Made available in DSpace on 2014-12-17T14:07:15Z (GMT). No. of bitstreams: 1 MirtaniaAL_TESE_pag1_pag73.pdf: 5781001 bytes, checksum: bc5b2f642130f3c856de876351a661e2 (MD5) Previous issue date: 2013-05-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The gradual replacement of conventional materials by the ones called composite materials is becoming a concern about the response of these composites against adverse environmental conditions, such as ultraviolet radiation, high temperature and moist. Also the search for new composite using natural fibers or a blend of it with synthetic fibers as reinforcement has been studied. In this sense, this research begins with a thorough study of microstructural characterization of licuri fiber, as a proposal of alternative reinforcement to polymeric composites. Thus, a study about the development of two composite laminates was done. The first one, involving only the fiber of licuri and the second comprising a hybrid composite based of fiber glass E and the fiber of licuri, in order to know the performance of the fiber when of fiber across the hybridization process. The laminates were made in the form of plates using the tereft?lica ortho-polyester resin as matrix. The composite laminate made only by licuri fiber had two reinforcing fabric layers of unidirectional licuri and the hybrid composite had two reinforcing layers of unidirectional licuri fabric and three layers of fiber short glass-E mat. Finally, both laminates was exposed to aging acceleration in order to study the influence of environmental degradation involving the mechanical properties and fracture characteristics thereof. Regarding the mechanical properties of composites, these were determined through uniaxial tensile tests, uniaxial compression and three bending points for both laminates in original state, and uniaxial tensile tests and three bending points after accelerated aging. As regards the study of structural degradation due to aging of the laminates, it was carried out based on microscopic analysis and microstructure, as well as measuring weight loss. The characteristics of the fracture was performed by macroscopic and microscopic (optical and SEM) analysis. In general, the laminated composites based on fiber licuri showed some advantages in their responses to environmental aging. These advantages are observed in the behavior related to stiffness as well as the microstructural degradation and photo-oxidation processes. However, the structural integrity of this laminate was more affected in case the action of uniaxial tensile loads, where it was noted a lower rate of withholding his last resistance property / A substitui??o gradativa dos materiais ditos convencionais por materiais comp?sitos vem se tornando uma preocupa??o quanto ? resposta destes frente a condi??es ambientais adversas, tais como, a presen?a de radia??o ultravioleta, alta temperatura e umidade. Tamb?m a busca de novos comp?sitos que utilizem fibras naturais ou uma mistura de fibras naturais com fibras sint?ticas como refor?o tem sido objeto de estudo. Neste sentido, o presente trabalho de pesquisa inicia com um completo estudo de caracteriza??o microestrutural da fibra de licuri, essa como proposta alternativa de refor?o aos comp?sitos polim?ricos. Em seguida, foi realizado um estudo do desenvolvimento de dois laminados comp?sitos, um somente a base de fibra de licuri e um laminado h?brido a base de fibra de licuri e fibra de vidro-E, de modo a conhecer o comportamento da fibra de licuri frente ao processo de hibridiza??o. Os laminados foram confeccionados em forma de placas utilizando a resina poli?ster orto-tereft?lica como matriz. O laminado comp?sito s? de fibras de licuri teve como refor?o duas l?minas de tecido unidirecional e o laminado h?brido teve como refor?o duas l?minas desse mesmo tecido unidirecional e tr?s l?minas de manta de fibras curtas de vidro-E. Por fim, os dois laminados comp?sitos foram submetidos ao processo de envelhecimento ambiental acelerado para o estudo da influ?ncia da degrada??o ambiental nas propriedades mec?nicas e caracter?sticas da fratura dos mesmos. Quanto ?s propriedades mec?nicas dos laminados comp?sitos, estas foram determinadas atrav?s dos ensaios de tra??o uniaxial, compress?o uniaxial e flex?o em tr?s pontos no estado original, e de tra??o uniaxial e flex?o em tr?s pontos ap?s envelhecimento acelerado. Quanto ao estudo da degrada??o estrutural dos laminados devido ao envelhecimento, o mesmo foi realizado com base nas an?lises microsc?picas da microestrutura e, bem como, da medi??o de perda de massa. As caracter?sticas da fratura foram realizadas atrav?s de an?lises macrosc?picas e microsc?picas (?tica e MEV). De forma geral os laminados comp?sitos a base de fibras de licuri, apresentaram algumas vantagens em suas respostas frente ao envelhecimento ambiental. Essas vantagens s?o evidenciadas no comportamento relacionado ? rigidez, bem como, aos processos fotoxida??o e degrada??o microestrutural. Entretanto, a integridade estrutural desse laminado foi mais afetada para o caso a??o de cargas uniaxiais de tra??o onde foi verificada uma menor taxa de reten??o de sua propriedade de resist?ncia ?ltima

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?

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