Exposição in utero ao desregulador endocrino bisfenol A e ao agente quimiopreventivo indol-3-carbinol: efeitos sobra a morfogênese e a suscetibilidade à carcinogênese prostática

Pós-graduação em Biologia Geral e Aplicada - IBB

Comportamiento de vigas de hormigón reforzadas a cortante con tejidos de fibras de carbono pegados con resina epoxi

El objetivo principal de este trabajo ha sido estudiar el comportamiento de vigas de hormigón, reforzadas a cortante con tejidos de fibra de carbono pegados con resinas epoxi. Para conseguir este objetivo se han planteado objetivos parciales como el análisis de la fisuración y de los movimientos en las vigas reforzadas. La metodología empleada ha sido principalmente experimental, realizándose una serie de diez vigas de hormigón en masa o armado. Se han comparado los resultados experimentales con los teóricos, obtenidos mediante la formulación analítica existente, como la recomendada por el fib Bulletin 14. Los resultados obtenidos demuestran que las vigas reforzadas ofrecen un comportamiento significativamente superior al de las vigas sin refuerzo, tanto en el valor de las cargas últimas como en la ductilidad de las piezas. Además se puede concluir que en todos los casos estudiados la rigidez prevista hasta la fisuración de las vigas es superior a la obtenida experimentalmente. Además las vigas reforzadas a cortante con tejido de fibra de carbono poseen una ductilidad superior a la de las vigas sin reforzar

Comportamiento de vigas de hormigón reforzadas a cortante con tejidos de fibras de carbono o basalto pegados con resina epoxi

Tanto en estructuras de edificación como de obra civil cada día resulta más frecuente la necesidad de su refuerzo, bien por problemas asociados a patologías o por el aumento de las cargas asociado generalmente a un cambio de uso. El objetivo principal de este trabajo ha sido estudiar el comportamiento de vigas de hormigón, reforzadas a cortante con tejidos de fibra de carbono o basalto pegados con resinas epoxi. Para conseguir este objetivo se han planteado objetivos parciales como el análisis de la fisuración y de los movimientos en las vigas reforzadas con polímeros reforzados con fibras (FRP) y la comparación del comportamiento mecánico de los sistemas de refuerzo estudiados.

Estudo de tolerância ao dano no compósito processado via RTM de fibra de carbono NCF/resina epóxi CYCOM 890

Pós-graduação em Engenharia Mecânica - FEG

Propriedades do sistema epoxídico DGEBA/TETA modificado com fibras naturais de bagaço de cana-de-açucar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Preparação e caracterização de resina epóxi transparente dopada com nanoestruturas semicondutoras de CdS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanocompósitos baseados no sistema epoxídico DEGBA/DETA modificado com uma resina epoxídica de silsesquioxano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades de materiais nanoestruturados do sistema epoxídico DGEBA/TETA modificado com um éster de silsesquioxano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência dos parâmetros de processamento por RTM no volume de vazios em compósitos carbono/epóxi

Pós-graduação em Engenharia Mecânica - FEG

Caracterização mecânica e térmica de compósitos naturais modificados com ciclodextrina e fibras vegetais utilizando como matriz uma resina termofixa DGEBA/TETA

Pós-graduação em Ciência dos Materiais - FEIS

Processamento e caracterização de compósito fibra de sisal/resina epóxi via RTM

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de compósitos produzidos por VARTM para aplicações aeronáuticas

In recent years the aeronautic industries has increased investment in areas of technological research aiming at materials that offer better performance, safety, weight reduction and fuel consumption. For this reason the most studied materials are polymeric materials, due to their higher mechanical strength and higher stiffness. This work evaluated characteristics of two composite laminates produced from the same process, but they differed only in regions where the resin was injected and the vacuum position. The composite laminates were SC-79 resin reinforced with glass fiber fabric (plain weave) processed via VARTM. For this reason the material was subjected to mechanical tests such as: tensile, and fatigue following standards ASTM D 3039 and ASTM D 3479, respectively. The latter was observed the S-N curve. It was performed the ultrassonic C-scan analysis to check impregnation of the fiber. Considering that the process was the same for the two laminates, with small variations in the injection and in vacum ports, it was expected to find similar characteristics

Análise estatística da vida em fadiga de compósitos estruturais pela distribuição de Weibull

Nowadays technological trend is based on finding materials that could support low weight with satisfactory mechanical properties and for this reason composite material became a very attractive topic in research projects all over the world. Due to its heterogenic properties, this type of material shows scatter in mechanical test results, especially in cyclic loading. Therefore it is important to predict its fatigue strength behaviour by statistic analysis, once fatigue causes approximately 90% of the failure in structural components. The present work aimed to investigate the fatigue behaviour of the Twill/Cycom 890 composite, which is carbon fiber reinforced with polymeric resin as matrix and manufactured via RTM process (Resin Transfer Molding). All samples were tested in different tensile level in triplicate in order to associate these values. The statistical analysis was conducted with Two-Parameter Weibull Distribution and then evaluated the fatigue life results for the composite. Weibull graphics were used to determine the scale and shape parameters. The S-N curve for the Twill/Cycom composite was drawn and indicated the number of cycles to occur the first damages in this material. The probability of failure was associated with material reliability, as shown in graphics for the different tensile levels and fatigue life. In addition, the laminate was evaluated by ultrasonic inspection showing a regular impregnation. The fractographic analysis conducted by SEM showed failure mechanisms for polymeric composites associated to cyclic loadings ... (Complete abstract click electronic access below)

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