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1
Paegelow, Raphaël. „Action des sous-groupes finis de SL2(C) sur la variété de carquois de Nakajima du carquois de Jordan et fibrés de Procesi“. Electronic Thesis or Diss., Université de Montpellier (2022-....), 2024. http://www.theses.fr/2024UMONS005.
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Dans cette thèse de doctorat, nous avons, dans un premier temps, étudié la décomposition en composantes irréductibles du lieu des points fixes sous l’action d’un sous-groupe fini Γ de SL2(C) de la variété de carquois de Nakajima du carquois de Jordan. La variété de carquois associé au carquois de Jordan est isomorphe soit au schéma ponctuel de Hilbert dans C2 soit à l’espace de Calogero-Moser. Nous avons décrit ces composantes irréductibles à l’aide de variétés de carquois du carquois de McKay associé au sous-groupe fini Γ. Nous nous sommes ensuite intéressés à la combinatoire découlant de l’ensemble d’indexation de ces composantes irréductibles en utilisant une action du groupe de Weyl affine introduite par Nakajima. De plus, nous avons construit un modèle combinatoire lorsque Γ est de type D, qui est le seul cas original et remarquable. En effet, si Γ est de type A, un tel travail a déjà été fait par Iain Gordon et si Γ est de type E, nous avons montré que les points fixes qui sont aussi des points fixes du tore diagonal maximal de SL2(C) sont les idéaux monomiaux du schéma ponctuel de Hilbert dans C2 indexés par les partitions en escaliers. De manière plus précise, si Γ est de type D, nous avons obtenu un modèle de l’ensemble indexant les composantes irréductibles contenant un point fixe du tore maximal diagonal de SL2(C) en termes de partitions symétriques. Enfin, si n est un entier plus grand que 1, en utilisant la classification des résolutions projectives et symplectiques de la singularité (C2)n/Γn où Γn est le produit en couronne du groupe symétrique Sn des n premiers entiers et de Γ, nous avons obtenu une description de toutes ces résolutions projectives et symplectiques en termes de composantes irréductibles du lieu des Γ-points fixes du schéma ponctuel de Hilbert dans C2.Dans un second temps, nous nous sommes intéressés à la restriction de deux fibrés vectoriels au-dessus d’une composante irréductible du lieu des Γ-points fixes du schéma de Hilbert dans C2 fixée. Le premier fibré est le fibré tautologique dont nous avons exprimé la restriction en termes de fibrés tautologiques de Nakajima sur la variété de carquois du carquois de McKay associée à la composante irréductible fixée. Le second fibré vectoriel est le fibré de Procesi. Ce fibré a été introduit par Marc Haiman dans ces travaux démontrant la conjecture n!. Nous avons étudié les fibres de ce fibré en tant que (Sn × Γ)-module. Dans la première partie du chapitre de cette thèse consacré au fibré de Procesi, nous avons démontré un théorème de réduction qui exprime le (Sn × Γ)-module associé à la fibre de la restriction du fibré de Procesi au-desus d’une composante irréductible C du lieu des Γ-points fixes du schéma de Hilbert de n points dans C2 comme l’induit de la fibre de la restriction du fibré de Procesi au-dessus d’une composante irréductible du lieu des Γ-points fixes du schéma de Hilbert de k points dans C2 où l’entier k ≤ n est explicite et dépend de la composante irréductible C et de Γ. Ce théorème est ensuite démontré avec d’autres outils dans deux cas particuliers pour Γ de type A. Enfin, lorsque Γ est de type D, certaines formules explicites de réduction des fibres de la restriction du fibré de Procesi au lieu des Γ-point fixes ont étéobtenues.Pour finir, si l est un entier plus grand que 1, alors dans le cas où Γ est le sous-groupe cyclique d’ordre l contenu dans le tore maximal diagonal de SL2(C) noté µl, le théorème de réduction restreint l’étude des fibres du fibré de Procesi au-dessus du lieu des µl-points fixes du schéma ponctuel de Hilbert dans C2 à l’étude des fibres au-dessus des points du schéma de Hilbert associés aux idéaux monomiaux paramétrés par les l-cœurs. Les (Sn × µl)-modules que l’on obtient semble être reliés à l’espace de Fock de l’algèbre de Kac-Moody ˆsll(C). Une conjecture dans ce sens est énoncée dans le dernier chapitreIn this doctoral thesis, first of all, we have studied the decomposition into irreducible components of the fixed point locus under the action of Γ a finite subgroup of SL2(C) of the Nakajima quiver variety of Jordan’s quiver. The quiver variety associated with Jordan’s quiver is either isomorphic to the punctual Hilbert scheme in C2 or to the Calogero-Moser space. We have described the irreducible components using quiver varieties of McKay’s quiver associated with the finite subgroup Γ. We were then interested in the combinatorics coming out of the indexing set of these irreducible components using an action of the affine Weyl group introduced by Nakajima. Moreover, we have constructed a combinatorial model when Γ is of type D, which is the only original and remarkable case. Indeed, when Γ is of type A, such work has already been done by Iain Gordon and if Γ is of type E, we have shown that the fixed points that are also fixed under the maximal diagonal torus of SL2(C) are the monomial ideals of the punctual Hilbert scheme in C2 indexed by staircase partitions. To be more precise, when Γ is of type D, we have obtained a model of the indexing set of the irreducible components containing a fixed point of the maximal diagonal torus of SL2(C) in terms of symmetric partitions. Finally, if n is an integer greater than 1, using the classification of the projective, symplectic resolutions of the singularity (C2)n/Γn where Γn is the wreath product of the symmetric group on n letters Sn with Γ, we have obtained a description of all such resolutions in terms of irreducible components of the Γ-fixedpoint locus of the Hilbert scheme of points in C2.Secondly, we were interested in the restriction of two vector bundles over a fixed irreducible component of the Γ-fixed point locus of the punctual Hilbert scheme in C2. The first vector bundle is the tautological vector bundle that we have expressed the restriction in terms of Nakajima’s tautological vector bundle on the quiver variety of McKay’s quiver associated with the fixed irreducible component. The second vector bundle is the Procesi bundle. This vector bundle was introduced by Marc Haiman in his work proving the n! conjecture. We have studied the fibers of this bundle as (Sn × Γ)-module. In the first part of the chapter of this thesis dedicated to the Procesi bundle, we have shown a reduction theorem that expresses the (Sn × Γ)-module associated with the fiber of the restriction of the Procesi bundle over an irreducible component C of the Γ-fixed point locus of Hilbert scheme of n points in C2 as the induced of the fiber of the restriction of the Procesi bundle over an irreducible component of the Γ-fixed point locus of the Hilbert scheme of k points in C2 where k ≤ n is explicit and depends on the irreducible component C and Γ. This theorem is then proven with other tools in two edge cases when Γ is of type A. Finally, when Γ is of type D, some explicit reduction formulas of the restriction of the Procesi bundle to the Γ-fixed point locus have been obtained.To finish, if l is an integer greater than 1, then in the case where Γ is the cyclic group of order l contained in the maximal diagonal torus of SL2(C) denoted by µl, the reduction theorem restricts the study of the fibers of the Procesi bundle over the µl-fixed points of the punctual Hilbert scheme in C2 to the study of the fibers over points in the Hilbert scheme associated with monomial ideals parametrized by the l-cores. The (Sn × Γ)-module that one obtains seems to be related to the Fock space of the Kac-Moody algebra ˆsll(C). A conjecture in this direction has been stated in the last chapter
2
Araújo, Maico Dutra de. „Efeito do processamento e da inclusão de fibras nas propriedades mecânicas e ópticas de uma porcelana odontológica“. Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-07112011-105946/.
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O objetivo dessa tese foi avaliar o efeito da adição de fibras e tipo de processamento (sinterização versus injeção) na microestrutura, propriedades mecânicas (resistência à flexão f e parâmetros de Weibull m, 0 e 5%), parâmetros de crescimento subcrítico (n e f0) e propriedades ópticas de razão de contraste (RC), parâmetro de translucidez (PT) e índice de opalescência (IO) de uma porcelana odontológica à base de leucita. Fibras de hexatitanato de potássio foram misturadas a uma porcelana à base de leucita que foi processada por sinterização e por injeção (com e sem fibras). Por meio de um estudo piloto realizado, variando-se temperaturas de sinterização e de injeção com 5% ou 10% de fibras, em massa, foram escolhidos o grupo controle (CS) sinterizado conforme recomendações do fabricante; o grupo sinterizado com fibras (SF), o grupo injetado sem fibras (ISF) e o grupo injetado com fibras (IF). A adição de fibras à porcelana processada por sinterização resultou em um material com fração volumétrica de poros mais do que duas vezes maior do que aquela encontrada para o grupo controle e a área média desses poros também foi mais do que o dobro da área média dos poros do controle. Outro problema apresentado pelo grupo sinterizado com fibras foi o aumento significativo da sua opacidade, representada pela razão de contraste que aumentou de 0,7 no controle para 1,0 no grupo sinterizado com fibras. Além disso, adição de fibras ao material processado por sinterização, apesar de ter causado aumento significativo da densidade e coeficiente de Poisson, não causou alterações significativas no módulo de elasticidade, dureza e tenacidade à fratura. Com relação à resistência à flexão biaxial, a adição de fibras na porcelana sinterizada causou aumento significativo da resistência média (f), porém os parâmetros da análise de Weibull (módulo de Weibull, m, resistência característica, 0, e resistência correspondente à probabilidade de falha de 5%, 5%) não foram alterados significativamente em relação ao grupo controle. Os parâmetros de crescimento subcrítico (coeficiente de susceptibilidade ao crescimento subcrítico, n, e resistência inicial, f0) também não foram alterados significativamente após a adição de fibras no material sinterizado. Embora o processamento por injeção sem adição de fibras não tenha afetado significativamente (em relação ao grupo controle) algumas propriedades como tenacidade à fratura, dureza, módulo de elasticidade, módulo de Weibull e 5%, houve um aumento significativo de parte das propriedades avaliadas como a resistência média, resistência característica e parâmetros de crescimento subcrítico. Com relação às propriedades ópticas, o processamento por injeção resultou em aumento da translucidez da porcelana, o que foi comprovado pela queda significativa no valor de razão de contraste e no aumento significativo no valor do parâmetro de translucidez em comparação com o grupo controle. Uma característica importante observada para o grupo injetado sem fibras foi seu baixo grau de porosidade em relação ao controle e também em relação aos outros dois grupos experimentais (SF e IF). Com relação ao grupo IF, o mesmo problema de alto grau de porosidade observado para o grupo sinterizado com fibras (SF) foi notado. Entretanto, os poros do grupo IF apresentaram área média significativamente menor e tamanho de poro aproximadamente 3 vezes menor do que os dos poros do grupo SF. Dentre as propriedades que não se alteraram comparando-se os grupos controle e injetado com fibras estão o módulo de elasticidade, coeficiente de Poisson, tenacidade à fratura, 5%, e as propriedades ópticas de razão de contraste e parâmetro de translucidez. Entretanto, é importante ressaltar que o grupo injetado com fibras obteve maiores valores médios em relação ao grupo controle para os seguintes parâmetros: densidade, dureza, resistência média, resistência característica, coeficiente de susceptibilidade ao crescimento subcrítico (foi o maior de todo o experimento) e resistência inicial (f0).The objective was to evaluate the processing methods (conventional sintering and heat pressing) and fibers incorporation on the microstructure, mechanical properties (flexural strength f, and Weibull parameters m, 0 e 5%), slow crack growth parameters (n e f0) and contrast ratio (CR), translucency parameter (TP), opalescence parameter (OP) optical properties. Potassium Titanate fibers were mixed with a feldspathic porcelain, and then processed with conventional sintering and heat pressing (with or without fibers). A pilot study was carried out varying the sintering and heat pressing temperature with 5 or 10 wt% of fibers. The selected groups were the control group (CG), conventionally sintered processes following manufactures recommendations; conventionally sintered with fibers (SF); heat pressed without fibers (HP) and heat pressed with fibers (HPF). The hypothesis were: 1) The incorporation of fibers to the conventionally processed porcelain would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties; 2) heat pressing the porcelain without fibers would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties. 3) heat pressing the porcelain with fibers would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties. Specimens were tested for biaxial flexural strength in water. Weibull analysis was used to determine m, 0 and 5% and the dynamic fatigue test was used to determine n e f0 values. The SF group showed percentage of porosity two times higher than the CG, higher values of f, but had no improvement on the Weibull parameters m, 0 and 5% values and slow crack growth parameters n and f0. It presented significant optical changes reaching 100% of opacity. The first hypothesis was partially accepted because there was increase only in f. The HP group presented 10 times lower porosity than CG. It showed higher values of f, and 0 but had no improvement on m and 5%. The HP group also showed higher values of n and f0 and significantly higher TP, and lower CR and OP. The second hypothesis was partially accepted as well because there were mechanical properties increases and changes in optical properties. The HPF group showed porosity two times higher than the CG, higher values of f, and showed an improvement on the Weibull parameters 0 and 5% and slow crack growth parameters n and f0. It presented significant changes OP.
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Romakkaniemi, I. (Idamaria). „Biodegradation of synthetic textile fibres“. Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201808232664.
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Synthetic fibres are a raw-materials, that have rapidly become more commonly used in the textile industry. They are used in many everyday products as such or as blends with other fibres like cotton. Synthetic fibres are utilized to achieve the wanted special abilities in textiles. Synthetic textile fibres are composed of polymers and mainly do not decompose in nature as such. Accumulation of these fibres is a growing environmental problem across the globe. If digested, synthetic fibres can be dangerous to organisms. To solve this problem, research has been done to find biological ways of degrading synthetic fibres. Different kinds of micro-organisms have been examined to find organisms that can utilize synthetic fibres in their metabolism. In this bachelor’s thesis the aim was to gather as much information as possible on researches done on synthetic fibre biodegradation to date. Different kinds of fibres and their components were identified and the production processes were examined. Biodegradation of each fibre and their components by microbes and enzymes was investigated. The majority of results were found on polyurethane fibres while less results related to aromatic polyamide fibres. As a result of this data collection it could be stated, that the topic needs more scientific research to find effective ways to biodegrade synthetic fibres. The goal of this literary research is to give an extensive overview on the pollution problem caused by synthetic textile fibres and the biological methods of degrading them as well as to emphasize that the gathered information should be utilized to solve the problemSynteettiset kuidut ovat nopeasti yleistynyt materiaali tekstiiliteollisuudessa. Niitä käytetään monissa arkipäiväisissäkin tuotteissa sellaisenaan tai sekoitettuna muiden kuitujen kuten puuvillan kanssa. Niillä pyritään saavuttamaan tekstiilille halutut erityisominaisuudet. Synteettiset tekstiilikuidut koostuvat polymeereistä ja eivät pääsääntöisesti hajoa luonnossa sellaisenaan. Niiden kerääntyminen luontoon ja meriin on kasvava ympäristöongelma ympäri maailmaa. Synteettiset polymeerit voivat olla vaarallisia eliöille joutuessaan niiden ruuansulatukseen. Tämän ongelman ratkaisemiseksi on pyritty löytämään biologisia menetelmiä hajottaa synteettisiä kuituja. Erilaisia mikro-organismeja on tutkittu, jotta löydettäisiin organismeja, jotka pystyisivät hyödyntämään synteettisiä kuituja metaboliassaan. Tässä kandidaatin työssä pyrittiin keräämään mahdollisimman kattavasti tietoa tähän päivään mennessä tehdyistä tutkimuksista synteettisten kuitujen biohajoamisesta. Erilaiset kuitulajit ja niiden komponentit määriteltiin ja selvitettiin, millaisella prosessilla niitä valmistetaan. Jokaisen kuidun ja niiden komponenttien biohajoamista selvitettiin mikrobien ja entsyymien avulla. Eniten tutkimustuloksia löytyi polyuretaanikuiduista ja vähiten aromaattisista polyamidikuiduista. Tiedonhankinnan tuloksena voisi todeta, että aihe vaatii yhä tieteellistä lisätutkimusta, jotta löydetään tehokas biologinen keino hajottaa synteettisiä kuituja. Tämä kirjallisuustutkielman tavoite on antaa laaja yleiskuva synteettisten tekstiilikuitujen aiheuttamasta saasteongelmasta ja niiden biologisesta hajottamisesta sekä pyrkiä korostamaan, että kerättyjä taustatietoja tulisi hyödyntää ongelman ratkaisemisessa
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López, Sánchez Ángel. „Influencia del proceso de reciclado sobre las propiedades de los materiales compuestos obtenidos por inyección de poliestireno reforzado con fibras lignocelulósicas“. Doctoral thesis, Universitat de Girona, 2004. http://hdl.handle.net/10803/7759.
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The objective of this research is to study the influence of several recycling cycles on the mechanical properties of four different materials made by the injection of polystyrene. The four materials studied have different characteristics. The first one is polystyrene (PS), the second one is polystyrene reinforced with hemp fibers (PSf), the third one is polystyrene reinforced with hemp fibers modified with AKD (PSft) and the last one is polystyrene reinforced with fiberglass (PSfv). With all these materials tensile strength, bending, hardness and impact is measured. After the measurement of these physical properties, materials are recycled to obtain new injection samples, and its physical properties are measured again. This process is repeated during 24 cycles.
After each recycling cycle material physical properties are related with polystyrene molecular weight, melt flow, FTIR spectra and DSC.
From reinforced materials, fibers are recovered and through microscopy and image analysis they are characterized to study the influence that recycling has on its structure.
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Poumadère, Thomas. „Etude du couplage procédé/propriétés d’un matériau à fibres discontinues de carbone et à matrice époxy mis en oeuvre par un procédé innovant d’injection/transfert“. Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0003.
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Les matériaux composites sont largement utilisés dans l'aéronautique où leurs hautes performances mécaniques combinées à leur légèreté leur permettent de concurrencer les matériaux métalliques. Cependant il est aujourd'hui difficile de fabriquer en série des pièces structurales ayant des formes tridimensionnelles complexes,Si les procédés d'injection de thermoplastiques chargés de fibres courtes (100 à 1 mm) sont bien connus, les études sur l'injection des thermodurcissables à fibres longues sont rares en raison de la difficulté à les faire s'écouler sur plusieurs dizaines de millimètres pour remplir complètement les moules.La société Equip'Aéro Technique a initié des travaux portant sur le développement d'un nouveau procédé de fabrication par injection-transfert (PIMOC) de composites thermodurcissables à fibres longues (> 1 mm) discontinues. Il permet de réaliser en une seule étape des pièces aux formes tridimensionnelles sans usinage.Dans ce travail de thèse le procédé d'injection-transfert a été mis au point et fiabilisé. Ses paramètres principaux ont été identifiés. L'influence des paramètres de fabrication sur les propriétés du matériau a été établie. Les propriétés mécaniques ont ainsi pu être optimisées. Enfin, un modèle de comportement élastique endommageable avec rupture et basé sur une approche multi-critères a été développé dans le but d'initier une méthodologie de dimensionnement de pièces composites à fibres discontinues. Ces critères d'endommagement et de rupture ont été développés en accord avec les observations du comportement mécanique du matériau. L'ensemble des résultats expérimentaux et numériques a été appliqué à la fabrication et au dimensionnement d'un démonstrateur technologiqueComposite materials are widely used in aeronautics. Their high mechanical properties combined to their lightness make it possible for thern to compete With metallic materials. However mass production of complex 3D shape composite structural parts is not usual.Injection process of short fibers (100um à 1 mm) filted thermoplastics is well known. Nevertheless there are few studies about long fibers (>1 mm) filled thermosets. It is very difficult to make the material flow into a closed mold.Equip iAéro Technique carried out research on the deve(opment of a new injection-transfer process (called PIMOC) to manufacture long discontinuous fibers filled thermoset composites. This process makes it possible to produce one shot complex 3D shape parts without machining.ln this work, the injection-transfer process has been developed and is now reliable. Its main parameters have been identified. The influence of manufacuring parameters on material properties have been determined, Thus mechanical properties have been optimizecl. Finally an elastic damage model has been devetoped in order to introduce a methodology or sizing discontinuous fibers composite parts. The model includes failure and is based on a multi-criteria approach. Theses damage and failure criteria have been deveioped according to observations of material mechanical behavior. Experimental and numerical results have been applied for sizing and manufacturing a technical demonstrator
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Riul, Cassius. „Desenvolvimento de compósitos estruturais de politetrafluoretileno (PTFE) com fibras contínuas“. Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-14082011-104816/.
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Este trabalho apresenta o desenvolvimento de compósitos estruturais de politetrafluoretileno (PTFE) com fibras de vidro contínuas e tem como objetivo a obtenção de um compósito com propriedades mecânicas que possibilite o uso em aplicações estruturais e que mantenham as características inerentes do PTFE sem reforços, tais como: baixo coeficiente de atrito, baixa interação química e elevada temperatura de trabalho. O PTFE é um polímero termoplástico, mas sua elevada viscosidade no estado fundido impede a utilização de moldagem por injeção. Componentes fabricados com PTFE são geralmente obtidos por compactação a frio do material granulado seguido de tratamento térmico. Neste estudo foi desenvolvida uma metodologia de fabricação de um laminado de PTFE e fibras contínuas, a partir do empilhamento, prensagem e tratamento térmico, de tecidos de fibra de vidro impregnados com PTFE. Foram estudadas as influências dos parâmetros de fabricação (prensagem e tratamento térmico) e de mecanismos que levam à degradação do laminado durante a fabricação, nas propriedades mecânicas finais dos compósitos. Foi também estudada a adição de uma quantidade complementar de PTFE ao laminado, com o intuito de se averiguar a possibilidade de se obter compósitos com revestimentos mais espessos de PTFE. O laminado foi avaliado por meio de ensaios de flexão 3-pontos e tração, para verificação dos ganhos na rigidez e resistência mecânica frente ao PTFE puro e por um ensaio de adesão fibra-matriz, baseado na norma ASTM D3167-03a. Como resultados, foram encontrados valores expressivos de resistência máxima aproximadamente 165 MPa e rigidez módulo de elasticidade de aproximadamente 14 GPa para valores adequados de processo de fabricação que minimizam efeitos de degradação dos laminados durante a fabricação. O trabalho mostrou a viabilidade de fabricação dos compósitos propostos e indicou uma rota a ser seguida para esta fabricação.This work presents a study of the manufacturing of Polytetrafluoretylene (PTFE) composite with continuous fibres, which has the purpose of obtaining a composite with mechanical properties equivalent or better than that of engineering polymers, but that preserve the characteristics of PTFE products with no reinforcement (as low friction coefficient, low chemical interaction and high work temperature amplitude). The PTFE is a thermoplastic material, however its high molten viscosity prevents the use of melt injection techniques, and its components are obtained through cold compaction process followed by sintering. In this study it is proposed a methodology of PTFE laminate with continuous fibre manufacturing. The laminate was obtained by the pilling of PTFE-coated glass-fibre fabric in a metallic mold for the pressing and that were sinterised afterwards. The mechanisms that lead to degradation of the laminate and process parameters which influence the final mechanical properties of the product were speciafied. It was also studied the possibility of addition of a larger quantity of PTFE to the laminate in order to verify the possibility of making continuous laminate coating. The material was analysed through three-point bending test and tensile test applied to the manufactured test specimen to verify the gains of mechanical stiffness and strength in comparison to the pure PTFE and an adhesion test based on ASTM D3167-03a. The experimental results showed significant values of mechanical stiffness and strength for appropriate values of process parameters that minimize the effects of degradation of the laminate.
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Cadu, Thomas. „Contribution au développement de l'utilisation des fibres naturelles dans les composites structuraux. Étude du comportement d'un composite Lin/Epoxy lors d'un vieillissement hygrothermique“. Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK055/document.
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Les composites bio-sourcés et notamment à base de fibres de lin connaissent depuis quelques années un regain d’intérêt, particulièrement dans les domaines des transports, de la mobilité et des loisirs. En effet, le faible coût énergétique et environnemental de la fibre de lin lui confère un avantage face à la fibre de verre, tout en la concurrençant en termes de propriétés mécaniques spécifiques. Cependant le comportement à long terme en environnement humide des composites à base de fibres de lin reste méconnu et constitue un frein à leur utilisation à plus grande échelle. Les objectifs de ces travaux sont de donner des clés pour produire un composite lin/époxy de haute qualité et de contribuer à l’amélioration de la connaissance de la durabilité de ces matériaux. Tout d’abord, l’influence de nombreux paramètres de mise en œuvre [(i) le pré conditionnement des renforts, (ii) la température de cuisson, (iii) la pression appliquée lors de la cuisson, (iv) la vitesse de refroidissement, (v) la température de sortie de la plaque, (vi) la température de post-cuisson et (vii) la durée de post-cuisson] sur les propriétés mécaniques des composites a été étudiée afin d’obtenir des matériaux de haute qualité. Une méthode de vieillissement « réaliste » a ensuite été développée afin d’étudier la durabilité de ce type de composites en présence d’eau. Des cycles de vieillissements hygrothermiques ont ainsi été menés en laboratoire sur des éprouvettes de composite, de résine et des faisceaux de fibres. Puis des analyses multi-échelles basées sur des caractérisations physico-chimiques, microstructurales et morphologiques du composite lin/époxy au cours de ce vieillissement ont permis de mieux comprendre les mécanismes responsables de leurs évolutions de propriétés mécaniques longitudinales et transverses au cours du tempsIn recent years there is renewed interest for bio-sourced composites, including those based on flax fibers, and especially in the field of transport, mobility and leisure. In fact, the lower energy cost and environmental impact of flax fiber give it an advantage over glass fiber, while competing with its specific mechanical properties. However, flax fibers based composites long-term behavior remains poorly known in damp environments and constitutes an obstacle to a wider use. This work aims to provide adapted parameters to produce a high-grade flax/epoxy composite and to contribute to improve the durability knowledge of these materials. First, the influence of many processing parameters [(i) conditioning of the reinforcements, (ii) curing temperature, (iii) curing pressure, (iv) cooling speed, (v) exit temperature, (vi) post curing temperature and (vii) post curing duration] on the composites’ mechanical properties have been studied in order to manufacture high-grade materials. Then a “realistic” ageing method has been developed to study the durability of this kind of composites when exposed to water. Thus cyclic hygrothermal ageing has been applied to composite, resin and fiber bundles in the laboratory. Then multi-scale analyzes based on physicochemical, microstructural and morphological characterizations of the flax/epoxy composites helped to better understand the mechanisms responsible for the longitudinal and transverse mechanical properties’ evolutions over time
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Sandhu, Suki. „Process-microstructure studies in TiAl/SiCâ†f composites“. Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267847.
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Kennerley, Jonathan. „Recycling fibres recovered from composite materials using a fluidised bed process“. Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/12849/.
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This work is concerned with the characterisation and reuse of fibres recovered from end of life thermoset composites by fluidised bed thermal processing. Emphasis is placed on the properties of recovered glass fibres and their reuse in a dough moulding compound and a tissue product. The need for a recycling process is demonstrated by a survey of the market for thermoset composites with particular consideration given to the potential growth in automotive applications. A study of processes developed to recycle such materials and the effect on the structural properties of composites containing such recyclate shows that a process capable of generating recyclate of greater value is required, particularly for the case of contaminated materials. A review of investigations into the effect of prior heat treatment on the mechanical properties of glass fibres shows that their strength will be reduced by a deterioration of the fibre surface during fluidised bed thermal recovery but that their stiffness is likely to be unaffected. The implications of these effects on possible applications for the recovered fibres are described. Tests are reported on the structural properties of laminates containing heat treated glass cloth which show that there is a strength reduction which is both time and temperature dependent but that modulus is not significantly affected. Strength loss increases with up to 20 minutes heating but then remains constant. In some cases the strength loss can be reduced by resizing the cloth. Measurement of the properties of fibres recovered using the fluidised bed process shows that the recovered fibre strength decreases with increasing processing temperature. Glass and carbon fibres recovered at 450°C retain approximately 50% and 80% of their virgin strengths respectively. The Young's modulus of the recovered fibres is shown to be largely unaffected by the process for both glass and carbon fibres. Investigation of the lengths of the recovered glass fibres by image analysis techniques suggests that their distribution depends on the structure of the composite and the method of size reduction. A weighted mean fibre length of 3.5 mm to 5.5 mm is possible with the apparatus described in this thesis. The reduced reinforcement potential of the recovered fibres is confirmed by experiment. Recovered glass fibres are used to displace virgin fibres in a dough moulding compound. At replacement levels of up to 50% there is no significant effect on the mechanical properties of a compression moulded plate. Above this level, tensile, flexural and impact strengths are reduced and with complete replacement the reduction is by approximately 40%, 50% and 70% respectively. These results are confirmed on a pilot plant scale. Recovered glass fibres can be successfully incorporated with virgin fibres into a veil. Replacement of virgin fibres reduces both wet and dry strength because the recovered fibres are both shorter and weaker. The permeability of the veil is found to depend on its porosity and not its recovered fibre content. The experimental veils can be used to protect and improve the surfaces of mouldings.
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Sinden, Jane. „The electrokinetic aspect of cellulose fibres used in the papermaking process“. Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244904.
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Phillips, Steven. „Characterization of flax fibres for application in the resin infusion process“. Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119345.
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Increasing concerns over depleting natural resources has led to the development of so-called biocomposites based on fibres from renewable resources such as flax. Although these fibres are seeing use in some applications, there is a lack of understanding concerning their processing requirements in relation to their unique physical and chemical properties. Furthermore, there is limited information regarding the links between their processing behaviour and mechanical performance. With the aim of addressing these missing links, this thesis presents a methodology for characterizing flax fibres for application in the resin infusion process and considers two important case studies with the overall goal of improving the state-of-the-art for this class of materials.Flax fibres were first characterized at the fibre level by advancing contact analysis, thermal gravimetric analysis, scanning electron microscopy and helium pycnometry. The advancing contact analysis revealed a reduction in the polar component of surface free energy after the application of silane and diluted epoxy treatments. A methodology was then developed for the characterization of the compaction and permeability of flax-based fabrics for the modelling of the resin infusion process. These parameters were quantified and used as input in a 1D process model that included capillary pressure. The model predictions for flow front evolution were shown to be in good agreement with experimental data. Alkaline treatments were shown to increase the required compaction pressure for a given porosity due to an increase in fibrillation. This had direct implications in the context of resin infusion processing due to the coupled nature of flow and compaction in this process. Consequently, a mechanical characterization revealed a decrease in flexural properties for alkaline-treated flax/epoxy composites manufactured by resin infusion due to a decrease in fibre volume fraction. A decrease in flexural properties was also noted with increasing void content.In an effort to improve the state-of-the-art for this class of materials, a case study was carried out on the incorporation of nano-modifiers in the resin infusion process. Nanocellulose was incorporated by two novel techniques; a 'grafting' method and a wet-layup method that incorporated an aqueous NC solution in the resin infusion pre-filling stage. Both methods were shown to lead to an increase in damage to the composites after subjection to a drop-weight impact event which suggested that the nano-modifier did not increase the interlaminar properties. However, an increase in interlaminar shear strength was observed by a short beam test due to an increase in fibre volume fraction as a result of softening and lubrication effects arising from the use of the aqueous NC solution.A second case study addressed the primary source of voids in a class of flax/epoxy prepregs which are generally used as a benchmark for composites manufactured by the resin infusion process. A series of compaction tests and thermal gravimetric analysis suggested that moisture and resin starvation were the primary source of voids in commercially available prepregs. Panels manufactured in an autoclave at varying pressures suggested that the latter of these issues was the dominant problem for the studied materials. The presence of voids was finally shown to lead to increased moisture sorption for flax/epoxy composites.This study stresses the coupled nature of the resin infusion process and the full implications of the use of chemical treated flax fibres. Additionally, it demonstrates the negative consequences of process-induced voids on the performance of flax/epoxy composites. It also provides useful data on the fibre surface chemistry, permeability, compaction and mechanical performance of flax-based composites. This assists in furthering the development of this class of materials with the goal of increasing their potential for use in load-bearing structures.La préoccupation avec l'épuisement des ressources naturelles a conduit à l'élaboration des bio-composites à base de fibres renouvelables telles que le lin. Bien que ces fibres sont utilisées dans certaines applications, il y a un manque de compréhension au sujet de leurs besoins de traitement par rapport à leurs uniques propriétés physiques et chimiques. En outre, il y a peu d'information sur les liens entre leur comportement et la performance des traitements mécaniques. Dans le but de répondre à ces liens inconnus, cette thèse présente une méthodologie de caractérisation des fibres de lin pour une utilisation dans le procédé d'infusion de résine et tient compte de deux études de cas importantes dans le but d'améliorer l'état-de-l'art pour cette classe de matériaux.Les fibres de lin ont d'abord été caractérisé au niveau des fibres en faisant l'analyse de l'angle de contact, analyse thermique gravimétrique, microscopie électronique à balayage et la pycnométrie hélium. L'analyse de l'angle de contact a révélé une réduction de la composante polaire de l'énergie de surface après l'application des traitements silane et époxy dilué. Une méthode a été ensuite développée pour la caractérisation de la compression et de la perméabilité de lin à base de tissus, pour la modélisation du processus d'infusion de résine. Ces paramètres ont été quantifiés et utilisés comme input dans un modèle de processus 1D qui comprenait la pression capillaire. Le traitements alcalin a démontré une augmentation de la pression de compactage nécessaire pour une porosité donnée, en raison de l'augmentation de la fibrillation. Par conséquent, une caractérisation mécanique a révélé une baisse de propriétés de flexion pour le lin/époxy composites fabriqués par infusion de résine pour des tissus traités avec alcalines en raison d'une diminution de la fraction volumique de fibres. Une diminution des propriétés en flexion a également été notée quand le contenu de vide augmente.Dans un effort pour améliorer l'état-de l'art pour cette classe de matériaux, une étude de cas a été réalisée sur l'incorporation de nano-modificateurs dans le procédé d'infusion de résine. Du nano-cellulose a été constituée par deux nouvelles techniques; une méthode de 'greffage' et un procédé 'wet-layup' qui intègre une solution aqueuse NC avant l'infusion. Les deux méthodes ont démontré une augmentation de l'endommagement des composites après avoir été soumis à des impacts, qui suggère que le nano-modificateur n'a pas augmenté les propriétés interlaminaires. Toutefois, une augmentation de la résistance au cisaillement interlaminaire a été observée par un faisceau de test court en raison d'une augmentation de la fraction volumique des fibres à la suite d'effets de ramollissement et de lubrification provenant de l'utilisation de la solution aqueuse NC.Une deuxième étude de cas a abordé la principale source de vides dans une classe de lin/époxy préimprégnés. Une série d'essais de compactage et d'analyse thermique gravimétrique suggère que la manque d'humidité et de résine ont été la principale source de vides dans préimprégnés disponibles. Des panneaux fabriqués dans un autoclave à pression variant suggére que le dernier de ces questions était le problème dominant pour les matériaux étudiés. La présence de vides a finalement causé une dégradation des propriétés d'absorption d'humidité pour les composites lin/époxy.Cette étude souligne le caractère couplé du procédé d'infusion de résine et les implications de l'utilisation de traitement chimique des fibres de lin. En outre, il met en évidence les conséquences négatives de vides sur la performance des composites lin/époxy. Il fournit également des données utiles sur la chimie de surface des fibres, perméabilité, le compactage et la performance mécanique des composites à base de lin. Cette aide favorise le développement de cette classe de matériaux dans le but d'augmenter leur potentiel d'utilisation dans des structures portantes.
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Pineda, Rocio Nahir. „Biocomposite with Continuous Spun Cellulose Fibers“. Thesis, Luleå tekniska universitet, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80968.
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The subject of this project is to study spun cellulose fibers made by Spinnova Oy inFinland. The fibers are spun using an environmentally friendly spinning process withoutuse of harsh chemicals.The spun filaments and the yarn based on these filaments were characterized and usedas reinforcement in polylactic acid biopolymer (PLA) and in biobased epoxy resin. Acomprehensive mechanical and morphological characterization of the single filamentsand their yarn was conducted. It was found that the single filaments are flat with a largewidth/thickness ratio, they are porous especially on one side and some cellulosemicrofibril orientation is observed on the filament surface. The single filaments are stiffand strong if compared to commercial regenerated cellulose filaments but are difficultto handle as they are very small and extremely light. The yarn showed to have lowermechanical properties but is easier to handle during the process of compositemanufacturing. Unidirectional fiber-reinforced composites were made using theSpinnova-yarn and PLA polymer applying film-stacking processing method. Thecomposite mechanical properties were studied and the results showed that themechanical performance of the PLA was significantly improved. The strength improvedfrom 54 MPa of the neat PLA to 95 MPa and the stiffness from 3.4 to 8.6 GPa withaddition of 22 wt% Spinnova-yarn.The main challenge of the project was handling the single filaments and their yarn todevelop a suitable manufacturing process which allows to exploit the potential of themto obtain a homogeneous fiber “preform” and to achieve good impregnation with the PLA matrix.
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Watts, Jeremy S. „Modeling the fiberglass spinning process“. Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5197.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains vii, 92 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 73-74).
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Pearce, Neil Robert Lewarne. „Process-property-fabric architecture relationships in fibre-reinforced composites“. Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/2596.
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The use of fibre-reinforced polymer matrix composite materials is growing at a faster rate than GDP in many countries. An improved understanding of their processing and mechanical behaviour would extend the potential applications of these materials. For unidirectional composites, it is predicted that localised absence of fibres is related to longitudinal compression failure. The use of woven reinforcements permits more effective manufacture than for unidirectional fibres. It has been demonstrated experimentally that compression strengths of woven composites are reduced when fibres are clustered. Summerscales predicted that clustering of fibres would increase the permeability of the reinforcement and hence expedite the processing of these materials. Commercial fabrics are available which employ this concept using flow-enhancing bound tows. The net effect of clustering fibres is to enhance processability whilst reducing the mechanical properties. The effects reported above were qualitative correlations. Gross differences in the appearance of laminate sections are apparent for different weave styles. For the quantification of subtle changes in fabric architecture, the use of automated image analysis is essential. Griffm used Voronoi tessellation to measure the microstructures of composites made using flow-enhancing tows. The data was presented as histograms with no single parameter to quantify microstructure. This thesis describes the use of automated image analysis for the measurement of the microstructures of woven fibre-reinforced composites, and pioneers the use of fractal dimensions as a single parameter for their quantification. It further considers the process-property- structure relationships for commercial and experimental fabric reinforcements in an attempt to resolve the processing versus properties dilemma. A new flow-enhancement concept has been developed which has a reduced impact on laminate mechanical properties.
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Grady, L. „The contribution of textile design to the development of a novel textile process“. Thesis, University of Huddersfield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233576.
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Kamble, Vishal D. „Optimization of thermoplastic pultrusion process using commingled fibers“. Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/kamble.pdf.
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Thesis (M.S.)--University of Alabama at Birmingham, 2008.Additional advisors: Burton Patterson, Derrick Dean, Selvum (Brian) Pillay. Description based on contents viewed Feb. 10, 2009; title from PDF t.p. Includes bibliographical references (p. 80-83).
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Musa, Shah Mohammed. „Improved draw process in optical fiber fabrication“. Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07212009-040405/.
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Xin, Yu. „Electrospinning Process and Resulting Nanofibers“. University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1321286561.
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Di, Francesco Mattia. „Laser-assisted automated fibre placement process development“. Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752749.
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Velarde, Santos Rina Esther. „Implementación de mejoras en el proceso de teñido disperso sobre fibra poliéster“. Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2013. https://hdl.handle.net/20.500.12672/12791.
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El presente trabajo expone la implementación de mejoras en el Proceso de Teñido en la Fibra de Poliéster, en la empresa Textil El Amazonas S.A. durante los años 2007-2011 hasta la fecha, como parte de la contribución profesional de ingeniería, que se descarga en el área de producción.
Los parámetros involucrados en el proceso de teñido son: el tipo de colorante disperso a usar, las condiciones de operación como: PH, temperatura, tiempo, auxiliares y material.
Los colores desarrollados, con un nuevo proceso de tintura rápida fueron con colorantes Rapid Dyeind que tuvieron mejores resultados que los colorantes que se encontraron, en la dirección anterior. Los resultados obtenidos demuestran un mejor desarrollo de color, en menos tiempo.
Las mejoras de la tintura, se consiguió realizando pruebas en laboratorio: bajando los tiempos, evaluando paralelamente los rendimientos del colorante y controlando las condiciones de operación. Así mismo en la planta se modificó la relación de baño, bajando el nivel de agua por ajustes mecánicos, en la máquina de teñido.
Con los cambios aplicados se ha conseguido aumentar el número de lotes producidos satisfactoriamente, elevando la producción diaria con el mismo número de maquinaria.
El ahorro que se obtiene, al tomar las medidas se refleja en la reducción de los costos al comparar entre los años 2007 antes y 2011 después del cambio bajando en un 10 % el costo de tintura.
Es recomendable continuar las investigaciones para mejorar y reducir el tiempo del proceso, implementar y hacer pruebas de nuevos procedimientos de auxiliares y acabados, con este proceso se mejora, para alcanzar permanentemente niveles de competitividad.Trabajo de suficiencia profesional
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Velarde, Santos Rina Esther. „Implementación de mejoras en el proceso de teñido disperso sobre fibra poliéster“. Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2012. https://hdl.handle.net/20.500.12672/14844.
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Publicación a texto completo no autorizada por el autorEl documento digital no refiere asesor
Expone la implementación de mejoras en el Proceso de Teñido en la Fibra de Poliéster, en la empresa Textil El Amazonas S.A. durante los años 2007-2011 hasta la fecha, como parte de la contribución profesional de ingeniería, que se descarga en el área de producción. Los parámetros involucrados en el proceso de teñido son: el tipo de colorante disperso a usar, las condiciones de operación como: PH, temperatura, tiempo, auxiliares y material. Los colores desarrollados, con un nuevo proceso de tintura rápida fueron con colorantes Rapid Dyeind que tuvieron mejores resultados que los colorantes que se encontraron, en la dirección anterior. Los resultados obtenidos demuestran un mejor desarrollo de color, en menos tiempo. Las mejoras de la tintura, se consiguió realizando pruebas en laboratorio: bajando los tiempos, evaluando paralelamente los rendimientos del colorante y controlando las condiciones de operación. Así mismo en la planta se modificó la relación de baño, bajando el nivel de agua por ajustes mecánicos, en la máquina de teñido. Con los cambios aplicados se ha conseguido aumentar el número de lotes producidos satisfactoriamente, elevando la producción diaria con el mismo número de maquinaria. El ahorro que se obtiene, al tomar las medidas se refleja en la reducción de los costos al comparar entre los años 2007 antes y 2011 después del cambio bajando en un 10 % el costo de tintura. Es recomendable continuar las investigaciones para mejorar y reducir el tiempo del proceso, implementar y hacer pruebas de nuevos procedimientos de auxiliares y acabados, con este proceso se mejora, para alcanzar permanentemente niveles de competitividad.
Trabajo de suficiencia profesional
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Jabbour, Lara. „Utilisation de procédés papetiers et de fibres cellulosiques pour l'élaboration de batteries Li-ion Elaboration of Li-ion batteries using cellulose fibers and papermaking techniques“. Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00998372.
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L'objectif du travail décrit dans cette thèse est de développer des batteries Li-ion peu coûteuses, respectueuses de l'environnement, facilement industrialisables et recyclables, tout en utilisant des fibres cellulosiques et un procédé en milieu aqueux. Deux approches ont été adoptées pendant ce travail expérimental. Dans un premier temps, les microfibrilles de cellulose ont été utilisées pour la production d'anodes par un procédé de casting. Puis, une approche papetière a été adoptée. La plupart des travaux expérimentaux se sont focalisés sur l'utilisation de fibres de cellulose pour la production d'électrodes papier (anodes et cathodes) et de séparateurs-papier par procédé de filtration en milieu aqueux pour obtenir des cellules complètes à base de cellulose. Les électrodes obtenues sont homogènes, souples et leurs propriétés électrochimiques comparables à celles d'électrodes de références utilisant un polymère de synthèse comme liant.
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Benavides, Rafael Esteban. „Gas Jet Process for Production of Sub-micron Fibers“. University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1365991608.
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Demir, Ali. „The air-jet yarn texturing process with particular reference to nozzle design and improved yarn test methods“. Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/12477.
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Khalf, Abdurizzagh. „Production of hollow fibers by co-electrospinning of cellulose acetate“. Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1908.
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Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009.The study concerns the use of the electrospinning technique for the formation of cellulose acetate hollow nanofibers. These hollow fibers are used to manufacture hollow fiber membranes. Important properties that should be inherent to these hollow-nanofibers include excellent permeability and separation characteristics, and long useful life. They have potential applications in filtration, reverse osmosis, and the separation of liquids and gases. It is apparent from the available literature on electrospinning and co-electrospinning that the diameter and the morphology of the resulting fibers are significantly influenced by variations in the system and process parameters, which include the solution concentration, solvent volatility, solution viscosity, surface tension and the conductivity of the spinning solution. The materials used include cellulose acetate (CA) (concentration = 11~14 wt %), (feed rate = 1~3 ml/h), acetone:dioxane (2:1) and mineral oil (feed rate = 0.5~1 ml/h) with core and shell linear velocity of 2 and 0.7 mm/min respectively. These materials were used as received without further purification. The co-electrospinning setup used comprised a compound spinneret, consisting of two concentric small-diameter capillary tubes/needles, one located inside another (core-shell/co-axial design). The internal and external diameters of the inside and outside needles were 0.3 and 1.2 mm respectively (0.3 mm shell/core gap space). The liquids CA (shell) and mineral oil (core) are pumped to the coaxial needle by a syringe pump, forming a compound droplet at the tip of the needle. A high voltage source is used to apply a potential of several kilovolts over the electrospinning distance. One electrode is placed into the spinning solution and the other oppositely charged (or neutral) electrode attached to a conductive collector. If the charge build up reaches approximately 15 kV the charged compound droplet, (poorly conductive polymer solution) deforms into a conical structure called a Taylor cone. On further increasing, the charge at the Taylor cone to some critical value (unique to each polymer system) the surface tension of the compound Taylor cone is broken and a core-shell jet of polymer solution ejects from the apex of the Taylor cone. This jet is linear over a small distance, and then deviates in a course of violent whipping from bending instabilities brought about by repulsive charges existing along the jet length. The core-shell jet is stretched and solvent is evaporated and expelled, resulting in the thinning and alignment of the fiber. Ultimately dry (most solvent having been removed) submicron fibers are collected in alignment form in a simple collector design (water bath). The shell to core solution flow rate ratio was chosen according to the parameter response of shell-core diameter of the resulting fibers in order to achieve an optimal hollow structure after removal of the mineral oil core. The mineral oil of the dry collected core-shell fibers is removed by immersion in octane. The aforementioned response is determined by measurement of core-shell diameters using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results showed that the ability of the spinning solution to be electrospun was directly dependent on its concentration and the feed rate of the spinning solution and also parameters such as the spinning distance and type of solvents used. The preferable polymer solution concentration is 14 wt %, shell feed rate of 3 ml/hr, core feed rate of 0.5 ml/hr (2 and 0.7 mm/s core and shell linear velocity respectively), applied voltage of 15 KV, spinning distance of 8 cm and coaxial spinnerets having internal diameters of 0.3 mm and 1.2 mm core and shell needles respectively (0.3 mm shell/core gap space) have been found to make uniform cellulose acetate hollow fibers with an average inside and outside diameter of approximately 495 and 1266 nm, respectively.
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Reme, Philip André. „Some effects of wood characteristics and the pulping process on mechanical pulp fibres“. Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1774.
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The thesis comprises three parts: Existing methods for characterisation of fibre crosssections have been improved, and new methods have been developed. These methods have then been applied to study the effects of wood characteristics and the pulping process on mechanical pulp fibres. Links have been established between fibre structure and paper properties such as surface smoothness and light scattering coefficient.
New methods, based on SEM-images and image analysis, are described for providing cross-sectional fibre dimensions for large fibre populations, for wood tracheids (app. 60 000 tracheids in a wood trunk) and for processed pulp fibres (app. 1000 fibres per sample). The methods are suited e.g. for evaluation of changes in the fibre cross-sections from wood to the finished paper, or for mapping of fibre parameters within and between growth rings in a wood trunk. The treatment of data is discussed, showing how one may examine the changes in different groups of fibres (earlywood fibres, latewood fibres, split fibres) throughout a process.
It is known from the literature that groundwood-based paper is superior to TMP-based paper with respect to printability. Fibres from SGW and PGW-pulp were found to be much more split in the longitudinal direction than TMP-fibres at comparable freeness. Intact groundwood fibres had thicker walls than intact TMP-fibres, but nevertheless super calendered hand sheets made from groundwood fibres were less roughened by moistening than were TMP-based sheets. Both for groundwood pulps and for TMPpulps, it was shown that reduced fibre wall thickness and increased fibre splitting was beneficial for improved surface smoothness and opacity.
Latewood defibrate easier than earlywood during refining. In the case of grinding, there was no particular preference for earlywood or latewood to be defibrated. Reject refining of groundwood reject was, however, found to be very important for defibration of latewood-containing shives. Pulps made from a raw material with more compact fibres (high wall area to lumen area ratio) were found to defibrate easier, and contain less shives. It was found that refining tends to reduce wall thickness most on thickwalled parts of the fibre, thus causing a reduction of the wall thickness variation around the perimeter.
Earlywood fibres were found to be preferentially split during refining. Most fibre splitting occurs during the primary stage, while the fibres are firmly attached to chips or fibre bundles. Latewood fibre wall thickness decreases considerably more than earlywood fibre wall thickness during refining. It seems that choosing an appropriate raw material is more effective than using excessive energy on reducing the wall thickness of thickwalled fibres. Earlywood fibres became more flattened during refining compared to latewood fibres, possibly due to repeated compressions and relaxations in the refiner.
The energy consumption to a given freeness was found to be considerably larger for Scots Pine than for Norway Spruce. However, the fibre transverse dimensions did not differ much between Norway Spruce and Scots Pine. Pine pulps were far less developed than spruce pulps at similar energy level. A possible explanation for the large energy consumption may be that redistribution of extractives at the fibre surface could reduce friction in the refiner. This hypothesis should be further explored.
The results in this study improve the knowledge of which fibre parameters that matter for surface smoothness and opacity of wood-containing publication paper. Further, this study elucidates how important fibre parameters such as wall thickness and fibre splitting are altered during a refining process. The results may be utilized to identify possible ways of modifying the TMP-process in order to produce paper with improved surface smoothness and opacity.
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Osorio, Sergio Paulo Amaral. „Fabricação e caracterização de fibras microestruturadas de vidros teluritos dopados com érbio“. [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278259.
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Orientador: Luiz Carlos BarbosaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Neste trabalho três tipos de vidro telurito são estudados, fabricados e caracterizados, tendo em vista a fabricação de fibras ópticas de cristal fotônico. Basicamente, dois processos de fabricação de fibras de cristal fotônico foram considerados: 1) Empilhamento e puxamento, e 2) Extrusão. Os vidros teluritos fabricados são: 0,77TeO2¿0,23WO3; 0,75TeO2¿0,20Li2O¿0,05TiO2 e 0,68TeO2¿0,155ZnO¿0,05Li2CO3¿0,015Bi2O3¿0,095CsCl (mol%), dos tipos binário, ternário e quinqüenário, respectivamente, os quais foram dopados com Er2O3. As caracterizações efetuadas foram: a) Medida do índice de refração, 2) Fotoluminescência, 3) Absorbância, 4) Tempo de vida dos íons de Érbio, 5) Análise Térmica Diferencial, 6) Análise termogravimétrica e, 7) Viscosidade. Como dito anteriormente, pode-se fabricar fibras microestruturadas de telurito por extrusão, ou pelo método de empilhamento e puxamento. A extrusora disponível no laboratório de materiais vítreos foi feita para extrudar materiais polímeros. Nossa tentativa de utilizá-la para vidros telurito não foi bem sucedida. Porém, pudemos tirar algum proveito desta experiência para futuros projetos. Os tubos de vidro telurito utilizados no método de empilhamento e puxamento foram fabricados tanto por sucção vertical do vidro fundido, quanto por rotação horizontal dos tubos em chama. No primeiro método, o diâmetro interno dos tubos de revestimento diminuiu de baixo para cima, devido ao efeito da gravidade, fazendo com que o preenchimento dos mesmos com tubos capilares fosse inadequado, ou seja, a secção transversal da fibra apresentou espaços vazios não preenchidos pelos capilares. No segundo método, o diâmetro interno dos tubos de revestimento não apresentou variação significativa ao longo de seu comprimento, possibilitando, assim, um melhor preenchimento dos mesmos por tubos capilares. Embora as fibras fabricadas com tubos feitos por rotação horizontal em chama apresentem boa geometria de secção transversal, a contaminação do vidro pela chama acarreta um aumento nas perdas de potência óptica dos modos guiados. Este efeito foi eliminado pela utilização de centrifugação em um forno radiante. Verificamos, também, que as fibras microestruturadas com somente um anel de capilares ao redor do núcleo apresentam grandes perdas por confinamento.
Abstract: In this work, three types of tellurite glasses are synthesized and characterized, aiming the manufacturing of photonic crystal fibers or microstructured fibers. Basically, two types of manufacturing processes are considered: 1) Stacking and draw, and 2) Extrusion. The tellurite glasses are: 0,77TeO 2¿0,23WO3; 0,75TeO2¿0,20Li2O¿0,05TiO2 e 0,68TeO2¿ 0,155ZnO¿0,05Li2C3¿0,015Bi2O3¿0,095CsCl (mol%), composed by two, three and five types of oxides, respectively, and Erbium oxide. The glasses were characterized by: a) index of refraction, 2) photoluminescence, 3) absorbance, 4) Erbium ions lifetime, 5) Differential Thermal Analysis, 6) Thermo gravimetric Analysis, and 7) Viscosity. The extrusion machine of the laboratory was devised for polymers. Nevertheless, we tried with telluride glass but without success. The tellurite glass tubes used for the stack and draw process were manufactured by vertical suction of the melted glass as well as by horizontal rotation of the tubes in flame. For the vertical suction method, the tellurite tube inner diameter shows a taper feature from the bottom to the top of the tube, due to the gravity effect, that makes the jacket tube unsuitable for capillary filling, that is, the fiber transversal section shows empty spaces that could not be filled with capillaries. For the second method, the telluride jacket tube inner diameter do not shows a significant variation with length, so it was possible to better fill it with the capillaries. Although the fibers made with tubes manufactured by horizontal rotation in flame shows good transversal geometry, the contamination of the glass by the flame gases brought about great losses for optical guided modes. The burner was replaced by a radiant oven. We verified, also, that micro structured fibers with only one ring of capillaries around the nucleus shows great confinement loss arising from the leaky nature of the modes
Doutorado
Física da Matéria Condensada
Doutor em Física
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James, Darryl L. „Thermal analysis of the continuous filament winding process“. Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16078.
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Vidart, Jacyara Moreira Martins 1988. „Simulação da difusão de corantes reativos em fibras de algodão“. [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266584.
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Orientador: Sergio Persio RavagnaniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O processo de tingimento empregado nas indústrias têxteis é de fundamental importância para o setor. A fim de garantir a satisfação dos consumidores, com produtos de boa solidez e uniformidade de cor, é necessário que o corante utilizado no processo de tingimento apresente alta afinidade com as fibras. Além da cobrança por parte dos consumidores em relação a produtos de alta qualidade, o setor têxtil enfrenta rígidas normas ambientais relacionadas ao lançamento de seus efluentes altamente tóxicos. Desta forma, a escolha de corantes e fibras com maior afinidade entre si se faz necessária para menor geração de resíduos, pois um tingimento com maior afinidade necessita de menor quantidade de auxiliares de tingimento e menor consumo de água. Conhecendo-se a difusividade de um corante em uma fibra, pode-se determinar a afinidade entre eles e, consequentemente, otimizar o processo de tingimento, escolhendo corantes com maior difusividade. Neste trabalho, buscou-se determinar os coeficientes de difusividade de corantes reativos Cosmos Bezaktiv S-C no tingimento de fibras de algodão. Para tanto, ensaios experimentais de tingimento foram realizados e, dados referentes à concentração de corante remanescente no banho de tingimento foram coletados. A partir dos dados obtidos experimentalmente, foi possível realizar a simulação computacional baseada na lei de difusividade de Fick para a determinação dos coeficientes de difusão dos corantes estudados. Os resultados mostraram que o modelo de difusão de Fick é adequado para a representação experimental do tingimento empregado. Além disso, os corantes Cosmos Bezaktiv S-C apresentaram alta difusividade nas fibras de algodão, sendo portanto, excelentes para este tipo de tingimento
Abstract: The dyeing process used in textile industries is very important to the sector. In order to guarantee the satisfaction of consumers with products of good color uniformity and strength, it is required that the dye used in the dyeing process has high affinity with the fibers. Besides collecting from consumers in relation to high-quality products, the textile sector is facing strict environmental standards related to the launch of its wastewaters highly toxic. Thus, the choice of dyes and fibers with higher affinity between them is required to generate less waste, since a dye with a higher affinity require fewer dyeing auxiliaries and lower water consumption. Knowing the diffusivity of a dye in a fiber, can be determine the affinity between them, and consequently optimize the dyeing process, by selecting dyes with higher diffusivity. In this study, we sought to determine the coefficients of diffusivity of reactive dyes Cosmos Bezaktiv S-C in dyeing of cotton fibers. To this end, experimental tests were carried out dyeing and data relating to the concentration of dye remaining in the dyebath was collected. From the experimental data, it was possible to carry out computer simulation based on Fick's law diffusivity for the determination of diffusion coefficients of the dyes studied. The results showed that the Fick's diffusion model is suitable for dyeing representation of experimental employed. In addition, the dyes Cosmos Bezaktiv S-C showed high diffusivity in cotton fibers, and therefore excellent for this kind of dyeing
Mestrado
Ciencia e Tecnologia de Materiais
Mestra em Engenharia Química
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Høiseth, Kjell. „A micromechanics study of transverse matrix cracking in cross-ply composites“. Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/16672.
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Pourmohammadi, Alireza. „Fibre dynamics in the air-laid nonwoven process“. Thesis, University of Leeds, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445201.
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Greaves, James David. „Numerical analysis of the outside vapor deposition process“. Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1183491109.
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Kong, Kenny. „Deformation micromechanics of process controlled cellulose fibres using Raman spectroscopy and X-ray diffraction“. Thesis, University of Manchester, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545914.
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Raman spectroscopy has been used to follow the defonnation micromechanics of a range of process---controlled fibres. The fibres were solvent spun using a N-methylmorpholine N-{)xide/ cellulose system. Single fibres are defonned in tension, and it is shown that the 1095 cm-l and 1414 cm-l Raman bands, corresponding to the C-O stretch mode and the side group (C-O--H) along the chain respectively, shift towards a lower wavenumber upon the application of external tensile defonnation. The shift profile of the 1095 cm-' band is shown to be non-linear, following the shape of the stress-strain curve, and the initial shift rate is shown to be directly related to the stiffness of the fibre. This band shift rate with respect to strain is shown to increase with increasing crystall ine orientation. The 1414 cm·1 band also shifts non-linearly and rapidly reaches a plateau with both strain and stress. This is thought to be due to the breakdown of hydrogen bonding in the structure, and a potential cause of the yield point in the mechanics of the fibres. The crystalline modulus and orientation of regenerated cellulose are measured using a wide-angle X-ray diffraction method. The crystalline modulus appears to vary with fibres having different orientations. It is shown that whilst the c-spacing of crystals increases with tensile stress, the crystalline fraction reorients to the direction of the fibre axis. An average shear modulus for these fibres is detennined by placing the data on a master curve and fitting with a model equation. Structure-property relationships are derived from the molecular and crystal defonnation characteristics of cellulose fibres using Raman spectroscopy and X-ray diffraction. This represents, for the first time, a full analysis of the relationship between structure and mechanics. at a local scale, of these regenerated cellulose fibres. Using a set of hypotheses tested on the experimental data, it is possible to distinguish unifonn stress and unifonn strain beha"iourNo portion of work referred to within this thesis has been submitted in support of an application for another degree or qualification of this or any other uni\crsity. or other institution of learning
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Kaimouz, Ahmad Wassim. „An investigation of the printing process for lyocell and cotton fibres using inkjet technology“. Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2366.
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Sample preparation has been described as the weak link in microfluidics. In particular, plasma has to be extracted from whole blood for many analysis including protein analysis, cell-free DNA detection for prenatal diagnosis and transplant monitoring. The lack of suitable devices to perform the separation at the microscale means that Lab On Chip (LOC) modules cannot be fully operated without sample preparation in a full-scale laboratory. In order to address this issue, blood flow in microchannels has been studied, and red blood cells behaviours in different geometrical environments have been classified. Several designs have been subsequently proposed to exploit some natural properties of blood flow and extract pure plasma without disturbing the cells. Furthermore, a high-level modelling method was developed to predict the behaviour of passive microfluidic networks. Additionally, the technique proposed provides useful guidance over the use of systems in more complex external environments. Experimental results have shown that plasma could be separated from undiluted whole blood in 10μm width microchannels at a flow rate of 2mL/hr. Using slightly larger structures (20μm) suitable for mass-manufacturing, diluted blood can be separated with 100% purity efficiency at high flow rate. An extensive biological validation of the extracted plasma was carried out to demonstrate its quality. To this effect Polymerase Chain Reaction (PCR) was performed to amplify targeted human genomic sequence from cell-free DNA present in the plasma. Furthermore, the influence of the sample dilution and separation efficiency on the amplification was characterised. It was shown that the sample dilution does have an influence on the amplification of house-keeping gene, but that amplification can be achieved even on high diluted samples. Additionally amplification can also be obtained on plasma samples with a range of separation efficiencies from 100% to 84%. In particular, two main points have been demonstrated (i) the extraction of plasma using combination of constrictions and bifurcations, (ii) the biological validation of the extracted plasma.
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Nair, Abilash Kumar Kochumulappon Raghavan. „Process and structural health monitoring of advanced fibre reinforced composites using optical fibre sensors“. Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5662/.
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The focus of this research was to design, optimise and deploy a practical multi-measurand sensor (MMS) for process monitoring of glass and carbon fibre preforms in an autoclave. The MMS design was based on the optical fibre-based extrinsic Fabry-Perot interferometric (EFPI) strain sensor. The EFPI sensor consisted of a pair of cleaved optical fibres, with a defined gap that were housed in a precision bore capillary. Interferometric interrogation was used to measure the cavity length hence, permitting the strain to be determined. The basic EFPI sensor design was modified in the following manner to enable multi-measurand monitoring. Firstly, a fibre Bragg grating (FBG) was inscribed on one of the optical fibres that were destined to be housed in the capillary; the end-face of this cleaved optical fibre was sputter coated with Au/Pd to produce a reflective surface. This FBG is in a relatively strain-free condition and only responds to temperature. Secondly, a technique was developed to manufacture optical-quality end-faces of the capillary and this too was sputter coated with Au/Pd. Thirdly, secondary cleaved optical fibres were packed around the lead-in optical fibre of the EFPI sensor with a defined (secondary) cavity thus, permitting transmission/reflection FTNIR spectroscopy. Finally, cleaved secondary optical fibres were also secured to the lead-in fibre and these served as Fresnel reflection sensors. The interrogation of the MMS was carried out using a conventional fibre-coupled multi-channel FTNIR spectrometer. The feasibility of monitoring strain, temperature, cross-linking kinetics and refractive index simultaneously during the processing of glass and carbon fibre preforms was demonstrated.
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Ghorbel, Amina. „Flottation réactive à l'ozone : impacts sur les qualités papetières, procédés, fibres et effluents des suspensions de fibres lignocellulosiques“. Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI042.
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L’objectif de cette étude est d’accroître les connaissances de l’effet de l’ozone introduit comme gaz réactif dans le procédé de flottation sur les performances du désencrage de papiers imprimés ainsi que sur les propriétés papetières des fibres cellulosiques recyclées (propriétés physiques et optiques, aptitude papetière). Des essais à forte dose d’ozone (2,97% par rapport à la masse de fibres) ont été investigués et conduits dans une cellule de flottation pilote de laboratoire (15 L). Plusieurs mélanges de papiers récupérés ont été étudiés : (i) un mélange 50%/50% magazines/journaux, (ii) deux mélanges modèles à base de fibres vierges sans bois (taux de lignine inférieure à 15%) pour limiter l’effet du jaunissement des fibres lignifiées, et (iii) un mélange industriel sans bois composé de 90% de papiers de bureaux et 10% de magazines. L’eau du réseau et une eau de procédé modèle ont été utilisées pour diluer les fibres avant désencrage. Pour une meilleure compréhension de la réactivité de l’ozone, des essais ont également été conduits sur les deux types d’eaux, en l’absence de fibre. Les principaux avantages du procédé de flottation réactive à l'ozone sont (1) la forte réduction de la DCO soluble dans les effluents jusqu’à 63% par rapport à la flottation à l’air dans le cas d’essais avec des papiers industriels, en utilisant une eau de procédé modèle, (2) l’augmentation du rendement en fibres de 1 point et (3) une conservation ou amélioration des propriétés papetières des fibres recyclées. L’ozone réagit préférentiellement avec les contaminants solubles de sorte que les fibres ne sont pas affectées.Ce procédé est tout à fait adapté au désencrage de papiers imprimés sans boisThe objective of this study is to broaden the knowledge about the effect of ozone, when introduced as a reactive gas in the flotation cell, on the deinking performance of printed papers as well as on the papermaking properties of recycled cellulosic fibers (physical and optical properties, papermaking ability). Trials, with high ozone dose (2.97% ozone/fibers w/w), have been investigated and conducted in a laboratory flotation cell pilot (15 L). Several mixtures of recovered papers have been studied: (i) an industrial mix made of 50%/50% magazines/newspapers, (ii) two wood-free recovered lignocellulosic fiber pulp models (lignin content lower than 15%) to limit the yellowing effect of lignified fibers, and (iii) a wood-free industrial pulp mixture composed of 90% office papers and 10% magazines. Tap water and model process water have been used to dilute the fibers before deinking. For a better understanding of the ozone reactivity, experiments have been also conducted on both types of waters in the absence of fiber. The main benefits of the ozone reactive flotation process are (1) the strong reduction of the effluent soluble COD of about 63% compared to air flotation in the case of the industrial pulp mixture deinking using the model process water, (2) the increase of the fiber yield by 1 point and (3) the preservation or the improvement of the papermaking properties of the recycled fibers. Ozone preferentially reacts with soluble contaminants, so that fibers and pulp papermaking properties are not affected. This process is utterly suitable for the deinking of wood-free papers
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Kokan, David R. „Development and use of an improved filament-winding process model“. Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/12261.
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Hong, Joohyun. „Structure-process-property relationships in polyester spun yarns : the role of fiber friction“. Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/10118.
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Kuan, Yean-Der. „Process-induced damage evolution and management in resin transfer molding of composite panels /“. free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9998490.
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Buggy, Stephen J. „Composite material process monitoring using optical fibre grating sensors“. Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/4035.
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In this thesis a long period grating (LPG) based sensor is investigated as a possible
alternative to current process monitoring sensors used in the manufacture of composites
to monitor cure. An LPG is demonstrated as a means of monitoring the cure of a UVcured
epoxy resin. The wavelength shift of the attenuation bands were measured during
the cure of the resin and compared with measurements made using a fibre optic Fresnel
based refractometer. The results showed a good correlation (6 x 10
-3
rius) and illustrate
the potential of the techniques for non-invasive composite material cure monitoring.
Alternative fibre grating methods; a chirped LPG sensor, an in-fire Mach-Zehnder
interferometer and a tilted fibre Bragg grating sensor, are also presented to demonstrate
the versatility of grating based sensors for flow, high sensitivity refractive index and
multi-parameter sensing, respectively. Demonstrations of LPG sensors in industrial
applications are also presented and highlight the technical issues of integrating such
devices in composite components and composite manufacturing processes.
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Yang, Ruodan. „A systematic statistical approach to polypropylene fibre process technology“. Thesis, Heriot-Watt University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440329.
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Del, Campo Menoyo Javier. „Compatibilisation of polyimide-silica ceramers and interfacial interactions with carbon fibres in high-temperature matrix composites“. Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/27080.
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When the inorganic domain sizes in a composite are reduced to a level such that a "molecular composite" is formed, the hybrid materials are commonly referred to as "ceramers". Hybrid materials span from inorganically modified organic polymers to inorganic g1asses slightly modified by organic polymers. The incorporation of an inorganic phase into an organic polymer is done almost exclusively by the "sol-gel" process.
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França, Morgana Cristina. „Produção de painéis aglomerados de fibras oversize de uma indústria de mdf“. Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/1949.
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Previous issue date: 2015-02-06The motivation for the development of this study was the use of an oversize fibers MDF company that had already incorporated resin and paraffin in its structure, for the manufacture of a new product. As a result it would reduce the emission of gases (formaldehyde), because when the raw material is discarded, it can be used .Thus, the objective of this study was to evaluate the technical feasibility of the production of particleboard from oversize fibers taken from the MDF production process through the technological properties of the panels. The raw material which was used, was composed of flake particles, a MDP company, and resin-coated fibers removed before the formation of the mattress of MDF panels, both formed by the mix of Pinus taeda and Pinus elliottii. The experiment involved 14 treatments: 10 treatments with homogeneous panels in the proportions 100 parts of particles to 0 shares fibers, 75:25, 50:50, 25:75, 0: 100, and 4 multi treatments particles in the core, at the fiber surface and the reverse composition. It is noted that each composition was evaluated at two levels of resin, 8% and 12%. Assays were developed in accordance with ASTM D1037 (1993), DIN 52 362 (1982) e NBR 14810 (2006). The results were evaluated by using factor analysis and multiple comparisons with Scott- Knott to 95% probability. In addition, the data were compared with reference standards. As a result, it showed a positive influence of the use of resin-coated oversize fibers and the application of 12% resin in technological properties. Thus, the best study treatments were homogenous panels amount of oversize fibers above 50% and multilayer boards with fibers in the surface layers
A motivação para o desenvolvimento do presente estudo foi a utilização de fibras oversize de uma empresa de MDF que já possuíam incorporadas em sua estrutura resina e parafina, para a fabricação de um novo produto. Em consequência a isso se reduziria a emissão de gases (formaldeído), pelo fato da matéria prima, quando descartada, ser utilizada na geração de energia (queima). Desta forma, o objetivo do presente estudo, foi avaliar a viabilidade técnica da produção de painéis aglomerados a partir de fibras oversize retiradas do processo de produção de MDF por meio das propriedades tecnológicas dos painéis. A matéria-prima utilizada foi composta por partículas flake, de uma empresa de MDP, e fibras resinadas retiradas antes da formação do colchão dos painéis MDF, ambas formadas pelo mix de Pinus taeda e Pinus elliottii. O delineamento experimental envolveu 14 tratamentos, sendo: 10 tratamentos com painéis homogêneos nas proporções 100 partes de partículas para 0 partes de fibras, 75:25, 50:50, 25:75, 0:100, e 4 tratamentos multicamadas com partículas no miolo, fibras na superfície e na composição inversa. Salienta-se que cada composição foi avaliada em dois teores de resina, 8% e 12%. Os ensaios foram desenvolvidos de acordo com a ASTM D1037 (1993), DIN 52362 (1982) e NBR 14810 (2006). Os resultados foram avaliados por meio de análise fatorial e comparação múltipla com Scott-Knott a 95% de probabilidade. Além disso, os dados foram comparados com normas de referência. Como resultados, foi verificada a influência positiva da utilização de fibras oversize resinadas e da aplicação de 12% de resina nas propriedades tecnológicas. Desta forma, os melhores tratamentos do estudo foram compostos por painéis homogêneos com quantidade de fibras oversize acima de 50% e painéis multicamadas com fibras nas camadas superficiais
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Vilcayauri, Rios Ademir Alejandro. „Estado de la tecnología del proceso de moldeo rotacional de polímeros reforzados con fibras naturales“. Bachelor's thesis, Pontificia Universidad Católica del Perú, 2020. http://hdl.handle.net/20.500.12404/18374.
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El moldeo rotacional de polímeros es un proceso seleccionado únicamente con el objetivo de fabricar objetos huecos, mediante la rotación de un molde dentro de un horno. La aparente simplicidad del proceso no incentivó la investigación ni su desarrollo. En los últimos 20 años se ha perfeccionado este proceso y sus productos, asimismo se ha ampliado la diversidad de materiales que pueden ser empleados como materia prima. Con el fin de reducir costos y tener buenas propiedades mecánicas en los productos, se fabricaron materiales compuestos reforzados con fibras naturales tales como: sisal, linaza, hoja de plátano, cáscara de arroz, salvado de trigo, agave, coco, abacá y madera, entre otras. Los investigadores estudiaron el sinterizado de diferentes matrices y fibras natural, así como el tratamiento químico del refuerzo y determinaron los parámetros de fabricación para obtener el mejor comportamiento mecánico.
El objetivo del presente trabajo de investigación es realizar una revisión sobre el estado de la tecnología del proceso de moldeo rotacional de materiales compuestos de matriz polimérica reforzados con fibras naturales. En esta perspectiva, para todas las investigaciones exploradas, inicialmente se revisó acerca de los constituyentes empleados, así como la preparación y el tratamiento químico al que fueron sometidos. Luego, se identificó las condiciones de fabricación y los parámetros de moldeo: velocidades de giro de los ejes, temperaturas del horno, tiempos de calentamiento y enfriamiento. A continuación, se abordaron los diseños experimentales utilizados. Se presentaron los ensayos, las normas y las maquinas utilizadas. Finalmente, se realizó una comparación de las propiedades de los materiales resultantes. Como resultado de este trabajo se ha concluido que las muestras óptimas se encuentran en el rango de 10% y 20% en peso de refuerzo, ya que con cantidades mayores a 20% de fibras no se genera una buena adhesión entre matriz y refuerzo. Se alcanzaron incrementos en el módulo elástico fue de hasta 25% respecto a la matriz e incluso de hasta 56% cuando se trata químicamente el refuerzo. Sin embargo, la reducción de la resistencia a la tracción y a la flexión pertenecen al rango de 3% a 26% y de hasta 75%, en el caso de la energía absorbida al impacto; en todos los casos, el incremento por tratamiento químico es bajo o nulo. Para obtener una muestra con alto contenido de refuerzo, con el propósito de mejorar considerablemente sus propiedades, es necesario recurrir a un tratamiento químico; pero en muestras con cantidades menores a 20% de refuerzo, dicho tratamiento no brinda beneficios y solo representa un gasto económico.Trabajo de investigación
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Hehr, Adam J. „Process Control and Development for Ultrasonic Additive Manufacturing with Embedded Fibers“. The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461153463.
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Laurent, Fabrice. „Croissance de nanotubes de carbone sur des fibres de carbone : application aux matériaux composites“. Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH7632/document.
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Le travail présenté dans ce mémoire de thèse s’est inscrit dans le cadre du développement de la technologie flamme oxyacétylénique pour la synthèse de nanotubes de carbone (NTC) au Laboratoire de Physique et Mécanique Textile. La simplicité et l’originalité de ce procédé en font un candidat très sérieux pour envisager la mise en œuvre d’un pilote industriel pour la production de fibres de renforcement multidimensionnelles, notamment composées de fibres de carbone sur lesquelles ont cru de nanotubes de carbone. Ce travail a consisté à :- Réaliser une étude bibliographique sur les procédés de croissance de NTC,- Etablir la preuve de concept de la croissance des nanotubes sur des fibres,- Concevoir et réaliser un dispositif assurant une bonne maîtrise de la croissance,- Mettre au point le procédé de croissance sur des fibres,- Identifier les principaux paramètres influençant la qualité et la quantité des nanotubes,- Caractériser les nanotubes obtenus,- Faire croître ces nanotubes sur des fibres de carbone,- Intégrer des nouveaux matériaux multidimensionnels dans des matrices afin de réaliser des matériaux composites structurels,- Caractériser ces matériaux,- Décrire les mécanismes de croissance dans la flamme.Notre effort a porté sur le traitement des fibres avant exposition à la flamme et à évaluer les conditions de croissance des NTC en faisant varier notamment, la température d’exposition des fibres et la qualité des catalyseurs de croissance. Après synthèse des NTC sur les fibres de carbone et leur caractérisation nous avons réalisé des matériaux composites. Nous avons mesuré que les NTC améliorent significativement le module d’Young des composites mais altèrent sensiblement la contrainte à la rupture. Les propriétés électriques longitudinales et transversales sont améliorées d’un facteur 8 et 5 respectivement. Nous avons proposé des mécanismes de croissance des NTC. Ces mécanismes sont directement en relation avec propriétés physiques et chimiques des particules de catalyseurThe research presented in this work aims to develop the oxyacetylene flame method for the Carbon Nanotubes (CNT) synthesis at the Laboratory of Physics and Mechanics of Textiles. The simplicity and the degree of innovation of this process make of it a serious candidate for manufacturing a pilot in order to produce new kind of tridimensional material made of CNT having grew on carbon fibres. This work consisted of:- Make a bibliographic study,- Establish a proof of concept of the growth of CNT,- Design and manufacture a device allowing process control,- Setup the process of growth on the fibres,- Identify the main parameters influencing CNT quality and quantity,- Characterize CNT,- Assume the CNT growth on carbon fibers,- Integrate these multidimensional materials into an organic matrix to realize structural composite materials,- Characterize these materials,- Describe and explain the growth mechanism in the flame.First, we focused our work on the fibres chemical treatment before flame exposition to evaluate the NTC growth conditions by varying notably, the fibres exposition temperature and the quality of the catalysts. After, the NTC syntheses on carbon fibres (CF) was done. The multidimensional product was characterized par various examinations and analyses. Composite materials were molded with epoxy resin to evaluate mechanical properties of NTC-FC. Young’s modulus was increased and tensile strength at break decreased. Transverse and longitudinal electrical properties were increased by 500 to 800 % respectively. Finally, we proposed NTC growth mechanisms. They are directly linked to the chemical and physical catalyst particles properties
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Berg, Jan-Erik. „Wood and fibre mechanics related to the thermomechanical pulping process“. Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-6725.
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The main objective of this thesis was to improve the understanding of some aspects on wood and fibre mechanics related to conditions in the thermomechanical pulping process. Another objective was to measure the power distribution between the rotating plates in a refiner. The thesis comprises the following parts: –A literature review aimed at describing fracture in wood and fibres as related to the thermomechanical pulping process –An experimental study of fracture in wood under compression, at conditions similar to those in feeding of chips into preheaters and chip refiners –An experimental study of the effect of impact velocity on the fracture of wood, related to conditions of fibre separation in the breaker bar zone in a chip refiner –A micromechanical model of the deterioration of wood fibres, related to the development of fibre properties during the intense treatment in the small gap in the refining zone –Measurements of the power distribution in a refiner. The fracture in wood under compression was investigated by use of acoustic emission monitoring. The wood was compressed in both lateral and longitudinal directions to predict preferred modes of deformation in order to achieve desired irreversible changes in the wood structure. It was concluded that the most efficient compression direction in this respect is longitudinal. Preferable temperature at which the compression should be carried out and specific energy input needed in order to achieve substantial changes in the wood structure were also given. The fibre separation step and specifically the effect of impact velocity on the fracture energy were studied by use of a falling weight impact tester. The fracture surfaces were also examined under a microscope. An increase in impact velocity resulted in an increase in fracture energy. In the thermomechanical pulping process the fibres are subjected to lateral compression, tension and shear which causes the creation of microcracks in the fibre wall. This damage reduces the fibre wall stiffness. A simplified analytical model is presented for the prediction of the stiffness degradation due to the damage state in a wood fibre, loaded in uni-axial tension or shear. The model was based on an assumed displacement field together with the minimum total potential energy theorem. For the damage development an energy criterion was employed. The model was applied to calculate the relevant stiffness coefficients as a function of the damage state. The energy consumption in order to achieve a certain damage state in a softwood fibre by uniaxial tension or shear load was also calculated. The energy consumption was found to be dependent on the microfibril angle in the middle secondary wall, the loading case, the thicknesses of the fibre cell wall layers, and conditions such as moisture content and temperature. At conditions, prevailing at the entrance of the gap between the plates in a refiner and at relative high damage states, more energy was needed to create cracks at higher microfibril angles. The energy consumption was lower for earlywood compared to latewood fibres. For low microfibril angles, the energy consumption was lower for loading in shear compared to tension for both earlywood and latewood fibres. Material parameters, such as initial damage state and specific fracture energy, were determined by fitting of input parameters to experimental data. Only a part of the electrical energy demand in the thermomechanical pulping process is considered to be effective in fibre separation and developing fibre properties. Therefore it is important to improve the understanding of how this energy is distributed along the refining zone. Investigations have been carried out in a laboratory single-disc refiner. It was found that a new developed force sensor is an effective way of measuring the power distribution within the refining zone. The collected data show that the tangential force per area and consequently also the power per unit area increased with radial position. The results in this thesis improve the understanding of the influence of some process parameters in thermomechanical pulping related wood and fibre mechanics such as loading rate, loading direction, moisture content and temperature to separate the fibres from the wood and to achieve desired irreversible changes in the fibre structure. Further, the thesis gives an insight of the spatial energy distribution in a refiner during thermomechanical pulping.
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Bates, Philip J. „Improving long-fibre compounding via a novel thermoplastic pultrusion process“. Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59584.
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A pultrusion process using staggered cylindrical pins in a molten polymer reservoir is one method of pre-compounding long glass fibre-reinforced thermoplastic materials. This material, if well impregnated with resin, will maintain much of its aspect ratio during subsequent moulding. The longer fiber length translates into improved mechanical properties versus conventional extrusion compounded material. This research studies the effect of a novel pin shape and configuration on the wetting of glass roving during thermoplastic pultrusion compounding.Experimental pultrusion studies using polypropylene indicate that alternating concave (collecting) and convex (spreading) contoured pins promote superior resin impregnation compared to conventional cylindrically shaped pins. A mathematical model describes the necessary convex pin contour and was used to fabricate the convex pins employed in the research. Pins thus designed promote uniform filament spreading across the wide convex contour which in turn favours good resin impregnation.
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Yip, Hang Leong Henry. „Recycling of carbon fibre composites using a fluidised bed process“. Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404048.
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King, David Gareth. „Fibre-optic sensor development for process monitoring of epoxy resins“. Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8698/.
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An investigation was undertaken to examine the performance of a Fresnel reflection sensor (FRS) incorporated into a differential scanning calorimeter (DSC) to track the cross-linking of epoxy resins. The initial design used a micrometer translation stage to lower the FRS through an orifice in the DSC platinum lid and onto the pan containing the sample. During exothermic cross-linking experiments, the resin refractive index and the heat evolved were measured simultaneously, allowing for direct comparison between the data. Combining the two measurement techniques produced a powerful hyphenated analytical procedure that demonstrated the feasibility of using the FRS for in-situ cure monitoring of epoxy resin systems. During the cross-linking of specified resins, the sensor revealed optical phenomena throughout the latter stages and was shown to be sensitive to the glass transition temperature, nano-particulate movement, nano-particulate concentration and phase separation. Therefore, the introduction of the FRS to the DSC provided valuable cross-linking information. A second modification to the DSC permitted the accommodation of an optical fibre probe, which facilitated simultaneous DSC/FRS/Fourier transform infrared spectroscopy (FTIRS) analysis. Good correlation between the cross-linking kinetics of an epoxy resin system was demonstrated using the hyphenated techniques and hence alleviated the issues of cross-correlation between individual experiments.