Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-01-15T21:40:49Z No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-01-17T15:55:28Z (GMT) No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) / Made available in DSpace on 2018-01-17T15:55:28Z (GMT). No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) Previous issue date: 2017-08-10 / A constante busca de materiais mais eficientes e com alto desempenho mec?nico, contribue efetivamente para a crescente demanda na utiliza??o de comp?sitos h?bridos. O processo de hibridiza??o pode propiciar melhoria significativa na combina??o global de propriedades, possibilitando assim aplica??es espec?ficas em elementos estruturais que requerem excel?ncia em suas propriedades mec?nicas e baixa massa espec?fica. Atrelado ? gradativa utiliza??o destes materiais, estudos que incidem nas previs?es de falha e, consequentemente, an?lises das cargas m?ximas que estes materiais podem suportar tornam-se essenciais para garantia da confiabilidade quanto a sua aplica??o. Neste sentido, a presente pesquisa buscou analisar o comportamento mec?nico de uma l?mina constitu?da ? base de tecido h?brido bidirecional (vidro/carbono) e resina ep?xi ?ster-vin?lica. Bem como, avaliar a representatividade de crit?rios de falhas desenvolvidos para comp?sitos unidirecionais quando aplicados em comp?sito h?brido de natureza bidirecional. A l?mina estudada foi caracterizada mecanicamente com base nos resultados obtidos pelos ensaios de tra??o e cisalhamento realizados em amostras com fibras de carbono orientadas a 0?, 30?, 45?, 60? e 90?. Observou-se a partir destes ensaios que materiais com fibras em ?ngulos fora do eixo (off-axis) de aplica??o de carga apresentam resist?ncia menor, embora apresentem maiores alongamentos, quando comparados a amostras com fibras alinhadas na dire??o principal do carregamento. Os dados experimentais referentes ?s propriedades cisalhantes, normatizados pela ASTM D3518M-13 (ensaio de cisalhamento por tra??o ?45?) e ASTM D5379-12 (ensaio de Iosipescu), apresentaram diferen?as significativas para a resist?ncia ao cisalhamento e similaridade nos valores do m?dulo de cisalhamento. O ensaio de tra??o ?45?, conforme an?lise macromec?nica, mostrou-se como o mais adequado para comp?sito com caracter?sticas similares ao analisado. Ao inserir os dados dos ensaios nas equa??es te?ricas que definem os crit?rios de falhas da M?xima Tens?o, Tsai-Hill, Tsai-Wu e Hashin e, analis?-los estatisticamente, contatou-se que estas teorias de falhas descrevem satisfatoriamente o comportamento experimental da l?mina, e, portanto, podem ser utilizados para predizer a resist?ncia mec?nica em comp?sitos como o avaliado, embora se tenha observado ?ndices de representatividade maiores quando se utiliza o ensaio de cisalhamento por tra??o ?45?. / The constant search for more efficient materials and with high mechanical performance, contributes effectively to the growing demand in the use of hybrid composites. The hybridization process can provide significant improvement in the overall combination of properties, thus enabling specific applications in structural elements that require excellence in their mechanical properties and low specific mass. Coupled with the gradual use of these materials, studies that focus on fault predictions and, consequently, analyzes of the maximum loads that these materials can withstand become essential to guarantee the reliability of their application. In this sense, the present research sought to analyze the mechanical behavior of laminae composed of two-way hybrid fabric (glass/carbon) and epoxy resin vinyl ester. As well as evaluating the representativeness of failure criteria developed for unidirectional composites when applied in hybrid composites of a bidirectional nature. The laminas studied were mechanically characterized based on the results obtained by tensile and shear tests performed on samples with carbon fibers orientated at 0?, 30?, 45?, 60? and 90?. It was observed from these tests that materials with fibers at off-axis loading angles exhibit lower strength, although they exhibit greater elongations when compared to samples with fibers aligned in the main direction of loading. Experimental data on shear properties, standardized by ASTM D3518M-13 (tensile shear test ?45?) and ASTM D5379-12 (Iosipescu's test), showed significant differences for shear strength and similarity in the modulus values of Shear. The tensile test ? 45?, according to macromechanical analysis, proved to be the most suitable for composite with characteristics similar to the one analyzed. By inserting test data into the theoretical equations defining Tsai-Hill, Tsai-Wu, and Hashin fault criteria, and statistically analyzing them, it was found that these fault theories satisfactorily describe the experimental behavior of the blade , and therefore can be used to predict mechanical strength in composites as evaluated, although higher representativity indices were observed when using the ? 45? traction shear test.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-03-12T13:28:18Z No. of bitstreams: 1 JoseclebioDaFonsecaLucena_DISSERT.pdf: 1438787 bytes, checksum: 0316690714d7086e6bac43c938ec58c9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-03-14T18:34:15Z (GMT) No. of bitstreams: 1 JoseclebioDaFonsecaLucena_DISSERT.pdf: 1438787 bytes, checksum: 0316690714d7086e6bac43c938ec58c9 (MD5) / Made available in DSpace on 2018-03-14T18:34:15Z (GMT). No. of bitstreams: 1 JoseclebioDaFonsecaLucena_DISSERT.pdf: 1438787 bytes, checksum: 0316690714d7086e6bac43c938ec58c9 (MD5) Previous issue date: 2017-07-31 / A utiliza??o da energia e?lica em larga escala j? evidenciou seus benef?cios com grandes projetos ao redor do mundo. Devido ao baixo n?vel tecnol?gico dos processos produtivos dos componentes de uma torre de produ??o deste tipo de energia, ocorre a gera??o de enormes quantidades de res?duos que podem causar impacto negativo ao meio ambiente. Um dos principais componentes para a concep??o dos geradores e?licos s?o as p?s, que s?o produzidas atrav?s da lamina??o de grandes moldes que cont?m, entre outros componentes, a fibra de vidro na forma de n?otecidos, da qual 10 a 15% de retalhos ? eliminado no momento do corte durante sua fabrica??o. Uma forma de se contornar o problema do descarte dos res?duos provenientes da produ??o das p?s e?licas ? a reutiliza??o destes no desenvolvimento de comp?sitos. Os materiais comp?sitos, impulsionados pela ind?stria aeroespacial e militar, desenvolveram-se de forma bastante significativa nos ?ltimos anos, proliferando em diversas ?reas, devido as suas propriedades ?nicas, tais como: a elevada resist?ncia mec?nica, baixa densidade, excelente resist?ncia t?rmica e ? corros?o dentre outras. A fibra de Juta por apresentar um baixo custo, ser facilmente encontrada na regi?o e apresentar bons resultados de resist?ncia, foi utilizada em densidades diferentes para verificar sua influ?ncia, nas propriedades mec?nicas do comp?sito hibrido. O presente trabalho teve como objetivo desenvolver materiais comp?sitos h?bridos (fibra natural + fibra de vidro) resinados com poli?ster avaliando o comportamento dos comp?sitos refor?ados com res?duos (retalhos) de manta de fibra de vidro oriundos da ind?stria e?lica. Foram realizadas an?lises do percentual de refor?o, resist?ncia ? tra??o e flex?o, absor??o de ?gua e resist?ncia ? intemp?ries para verificar o desempenho dos comp?sitos desenvolvidos. Os resultados obtidos com os materiais comp?sitos refor?ados com tr?s camadas de vidro, quando submetidos a ensaios de tra??o, apresentaram valores 10 vezes superiores ao material sem refor?o. Nos ensaios de flex?o, quando comparados os mesmos as for?as utilizadas foram entre 117 N, para materiais sem refor?o, e 691 N para comp?sitos refor?ados com tr?s camadas de vidro, abrindo novas oportunidades para o desenvolvimento de materiais produzidos com substratos que s?o normalmente descartados para o meio ambiente. / The use of wind energy on a large scale has already shown its benefits with major projects around the world. Due to the low technological level of the productive processes of the wind towers components, the generation of enormous amounts of waste occurs, which can cause negative impact to the environment. One of the main components for the design of wind generators are the blades. They are produced by laminating of large molds that contain, among other components, glass fiber in the form of nonwoven, of which 10% to 15% of flaps are eliminated at the time of cutting during manufacture. One way of avoiding the problem of discarding waste from the production of wind turbines is to reuse them in the development of composites. Composite materials, driven by the aerospace and military industries, have developed quite significantly in recent years, proliferating in several areas due to their unique properties, such as; High mechanical strength, low density, excellent thermal and corrosion resistance among others. The Jute fiber presented a low cost, easily found in the region and presented good resistance results, was used in different densities to verify its influence on the mechanical properties of the hybrid composite. The present work aims to develop hybrid composite materials (natural fiber + glass fiber) with polyester resins , evaluating the influence of the use of fiberglass residues from the wind industry. Density, count yarns, twist tests were used to characterize the reinforcement materials, as well as fiber content, tensile strength, flexural strength, water absorption and weathering analyzes for the performance of the composites developed. The results obtained with the reinforced composites with three layers of glass, when subjected to tensile tests, presented values 10 times higher than the material without reinforcement. In the flexural tests, when compared, the forces used were between 117 N for non-reinforced materials and 691 N for reinforced composites with three layers of glass, opening new opportunities for the development of materials produced with substrates that are normally discarded for the environment.

Made available in DSpace on 2014-12-17T14:57:43Z (GMT). No. of bitstreams: 1 AlyssonRFB.pdf: 2167882 bytes, checksum: 8299a168b4ffa71ad51d65356a2a5ae5 (MD5) Previous issue date: 2006-12-21 / The advantage in using vegetable fibres in place of synthetic fibres such as glass fibre, for reinforcements in composites are: biodegradability, low cost, low density, good tenacity, good thermal properties, low energy content and reduced use of instruments for its treatment or processing. Even though, problems related to low mechanical performance of some of the natural fibres, has caused difficulty in their direct application in structural elements. The use of alternative materials like hybrid composites has been encouraged, thus trying to better the structural performance of the composites with natural fibres. This work presents a comparative study of the strength and stiffness of hybrid composites with orthopthalic polyester matrix reinforced with E-fibre glass, jute and curau?. The experimental part includes uniaxial tension and three point bending tests to determine the mechanical properties of the final product. The hybrid composite was manufactured in a local industry and was in the form of laminates. All the samples were projected to withstand the possible structural applications as reservoirs and pipes. CH (laminated hybrid composite with glass and curau? fibres). The results obtained show clearly the influence of the hybridization in all the types tested and indicate a good mechanical performance of the composite with glass/curau? fibres in relation to the composite with glass fibres. Aspects in relation to the interfaces glass/curau? composites besides the fracture characteristics for all loading types were also analysed / As vantagens do uso de fibras vegetais sobre as fibras sint?ticas, como as fibras de vidro, no refor?o de comp?sitos s?o: biodegradabilidade, baixo custo, baixa densidade, boa tenacidade, boas propriedades t?rmicas e uso reduzido de instrumentos para o seu tratamento ou processamento. Por?m, problemas relacionados com o baixo desempenho mec?nico de algumas fibras naturais, t?m dificultado seu uso direto em elementos estruturais. Neste sentido, o aparecimento de materiais alternativos, como os comp?sitos h?bridos, vem sendo incentivado buscando-se melhorar o desempenho estrutural dos comp?sitos com fibras naturais. O presente trabalho de investiga??o apresenta um estudo comparativo da resist?ncia e rigidez de comp?sito de matriz poli?ster ortoft?lica refor?ada com fibras de vidro-E e h?brido com fibras naturais de curau?. A investiga??o experimental inclui testes de absor??o de umidade, tra??o uniaxial e de flex?o-em-tr?s-pontos para a determina??o das propriedades mec?nicas do produto final. Os comp?sitos de fibra de vidro e h?bridos s?o de fabrica??o industrial e foram desenvolvidos na forma de laminados. Todos foram projetados para atender poss?veis aplica??es estruturais como reservat?rios e tubula??es: Laminados de fibras de vidro (CV) e h?bridos (CH) (comp?sito laminado h?brido de fibras de vidro/curau?). Os refor?os utilizados nos comp?sitos foram na formas de tecidos aleat?rios (vidro-E) e mechas de fios cont?nuos (curau?). Os resultados obtidos mostram claramente a influ?ncia da hibridiza??o e meios de absor??o de umidade e indicam um bom desempenho mec?nico do comp?sito curau?/vidro. Tamb?m foram analisados aspectos referentes ? interface curau?/vidro e as caracter?sticas finais da fratura para todos os tipos de carregamentos estudados

Made available in DSpace on 2014-12-17T14:57:44Z (GMT). No. of bitstreams: 1 LeonardoPSR.pdf: 5835314 bytes, checksum: 12deb1964ac794f5dcc1b8fb3ba5e4c9 (MD5) Previous issue date: 2007-12-26 / The advantages of the use of vegetable fibers on the synthetic fibers, such as glass fibers, in the reinforcements in composites are: low cost, low density, good tenacity, good thermal properties and reduced use of instruments for their treatment or processing. However, problems related to poor performance of some mechanical natural fibers, have hindered its direct use in structural elements. In this sense, the emergence of alternative materials such as hybrids composites, involving natural and synthetic fibers, has been encouraged by seeking to improve the performance of structural composites based only on natural fibers. The differences between the physical, chemical and mechanical properties of these fibers, especially facing the adverse environmental conditions such as the presence of moisture and ultraviolet radiation, is also becoming a concern in the final response of these composites. This piece of research presents a comparative study of the strength and stiffness between two composite, both of ortoftalic polyester matrix, one reinforced with fibers of glass-E (CV) and other hybrid reinforced with natural fibers of curau? and fiberglass-E (CH). All the comparative study is based on the influence of exposure to UV rays and steam heated water in composites, simulating the aging environment. The conditions for the tests are accelerated through the use of the aging chamber. The composites will be evaluated through tests of uniaxial static mechanical traction and bending on three points. The composite of glass fiber and hybrid manufacturing industry are using the rolling manual (hand lay-up) and have been developed in the form of composites. All were designed to meet possible structural applications such as tanks and pipes. The reinforcements used in composites were in the forms of short fiber glass-E quilts (450g/m2 - 5cm) of continuous wires and fuses (whose title was of 0.9 dtex) for the curau? fibers. The results clearly show the influence of aging on the environmental mechanical performance of the composite CV and CH. The issues concerning the final characteristics of the fracture for all types of cargoes studied were also analyzed / As vantagens do uso de fibras vegetais sobre as fibras sint?ticas, como as fibras de vidro, no refor?o de comp?sitos s?o: baixo custo, baixa densidade, boa tenacidade, boas propriedades t?rmicas e uso reduzido de instrumentos para o seu tratamento ou processamento. Por?m, problemas relacionados com o baixo desempenho mec?nico de algumas fibras vegetais, t?m dificultado seu uso direto em elementos estruturais. Neste sentido, o aparecimento de materiais alternativos, como os comp?sitos h?bridos, envolvendo fibras sint?ticas e naturais, vem sendo incentivado buscando-se melhorar o desempenho estrutural dos comp?sitos a base s? de fibras vegetais. As diferen?as entre as propriedades f?sicas, qu?micas e mec?nicas dessas fibras, principalmente frente ?s condi??es ambientais adversas, como a presen?a de umidade e radia??o ultravioleta, vem se tornando uma preocupa??o a mais na resposta final desses comp?sitos. No presente trabalho de investiga??o apresenta-se um estudo comparativo da resist?ncia e rigidez entre dois comp?sitos, ambos de matriz poli?ster ortoft?lica, sendo um refor?ado com fibras de vidro-E (CV) e o outro h?brido refor?ado com fibras vegetais de curau? e fibra de vidro-E (CH). Todo o estudo comparativo teve como base a influ?ncia da exposi??o ? raios UV e vapor d ?gua aquecido nos comp?sitos, simulando o envelhecimento ambiental. As condi??es de ensaios s?o aceleradas atrav?s do uso da c?mara de envelhecimento. Os comp?sitos ser?o avaliados atrav?s de ensaios mec?nicos est?ticos de tra??o uniaxial e flex?o em tr?s pontos. Os comp?sitos de fibra de vidro e h?bridos s?o de fabrica??o industrial utilizando o processo de lamina??o manual (hand lay-up) e foram desenvolvidos na forma de comp?sitos. Todos foram projetados para atender poss?veis aplica??es estruturais, como reservat?rios e tubula??es. Os refor?os utilizados nos comp?sitos foram na formas de mantas de fibras vidro-E curtas (450g/m2 5cm) e mechas de fios cont?nuos (cujo t?tulo foi de 0,9 dtex) para as fibras de curau?. Os resultados obtidos mostram claramente a influ?ncia do envelhecimento ambiental no desempenho mec?nico dos comp?sitos CV e CH. Tamb?m foram analisados aspectos referentes ?s caracter?sticas finais da fratura para todos os tipos de carregamentos estudados

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%