Cinética de degradação do sistema resina epóxi/fibra de carbono

With the increasing demand for electricity, the retraining of transmission lines is necessary despite environmental restrictions and crossings in densely populated areas to build new transmission and distribution lines. Solution is reuse the existent cables, replacing the old conductor cables for new cables with higher capacity power transmission, and control of sag installed. The increasing demand for electrical power has increased the electric current on the wires and therefore, it must bear out temperatures of 150°C or more, without the risk of the increasing sag beyond the established limits. In the case of long crossings or densely populated areas, sag is due to high weight of the cable on clearance. The cable type determines the weight, sag, height and the towers dimensions, which are the items that most influence the investment of the transmission line. Hence, to reduce both cost of investment and maintenance of the line, the use of a lighter cable can reduce both number and the height of the towers, with financial return on short and long term. Therefore, in order to increase the amount of transmitted energy and reduce the number of built towers and sag, is recommended in the current work substitute the current core material (steel or aluminium) for alternatives alloys or new materials, in this case a composite, which has low density, elevated stiffness (elasticity module), thus apply the pultruded carbon fiber with epoxy resin as matrix systems and perform the study of the kinetics of degradation by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), according to their respective standards

Processamento do compósito de fibra de capim-sapê / epóxi e avaliação da resistência à flexão “t” de Student

In recent years a great worldwide interest has arisen for the development of new technologies that enable the use of products with less environmental impact. The replacement of synthetic fiber plants is a possibility very important because this fiber is renewable, biodegradable and few cost and cause less environmental impact. Given the above, this work proposes to develop polymeric composites of epoxy resin and study the behavior of these materials. Both, the epoxy resin used as matrix in the manufacture of sapegrass fiber composite, as tree composites formed by: epoxy/unidirectional sapegrass long fiber, 75% epoxy/25% short fiber, by volume, and 80% epoxy/20% short fiber, by volume, were characterized by bending, and the composites produced with short fibers random were inspected by Optical Microscopy and Acoustics Inspection (C-Scan). For the analysis of the sapegrass fiber morphology, composites 75% epoxy/25% short fiber (sheet chopped) and 80% epoxy/20% short fiber images were obtained by optical microscope and the adhesion between polymer/fiber was visualized. As results, the flexural strength of composites epoxy/unidirectional long fibers, 75% epoxy/25% short fiber and 80% epoxy/20% short fiber were 70.36 MPa, 21.26 MPa, 25.07 MPa, respectively. Being that composite showed that the best results was made up of long fibers, because it had a value of higher flexural strength than other composites analyzed

Estudo do efeito da classe de furação na resistência à fadiga em junta alumínio – fibra de carbono

This work performs a comparative study of fatigue life of riveted lap joints involving classes of drilling which adjustment is made with interference or clearance. For this study, representative specimens of this joints were manufactured with four rivets distributed in two rows. In this context, are presented the test matrix, the methodology employed in performing of the tests, the used mathematical modeling, and that methods that are the basis for the latter are described through the theoretical foundation. Next, are present the results obtained in fatigue tests and images of the region of failure of the specimens. Finally, are present some comments and conclusions related to the results obtained

Produção de polpa solúvel a partir de Eucalyptus urograndis

The wood of the gender Eucalyptus occupies a prominence place in relation to other cellulose sources, due to its chemical composition, its low cost, abundance and availability. The dissolving pulp obtaining occurs basically starting from three stages: prehydrolysis of the wood following by cooking and finally by the bleaching process. In the dissolving pulp production is necessary a pretreatment stage for the hemicelluloses removal. Among the chemical cooking processes, the Kraft process is the most used for cellulosic pulps production starting from eucalyptus, in the additive presence or not. The anthraquinone uses in the pulping process has as main purposes increasing the delignification rate as well as protecting the pulp regarding the degradation of the polysaccharide chains. The ECF bleaching process consists of the purification of the pulp through bleaching agents, being excepted the elementary chlorine. The dissolving pulp is a pulp of high a-cellulose content and purity destined to the cellulose derivatives production as carboxymethyl cellulose, nitrocellulose and microcrystalline cellulose. The production of a certain product, as well as its final application, is determined by the chemical properties of the pulp. The present work had as purpose producing cellulosic pulp with kappa number around 9 destined to the production of dissolving pulp in way to evaluate the use of the anthraquinone (AQ) in the Kraft process according to the chemical properties of the obtained pulps. It has been still intended developing an effective technology of bleaching for the high purity and quality dissolving pulp production. The prehydrolysis was accomplished in laboratory rotational autoclave for 30 minutes at 170ºC in the water:wood rate 3,5:1 (L:kg). The Kraft/AQ pulping were accomplished in laboratory rotational autoclave being initially modified the active alkali load (10, 13, 16 and 19%) at sulfidity of 25% ...

Avaliação do efeito ambiental nas propriedades mecânicas e viscoelásticas de compósitos híbridos de titânio/fibra de carbono/resina epóxi

Hybrid composites combining metal plates and laminates with continuous fiber reinforced polymer, called fiber-metal (CHMF), have been particularly attractive for aerospace applications, due mainly to their high mechanical strength and stiffness associated with low density. These laminates (CHMF) consist of a sandwich structure consisting of layers of polymer composites and metal plates, stacked alternately. This setting allows you to combine the best mechanical performance of polymer composites reinforced with long fibers, to the high toughness of metals. Environmental effects should always be considered in the design of structural components, because these materials in applications are submitted to the effects of moisture in the atmosphere, the large cyclical variations of temperature around 82 ° C to -56 ° C, and high effort mechanical. The specimens of fibermetal composite were prepared at EMBRAER with titanium plates and laminates of carbon fiber/epoxy resin. This study aims to evaluate the effect of different environmental conditions (water immersion, hygrothermal chamber and thermal shock) of laminate hybrid titanium/carbon fiber/epoxy resin. The effects of conditioning were evaluated by interlaminar shear tests - ILSS, tensile, and vibration free

Efeito do tratamento alcalino da fibra na resistência mecânica do compósito epóxi/capim-sapê

Due to growing concerns for reducing environmental damage caused by the use of non-renewable raw materials, there is a growing demand for research related to aggregate technology with environmental preservation. Thus, the use of non-renewable materials and less aggressive materials has been gaining attention. About composite materials, the exchange of synthetic fibers by natural fibers, especially vegetable fiber as reinforcement, has been increasing, due to its physical-chemical properties such as mechanical strength, nontoxic, low cost, low density, processing flexibility, non-abrasive to the process equipment, requiring simple surface treatments, etc. This objective was to process composites reinforced with long fibers of sapegrass in epoxy matrix and characterize the composites through mechanical tests. Three groups of composites were prepared according to the treatment received by the reinforcement: without treatment, alkali treatment at concentration of 5% w/v and alkali treatment at 10% w/v concentration. The materials were analyzed by tensile and flexural, and tests also optical microscopy and scanning electron microscopy (SEM). The results were statistically analyzed. As the main result, the alkali treatment of 5% in the sapegrass fibers increases the tensile and flexural strength, as a consequence of the improve adhesion between matrix and reinforcement

Estudo da modificação superficial de fibras de carbono por meio de tratamentos a plasma para o aumento da adesão na interface de compósitos fibra de carbono/PPS

Pós-graduação em Engenharia Mecânica - FEG

Associação de facetas diretas e fibra de reforço para restabelecimento estético do sorriso: relato de caso clínico

Esse artigo tem como objetivo demonstrar o restabelecimento estético do sorriso obtido por meio da associação de facetas diretas e fibra de reforço. As fibras de reforço são utilizadas como alternativa para substituição de elementos dentários perdidos e possuem indicações precisas, sendo empregadas em diversas especialidades da Odontologia, devido à sua capacidade de aumentar a resistência à tração dos compósitos, o que aumenta a resistência à compressão das fibras. Para o completo restabelecimento do sorriso, muitas vezes é necessário reanatomizar os dentes adjacentes, considerando as condições em que esses se apresentam. Sendo assim, o profissional deve ter conhecimento para aplicação correta da técnica e restabelecimento da estética ao paciente.

Farelo de abacaxi como fonte de fibra na alimentação de leitões desmamados

Pós-graduação em Ciência e Tecnologia Animal - FEIS

Obtenção e caracterização de compósitos de benzoxazina/fibra de carbono

Pós-graduação em Engenharia Mecânica - FEG

Fibra para cães: efeitos sobre o processo de extrusão, digestibilidade, fermentação microbiana, tempo de retenção intestinal e palatabilidade de rações para cães

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação dos fatores críticos para a seleção e aplicação clínica dos pinos de fibra: relato de caso cliínico

Teeth that have lost much of their coronal tooth structure need intraradical devices to achieve a desired retention of the restorative material, restoring aesthetics and function to the patient. For this purpose, various types of intracanal posts have been studied, of wich the fiber posts have been highlighted with its increasing use in the dental market. The purpose of this study was to present a clinical case of using fiberglass post. As well as critically analyze the published works and points of controversy described by different authors related to factors such as different protocols cementation, surface treatments pins, fracture toughness and compression, the possibility of microleakage, diameter and length of the pin, and the various materials used in conjunction with the intracanal retainers. Thus, we concluded that fiber posts showed as an excellent alternative for anterior teeth, since have least 2 mm of tooth remaining.

Análise da interface adesiva entre pinos de fibra de vidro e dentina intrarradicular submetida à irrigação com diferentes agentes condicionantes

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

Fibra da cana-de-açúcar para suínos pesados em restrição alimentar qualitativa

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