Made available in DSpace on 2014-12-17T14:58:20Z (GMT). No. of bitstreams: 1 AnaCMCB_DISSERT.pdf: 5204946 bytes, checksum: 70bedde30acbc8578034105c8c4fc24e (MD5) Previous issue date: 2013-07-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The utilization of synthetic fibers for plastic reinforcement is more and more frequent and this growing interest requires that their mechanic behavior under the most variable conditions of structural applications be known. The use of such materials in the open and exposed to the elements is one of them. In this case, it becomes extremely necessary to study their mechanical properties (strength, stiffness) and the mechanism of fracture by which the environment aging them out. In order to do that, the material must be submitted to hot steam and ultraviolet radiation exposure cycles, according to periods of time determined by the norms. This study proposal deals with the investigation of accelerated environmental aging in two laminated polymeric composites reinforced by hybrid woven made up of synthetic fibers. The configurations of the laminated composites are defined as: one laminate reinforced with hybrid woven of glass fibers/E and Kevlar fibers/49 (LHVK) and the other laminate is reinforced with hybrid tissue of glass fibers/E and of carbon fibers AS4 (LHVC). The woven are plane and bidirectional. Both laminates are impregnated with a thermofix resin called Derakane 470-300 Epoxy Vinyl-Ester and they form a total of four layers. The laminates were industrially manufactured and were made through the process of hand-lay-up. Comparative analyses were carried out between their mechanical properties by submitting specimen to uniaxial loading tractions and three-point flexion. The specimen were tested both from their original state, that is, without being environmentally aging out, and after environmental aging. This last state was reached by using the environmental aging chamber / O interesse na utiliza??o dos pl?sticos refor?ados por fibras sint?ticas ? cada vez mais crescente e esse grande interesse na utiliza??o dos mesmos faz com que seja necess?rio o conhecimento do comportamento mec?nico desses materiais sob as mais variadas condi??es de aplica??o estrutural. Dentre estas pode ser destacada a aplica??o desses materiais em situa??es em o elemento encontra-se exposto ? intemp?rie, e nesse caso os estudos das propriedades mec?nicas (resist?ncia, rigidez) al?m do mecanismo fratura frente ao envelhecimento ambiental s?o de extrema necessidade. Para tanto, submeter o material ? per?odos c?clicos de exposi??o ao vapor aquecido e ? de radia??o ultravioleta, por tempo definido em norma, se faz necess?rio. A presente proposta de trabalho de investiga??o consiste no estudo do envelhecimento ambiental acelerado em dois laminados comp?sitos polim?ricos refor?ados por tecidos h?bridos ? base de fibras sint?ticas. As configura??es dos laminados comp?sitos s?o definidas como: um laminado refor?ado com tecido h?brido de fibras de vidro/E e de fibras kevlar/49 (LHVK) e outro laminado refor?ado com tecido h?brido de fibras de vidro/E e de fibras de carbono AS4 (LHVC). Os tecidos s?o dos tipos planos e bidirecionais. Ambos os laminados foram impregnados a base de resina termofixa Derakane 470-300 Ep?xi Vinil-Ester e constitu?dos com quatro camadas no total. Os laminados t?m fabrica??o industrial e foram obtidos atrav?s do processo de lamina??o manual (Hand-lay-up). Foram realizados estudos comparativos entre as propriedades mec?nicas sob a a??o dos carregamentos de tra??o uniaxial e flex?o em tr?s pontos, nas condi??es dos corpos de prova sem o efeito do envelhecimento ambiental (estado original) e sob o efeito desse envelhecimento (estado envelhecido). O envelhecimento ambiental foi acelerado atrav?s do uso da c?mara de envelhecimento

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 HarrisonAD.pdf: 3488100 bytes, checksum: 805801db06d21e5667735d16a5799fe2 (MD5) Previous issue date: 2008-05-30 / The cobalt-chromium alloy is extensively used in the Odontology for the confection of metallic scaffolding in partial removable denture. During the last few years, it has been reported an increasing number of premature imperfections, with a few months of prosthesis use. The manufacture of these components is made in prosthetic laboratories and normally involves recasting, using parts of casting alloy and parts of virgin alloy. Therefore, the objective of the present study was to analyze the mechanical properties of a commercial cobalt-chromium alloy of odontological use after successive recasting, searching information to guide the dental prosthesis laboratories in the correct manipulation of the cobalt-chromium alloy in the process of casting and the possible limits of recasting in the mechanical properties of this material. Seven sample groups were confectioned, each one containing five test bodies, divided in the following way: G1: casting only with virgin alloy; G2: casting with 50% of the alloy of the G1 + 50% of virgin alloy; G3: casting with 50% of the alloy of the G2 + 50% of virgin alloy; G4: casting with 50% of the alloy of the G3 + 50% of virgin alloy; G5: 50% of alloy of the G4 + 50% of virgin alloy; G6: 50% of alloy of the G5 + 50% of virgin alloy and finally the G7, only with recasting alloy. The modifications in the mechanical behavior of the alloy were evaluated. Moreover, it was carried the micro structural characterization of the material by optic and electronic scanning microscopy, and X ray diffraction.and fluorescence looking into the correlatation of the mechanical alterations with structural modifications of the material caused by successive recasting process. Generally the results showed alterations in the fracture energy of the alloy after successive recasting, resulting mainly of the increasing presence of pores and large voids, characteristic of the casting material. Thus, the interpretation of the results showed that the material did not reveal significant differences with respect to the tensile strength or elastic limit, as a function of successive recasting. The elastic modulus increased from the third recasting cycle on, indicating that the material can be recast only twice. The fracture energy of the material decreased, as the number of recasting cycles increased. With respect to the microhardness, the statistical analyses showedno significant differences. Electronic scanning microscopy revealed the presence of imperfections and defects, resulting of the recasting process. X ray diffraction and fluorescence did not show alterations in the composition of the alloy or the formation of crystalline phases between the analyzed groups. The optical micrographs showed an increasing number of voids and porosity as the material was recast. Therefore, the general conclusion of this study is that the successive recasting of of Co-Cr alloys affects the mechanical properties of the material, consequently leading to the failure of the prosthetic work. Based on the results, the best recommendadition is that the use of the material should be limited to two recasting cycles / Ligas cobalto-cromo s?o extensivamente utilizadas na Odontologia para a confec??o de arma??es met?licas em pr?teses parciais remov?veis. Durante os ?ltimos anos, tem sido reportado um n?mero crescente de falhas prematuras, com poucos meses de utiliza??o das pr?teses. A fabrica??o desses componentes ? feita em laborat?rios prot?ticos e normalmente envolve a refundi??o, utilizando partes de liga fundida e partes de liga virgem. Portanto, o objetivo do presente estudo foi analisar as propriedades mec?nicas de uma liga comercial de cobalto-cromo de uso odontol?gico ap?s sucessivas refundi??es, buscando informa??es no sentido de orientar os laborat?rios de pr?tese dent?ria na correta manipula??o dessa liga no processo de fundi??o e nos poss?veis limites de refundi??o desse material. Foram confeccionados sete grupos de amostras, cada um contendo cinco corpos de prova, divididos da seguinte maneira: G1: fundi??o apenas com liga virgem; G2: fundi??o com 50% da liga do G1 + 50% de liga virgem; G3: fundi??o com 50% da liga do G2 + 50% de liga virgem; G4: fundi??o com 50% da liga do G3 + 50% de liga virgem; G5: 50% de liga do G4 + 50% de liga virgem; G6: 50% de liga do G5 + 50% de liga virgem e finalmente o G7, s? com liga refundida. Foram avaliadas as principais modifica??es ocorridas no comportamento mec?nico dessa liga por meio de ensaios de tra??o e microdureza. Al?m disso, foi realizada a caracteriza??o microestrutural do material por meio de microscopia ?ptica e eletr?nica de varredura, difra??o e fluoresc?ncia de raios X procurando correlacionar as altera??es mec?nicas com modifica??es estruturais do material ocasionadas pelos sucessivos processos de refundi??o. De forma geral os resultados mostraram altera??es na plasticidade e energia de fratura da liga ap?s sucessivas refundi??es, decorrentes principalmente da crescente presen?a de poros e vazios, defeitos caracter?sticos da fundi??o do material. A interpreta??o dos resultados permitiu concluir que o material n?o apresentou diferen?as significativas em rela??o ? resist?ncia ? tra??o ou ao limite el?stico, em fun??o das sucessivas refundi??es. A energia de fratura do material mostrou tend?ncia ? diminui??o, ? medida que o material foi refundido. Em rela??o ? microdureza, as an?lises estat?sticas mostraram n?o haver diferen?as significativas. A microscopia eletr?nica revelou a presen?a de falhas e defeitos, resultantes dos processos de refundi??es. A an?lise por fluoresc?ncia e difra??o de raios X n?o mostrou altera??es na composi??o da liga ou na forma??o de fases cristalinas entre os grupos analisados. As micrografias ?pticas mostraram um crescente n?mero de vazios e aumento da porosidade ? medida que o material foi refundido. Assim, a conclus?o geral do trabalho ? que as sucessivas refundi??es em ligas de Co-Cr comprometem as propriedades mec?nicas do material, o que pode levar a falhas e consequentemente, ao fracasso do trabalho prot?tico. Com base nos resultados, o mais recomendado ? a utiliza??o de no m?ximo duas refundi??es, para que as propriedades do material n?o sejam comprometidas

Made available in DSpace on 2014-12-17T14:07:07Z (GMT). No. of bitstreams: 1 MarcioCSM_TESE.pdf: 957118 bytes, checksum: 7c10d815ada900ecb0efde8936a6064e (MD5) Previous issue date: 2011-07-29 / The growing concern with the solid residues management, observed in the last decade, due to its huge amount and impact, has motivated the search for recycling processes, where these residues can be reprocessed to generate new products, enlarging the cycle of materials and energy which are present. Among the polymeric residues, there is poly (ethylene terephthalate) (PET). PET is used in food packaging, preferably in the bottling of carbonated beverages. The reintegration of post-consumer PET in half can be considered a productive action mitigation of environmental impacts caused by these wastes and it is done through the preparation of several different products at the origin, i.e. food packaging, with recycling rates increasing to each year. This work focused on the development and characterization mechanical, thermal, thermo-mechanical, dynamic mechanical thermal and morphology of the pure recycled PET and recycled PET composites with glass flakes in the weight fraction of 5%, 10% and 20% processed in a single screw extruder, using the following analytical techniques: thermogravimetry (TG), differential scanning calorimetry (DSC), tensile, Izod impact, Rockwell hardness, Vicat softening temperature, melt flow rate, burn rate, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The results of thermal analysis and mechanical properties leading to a positive evaluation, because in the thermograms the addition of glass flakes showed increasing behavior in the initial temperatures of thermal decomposition and melting crystalline, Furthermore was observed growing behavior in the mechanical performance of polymer composites, whose morphological structure was observed by SEM, verifying a good distribution of glass flakes, showing difference orientation in the center and in the surface layer of test body of composites with 10 and 20% of glass flakes. The results of DMTA Tg values of the composites obtained from the peak of tan ? showed little reductions due to poor interfacial adhesion between PET and recycled glass flakes. / A crescente preocupa??o com a gest?o de res?duos s?lidos, observada na ?ltima d?cada, em virtude de sua enorme quantidade e impacto ambiental, tem motivado a busca por processos de reciclagem, onde estes res?duos podem ser reprocessados de modo a gerarem novos produtos, ampliando o ciclo dos materiais e energia neles contidos. Dentre os res?duos polim?ricos, destaca-se o poli(tereftalato de etileno) (PET). O PET ? utilizado em embalagens de alimentos, preferencialmente, no envase de bebidas carbonatadas. A reintegra??o do PET p?s-consumo ao meio produtivo pode ser considerada uma a??o mitigat?ria dos impactos ambientais causados por estes res?duos e j? ? realizada por meio da obten??o de diversos produtos diferentes ao da origem, ou seja, embalagens para alimento, com taxas de reciclagem crescente a cada ano. Este trabalho focou o desenvolvimento e a caracteriza??o mec?nica, t?rmica, termo-mec?nica, termo-din?mico-mec?nica e morfol?gica do PET reciclado processado e dos comp?sitos de PET reciclado com flocos de vidro na fra??o em peso de 5%, 10% e 20% processados em uma extrusora rosca simples, utilizando as seguintes t?cnicas de an?lise: termogravimetria (TG), calorimetria explorat?ria diferencial (DSC), tra??o uniaxial, impacto Izod, dureza Rockwel, temperatura de amolecimento Vicat, ?ndice de fluidez, taxa de queima, an?lise termo-din?mico-mec?nica (DMTA) e microscopia eletr?nica de varredura (MEV). Os resultados das an?lises t?rmicas e das propriedades mec?nicas conduziram a uma avalia??o positiva, pois nos termogramas as adi??es dos flocos de vidro mostraram comportamento crescente nas temperaturas inicial de decomposi??o t?rmica e de fus?o cristalina, al?m disso, observou-se comportamento crescente no desempenho mec?nico dos comp?sitos polim?ricos, cuja estrutura morfol?gica foi observada por MEV, verificando uma boa distribui??o dos flocos de vidro, apresentando diferen?a na orienta??o no centro e na camada superficial do corpo de prova dos comp?sitos com 10 e 20% de flocos de vidro. Nos resultados de DMTA os valores de Tg dos comp?sitos obtidos a partir do pico de tan ?, apresentaram pequenas redu??es, devido a pobre ades?o interfacial entre o PET reciclado e os flocos de vidro.

Made available in DSpace on 2014-12-17T14:07:22Z (GMT). No. of bitstreams: 1 JorgeFSO_TESE.pdf: 9384301 bytes, checksum: 94f6528a142b55c3b875e331722c4d8d (MD5) Previous issue date: 2013-12-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / As most current studies, reinforced plastics have been, in recent years, a viable alternative in building structural elements of medium and large, since the lightness accompanied by high performance possible. The design of hybrid polymer composites (combination of different types of reinforcements) may enable structural applications thereof, facing the most severe service conditions. Within this class of composite materials, reinforced the underlying tissues hybrid high performance are taking space when your application requires high load bearing and high rigidity. The objective of this research work is to study the challenges in designing these fabrics bring these materials as to its mechanical characterization and fracture mechanisms involved. Some parameters associated with the process and / or form of hybridization stand out as influential factors in the final performance of the material such as the presence of anisotropy, so the fabric weave, the process of making the same, normative geometry of the specimens, among others. This sense, four laminates were developed based hybrid reinforcement fabrics involving AS4 carbon fiber, kevlar and glass 49-E as the matrix epoxy vinyl ester resin (DERAKANE 411-350). All laminates were formed each with four layers of reinforcements. Depending on the hybrid fabric, all the influencing factors mentioned above have been studied for laminates. All laminates were manufactured industrially used being the lamination process manual (hand-lay-up). All mechanical characterization and study of the mechanism of fracture (fracture mechanics) was developed for laminates subjected to uniaxial tensile test, bending in three and uniaxial compression. The analysis of fracture mechanisms were held involving the macroscopic, optical microscopy and scanning electron microscopy / Conforme estudos mais atuais, os pl?sticos refor?ados v?m sendo, nos ?ltimos anos, uma alternativa vi?vel na constru??o de elementos estruturais de m?dio e grande porte, desde que a leveza acompanhada de alto desempenho seja poss?vel. A concep??o de comp?sitos polim?ricos h?bridos (combina??o entre tipos diferentes de refor?os) pode possibilitar aplica??es estruturais dos mesmos, frente ?s mais adversas condi??es de servi?os. Dentro dessa classe de materiais comp?sitos, os refor?ados a base de tecidos h?bridos de alto desempenho v?m tomando espa?o quando a sua aplica??o requer alto suporte de carga e alta rigidez. O objetivo desse trabalho de investiga??o ? o estudo da influ?ncia que esses tecidos trazem na concep??o desses materiais quanto a sua caracteriza??o mec?nica e mecanismos de fratura envolvidos. Alguns par?metros associados ao processo e/ou forma de hibridiza??o se destacam como fatores influenciadores no desempenho final do material tais como a presen?a de anisotropia, forma da trama tecido, processo de confec??o dos mesmos, geometria normativa dos corpos de prova, entre outros. Neste sentido, quatro laminados comp?sitos foram desenvolvidos ? base de tecidos de refor?os h?bridos envolvendo fibras de carbono AS4, kevlar 49 e vidro-E e como matriz a resina ep?xi ?ster vin?lica (DERAKANE 411-350). Todos os laminados comp?sitos foram constitu?dos com quatro camadas de refor?os. Dependendo do tipo de tecido h?brido, todos os fatores influenciadores acima mencionados foram estudados para os laminados. Todos os laminados foram fabricados industrialmente sendo empregado o processo de lamina??o manual (hand-lay-up). Todo o estudo da caracteriza??o mec?nica e do mecanismo de fratura (fratura mec?nica) foi desenvolvido para os laminados submetidos aos ensaios mec?nicos de tra??o uniaxial, flex?o em tr?s e compress?o uniaxial. As an?lises dos mecanismos de fratura foram realizadas envolvendo a macroscopia, microscopia ?tica e eletr?nica de varredura

Made available in DSpace on 2014-12-17T14:57:56Z (GMT). No. of bitstreams: 1 SergioRLT_TESE_Capa_ate_pag58.pdf: 1954386 bytes, checksum: d88b3653eaeaeec9f2c0ce6f5549f9ef (MD5) Previous issue date: 2014-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The growing demand in the use of composite materials necessitates a better understanding of its behavior related to many conditions of loading and service, as well as under several ways of connections involved in mechanisms of structural projects. Within these project conditions are highlighted the presence of geometrical discontinuities in the area of cross and longitudinal sections of structural elements and environmental conditions of work like UV radiation, moisture, heat, leading to a decrease in final mechanical response of the material. In this sense, this thesis aims to develop studies detailed (experimental and semi-empirical models) the effects caused by the presence of geometric discontinuity, more specifically, a central hole in the longitudinal section (with reduced cross section) and the influence of accelerated environmental aging on the mechanical properties and fracture mechanism of FGRP composite laminates under the action of uniaxial tensile loads. Studies on morphological behavior and structural degradation of composite laminates are performed by macroscopic and microscopic analysis of affected surfaces, in addition to evaluation by the Measurement technique for mass variation (TMVM). The accelerated environmental aging conditions are simulated by aging chamber. To study the simultaneous influence of aging/geometric discontinuity in the mechanical properties of composite laminates, a semiempirical model is proposed and called IE/FCPM Model. For the stress concentration due to the central hole, an analisys by failures criteria were performed by Average-Stress Criterion (ASC) and Point-Stress Criterion (PSC). Two polymeric composite laminates, manufactured industrially were studied: the first is only reinforced by short mats of fiberglass-E (LM) and the second where the reinforced by glass fiber/E comes in the form of bidirectional fabric (LT). In the conception configurations of laminates the anisotropy is crucial to the final mechanical response of the same. Finally, a comparative study of all parameters was performed for a better understanding of the results. How conclusive study, the characteristics of the final fracture of the laminate under all conditions that they were subjected, were analyzed. These analyzes were made at the macroscopic level (scanner) microscope (optical and scanning electron). At the end of the analyzes, it was observed that the degradation process occurs similarly for each composite researched, however, the LM composite compared to composite LT (configurations LT 0/90? and LT ?45?) proved to be more susceptible to loss of mechanical properties in both regarding with the central hole as well to accelerated environmental aging / A crescente demanda na utiliza??o dos materiais comp?sitos torna imprescind?vel uma melhor compreens?o do seu comportamento frente ?s mais diversas condi??es de carga e servi?o, bem como sob as variadas formas de conex?es envolvendo mecanismos nos projetos estruturais. Dentro dessas condi??es de projeto destaque se faz para a presen?a de descontinuidades geom?tricas na ?rea de se??es transversal e ou longitudinal dos elementos estruturais, assim como, condi??es ambientais de servi?o como a radia??o UV, a umidade, o calor, que levam a um decr?scimo na resposta mec?nica final do material. Neste sentido, essa tese tem como objetivo o desenvolvimento de estudos (experimental e modelos semi-emp?ricos) detalhados dos efeitos causados pela presen?a de descontinuidade geom?trica, mais especificamente um furo conc?ntrico na se??o longitudinal (com redu??o da se??o transversal), assim como, da influ?ncia do envelhecimento ambiental acelerado nas propriedades mec?nicas e mecanismo de fratura de laminados comp?sitos de PRFV sob a a??o de cargas uniaxiais de tra??o. Estudos referentes ao comportamento morfol?gico e de degrada??o estrutural dos laminados comp?sitos s?o realizados, atrav?s de an?lises macrosc?picas e microsc?picas das superf?cies afetadas, al?m da avalia??o mediante a T?cnica de Media??o de Varia??o de Massa (TMVM). As condi??es de envelhecimento ambiental acelerado ser?o simuladas atrav?s da c?mara de envelhecimento. Para avalia??o da influ?ncia simult?nea do envelhecimento/descontinuidade geom?trica nas propriedades mec?nicas dos laminados comp?sitos, um modelo semi-empirico ? proposto e denominado de Modelo IE/FCPM. Para o caso da presen?a da concentra??o de tens?o devido ao furo conc?ntrico, a mesma ? avaliada a partir do uso dos crit?rios de falhas da Tens?o M?dia (Average-Stress Criterion) e da Tens?o Pontual (Point-Stress Criterion). Dois laminados comp?sitos polim?ricos, confeccionados industrialmente, foram estudados: o primeiro ? unicamente refor?ado com mantas de fibras curtas de vidro/E (LM) e o segundo onde o refor?o de fibras de vidro/E vem na forma de tecido bidirecional (LT). Na concep??o das configura??es dos laminados a presen?a da anisotropia ? fundamental para a resposta mec?nica final dos mesmos. Por fim, um estudo comparativo entre todos os par?metros foi realizado para uma melhor compreens?o dos resultados. Como estudo conclusivo, as caracter?sticas da fratura final dos laminados sob todas as condi??es que os mesmos foram submetidos, foram analisadas. Essas an?lises foram feitas em n?veis macrosc?pico (scanner) microsc?pico (?ptico e eletr?nico de varredura). Ao t?rmino das an?lises foi observado que o processo de degrada??o se d? de forma semelhante para cada comp?sito pesquisado, no entanto, o laminado comp?sito LM quando comparado ?s configura??es LT 0/90? e LT ?45? do laminado comp?sito LT, se mostrou mais suscept?vel a perda de propriedades mec?nicas tanto em rela??o ? presen?a do furo conc?ntrico como em rela??o ao envelhecimento ambiental acelerado

Made available in DSpace on 2014-12-17T14:58:04Z (GMT). No. of bitstreams: 1 JoseAMN_DISSERT.pdf: 2578831 bytes, checksum: 78ca7925672b7876fad1b54e774b3827 (MD5) Previous issue date: 2010-12-30 / With the objective to promote sustainable development, the fibres found in nature in abundance, which are biodegradable, of low cost in comparison to synthetic fibres are being used in the manufacture of composites. The mechanical behavior of the curau? and pineapple leaf fibre (PALF) composites in different proportions, 25% x 75% (P1), 50% x 50% (P2) e 75% x 25% (P3) were respectively studied, being initially treated with a 2% aqueous solution of sodium hydroxide. Mechanical analyses indicated that with respect to studies of traction, for the combination of P1 and P3, better results of 22.17 MPa and 16.98 MPa, were obtained respectively, which are higher than that of the combination P2. The results of the same pattern were obtained for analysis of bending resistance where P1 is 1.21% and P3 represents 0.96%. In the case of resistance to bending, best results were obtained for the combination P1 at 49.07 MPa. However, when Young's modulus values were calculated, the values were different to the pattern of the results of other tests, where the combination P2 with the value of 4.06 GPa is greater than the other combinations. This shows that the PALF had a greater influence in relation to curau? fibre. The analysis of the results generally shows that in combinations of two vegetable fibers of cellulosic origin, the fiber which shows higher percentage (75%) is the best option than to the composition of 50%/50%. In the meantime, according to the results obtained in this study, in the case where the application should withstand bending loads, the better composition would be 50%/50% / Com o objetivo de promover o desenvolvimento sustent?vel, as fibras encontradas em abund?ncia na natureza, que s?o biodegrad?veis e de baixo custo quando comparado com as fibras sint?ticas, vem sendo utilizadas na aplica??o de produ??o de comp?sitos. Neste trabalho foi analisado o comportamento mec?nico ? partir do ensaio de tra??o e flex?o, em um comp?sito h?brido tendo como matriz uma resina sint?tica ortoft?lica refor?ada com fibras de curau? e fibras da folha de abacaxizeiro (PALF), nas propor??es de 25% x 75% (P1), 50% x 50% (P2) e 75% x 25% (P3), respectivamente, com as fibras de curau? e as fibras da folha do abacaxizeiro sendo tratadas quimicamente por uma solu??o aquosa de hidr?xido de s?dio (NaOH) com 8% de concentra??o. As an?lises mec?nicas indicaram que com rela??o aos estudos de tra??o, para a combina??o P1 e P3, foram obtidas melhores resultados de 22,17 MPa e 16,98 MPa, respectivamente, que ? maior que da outra combina??o de P2. Os resultados do mesmo padr?o foram obtidos para an?lise de flex?o onde P1 ? 1,21% e P3 de 0,96% que s?o maiores do que o resultado obtido da combina??o P2. No caso de resist?ncia ? flex?o, melhores resultados foram obtidos para a combina??o P1 de 49,07 MPa. Mas, quando foi calculado o m?dulo de Young, os valores foram diferentes do padr?o dos resultados dos outros testes realizados, com a combina??o P2 com o valor de 4,06 GPa que ? maior que das outras combina??es. Isto mostra que as fibras PALF tiveram uma influ?ncia maior com rela??o ? fibra de curau?. A an?lise dos resultados em geral demonstra que nas combina??es de duas fibras vegetais celul?sicas, uma ou a outra fibra com porcentagem maior (75%) ? a melhor op??o do que na composi??o de 50%/50%, entretanto no caso onde a aplica??o ser? para suportar cargas de flex?o, a melhor composi??o seria 50%/50%

Made available in DSpace on 2014-12-17T14:58:19Z (GMT). No. of bitstreams: 1 RaphaelSF_DISSERT.pdf: 3572126 bytes, checksum: c44c0bf716695541147f2e019fde49de (MD5) Previous issue date: 2013-04-12 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The growing demand in the use of hybrid composite materials makes it essential a better understanding of their behavior face of various design conditions, such as the presence of geometric discontinuities in the cross section of structural elements. This way, the purpose of this dissertation is a study of the mechanical response (strength and stiffness), modes (characteristics) of fracture and Residual Strength of an hybrid polymeric composite with and without a geometric discontinuity in its longitudinal section (with a reduction in the cross section) loaded by uniaxial tension. This geometric discontinuity is characterized by central holes of different diameters. The hybrid composite was fabricated as laminate (plate) and consisting of ortho-tereftalic polyester matrix reinforced by 04 outer layers of Jute fibers bidirectional fabrics and 01 central layer of E-glass bidirectional fabric. The laminate was industrially manufactured (Tecniplas Nordeste Ind?stria e Com?rcio Ltda.), obtained by the hand lay-up technique. Initially, a study of the volumetric density of the laminate was made in order to verify its use in lightweight structures. Also were performed comparative studies on the mechanical properties and fracture modes under the conditions of the specimens without the central hole and with the different holes. For evaluating the possible influence of the holes in the structural stability of the laminate, the Residual Strength of the composite was determined for each case of variation in hole diameter. As a complementary study, analyses of the macroscopic final fracture characteristic of the laminates were developed. The presence of the central hole of any sizes, negatively changed the ultimate tensile strength. Regarding the elastic modulus, moreover, the difference found between the specimens was within the range of tests displacement, showing the laminate stability related to the stiffness / A crescente demanda na utiliza??o dos materiais comp?sitos h?bridos torna imprescind?vel uma melhor compreens?o do seu comportamento frente ?s mais diversas condi??es de projeto, como a presen?a de descontinuidades geom?tricas nos elementos estruturais. Nesse sentido, a proposta desta disserta??o ? um estudo envolvendo a resposta mec?nica (resist?ncia e rigidez), os modos (caracter?sticas) da fratura e Resist?ncia Residual de um laminado comp?sito h?brido de matriz polim?rica com e sem presen?a de descontinuidade geom?trica em sua se??o longitudinal (com redu??o da se??o transversal), sob a a??o de tra??o uniaxial. Essa descontinuidade geom?trica ? caracterizada por furos centrais de diferentes di?metros. O laminado comp?sito h?brido foi confeccionado na forma de placa e composto por matriz poli?ster orto-tereft?lica refor?ada por 04 camadas externas de tecidos bidirecionais de fibras de juta e 01 camada central de tecidos bidirecionais de fibras de vidro-E. O laminado foi fabricado industrialmente (Tecniplas Nordeste Ind?stria e Com?rcio Ltda.), obtido atrav?s do processo de lamina??o manual (hand lay-up). Inicialmente, foi feito um estudo da densidade volum?trica do laminado, de modo a comprovar sua aplica??o em estruturas leves. Foram realizados estudos comparativos entre as propriedades mec?nicas nas condi??es dos corpos de prova sem o furo e com os diferentes di?metros do furo. Para a avalia??o de poss?vel influ?ncia da presen?a dos furos centrais na estabilidade estrutural do laminado, a Resist?ncia Residual foi determinada para cada caso de varia??o do di?metro do furo. Como estudo complementar, an?lises macrosc?picas da caracter?stica de fratura final dos laminados foram desenvolvidas. A presen?a do furo central, independente do di?metro, influiu de forma danosa, principalmente na resist?ncia ?ltima ? tra??o. Quanto ao m?dulo de elasticidade, por outro lado, a diferen?a encontrada entre os corpos de prova apresentou-se dentro da faixa da dispers?o dos ensaios, mostrando estabilidade com rela??o ? rigidez do laminado

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 MariaDMP_pre_textuais_ate_cap_3.pdf: 1552357 bytes, checksum: 286c69a88a6d2c4ec8689ee9514da8ec (MD5) Previous issue date: 2008-10-28 / Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and thermal stability. Basic geopolymeric formulations can be found in the literature, which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21? for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3 for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204?F (400?C) and geopolymeric slurries are viable above 500?F (260?C) / Po?os sujeitos ? inje??o c?clica de vapor apresentam importantes desafios para desenvolvimento de pastas de cimenta??o, devido principalmente aos esfor?os de tra??o causados pelos gradientes t?rmicos durante a sua vida ?til. Falhas em cimenta??es que empregaram pastas convencionais de elevada resist?ncia ? compress?o levaram ao emprego de pastas mais flex?veis e/ou d?cteis, com destaque para as pastas de cimento Portland com adi??o de l?tex. Recentes pesquisas t?m apresentado pastas geopolim?ricas como alternativa. Estas pastas cimentantes s?o baseadas na ativa??o alcalina de aluminosilicatos amorfos como o metacaulim ou a cinza volante e possuem propriedades vantajosas como alta resist?ncia ? compress?o, r?pido endurecimento e estabilidade t?rmica. Encontram-se na literatura formula??es geopolim?ricas b?sicas que atendem ?s especifica??es da ind?stria de petr?leo, incluindo reologia, resist?ncia ? compress?o e tempo de espessamento. Neste trabalho, desenvolveu-se novas formula??es geopolim?ricas ? base de metacaulim, silicato de pot?ssio, hidr?xido de pot?ssio, micross?lica e fibra mineral, utilizando o estado da arte em composi??o qu?mica, modelagem de misturas e aditiva??o para otimizar as propriedades relevantes para a cimenta??o de po?os. Partindo de raz?es molares consideradas ideais na literatura (SiO2/Al2O3 = 3,8 e K2O/Al2O3 = 1,0), realizou-se um estudo de misturas secas baseado no modelo do empacotamento compress?vel, obtendo-se um volume ?timo de 6% para o material s?lido adicional. Este material (micross?lica e fibra mineral) serve tanto como fonte de s?lica adicional (no caso da micross?lica) quanto refor?o mec?nico, principalmente no caso da fibra mineral, a qual incrementou a resist?ncia ? tra??o. Realizou-se o primeiro estudo mec?nico triaxial desta classe de pastas. Para efeito de compara??o, tamb?m foi realizado um estudo mec?nico de pastas convencionais ? base de l?tex. Apesar de diferen?as no modo de ruptura (fr?gil no caso dos geopol?meros, d?ctil no caso das pastas com l?tex), a superior resist?ncia compressiva uniaxial (37 MPa para a pasta geopolim?rica P5 versus 18 MPa para a pasta convencional P2), comportamento triaxial similar (?ngulo de atrito 21? para P5 e P2) e menor rigidez (na regi?o el?stica 5,1 GPa para P5 versus 6,8 GPa para P2) das pastas geopolim?ricas permitiu uma capacidade de absor??o de energia (155 kJ/m3 para P5 versus 208 kJ/m3 para P2) compar?vel entre as duas, sendo que os geopol?meros atuam no regime el?stico, sem a microfissura??o presente nas pastas com l?tex. Assim, os geopol?meros estudados neste trabalho devem ser dimensionados para aplica??es no regime el?stico para evitar fraturas fr?geis. Finalmente, a resist?ncia ? tra??o do geopol?mero ? originalmente pobre (1,3 MPa para a pasta geopolim?rica P3) devido ? sua estrutura fr?gil. Entretanto, ap?s a aditiva??o desse sistema com fibra mineral, a resist?ncia ? tra??o do mesmo tornou-se equivalente (2,3 MPa para P5 e 2,1 MPa para P2) ? das pastas com l?tex. A viabilidade t?cnica das formula??es convencionais e geopolim?ricas foi avaliada durante toda a vida ?til do po?o, incluindo os esfor?os devidos ? inje??o c?clica de vapor. Esta an?lise foi feita utilizando um software de simula??o ? base de elementos finitos. Verificou-se que as pastas convencionais s?o vi?veis at? a temperatura de 204?C (400?F) e as geopolim?ricas acima de 260?C (500?F)