Os compósitos são materiais formados por duas fases de diferentes propriedades químicas e físicas, sendo uma matriz e um reforço, que apresentam alta rigidez, melhores respostas à fadiga sob cargas cíclicas, leveza e resistência mecânica, o que os torna viáveis para substituir materiais nobres e de custo elevado, com diversas aplicações na aeronáutica, nos esportes, na indústria bélica e principalmente na construção civil. Além disso, os compósitos podem ser obtidos a partir da incorporação de resíduos em sua composição, solucionando problemas como o descarte irregular. Com o intuito de contribuir nessa área de conhecimento o presente estudo propôs o desenvolvimento de um compósito em forma de placas poliméricas a partir da incorporação do agregado reciclado de poliuretana termofixa reciclado à resina vegetal de mamona e à mantas de fibra de vidro. Para isso, o trabalho estabeleceu uma metodologia na qual o resíduo industrial de poliuretana termofixa é transformado em agregado reciclado, a partir de processos de corte e moagem, caracterização e classificação segundo as normas NBR 10.004 a 10.007 (ABNT, 2004). Na sequência, com o auxílio de uma prensa térmica, foi possível confeccionar as placas poliméricas e caracterizálas quanto às suas propriedades mecânicas (tração, flexão, punção), físicas (absorção em água, inchamento, densidade e dureza), térmicas (condutividade térmica) e quanto ao seu potencial de durabilidade (resistência ao impacto, à abrasão superficial, ao ataque químico, à exposição ao ultravioleta e às intempéries, resistividade elétrica e flamabilidade). Os resultados obtidos por meio dos ensaios realizados apontaram que os parâmetros ensaiados comportaram-se como materiais semelhantes àqueles utilizados na construção civil, o que possibilita a utilização do material desenvolvido nesta pesquisa em aplicações por este setor. / This study proposes the development of a composite material in the form of polymer slabs. The material is created from the incorporation of recycled thermoset polyurethane to castor oil resin and glass fiber mats. Composite materials are formed by two phases with different chemical and physical properties. One phase is a matrix, and the other a reinforcement. These materials are highly stiff, light, have mechanical strength and present better responses to fatigue under cyclic loads. These properties make them a substitute for noble materials, being eligible for uses in aviation, sports, the arms industry and, specially, civil construction. Furthermore, composites may be obtained by the incorporation of residue, solving problems of waste disposal. In the procedures undertaken, the industrial waste of thermoset polyurethane is transformed into a recycled aggregate, achieved by the cutting, grinding, characterization and classification in compliance to the ABNT standards (NBR 10.004 to10.007). Afterwards, with the use of a thermal press, it was possible to produce the slabs and characterize them according to the following properties: mechanical (tensile strength, and puncture), physical (water absorption, swelling and stiffness), thermal (conductivity) and the potential durability (resistance to impact, abrasion, chemical attack. ultraviolet and weather exposure, electrical resistance, and flammability). The test results indicated that the composite behaves similarly to materials used in civil construction, which enables its use in the area.

En raison de leurs propriétés mécaniques, électriques et thermiques exceptionnelles, les nanotubes de carbone (NTC) ont reçu une importante attention mondiale. Les NTC ont un grand potentiel dans différents domaines d'applications tels que le stockage d'énergie et la microélectronique. Grâce à leur structure unidimensionnelle, leur important facteur d'aspect et leur faible densité, les NTC servent comme charges dans les composites. Par contre, en raison des fortes interactions entre eux, il est difficile de les disperser et de les aligner dans une matrice de polymère.Il est connu qu'une bonne conception d'hybrides, constitués de NTC verticalement lignés sur des substrats, améliore de manière significative la dispersion de ces derniers dans la matrice. Ces hybrides sont préparés par le procédé de dépôt chimique en phase vapeur (CVD). Une fois, ces hybrides sont dispersés dans la matrice du composite cela conduit à une nette amélioration des propriétés multifonctionnelles de ce composite. Les substrats utilisés dans cette thèse sont les nanoplaquettes de graphite (NPG) pour donner des hybrides NPG-NTC que nous appellerons par la suite GCHs. Les GCHs ont l'avantage d'avoir une faible densité et une structure totalement conductrice qui améliore les propriétés diélectriques et électriques des composites.Dans l'état de l'art, les relations entre l'organisation des GCHs et les conditions de synthèse par CVD et entre l'ajout des GCHs dans les composites et les réseaux conducteur interne dans les composites n'ont jamais été étudiées. Pour cela, dans cette thèse, nous allons soigneusement étudier et discuter ces problèmes mentionnés.Dans le premier chapitre, nous présentons une revue générale de la structure, des propriétés, des applications et de la synthèse des NTC et des NPG. Nous présentons aussi les procédures de l'intégration des nanoparticules dans des matrices polymères et les méthodes de fonctionnalisation des NTC. Nous discutons aussi des états électriques et les caractéristiques (di)électriques des composites en fonction de la quantité de la charge conductrice.Le deuxième chapitre présente tout d'abord la synthèse des NTC sur les NPG par CVD. Ensuite, l'influence des paramètres de la CVD, la température, la composition du gaz et le temps de la réaction, ont été étudié. Les résultats qualitatifs et quantitatifs obtenus d'après les caractérisations des ces hybrides peuvent servir comme base de données pour l'intégration et l'influence des ces hybrides dans les composites.Le troisième chapitre présente les composites binaires polyvinylidene fluoride/GCHs et leurs propriétés diélectriques qui sont nettement améliorées par rapport aux composites ternaires composés de polyvinylidene fluoride/NPG/NTC. Les composites obtenus par dispersion des GCHs dans la matrice à l'aide du procédé d'extrusion-injection, présentent un seuil de percolation fortement réduit (5,53 vol%) et une stabilité thermique relativement élevée. Leurs propriétés diélectriques améliorées peuvent être attribuées à des réseaux sous forme de micro-condensateurs et le changement de la cristallinité de la matrice peut être attribué à la bonne conception des hybrides.Le quatrième chapitre étudie les composites GCHs/polydiméthylsiloxane (PDMS) avec la haute performance piézo-résistive dans une large gamme de température. Le composite présente un seuil de percolation ultra-bas et une grande sensibilité piézo-résistive. En particulier, les autres améliorations des propriétés électriques obtenues dans les composites GCHs/PDMS par rapport à celles des composites à base de NTC/PDMS, de NPG/PDMS ou encore de NTC-NPG/PDMS. Les légers mouvements des doigts peuvent être détectés grâce à l'usage de ces films composites en tant que capteurs de mouvement. / Due to the outstanding mechanical electrical and thermal properties, carbon nanotubes (CNTs) received worldwide attentions and intensive investigations in last decades. CNTs are greatly potential in applications such as energy storage and microelectronics. The one dimensional structure, high aspect ratio and low density, promote CNTs serving as the excellent fillers in composites field. However, due to the strong interactions, CNTs are usually difficult to be dispersed and aligned in a polymer matrix. Designing the CNTs construction reasonably is an effective way to ameliorate the dispersion states of CNTs in matrix. These specific hybrid constructions allowed CNTs arrays synthesized vertically onto the substrates through catalyst chemical vapor deposition method. These CNT arrays effectively overcome the problem of CNTs aggregation and promote the interconnection among CNTs, leading to a considerable improvement of multi-functional properties of composites. Graphite nanoplatelets (GNPs) served as substrate make their synthesizing products-GNP-CNTs hybrids (GCHs) possess distinct merits of all-carbon composition, totally-conductive coupling structure and the low intrinsic density. These GCHs constructions provide a great improvement in the dielectric and electrical properties of composites. However, the relationship between GCHs organization and synthesizing conditions during CVD process and the influence of the addition of GCHs to internal conductive networks have not been reported in detail. These mentioned issues will be investigated and discussed in this thesis, which is divided into four chapters:The first chapter makes a general review of the structure, properties, application and synthesis of CNTs and GNP substrates, and the main procedures of fabricating composites and surface functionalization of CNTs. Moreover, a short introduction of the development of micro-nano hybrids applied to the functional composites is made. Most importantly, the developing electrical states and (di) electrical characteristics of composites with ever-increasing conducting filler loading are reviewed in detail at the last part.The second chapter discusses firstly the synthesis process through the CCVD approach and the relationship between CVD parameters and the corresponding construction of GCHs, where the temperature, gas composition and reaction time were controlled. The constructions CNT arrays are dependent on the synthesis conditions. Furthermore, the results obtained from analysis can provide a structural foundation for the huge application potential of GCHs constructions. The third chapter introduces the poly(vinylidene fluoride)-based nanocomposites containing GCH particles, the dielectric properties of which are improved more greatly than the ternary composites loading equivalent mixture of GNPs and CNTs. The composites achieved by dispersing GCH particles into matrix using the mechanical melt-mixing process, showing a strongly reduced percolation threshold (5.53 vol %) and the relatively high thermal stability. Their improved dielectric properties can be attributed to the formed microcapacitor networks and the change of crystalline formation of matrix, caused by well-designed CNT arrays constructions. The fourth chapter investigates the advanced GCHs/ polydimethylsilicone (PDMS) composites with high piezo-resistive performance at wide temperature range. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. The flexible composite shows an ultra-low percolation threshold (0.64 vol%) and high piezo-resistive sensitivity (gauge factor ~103 and pressure sensitivity ~ 0.6 kPa-1). Particularly, the much improvements of electrical properties achieved in GCHs/PDMS composites compared with composites filled with equivalent CNT, GNP or mixture of CNTs/GNPs. Slight motions of finger can be detected and distinguished accurately using the composites film as typical wearable sensor.

An intracranial aneurysm can be a serious, life-threatening condition which may go undetected until the aneurysm ruptures causing hemorrhaging within the brain. The typical treatment method for large aneurysms is by embolization using platinum coils. However, in about 15% of the cases treated by platinum coils, the aneurysm eventually re-opens. The solution to the problem of aneurysm recurrence may be to develop more bio-active materials, including certain polymers, to use as coil implants. In this research, a shape memory polymer (SMP) was investigated as a potential candidate for aneurysm coils. The benefit of a shape memory polymer is that a small diameter fiber can be fed through a micro-catheter and then change its shape into a three-dimensional configuration when heated to body temperature. The SMP was tested to determine its thermo-mechanical properties and the strength of the shape recovery force. In addition, composite specimens containing tantalum filler were produced and tested to determine the mechanical effect of adding this radio-opaque metal. Thermo-mechanical testing showed that the material exhibited a shape recovery force a few degrees above Tg. The effects of the metal filler were small and included depression of Tg and recovery force. SMP coils deployed inside a simulated aneurysm model demonstrated that typical hemodynamic forces would not hinder the shape recovery process. The x-ray absorption capability the tantalum-filled material was characterized using x-ray diffractometry and clinical fluoroscopy. Diffractometry revealed that x-ray absorption increased with tantalum concentration, however, not as the rule of mixtures would predict. Fluoroscopic imaging of the composite coils in a clinical setting verified the radio-opacity of the material.

The main theme of this dissertation is to engineer nanoporous materials and nanostructured surfaces for applications in gas separation membranes. Tunable methods have been developed to create inorganic hydroxide nanostructures on zeolite surfaces, and used to control the inorganic/polymer interfacial morphology in zeolite/polymer composite membranes. The study of the structure-property relationships in this material system showed that appropriate tuning of the surface modification methods leads to quite promising structural and permeation properties of the membranes made with the modified zeolites. First, a facile solvothermal deposition process was developed to prepare roughened inorganic nanostructures on zeolite pure silica MFI crystal surfaces. The functionalized zeolite crystals resulted in high-quality ̒mixed matrix̕ membranes, wherein the zeolite crystals were well-adhered to the polymeric matrix. Substantially enhanced gas separation characteristics were observed in mixed matrix membranes containing solvothermally modified MFI crystals. Gas permeation measurements on membranes containing nonporous uncalcined MFI revealed that the performance enhancements were due to significantly enhanced MFI-polymer adhesion and distribution of the MFI crystals. Solvothermal deposition of inorganic nanostructures was successfully applied to aluminosilicate LTA surfaces. Solvothermal treatment of LTA was tuned to deposit smaller/finer Mg(OH)₂ nanostructures, resulting in a more highly roughened zeolite surface. Characterization of particles and mixed matrix membranes revealed that the solvothermally surface-treated LTA particles were promising for application in mixed matrix membranes. Zeolite LTA materials with highly roughened surfaces were also successfully prepared by a new method: the ion-exchange-induced growth of Mg(OH)₂ nanostructures using the zeolite as the source of the Mg²⁺ ions. The size/shape of the inorganic nanostructures was tuned by adjusting several parameters such as the pH of the reagent solution and the amount of magnesium in the substrates and systematic modification of reaction conditions allowed generation of a good candidate for application in mixed matrix membranes. Zeolite/polymer adhesion properties in mixed matrix membranes were improved after the surface treatment compared to the untreated bare LTA. Surface modified zeolite 5A/6FDA-DAM mixed matrix membranes showed significant enhancement in CO₂ permeability with slight increases in CO₂/CH₄ selectivity as compared to the pure polymer membrane. The CO₂/CH₄ selectivity of the membrane containing surface treated zeolite 5A was much higher than that of membrane with untreated zeolite 5A. In addition, the use of metal organic framework (MOF) materials has been explored in mixed matrix membrane applications. ZIF-90 crystals with submicron and 2-μm sizes were successfully synthesized by a nonsolvent induced crystallization technique. Structural investigation revealed that the ZIF-90 particles synthesized by this method had high crystallinity, microporosity and thermal stability. The ZIF-90 particles showed good adhesion with polymers in mixed matrix membranes without any compatibilization. A significant increase in CO₂ permeability was observed without sacrificing CO₂/CH₄ selectivity when Ultem® and Matrimd® were used as the polymer matrix. In contrast, mixed matrix membranes with the highly permeable polymer 6FDA-DAM showed substantial enhancement in both permeability and selectivity, as the transport properties of the two phases were more closely matched.

Die im Folgenden vorgestellten Arbeiten sollen zur Erweiterung der Einsatzmöglichkeiten von WPC-Bauteilen beitragen, wobei die Untersuchung möglicher Fügetechnologien und ein praxisnahes Anwendungsbeispiel die Schwerpunkte bilden. Mittels Heizelement- und Vibrationsschweißens ist es gelungen, WPC-Bauteile sowohl mit gleichen Materialien als auch mit dem jeweiligen reinen Matrixmaterialien in Mischbauweisen zu verbinden. Deutlich werden hierbei verfahrensbedingte Einflüsse der Temperaturen bzw. des Energieeintrages, der Krafteinleitung (Fügedruck) sowie rezepturbedingte Einflüsse des Anteiles von Haftvermittlern. Durch entsprechende Verfahrensführung können Festigkeiten der Schweißverbindung im Bereich der WPC-Grundmaterialfestigkeit erreicht werden. Im Praxistest wurde das Dauerlaufverhalten eines Hybridprofils aus Aluminium und WPC in einem Hängefördersystem unter dynamischen Belastungen untersucht. Die Ergebnisse zeigen, dass die WPC-Bauteile des Hybriden den unterschiedlichen Beanspruchungen und den daraus resultierenden Verformungen nach in Summe 3000 h Testbetrieb, ohne sichtbare Schäden standhielten. Weiterhin waren keine Nachteile bezüglich der Praxistauglichkeit im Vergleich zu dem Standardprofil aus Aluminium feststellbar.

Cette thèse a pour but de contribuer à la mise au point et le développement, de plaques mono ou bipolaires composites pour piles à combustibles à membranes échangeuses de protons (ou PEMFC). Les plaques mono ou bipolaires (selon le type de refroidissement choisi) sont un élément essentiel au fonctionnement des piles car elles l’alimentent en gaz réactifs (hydrogène et oxygène de l’air), assurent la tenue mécanique des cellules, la séparation des compartiments anodique et cathodique, le collectage des électrons, et l’évacuation des « sous-produits » eau et chaleur. L’optimisation des propriétés physico-chimiques et mécaniques des plaques, et de leur procédé d’élaboration, permettra de rendre de ce fait la technologie pile à combustible plus accessible Après une étude bibliographique centrée sur les systèmes composites à taux de charges ou de renforts élevé et leurs propriétés physicochimiques, mécaniques et électriques, la 2ème phase sera axée sur une contribution à l’optimisation des formulations par des analyses morphologiques, physiques et physicochimiques pertinentes. La 3ème phase sera dédiée à l’analyse des plaques mono ou bipolaires après tests en piles afin de permettre des choix entre les différentes formulations ou procédés de mise en œuvre des plaques mono et bipolaires et dégager des paramètres pertinents reliés aux propriétés d’usage et à leur évolution au cours du temps en conditions réelles d’utilisation. / The objective of this work is to design carbon polymer composites for bipolar plates, with high and homogeneous electrical and mechanical properties. A method was designed in order to analyze the electrical conductivity homogeneity of the bipolar plates. Several designs of experiments were formulated after optimization of the most influencing formulation parameters on the use properties. This first step enhanced the use properties of the resulting materials, though insufficiently. The plates characterization showed highly heterogeneous and anisotropic use properties. The fabrication process conditions optimization (thermosets formulations) and the addition of an annealing step (thermoplastic formulations) then improved significantly the use properties and their homogeneity.

In diesem Paper werden Untersuchungen eines Tiefziehwerkzeugs aus Mineralguss vorgestellt. Der Grund für die Verwendung von Mineralguss als alternativen Werkstoff für schnelle Werkzeuge liegt in den relativ geringen Initialkosten zur Herstellung und seiner Eignung für Kleinserien und Prototypenversuche. Ähnliche Konzepte mit Werkzeugen aus Mineralguss haben gezeigt, dass eine entscheidende Grenze in der Tribologie und dem bei diesem Werkstoff großen Oberflächenverschleiß liegt. Daher fokussiert das vorliegende Paper auf die Ergebnisse der Analyse verschiedener Mineralgussmischungen unter Anwendung von Streifenzugbiegeversuchen. Die Reibzahl wurde hierbei berechnet und vergleichend einem Stahlwerkzeug gegenübergestellt. / This paper presents the investigation of polymer concrete drawing tools for deep drawing operations. The goal of using polymer concrete as an alternative material is a rapid tooling process at relatively low initial tools costs that is suitable for small batch production. Similar concepts based on hydraulic concrete and polymer composites have shown that the surface tri-bology and consequently wear is the main limiting factor. Therefore, this paper focusses on the results of strip draw-bending tests with different polymer concrete mixtures. The friction coefficient is calculated and compared to a steel tool.

Made available in DSpace on 2014-12-17T14:57:54Z (GMT). No. of bitstreams: 1 RenataCTSF_TESE_1-81.pdf: 4666386 bytes, checksum: 75d1cdda6a2cab121f77f0774f7de4e7 (MD5) Previous issue date: 2012-09-14 / There are a number of damaging mechanisms that various materials can suffer in service. However, when working with polymer composite materials, this is something that requires analysis, especially when exposed to adverse environmental conditions. Thus, the objective of the present thesis is the study of the direct influence of environmental aging and the form of hybridization of the reinforcement woven on the structural stability, surfacedegradation and fracture process of polymer composites laminates. For this, the development of two polymer composite laminates was necessary, where one of them was reinforced with a bi-directional woven with hybrid strandsofkevlar-49/glass-Efibers, and the other also with a bi-directionalwoven, however with weft and warpformed of alternating strandsof Kevlar-49 fibers and glass-E fiber The reinforcementwoven are industrially manufactured. Both laminates use a polyester resin as a matrixand are made up of four layers each. All laminates were industrially prepared by the hand lay-up method of manufacturing. To do this, test specimens were manufactured of the respective laminates and submitted to environmental aging accelerated through the aging chamber. They were exposed to alternating cycles of UV radiation and moisture (heated steam) for a standard defined period. At the end of the exposure period the specimens were subjected to mechanical tests of uniaxial tensile and bending in three points and to the characterizationsof the fracture and surface deterioration. In addition, they were submitted to a structural degradation assessment by the measurement of mass variation technique (MMVT) and the measurement of thickness variation technique (MTVT), this last technique being developed in this thesis. At the end of the analysis it was observed that the form of hybridization of the reinforcement woven and the aging process directly influence with losses or gain in mechanical properties, with losses in the structural degradation and in the formation and propagation of damage mechanism of the developedcomposite laminates / S?o v?rios os mecanismos de danos que os diversos materiais podem sofrer em servi?o. No entanto, ao se trabalhar com os materiais comp?sitos polim?ricos isso ? algo que necessita de an?lises principalmente quando expostos a condi??es ambientais adversas. Logo, a respectiva tese objetiva o estudo da influ?ncia direta do envelhecimento ambiental e da forma de hibridiza??o dos tecidos de refor?o no comportamento mec?nico, degrada??o estrutural (dimensional e de massa) de laminados comp?sitos polim?ricos. Para tanto se fez necess?rio o desenvolvimento de dois laminados comp?sitos polim?ricos, onde um deles ? refor?ado com um tecido bidirecional com mecha h?brida de fibras de kevlar-49/vidro-E e o outro com um tecido tamb?m bidirecional, por?m com trama e urdume formadas com mechas alternadas de fibras kevlar-49 e fibras de vidro-E. Os tecidos de refor?o s?o de fabrica??o industrial. Ambos os laminados utilizam como matriz a resina de poli?ster, sendo constitu?dos de quatro camadas cada. Todos os laminados foram confeccionados industrialmente pelo m?todo de fabrica??o handlay-up. Desta forma, foram fabricados corpos de provas (CP s) dos respectivos laminados e submetidos ao envelhecimento ambiental acelerado atrav?s da c?mara de envelhecimento. Os mesmos foram expostos aos ciclos alternados de radia??o UV e umidade (vapor aquecido) por um per?odo definido em norma. Ao t?rmino do per?odo de exposi??o os CP s foram submetidos aos ensaios mec?nicos de tra??o uniaxial e flex?o em tr?s pontos e ?s caracteriza??es da fratura e da deteriora??o superficial. Al?m disso, foram submetidos ? avalia??o da degrada??o estrutural mediante a t?cnica de media??o de varia??o de massa (TMVM) e a t?cnica de medi??o de varia??o de espessura (TMVE), sendo essa ?ltima desenvolvida nesta tese. Ao t?rmino das an?lises foi observado que a forma de hibridiza??o dos tecidos de refor?o e o processo de envelhecimento influenciam diretamente, seja com perdas ou ganho naspropriedades mec?nicas, com perdas na degrada??o estrutural e na forma??o e propaga??o do mecanismo de dano dos laminados comp?sitos desenvolvidos

Made available in DSpace on 2014-12-17T14:57:54Z (GMT). No. of bitstreams: 1 RaimundoNBF_TESE_1-104.pdf: 5288172 bytes, checksum: 0543c551bb4ef0aded2a4c286f66043d (MD5) Previous issue date: 2012-09-28 / The application of composite materials and in particular the fiber-reinforced plastics (FRP) has gradually conquered space from the so called conventional materials. However, challenges have arisen when their application occurs in equipment and mechanical structures which will be exposed to harsh environmental conditions, especially when there is the influence of environmental degradation due to temperature, UV radiation and moisture in the mechanical performance of these structures, causing irreversible structural damage such as loss of dimensional stability, interfacial degradation, loss of mass, loss of structural properties and changes in the damage mechanism. In this context, the objective of this thesis is the development of a process for monitoring and modeling structural degradation, and the study of the physical and mechanical properties in FRP when in the presence of adverse environmental conditions (ageing). The mechanism of ageing is characterized by controlled environmental conditions of heated steam and ultraviolet radiation. For the research, it was necessary to develop three polymer composites. The first was a lamina of polyester resin reinforced with a short glass-E fiber mat (representing the layer exposed to ageing), and the other two were laminates, both of seven layers of reinforcement, one being made up only of short fibers of glass-E, and the other a hybrid type reinforced with fibers of glass-E/ fibers of curaua. It should be noted that the two laminates have the lamina of short glass-E fibers as a layer of the ageing process incidence. The specimens were removed from the composites mentioned and submitted to environmental ageing accelerated by an ageing chamber. To study the monitoring and modeling of degradation, the ageing cycles to which the lamina was exposed were: alternating cycles of UV radiation and heated steam, a cycle only of UV radiation and a cycle only of heated steam, for a period defined by norm. The laminates have already undergone only the alternating cycle of UV and heated steam. At the end of the exposure period the specimens were subjected to a structural stability assessment by means of the developed measurement of thickness variation technique (MTVT) and the measurement of mass variation technique (MMVT). Then they were subjected to the mechanical tests of uniaxial tension for the lamina and all the laminates, besides the bending test on three points for the laminates. This study was followed by characterization of the fracture and the surface degradation. Finally, a model was developed for the composites called Ageing Zone Diagram (AZD) for monitoring and predicting the tensile strength after the ageing processes. From the results it was observed that the process of degradation occurs Abstract Raimundo Nonato Barbosa Felipe xiv differently for each composite studied, although all were affected in certain way and that the most aggressive ageing process was that of UV radiation, and that the hybrid laminated fibers of glass-E/curaua composite was most affected in its mechanical properties / A aplica??o dos materiais comp?sitos e em particular os pl?sticos refor?ados por fibras (PRF) tem conquistado espa?o, gradativamente, dos materiais ditos convencionais, por?m desafios t?m sido colocados quando sua aplica??o ocorre em equipamentos e estruturas mec?nicas que ficar?o expostos a condi??es ambientais adversas, principalmente quando se tem a influ?ncia da degrada??o ambiental do tipo temperatura, radia??o UV e umidade, no desempenho mec?nico dessas estruturas, ocasionando danos estruturais irrevers?veis tais como: perda de estabilidade dimensional, degrada??o interfacial, perda de massa, perda das propriedades estruturais e altera??es no mecanismo de dano. Neste contexto a presente tese tem como objetivo o desenvolvimento de um processo de monitoramento e modelagem da degrada??o estrutural, e o estudo das propriedades f?sicas e mec?nicas, em PRF quando em presen?a de condi??es ambientais adversas (envelhecimento). O mecanismo de envelhecimento ? caracterizado por condi??es ambientais controladas de vapor aquecido e de radia??o ultravioleta. Para a pesquisa foi desenvolvido tr?s comp?sitos polim?ricos, o primeiro uma l?mina de resina poli?ster refor?ado com manta de fibras curtas de vidro-E (representando a camada exposta ao envelhecimento) e dois laminados, ambos de sete camadas de refor?o, sendo um constitu?do s? com manta de fibras curtas de vidro-E, e o outro do tipo h?brido refor?ado com fibras de vidro-E/fibras de curau?. Ressalta-se que os dois laminados t?m a l?mina de fibras curtas de vidro-E como camada de incid?ncia do processo de envelhecimento. Os corpos de provas (CP s) foram retirados dos comp?sitos citados e submetidos ao envelhecimento ambiental acelerado atrav?s da c?mara de envelhecimento. Para o estudo do monitoramento e modelagem da degrada??o, os ciclos de envelhecimento a que foram expostos ? l?mina foram: ciclos alternados de radia??o UV e vapor aquecido, ciclo somente de radia??o UV e o ciclo somente de vapor aquecido, por um per?odo definido em norma. J? os laminados foram submetidos a apenas ao ciclo alternado de UV e vapor aquecido. Ao t?rmino do per?odo de exposi??o os CP s foram submetidos ? avalia??o da estabilidade estrutural mediante a t?cnica desenvolvida de medi??o de varia??o de espessura (TMVE) e a t?cnica de media??o de varia??o de massa (TMVM). Em seguida os mesmos foram submetidos aos ensaios mec?nicos de tra??o uniaxial para a l?mina e todos os laminados, al?m do ensaio de flex?o em tr?s pontos para os laminados. Esse estudo foi seguido da caracteriza??o da fratura e da degrada??o superficial. Por fim, foi desenvolvido um modelo para os Resumo Raimundo Nonato Barbosa Felipe xii comp?sitos denominado de Diagrama da Zona de Envelhecimento (DZE) para o monitoramento e predi??o da resist?ncia mec?nica ? tra??o ap?s os processos de envelhecimento. Ao t?rmino das an?lises foi observado que o processo de degrada??o se d? de forma diferente para cada comp?sito pesquisado, no entanto todos foram afetados, o processo de envelhecimento mais agressivo foi o de radia??o UV, e que o comp?sito que foi mais afetado em suas propriedades mec?nicas foi o laminado h?brido de fibras de vidro-E/curau?

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-26T13:42:32Z No. of bitstreams: 1 MÚCIO MARCOS SILVA NÓBREGA - TESE (PPGEP) 2007.pdf: 5674260 bytes, checksum: b79349f8d5a305a7090f3fa7ae22559e (MD5) / Made available in DSpace on 2018-09-26T13:42:32Z (GMT). No. of bitstreams: 1 MÚCIO MARCOS SILVA NÓBREGA - TESE (PPGEP) 2007.pdf: 5674260 bytes, checksum: b79349f8d5a305a7090f3fa7ae22559e (MD5) Previous issue date: 2007-11-21 / CNPq / O presente trabalho tem como objetivo o desenvolvimento de compósitos poliméricos reforçados com fibras de Caroá Neoglaziovia variegata para avaliação de seu desempenho mecânico, bem como suas características de sorção de água. Foi utilizado como matriz polimérica uma resina de poliéster insaturado e fibras de Caroá originárias do cariri paraibano. Os compósitos foram confeccionados com diferentes teores de fibras, cortadas em tamanhos de aproximadamente 3 cm, e moldados por compressão em molde metálico para avaliação das propriedades mecânicas. A composição de amostras de melhor desempenho mecânico foi escolhida para os ensaios de sorção de água, com amostras de 20x20mm² com 3cm e 6cm de espessura na temperatura de 25°C, 50°C e 70°C. Uma modelagem matemática tridimensional transiente foi usada para predizer a transferência de massa durante a sorção de água destes compósitos. Os resultados indicam que as propriedades mecânicas em tração dos compósitos estudados aumentam com o teor de fibras acima de 24% em massa até um volume crítico, em torno de 30%.Resistência ao impacto aumentou para todas as composições em virtude da eficiência de transferência de tensão para as fibras. Os resultados obtidos para o módulo de elasticidade dos compósitos evidenciam que estes são superiores ao da matriz, para todos os teores abaixo de 45% de fibras, o que é associado às características das fibras. A cinética de sorção de água nos compósitos mostrou ser influenciada pela relação área/volume. Pôde-se observar que em tempos curtos, aproximadamente 100 horas, os corpos com menor relação apresentam uma maior velocidade de sorção. Em tempos longos os compósitos com maior relação área/volume apresentam maiores teores de água sorvida. O teor de umidade de equilíbrio dos compósitos com 30% de fibras de caroá apresentaram valores de 14,48% à 25ºC e 16,52% à 70ºC, para as espessuras de 3 e 6 mm, respectivamente. A modelagem matemática utilizada para a obtenção da solução numérica de sorção de água nos compósitos reforçados por fibras de caroá foi adequada e satisfatória e a técnica de volumes finitos mostrou-se eficiente para discretizar a equação de difusão no sistema de coordenadas cartesianas para um sólido paralelepípedo, possibilitando a análise de fenômenos difusivos transientes nestes sólidos. / This research has the objective of developing polymeric composites enhanced with Caroá fibers Neoglaziovia variegata, in order to evaluate its mechanical performance and water sorption. It was used as polymeric matrix an unsaturated polyester resin and Caroá fibers originated from Paraiba state. The composites were made with different fiber contents, cut approximately with 3cm length and molded by compression in a metallic mould in order to evaluate its mechanical properties. The better mechanical composition of the sample was chosen to water sorption test in sample with dimension 20x20mm² and 3cm and 6cm thickness in the temperature of 25°C, 50°C and 70°C. A tri-dimensional transient mathematical modeling was used to predict mass transfer during the water sorption by these composites. Results indicates enhancement of mechanical properties of composites with 24% of mass made of the fibers until a critical volume of 30%. For the impact resistance this increases occurred for all compositions because of the transference of tension for the fibers. The results for elasticity modulus of composite shows that are higher than to the matrix for all fiber contents lower than 45%, which is related with the fiber properties. The water sorption kinetic was related with the area/volume relationship. We can observe that in short period of time, 100 hours, that composites with lower area/volume relationship absorbs water faster. On the order hand, the ones with higher area/volume relationship show more sorption in longer periods of time. The equilibrium moisture content for 30% fiber composite show results of 14.48% in 25°C and 16.52% in 70°C, for 3mm and 6mm thickness respectively. Mathematical models used to obtain numerical solution of water sortion in composites enhanced with Caroá fibers were satisfactory and the finite volume techniques was adequated to discretize the diffusion equation in Cartesian coordinate system for a parallelepiped solids, permitting the analyze of transient diffusive phenomena in this solids.