbacks ». Sustainability 15, n^o 8 (17 avril 2023) : 6764. http://dx.doi.org/10.3390/su15086764.

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Shear thickening fluids (STF) are a class of fluids whose viscosity significantly rises under external loads. The research on these fluids has been advancing in recent years regarding prospective practical applications, including developing impact-absorbing composites. Following the green agendas governments and legislators advocate, this study investigates the combination of STF and other sustainable materials. Cork is a naturally occurring cellular material with a negative carbon footprint and superior energy absorption properties. With varying concentrations of STF material, cork agglomerates were formed. As an innovative point, the analysed blends are homogeneous, contrasting with previous literary works. Samples contained from 0 to 30 wt.% of STF. A series of experiments were conducted in quasi-static and dynamic conditions (100 J impact tests) to determine the various mechanical responses. Increasing the concentration of STF (20 and 30 wt.%) will influence the mechanical behaviour of cork agglomerates by providing softer deceleration rates and dispersing more energy through disaggregation mechanisms.

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Antunes e Sousa, Guilherme J., Afonso J. C. Silva, Gabriel F. Serra, Fábio A. O. Fernandes, Susana P. Silva et Ricardo J. Alves de Sousa. « Experimental and Numerical Insights into the Multi-Impact Response of Cork Agglomerates ». Materials 17, n^o 19 (28 septembre 2024) : 4772. http://dx.doi.org/10.3390/ma17194772.

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Due to their extraordinary qualities, including fire resistance, excellent crashworthiness, low thermal conductivity, permeability, non-toxicity, and reduced density, cellular materials have found extensive use in various engineering applications. This study uses a finite element analysis (FEA) to model the dynamic compressive behaviour of agglomerated cork to ascertain how its material density and stress relaxation behaviour are related. Adding the Mullins effect into the constitutive modelling of impact tests, its rebound phase and subsequent second impact were further examined and simulated. Quasi-static and dynamic compression tests were used to evaluate the mechanical properties of three distinct agglomerated cork composite samples to feed the numerical model. According to the results, agglomerated cork has a significant capacity for elastic rebound, especially under dynamic strain rates, with minimal permanent deformation. For instance, the minimum value of its bounce-back energy is 11.8% of the initial kinetic energy, and its maximum permanent plastic deformation is less than 10%. The material’s model simulation adequately depicts the agglomerated cork’s response to initial and follow-up impacts by accurately reproducing the material’s dynamic compressive behaviour. In terms of innovation, this work stands out since it tackles the rebounding phenomena, which was not previously investigated in this group’s prior publication, either numerically or experimentally. Thus, this group has expanded the research on cork materials’ attributes.

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Delucia, Marco, Anita Catapano, Marco Montemurro et Jérôme Pailhès. « Determination of the effective thermoelastic properties of cork-based agglomerates ». Journal of Reinforced Plastics and Composites 38, n^o 16 (2 mai 2019) : 760–76. http://dx.doi.org/10.1177/0731684419846991.

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Carmo Lança, M., Eugen R. Neagu, Paulo C. Silva, Luís Gil et José N. Marat-Mendes. « Study of Electrical Properties of Natural Cork and Two Derivative Products ». Materials Science Forum 514-516 (mai 2006) : 940–44. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.940.

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Electrical properties of natural cork, commercial cork agglomerates (for floor and wall coverings) and a recently developed composite of cork/TetraPak® were studied. Measurements of isothermal charge and discharge currents were made for natural cork samples in different directions (axial, radial and tangential cuts). The isothermal current characteristics and the samples conductivity were investigated under different conditions (electric field, temperature and environmental conditions: in air at ambient relative humidity (RH), dry air and vacuum), also the samples could be or not conditioned (dried in vacuum or in a P2O5 atmosphere at room temperature). From these results the influence of water on the electrical properties of natural cork could be seen. In order to compare the three different cork materials a preliminary study was made. Isothermal charge and discharge currents and conductivity after 1h charging were measured and compared for different electric fields and temperature in air at ambient RH.

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Lança, M. C., W. Wirges, E. R. Neagu, R. Gerhard et J. Marat-Mendes. « Influence of humidity on the electrical charging properties of cork agglomerates ». Journal of Non-Crystalline Solids 353, n^o 47-51 (décembre 2007) : 4501–5. http://dx.doi.org/10.1016/j.jnoncrysol.2007.03.037.

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Lakreb, Nadia, Boudjema Bezzazi et Helena Pereira. « Mechanical strength properties of innovative sandwich panels with expanded cork agglomerates ». European Journal of Wood and Wood Products 73, n^o 4 (10 avril 2015) : 465–73. http://dx.doi.org/10.1007/s00107-015-0908-y.

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Lakreb, Nadia, Boudjema Bezzazi et Helena Pereira. « Mechanical behavior of multilayered sandwich panels of wood veneer and a core of cork agglomerates ». Materials & ; Design (1980-2015) 65 (janvier 2015) : 627–36. http://dx.doi.org/10.1016/j.matdes.2014.09.059.

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Delucia, Marco, Anita Catapano, Marco Montemurro et Jérôme Pailhès. « Pre-stress state in cork agglomerates : simulation of the compression moulding process ». International Journal of Material Forming 14, n^o 3 (8 avril 2021) : 485–98. http://dx.doi.org/10.1007/s12289-021-01623-x.

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Buil, Ramon Miralbes, David Ranz Angulo, Jan Ivens et Javier Oscar Abad Blasco. « Experimental study of natural cork and cork agglomerates as a substitute for expanded polystyrene foams under compressive loads ». Wood Science and Technology 55, n^o 2 (23 janvier 2021) : 419–43. http://dx.doi.org/10.1007/s00226-020-01254-6.

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Miranda, Isabel, et Helena Pereira. « Cork Façades as an Innovative and Sustainable Approach in Architecture : A Review of Cork Materials, Properties and Case Studies ». Materials 17, n^o 17 (7 septembre 2024) : 4414. http://dx.doi.org/10.3390/ma17174414.

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Façades give the first impression of a structure, reflecting the overall aesthetic appeal, architectural styles, cultural influences, and technological advancements. Emphasis on sustainability is increasing, with a shift towards eco-friendly and energy-saving materials, triggered by decreasing the environmental impact of construction. Cork is a green competitive material for various engineering and design applications due to its biological formation, sustainable production and a portfolio of properties including low density, impermeability, viscoelastic behaviour and high thermal insulation that derive from its cellular and chemical features. This work presents cork materials used in building façades and their properties, also giving information on cork production and processing into cork-based products as a review of the existing published research, while also identifying knowledge gaps and further research needed. Historical examples of cladding of constructions with raw cork are given, while the contemporary innovative use of cork façades was triggered by some designs of well-known architects with outdoor application of expanded cork agglomerates. Examples of different historical and contemporary constructions were assembled and critically assessed by the authors. The aim is to give integrated information of cork as a natural, renewable and sustainable material to raise the interest of designers, architects and engineers to explore cork, blending aesthetics with environmental responsibility, targeting a more sustainable and resilient built environment.

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Matias, Maria Leonor, Maria Morais, Ana Pimentel, Francisco X. Vasconcelos, Ana S. Reis Machado, Joana Rodrigues, Elvira Fortunato, Rodrigo Martins et Daniela Nunes. « Floating TiO2-Cork Nano-Photocatalysts for Water Purification Using Sunlight ». Sustainability 14, n^o 15 (5 août 2022) : 9645. http://dx.doi.org/10.3390/su14159645.

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In the present study, titanium dioxide (TiO2) nano-photocatalysts were synthesized through microwave irradiation. In a typical microwave synthesis, TiO2 nanomaterials were simultaneously produced in powder form and also directly covering cork substrates. The TiO2 nanopowder was analyzed by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM), revealing that the solvothermal microwave synthesis resulted only in the TiO2 anatase phase. From Fourier-transform infrared spectroscopy (FTIR), cork’s organic species, along with bands of TiO2, were detected. UV–VIS absorption spectrum revealed an absorption extension to the visible region, since a brown powdered TiO2 product was obtained. Very fine nanoparticles were observed displaying a nearly spherical shape that agglomerates in larger particles. These larger particles fully covered the surface of the honeycomb cork cells, originating TiO2 functionalized cork platforms. The TiO2 functionalized substrates were further tested as floating photocatalysts and their photocatalytic activity was assessed from rhodamine B degradation under solar simulating light and natural sunlight. Reusability tests were also performed under natural sunlight. The strategy applied in this research work allowed the production of green and low-cost cork platforms based on TiO2 photoactive materials with the ability to purify polluted water under natural sunlight.

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Popov, Vladimir. « Several Aspects of Application of Nanodiamonds as Reinforcements for Metal Matrix Composites ». Applied Sciences 11, n^o 10 (20 mai 2021) : 4695. http://dx.doi.org/10.3390/app11104695.

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After detonation synthesis, primary nanodiamond particles are around 4–6 nm in size. However, they join into agglomerates with larger parameters and weak bonds between particles. The introduction of agglomerates into a metal matrix can lead to the weakness of composites. This paper demonstrates the possibility of obtaining a non-agglomerated distribution of nanodiamonds inside a metal matrix. The fabrication method was based on mechanical alloying to create additional stresses and deformations by phase transformations during treatment in a planetary mill. According to the findings, the starting temperature of the reaction between the non-agglomerated nanodiamonds and aluminium matrix reduces to 450 °C. Furthermore, the paper shows that existing methods (annealing for the transformation of a diamond structure into graphitic material and cleaning from this graphitic material) cannot reduce the sizes of nanodiamonds in the agglomerated state. Agglomerated nanodiamonds transform into carbon onions (graphitic material) during annealing in a vacuum in the following way: the nanodiamonds located in the surface layers of the agglomerate are the first to undergo the complete transformation followed by the transformation of nanoparticles in its deeper layers. In the intermediate state, the agglomerate has a graphitic surface layer and a core from nanodiamonds: cleaning from graphite cannot reduce nanodiamond particle size.

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Sousa, Guilherme J. A., Fábio A. O. Fernandes, Ana R. S. Rocha, Gabriel F. Serra et Ricardo J. Alves de Sousa. « Manufacturing of Novel Cork-STF Composites Designed for Impact Energy Absorption ». Key Engineering Materials 957 (2 octobre 2023) : 29–34. http://dx.doi.org/10.4028/p-7o8lxs.

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Shear thickening fluids (STF) viscosity significantly increases when subjected to an external dynamic load. Recent advances show their potential for engineering applications, such as developing shock absorbers and impact energy-absorbing structures. There is a search for sustainable materials for several applications due to the critical need to replace nonrenewable raw materials. Cork is a sustainable material reported to be an excellent alternative to synthetic energy absorbers thanks to its cellular microstructure and cell wall composition. This work explores the development of cork-STF composites designed for impact energy mitigation. The cork-STF composites were manufactured by compression moulding, exploring different compositions of both materials. Additionally, the manufactured compounds were characterized by submitting samples to impacts. The results made it possible to conclude that deagglomeration occurs for STF concentrations higher than 20%. On the other hand, good results were achieved with compounds that have less than 20% of STF in their composition and can withstand impact loading. Therefore, the energy absorption of white cork agglomerates decreases with STF. Nevertheless, the agglomeration was successful, and this design can be adapted for other specific purposes, applications, or even strain rates than the ones explored in this work.

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Brandão, Pedro F., Rui M. Ramos, Inês M. Valente, Paulo J. Almeida, Antonia M. Carro, Rosa A. Lorenzo et José A. Rodrigues. « Gas-diffusion microextraction coupled with spectrophotometry for the determination of formaldehyde in cork agglomerates ». Analytical and Bioanalytical Chemistry 409, n^o 11 (11 février 2017) : 2885–92. http://dx.doi.org/10.1007/s00216-017-0233-x.

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Joao Teixeira, M., Anabela C. Fernandes, Benilde Saramago, M. Emilia Rosa et Joao C. Bordado. « Influence of the wetting properties of polymeric adhesives on the mechanical behaviour of cork agglomerates ». Journal of Adhesion Science and Technology 10, n^o 11 (janvier 1996) : 1111–27. http://dx.doi.org/10.1163/156856196x00148.

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Pereira, H., et C. Baptista. « Influence of raw-material quality and process parameters in the production of insulation cork agglomerates ». Holz als Roh- und Werkstoff 51, n^o 5 (septembre 1993) : 301–8. http://dx.doi.org/10.1007/bf02663799.

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André, Catarina, Inês Delgado, Isabel Castanheira, João Bordado et Ana Sofia Matos. « Statistical experimental design screening strategies for free monomeric isocyanates determination by UPLC in materials used in cork stoppers manufacturing ». ACTA IMEKO 6, n^o 1 (25 avril 2017) : 50. http://dx.doi.org/10.21014/acta_imeko.v6i1.395.

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A statistical experimental design was used to screen variables of the analytical procedure to quantify free monomeric isocyanates presented in polyurethane based pre-polymers in trace amounts.For this purpose, diphenylmethane-4,4’-diisocyanate (4,4’-MDI), 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) were analysed by Ultra Performance Liquid Chromatography with a Photo Diode Array detector (UPLC-PDA). A preliminary study was performed with three derivatization agents, being 1-(2-piridyl) piperazine (1,2-PP) the most suitable one. Column temperature, flow and percentage of ammonium acetate (% NH4Ac.) were the factors studied at two levels each. A sequence of experiments was planned according to a 23 full factorial design with three replicates and two repetitions. Analysis of variance (ANOVA) was applied for the identification of significant factors and interactions.Higher responses were achieved when the column temperature was 30 °C, a flow of 0.3 mL/min and a solvent with a percentage of ammonium acetate of 0.1 %. Figures of merit were assessed within-laboratory as a preliminary step for method validation. Similar values were obtained for TDI and MDI. Recoveries are approximately 100 %. In addition, the values of detection limits (LODs) for MDI and TDI were 0.08 and 0.11 microgram/mL, respectively, and quantification limits (LOQs) were 0.25 and 0.33 microgram/mL for MDI and TDI, respectively. The working range was between 0.01 and 10.00 microgram/mL for MDI and 0.01 – 4.95 microgram/mL for TDI. These figures of merit seemed adequate to detect low amounts of free monomeric isocyanates presented in agglomerates and foams for agglomerated cork stoppers production. This data is suitable to address the optimization of an analytical method by a response surface methodology.

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Corte-Real, Luis M. R. M., Shahin Jalali, Catarina S. P. Borges, Eduardo A. S. Marques, Ricardo J. C. Carbas et Lucas F. M. da Silva. « Development and Characterisation of Joints with Novel Densified and Wood/Cork Composite Substrates ». Materials 15, n^o 20 (14 octobre 2022) : 7163. http://dx.doi.org/10.3390/ma15207163.

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The automotive industry, driven by the desire to decrease the environmental impact of vehicles, is permanently seeking to develop lightweight structural components, which lead to lower gas emissions and energy consumption, reducing their carbon footprint. In parallel, adopting innovative, constructive solutions, which dispense non-recyclable and energy-intensive materials, can increase the footprint reduction. Thus, an increase in the use of renewable materials for structural applications, including wood and its by-products, has been observed over the last few decades. Furthermore, composite materials are often joined by using petroleum-based synthetic adhesives, which should be progressively replaced by eco-friendly bio-adhesives. In this study, novel densified wood and wood/cork composites, joined with a bio-adhesive, are proposed and characterised. The densification of the wood aims to enhance the mechanical properties of the natural material, with the purpose of improving the energy absorption of the wood/bio-adhesive joint. To mitigate delamination and the brittle behaviour of wood/cork agglomerates were introduced between the wood substrate and the bio-adhesive. Different configurations of single lap joints (SLJ) were manufactured to study the effect of the overlap length and loading rate on the performance of the joints, both in terms of failure load and energy absorption. Afterward, the joints were numerically simulated. The densification process was successful, although it represents an additional challenge in terms of surface flatness, because the bio-adhesive requires zero bondline thickness. The increase of the overlap had a positive impact on the energy absorption of the joint, and the addition of cork resulted in a more consistent failure mode and higher strain to failure. The numerical models developed had a good correlation with the experimental results.

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Brandão, Pedro Francisco, Rui Miguel Ramos, Paulo Joaquim Almeida et José António Rodrigues. « Determination of Carbonyl Compounds in Cork Agglomerates by GDME-HPLC-UV : Identification of the Extracted Compounds by HPLC-MS/MS ». Journal of Agricultural and Food Chemistry 65, n^o 5 (30 janvier 2017) : 1037–42. http://dx.doi.org/10.1021/acs.jafc.6b05370.

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Horwatt, Steven W., Ica Manas-Zloczower et Donald L. Feke. « Simulation of the Breakup of Dense Agglomerates in Simple Shear Flows ». Rubber Chemistry and Technology 65, n^o 4 (1 septembre 1992) : 805–21. http://dx.doi.org/10.5254/1.3538643.

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Abstract The transmission of stress within an agglomerate and hence the stress required for the agglomerate breakup is strongly dependent on the agglomerate structure. In this work, the influence of agglomerate structure on the dispersion process has been investigated through the use of computer simulations. Two different particle-particle agglomeration mechanisms, similar to the conditions under which carbon black is pelletized, have been used in this study. The linear trajectory agglomeration mechanism results in highly branched structures having a dense core, while the Eden model results in very dense clusters exhibiting rough surfaces but little internal porosity. The critical stresses to initiate dispersion of these structures, as well as the fragment size distributions resulting from the application of a simple shear flow field at stresses in excess of the critical value, were simulated. The results show that for the highly ramified agglomerates, the amplification of stress at the roots of the branches in the structure is controlling the dispersion process, whereas for the dense, unbranched agglomerates, the presence of strength-limiting flaws determines the breakup behavior. The results of the simulations were compared to previously performed experimental studies of dispersion for carbon-black agglomerates.

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Thieringer, Julia R. D., Nicolas Hafen, Jörg Meyer, Mathias J. Krause et Achim Dittler. « Investigation of the Rearrangement of Reactive–Inert Particulate Structures in a Single Channel of a Wall-Flow Filter ». Separations 9, n^o 8 (27 juillet 2022) : 195. http://dx.doi.org/10.3390/separations9080195.

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Wall-flow filters are a standard component in exhaust gas aftertreatment and have become indispensable in vehicles. Ash and soot particles generated during engine combustion are deposited in diesel or gasoline particulate filters. During regeneration, the soot particles are oxidized. The remaining ash particles can form different deposition patterns: a homogenous layer or plug-end filling. It has not yet been clarified whether the plug-end filling is first formed by rearrangements of agglomerates before and during the regeneration of the reactive particles. In this study, experiments are carried out with a single channel of a wall-flow filter. For the investigations, a layer of inert and reactive particles is formed. The rearrangement of agglomerates is achieved by flowing through the model filter channel and observed with a high-speed camera. The particulate structures detach at the channel inlet, are transported along the channel and deposited at the plug. The velocity of the detached agglomerates depends on their size, shape, track and the gas velocity in the channel. If the agglomerate is near the walls of the model filter channel, the gas velocity deviates from the gas velocity in the core flow. The higher the gas velocity, the higher the agglomerate velocity achieved and the larger the detached agglomerates.

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Guo, Jin, Samira Hezaveh, Jana Tatur, An-Ping Zeng et Uwe Jandt. « Reengineering of the human pyruvate dehydrogenase complex : from disintegration to highly active agglomerates ». Biochemical Journal 474, n^o 5 (20 février 2017) : 865–75. http://dx.doi.org/10.1042/bcj20160916.

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The pyruvate dehydrogenase complex (PDC) plays a central role in cellular metabolism and regulation. As a metabolite-channeling multi-enzyme complex it acts as a complete nanomachine due to its unique geometry and by coupling a cascade of catalytic reactions using ‘swinging arms'. Mammalian and specifically human PDC (hPDC) is assembled from multiple copies of E1 and E3 bound to a large E2/E3BP 60-meric core. A less restrictive and smaller catalytic core, which is still active, is highly desired for both fundamental research on channeling mechanisms and also to create a basis for further modification and engineering of new enzyme cascades. Here, we present the first experimental results of the successful disintegration of the E2/E3BP core while retaining its activity. This was achieved by C-terminal α-helixes double truncations (eight residues from E2 and seven residues from E3BP). Disintegration of the hPDC core via double truncations led to the formation of highly active (approximately 70% of wildtype) apparently unordered clusters or agglomerates and inactive non-agglomerated species (hexamer/trimer). After additional deletion of N-terminal ‘swinging arms’, the aforementioned C-terminal truncations also caused the formation of agglomerates of minimized E2/E3BP complexes. It is likely that these ‘swinging arm’ regions are not solely responsible for the formation of the large agglomerates.

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Pernas-Sánchez, Jesús, Jose A. Artero-Guerrero, David Varas et Filipe Teixeira-Dias. « Cork Core Sandwich Plates for Blast Protection ». Applied Sciences 10, n^o 15 (28 juillet 2020) : 5180. http://dx.doi.org/10.3390/app10155180.

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A numerical model is developed and validated to analyse the performance of aluminium skin and agglomerated cork core sandwich plates subjected to blast loads. Two numerical approaches are used and thoroughly compared to generate the blast loading: an Arbitrary-Lagrangian–Eulerian approach and the Load Blast Enhanced method. Both of the models are validated by comparing the numerical results with experimental observations. A detailed analysis of the sandwich behaviour is done for both approaches showing small differences regarding the mechanical response of the sandwich structure. The results obtained from the numerical models uncover the specific energy absorption mechanisms happening within the sandwich plate components. A new core topology is proposed, based on these results, which maximises the energy absorption capacity of the plate, keeping the areal density unchanged. A wavy agglomerated cork core is proposed and the effects of different geometrical parameters on the energy absorption are thoroughly analysed and discussed. The proposed optimised plate configuration shows an increase in the total absorbed energy of close to 40% relative to a reference case with the same areal density. The adopted optimisation methodology can be applied to alternative configurations to increase the performance of sandwich structures under blast events.

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Porozova, S. E., V. B. Kul’met’eva, T. Yu Pozdeeva et V. O. Shokov. « Role of nanopowder agglomerates in forming the structure and properties of ceramic materials ». Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya, n^o 4 (15 décembre 2020) : 4–13. http://dx.doi.org/10.17073/1997-308x-2020-4-4-13.

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A comparative analysis of agglomerates obtained by spray drying and granulation methods and consolidated materials based on them was carried out. The paper provides the results obtained when studying zirconia nanopowders granulated in water medium with an agar agar additive obtained by chemical precipitation with zirconia partially stabilized by yttrium oxide (2.5 mol.%), and TZ-3Y-E powder manufactured by Tosoh Corp. (Japan) that was prepared by spray drying. Agglomerates as well as microsections and fractures of samples were studied by scanning electron, optical, atomic force microscopy, and Raman spectroscopy. The crack resistance coefficient (K1с) of samples was determined by indenting the polished surface of microsections with a Vickers pyramid. The specific surface of the powders measured by nitrogen thermal desorption during granulation remains unchanged indicating a significant open porosity of agglomerates obtained. With increasing compacting pressure under conditions of semi-dry compaction with an aqueous solution of PVA as a binder, agglomerates and even aggregates of granulated powders are destroyed, K1с increases with increasing compaction pressure and the accompanying material microstructure grinding. Powders agglomerated using spray drying break up much less intensively, K1с does not change with increasing pressure. The studies conducted allow us to agree with the authors pointing to the fractal nature of agglomerates obtained from chemically precipitated nanopowders without the use of spray drying. The use of granulated nanopowders in semi-dry compaction with the application of high pressures makes it possible to destroy not only agglomerates, but also aggregates, and to obtain nanostructured ceramics with grain sizes close to the size of initial particles.

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Varela, Miguel M., Fábio A. O. Fernandes et Ricardo J. Alves de Sousa. « Development of an Eco-Friendly Head Impact Protection Device ». Applied Sciences 10, n^o 7 (5 avril 2020) : 2492. http://dx.doi.org/10.3390/app10072492.

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Nowadays, the number of people practising contact sports has increased. In many of them, using head protective equipment is not mandatory, even if the use of headbands could increase the level of safety regarding several types of traumatic brain injuries. Many commercial solutions are currently available, based on plastic-based foams providing a decent level of protection and comfort to the user. This work introduces the use of agglomerated cork as an eco-friendly alternative to synthetic foams but at least keeping safety levels. Cork is a natural cellular material that has been showing excellent crashworthiness properties. In this study, cork agglomerate density is carefully chosen to be incorporated into a protective headband. Results are compared against three other commercial headbands. For each one, the risk of brain injury was analysed for different injury thresholds and impact energies. The results clearly demonstrate that the cork-based apparel may provide comparable, and in some cases, better performances, outlasting the commercial ones.

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Djemai Hocine, Hecini Mabrouk et Adnane Labed. « On the characterization of sandwich panels for solar flat plate collectors’ applications : theoretical and experimental investigation ». Journal of Applied Engineering Science & ; Technology 2, n^o 1 (27 mars 2016) : 8. http://dx.doi.org/10.69717/jaest.v2.i1.24.

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This paper presents an experimental characterization on the mechanical behaviour offour different sandwich panels, for use in thermal insulation. These Panels are the results of thecombination of four composite materials; two materials as skins (Glass-Polyester and Plywood)and two as cores (Polystyrene and Cork agglomerate). From the comparison between themechanical behaviour of these four sandwich panels which was tested for three point-bendingtests; the sandwich with Glass-Polyester as skin and Cork agglomerate as core has the highestoverall stiffness compared to the other sandwich panels. Furthermore, thermal characteristics ofthese four panels (insulation materials) were numerically used in a comparative study of thermalperformances of solar flat plate collectors, FPCs. Thus, we have proceeded to the comparison ofthese FPCs efficiencies in order to determine the best performing model for agro-alimentary dryingapplications. From the comparison between these four FPCs, the highest efficiency was obtainedfrom the FPC insulation panel with plywood as skin and cork agglomerate as core.

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Sergi, Claudia, Jacopo Tirillò, Fabrizio Sarasini, Enrique Barbero Pozuelo, Sonia Sanchez Saez et Christoph Burgstaller. « The Potential of Agglomerated Cork for Sandwich Structures : A Systematic Investigation of Physical, Thermal, and Mechanical Properties ». Polymers 11, n^o 12 (17 décembre 2019) : 2118. http://dx.doi.org/10.3390/polym11122118.

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Considering the major role played by sandwich structures in many fields where high stiffness-to-weight ratio is required, the selection of a suitable core material is of paramount importance. In order to face the environmental problems related to waste disposal, the selection of an eco-friendly core material is now included in the design criteria of sandwich structures. Agglomerated cork is recognized as a good solution that combines satisfactory mechanical performances and eco-sustainability. Many research studies individually addressed cork’s morphological, thermal, and mechanical features without providing a comprehensive overview of the relationships that exist between them. In this work, the investigation of the peculiar cork morphology allowed learning more about its good insulation capacity and its impressive recovery capability. The use of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) clarified the influence of temperature on both flexural and compressive performances. The effect of testing parameters such as temperature and speed on agglomerated cork properties was validated through statistical analysis. Moreover, to highlight agglomerated cork advantages and drawbacks, the work provides also a comparison with more traditional polyvinylchloride (PVC) foams commonly used in industrial applications.

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Kumar, S. Sathis, M. Milwich, B. L. Deopura et H. Plank. « Finite element analysis of Carbon composite sandwich material with agglomerated Cork core ». Procedia Engineering 10 (2011) : 478–83. http://dx.doi.org/10.1016/j.proeng.2011.04.081.

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Ivañez, I., S. Sánchez-Saez, S. K. Garcia-Castillo, E. Barbero, A. Amaro et P. N. B. Reis. « High-velocity impact behaviour of damaged sandwich plates with agglomerated cork core ». Composite Structures 248 (septembre 2020) : 112520. http://dx.doi.org/10.1016/j.compstruct.2020.112520.

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Reis, P. N. B., M. P. Silva, P. Santos, J. M. Parente, S. Valvez et A. Bezazi. « Mechanical performance of an optimized cork agglomerate core-glass fibre sandwich panel ». Composite Structures 245 (août 2020) : 112375. http://dx.doi.org/10.1016/j.compstruct.2020.112375.

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Roseta, Maria, et Carlos Pina dos Santos. « Study in Real Conditions and in Laboratory of the Application of Expanded Agglomerated Cork as Exterior Wall Covering ». Key Engineering Materials 634 (décembre 2014) : 367–78. http://dx.doi.org/10.4028/www.scientific.net/kem.634.367.

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The interest of the study on the implementation of expanded agglomerated cork as exterior wall covering derives from two critical factors in a perspective of sustainable development: the use of a product consisting of a renewable natural material – cork – and the concern to contribute to greater sustainability in construction. The study aims to assess the feasibility of its use by analyzing the corresponding behaviour under different conditions. Since this application is relatively recent, only about ten years old, there is still much to learn about the reliability of its long-term properties. In this context, this study aims to deepen and approach aspects, some of them poorly studied and even unknown, that deal with characteristics that will make the agglomerate a good choice for exterior wall covering. The analysis of these and other characteristics is being performed by testing both under actual exposure conditions, on an experimental cell at LNEC, and on laboratory. In this paper the main laboratory tests are presented and the obtained results are compared with the outcome of the field study.

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Fernandes, F. A. O., R. J. S. Pascoal et R. J. Alves de Sousa. « Modelling impact response of agglomerated cork ». Materials & ; Design 58 (juin 2014) : 499–507. http://dx.doi.org/10.1016/j.matdes.2014.02.011.

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Sanchez-Saez, S., S. K. García-Castillo, E. Barbero et J. Cirne. « Dynamic crushing behaviour of agglomerated cork ». Materials & ; Design (1980-2015) 65 (janvier 2015) : 743–48. http://dx.doi.org/10.1016/j.matdes.2014.09.054.

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Ferreira, Ricardo, Diogo Pereira, António Gago et Jorge Proença. « Experimental characterisation of cork agglomerate core sandwich panels for wall assemblies in buildings ». Journal of Building Engineering 5 (mars 2016) : 194–210. http://dx.doi.org/10.1016/j.jobe.2016.01.003.

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Pereira, Gabriel Thomaz de Aquino, Ricardo J. Alves de Sousa, I.-Shih Liu, Marcello Goulart Teixeira et Fábio A. O. Fernandes. « A New Material Model for Agglomerated Cork ». Mathematical and Computational Applications 27, n^o 6 (9 novembre 2022) : 92. http://dx.doi.org/10.3390/mca27060092.

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It is increasingly necessary to promote means of production that are less polluting and less harmful to the environment following the UN 2030 agenda for sustainable development. Using natural cellular materials in structural applications can be essential for enabling a future in this direction. Cork is a natural cellular material with an excellent energy absorption capacity. Its use in engineering applications and products has grown over time, so predicting its mechanical response through numerical tools is crucial. Classical cork modeling uses a model developed for foam material, including an adjustment function that does not have a clear physical interpretation. This work presents a new material model for an agglomerated cork based solely on well-known hypotheses of continuum mechanics using fewer parameters than the classical model and further a finite element framework to validate the new model against experimental data.

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Gomez, Arturo, Enrique Barbero et Sonia Sanchez-Saez. « Modelling of carbon/epoxy sandwich panels with agglomerated cork core subjected to impact loads ». International Journal of Impact Engineering 159 (janvier 2022) : 104047. http://dx.doi.org/10.1016/j.ijimpeng.2021.104047.

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Sergi, Claudia, Fabrizio Sarasini et Jacopo Tirillò. « The Compressive Behavior and Crashworthiness of Cork : A Review ». Polymers 14, n^o 1 (30 décembre 2021) : 134. http://dx.doi.org/10.3390/polym14010134.

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Cork, a natural material from renewable resources, is currently attracting increasing interest in different industrial fields because of its cellular structure and the presence of the flexible suberin as its main chemical component. In an agglomerated form, it proved to be a compelling product not only as a thermal and acoustic insulator, but also as core material in sandwich structures and as a liner or padding in energy absorbing equipment. From this perspective, the assessment of its compressive response is fundamental to ensure the right out-of-plane stiffness required to a core material and the proper crashworthiness in the safety devices. Considering the complex nature of cork and the resulting peculiar compressive response, the present review article provides an overview of this paramount property, assessing the main parameters (anisotropy, temperature, strain rate, etc.) and the peculiar features (near-zero Poisson’s ratio and unique dimensional recovery) that characterize it in its natural state. Furthermore, considering its massive exploitation in the agglomerated form, the design parameters that allow its compressive behavior to be tailored and the operating parameters that can affect its crashworthiness were assessed, reporting some potential industrial applications.

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