Avaliação de concretos reforçados por confinamento com manta de fibra de vidro estrutural e pré-impreganada

Due to the occurrence of diseases in the use of structural reinforcements in composites, with presentation of concrete blanket detachment, has been identified the need to evaluate the performance of concrete reinforced with glass fiber. This study aims to evaluate these concretes by means of testing methodologies, using concrete with low resistance with structural reinforcement for confinement by preimpregnated glass fiber and traditional fiberglass blanket. The first stage of work was the development of methodologies for analysis, opting for four types, such as the acoustic survey, strength to compressive, the pull-off and ultrasound. Next, tests were carried out using the four selected methodologies in 30 of proof-of-specimens by 5x10 cm, 15 were reinforced with the traditional fiberglass blanket with 5specimens exposed to test a marine environment of marine coastline of Natal-RN and 15 were reinforced with a pre-impregnated glass fiber blanket, as well as 5specimens exposed to a test environment of the marine coastline of Natal-RN. After conducting the acoustic survey, it has been verified a lack of delaminating and air bubbles in the samples, confirming the absence of gross shortcomings in the implementation of the ribs both the traditional fiberglass blanket and in the preimpregnated fiber glass blanket. After carrying out methods of pull-off and compressive strengthening test it was observed that the reinforced proof-bodies with pre-impregnated glass blanket showed maximum stresses higher than the traditional fiberglass blanket; consequently a greater grip with the formation of a smaller area of . fracture, unlike traditional glass mat, which showed lower maximum stresses, with a greater area of fracture. It was also found that the traditional fiberglass blanket presented detachment of blanket-concrete interface, unlike the pre-impregnated fiberglass blanket, which showed a better grip on the blanket-concrete interface. In the trial of ultrasound there was no presence of cracks in the blanket-concrete interface, yielding to both blankets good compactness of the concrete. At the end of this work, they were developed and proposed two methods of testing for evaluation of reinforced concrete structures with composites, for standardization, the acoustic survey and pull-off

Avaliação de concretos reforçados por confinamento com manta de fibra de vidro estrutural e pré-impreganada

Due to the occurrence of diseases in the use of structural reinforcements in composites, with presentation of concrete blanket detachment, has been identified the need to evaluate the performance of concrete reinforced with glass fiber. This study aims to evaluate these concretes by means of testing methodologies, using concrete with low resistance with structural reinforcement for confinement by preimpregnated glass fiber and traditional fiberglass blanket. The first stage of work was the development of methodologies for analysis, opting for four types, such as the acoustic survey, strength to compressive, the pull-off and ultrasound. Next, tests were carried out using the four selected methodologies in 30 of proof-of-specimens by 5x10 cm, 15 were reinforced with the traditional fiberglass blanket with 5specimens exposed to test a marine environment of marine coastline of Natal-RN and 15 were reinforced with a pre-impregnated glass fiber blanket, as well as 5specimens exposed to a test environment of the marine coastline of Natal-RN. After conducting the acoustic survey, it has been verified a lack of delaminating and air bubbles in the samples, confirming the absence of gross shortcomings in the implementation of the ribs both the traditional fiberglass blanket and in the preimpregnated fiber glass blanket. After carrying out methods of pull-off and compressive strengthening test it was observed that the reinforced proof-bodies with pre-impregnated glass blanket showed maximum stresses higher than the traditional fiberglass blanket; consequently a greater grip with the formation of a smaller area of . fracture, unlike traditional glass mat, which showed lower maximum stresses, with a greater area of fracture. It was also found that the traditional fiberglass blanket presented detachment of blanket-concrete interface, unlike the pre-impregnated fiberglass blanket, which showed a better grip on the blanket-concrete interface. In the trial of ultrasound there was no presence of cracks in the blanket-concrete interface, yielding to both blankets good compactness of the concrete. At the end of this work, they were developed and proposed two methods of testing for evaluation of reinforced concrete structures with composites, for standardization, the acoustic survey and pull-off

Estudo do comportamento estrutural de fachadas em vidro

Dissertação para obtenção do Grau de Mestre em Engenharia Civ

Controlo estrutural de uma fachada de vidro suspensa, sujeita à acção da explosão

Dissertação para obtenção do Grau de Mestre em Engenharia Civil - Perfil de Estruturas

Aspectos tecnológicos relativos a ensaio de vidro

Recentemente têm-se vindo a notar uma crescente utilização do vidro em edifícios motivada pelas actuais tendências arquitectónicas. Se no passado o vidro era visto como um elemento com funções não estruturais, hoje com a investigação científica em curso e com as novas técnicas de produção e tratamento final do vidro, é possível oferecer um vidro com funções portantes à mercê da imaginação dos arquitectos. Este trabalho está integrado num projecto de investigação em desenvolvimento no Departamento de Engenharia Civil da Universidade de Coimbra, denominado SGlass – Desempenho Estrutural e Regras de Projecto de Vigas de Vidro Reforçadas Externamente, cujo objectivo é dar um contributo para o desenvolvimento de normas europeias para vidro estrutural. O projecto S-Glass centrar-se-á no efeito da temperatura e de acções cíclicas, com e sem a inclusão de pré-esforço em elementos de vidro laminado, para tal serão realizados diversos ensaios que terão de simular com a máxima precisão as situações reais tais como temperaturas altas e sismos que têm forte probabilidade de ocorrerem nos países do sul da Europa. Este trabalho tem o objectivo de proporcionar todas as condições técnicas para que os ensaios sejam feitos com o máximo rigor, garantindo que todos os ensaios sejam considerados validos. Tal como quaisquer outros ensaios científicos, o equipamento utilizado é partilhado por diversos projectos assim como qualquer um que seja necessário adquirir tenha preços elevados, por isso é proposto algumas alternativas económicas e transmitido conhecimento para a manufactura e parametrização de alguns equipamentos de medição. Em cada serie haverá sempre um ensaio piloto para analisar possíveis melhorias a introduzir no layout, assim neste trabalho também serão propostas algumas técnicas de análise assim como a solução para possíveis problemas.

Envelhecimento ambiental acelerado em PRF a base de tecidos híbridos kevlar/vidro: propriedades e instabilidade estrutural

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

Fachada de vidro “inteligente”

Dissertação para obtenção do Grau de Mestre em Engenharia Civil - Perfil Estruturas

Efeitos da radiação uv, temperatura e vapor aquecido nos compósitos poliméricos: monitoramento, instabilidade estrutural e fratura

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

Obtenção e caracterização de um compósito de poliuretano de mamona e pó de vidro para aplicações em insolantes térmicos

Thermal insulation is used to protect the heated or cooled surfaces by the low thermal conductivity materials. The rigid ricin polyurethane foams (PURM) are used for thermal insulation and depend on the type and concentration of blowing agent. Obtaining PURM occurs by the use of polyol, silicone, catalyst and blowing agent are pre -mixed, reacting with the isocyanate. The glass is reusable, returnable and recyclable heat insulating material, whose time of heat dissipation determines the degree of relaxation of its structure; and viscosity determines the conditions for fusion, operating temperatures, annealing, etc. The production of PURM composites with waste glass powder (PV) represents economical and renewable actions of manufacturing of thermal insulating materials. Based on these aspects, the study aimed to produce and characterize the PURM composites with PV, whose the mass percentages were 5, 10, 20, 30, 40 and 50 wt%. PURM was obtained commercially, while the PV was recycled from the tailings of the stoning process of a glassmaking; when the refining process was applied to obtain micrometer particles. The PURM + PV composites were studied taking into account the standard sample of pure PURM and the influence of the percentage of PV in this PURM matrix. The results of the chemical, physical and morphological characterization were discussed taking into account the difference in the microstructural morphology of the PURM+PV composites and the pure PURM, as well the results of the physicochemical, mechanical e thermophysical tests by values obtained of density, hardness, compressive strength, specific heat, thermal conductivity and diffusivity. In general, the structure of pure PURM showed large, elongated and regular pores, while PURM+PV composites showed irregular, small and rounded pores with shapeless cells. This may have contributed to reducing their mechanical strength, especially for PURM - PV50. The hardness and density were found to have a proportional relationship with the PV content on PURM matrix. The specific heat, thermal diffusivity and thermal conductivity showed proportional relationship to each other. So, this has been realized that the increasing the PV content on PURM matrix resulted in the rise of diffusivity and thermal conductivity and the decrease of the specific heat. However, the values obtained by the PURM composites were similar the values of pure PURM, mainly the PURM-PV5 and PURM-PV10. Therefore, these composites can be applied like thermal insulator; furthermore, their use could reduce the production costs and to preserve the environment

Caracterização magnética e estrutural de filmes depositados por gaiola catódica

Iron nitrite films, with hundred of nanometers thick, were deposited using the Cathodic cage plasma nitriding method, with a N2/H2 plasma, over a common glass substract. The structure, surface morphology and magnetic properties were investigated using X-ray diffractometry (XRD), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM). XRD shows the formation of γ FeN phase and a combination of ζFe2N + ɛFe3N phases. The film s saturation magnetization and coercivity depends on morphology, composition, grain size and treatment temperature. Temperature raising from 250 ºC to 350 ºC were followed by an increase in saturation magnetization and film s surface coercivity on the parallel direction in relative proportion. This fact can be attributed to the grain sizes and to the different phases formed, since iron rich fases, like the ɛFe3N phase, emerges more frequently on more elevated treatment s temperature. Using this new and reasonably low cost method, it was possible to deposit films with both good adhesion and good magnetic properties, with wide application in magnetic devices

Preparação e caracterização estrutural e elétrica de células solares sensibilizadas por corantes empregando anodos nanoestruturados à base de 'TiO IND. 2'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo estrutural e cristalização em vidros fluorogermanatos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Técnicas de reforço estrutural para edificações antigas: estudo de caso na cidade de Rio Branco – Acre

Este trabalho visou a demonstrar o dimensionamento e verificação de cálculo da NBR 6118 (ABNT, 2007) com as suas características geométricas, cobrimento da armadura, armaduras, flambagem e a resistência de pilares à compressão centrada dos pilares em concreto armado, apresentando na revisão bibliográfica as principais técnicas de reforço estrutural de pilares de concreto armado para edificações antigas, identificando as principais metodologias e técnicas utilizadas no Brasil e apresentando os pontos positivos e negativos de cada técnica:encamisamento de concreto, perfis metálicos, chapa de aço colado, manta/tecido de carbono, aramida e vidro e polímeros reforçados com fibras de carbono (PRFC). Os pilares com aumento da seção transversal retangular, com adição de armação e concreto, sendo mais usual e prática a técnica apresenta dificuldades em obras antigas, geralmente devido à necessidade arquitetônica de permanecer o mais fiel a sua forma original. Justificando-se a necessidade de conhecimento das diversas técnicas de reforço estrutural descritas neste trabalho com aumento de capacidade de resistência, sem que haja aumento substancial, na seção transversal dos pilares e objetivando a análise do reforço proposto através dos cálculos do projeto, programa – PDOP 2.0 e parâmetros de cálculo da NBR 6118 (ABNT, 2007). Os resultados obtidos através da análise comparativa do reforço executado no estudo de caso “revitalização do casarão” - com relação à análise dos pilares retangulares submetidos à flexão composta oblíqua, esforços cortantes e torsores quanto à NBR 6118 (ABNT, 2007) utilizando o programa para dimensionamento otimizado de pilares – PDOP 2.0 - indicaram que a técnica de reforço estudada foi eficiente, pois todas as peças reforçadas tiveram uma capacidade portante maior que a do pilar original sem o reforço.

Avaliação mecânica da colagem estrutural entre compósitos poliméricos e materiais metálicos utilizados em dutos petroquímicos

The development of technology for structural composites has as one of its ends form a set of materials that combine high values of mechanical strength and stiffness and low density. Today, companies like Embraer and PETROBRAS and research institutions like NASA, working with these materials with recognized advantages in terms of weight gain, increased performance and low corrosion. We have developed a systematic study to determine the bond strength between composite carbon fiber / epoxy and fiberglass / epoxy laminate both bonded to a carbon steel which are widely used in the petrochemical industry and repair. For morphological evaluation and bonding between materials of different natures, ultrasound analysis, optical microscopy and stereoscopy were performed. To simulate actual conditions, the composites were subjected to conditioning by using heat shock temperatures from -50 to 80 ° C for 1000 cycles for composite carbon fiber / epoxy composites and 2000 cycles for fiberglass / epoxy . The use of composites studied here proved to be efficient to perform repairs in metallic pipes with application petrochemical, as when exposed to sudden changes of temperature (-50 ° to 80 ° C) cycling at 1000 to 2000 times, its mechanical properties (shear and tensile) practically do not change

Influência da desordem estrutural nas propriedades magnéticas de filmes finos de Co2FeAl

Thin films of Co2FeAl (CFA) and trilayers with CFA/M/CFA, where M is Au or Ag, produced by magnetron sputtering onto glass and oriented (MgO (100)) substrates were investigated. The structural, magnetic static and magnetic dynamics properties were analyzed by distinct experimental techniques. Through X-ray diffraction was observed an A2 phase for the samples (completely disordered), where the atoms are randomly located in the lattice. The static magnetic behavior, in some samples, reveal a plateau behavior generated by a biphasic system. The magnetoimpedance measurements were performed by varying the angle between the external magnetic field and current with respect of anisotropy direction. For this reason, the MI results show a asymmetric magnetoimpedance (AMI) behavior. For the single and trilayers samples with 500 nm-thick, the AMI effect is more evident in comparison with samples with 1000 nm-thick. Therefore, in this work was stablished a route to produce Heusler alloy samples with A2 phase in thin film geometry onto amorphous and oriented substrates, and due to structural disorder was possible to study the hysteretic and MI asymmetric effects.