487 resultados para Compósito reforçado


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The analysis of the extraction process in oil wells is presented exploring the challenges to the effectiveness of the procedure is shown step by step in the process. There is an analysis of the major tools and equipment needed in the drilling process, promoting the understanding of the challenges in the pre-salt layers, compared to conventional processes. The work is reinforced through studies of the influence of the corrosive compared not corrosive environment in drill strings

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The growth of urban population associated with the shortage of supply of public infrastructure such as hospitals, kindergartens, schools, among others, has reinforced the need to develop alternative methods that simplify the construction processes and allows for a reduction in these costs works. The conventional processes have increasingly been shown ineffective to solve the problem of demand for different types of urban and rural buildings. Given this fact, industrial construction processes can gain space and have proven to be highly interesting to solve the above problems, in particular, considering the cost-effective and time. Therefore, this study aimed to determine the influence of moisture on the strength of metal plate connections connectors (printed plate with teeth). For the sizing of the links between structural lumber using metal connectors with teeth prints; controlled process variables (drying of the wood and the different moisture contents), and finally found results and compare them with different literatures order to obtain a qualitative efficiency of the process. Some specimens had very low expectations, can be explained by the presence of bone marrow, and pre-existing cracks. Thus, the results were discarded for further analysis and more accurate results

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In the last decades it has been observed a substantial developing of the electrical energy demand in the societies all over the World. In consequence the electrical energy distribution companies are increasing the quantity of electrical energy through the electrical energy conductor cables, which had grown the sag in the towers of energy transmission. Furthermore, the construction of more transmission towers brings a lot of troubles due environmental protection laws. In this way, looking forward to increase the quantity of electrical energy transmitted through electrical cables conductors, reduce the need of constructing new transmission towers and the sag in them, we suggest in this work the replace of the traditional core of the conductors cables commonly used, made of steel, by a core made by a composite material, which one is made by carbon fibers pultruded with polymeric resins as matrix. In a order to evaluate if the resins more commonly used in structural composites can be applied as matrix to make possible to use the composite material as a core, we made carbon fibers systems pultruded with epoxy, phenolic and polyester resins as matrix and a mechanic and physic-chemistry characterization was done on the systems by Tensile and Poisson tests, differential sprobe calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transformed infrared spectroscopy (FTIR), following their correspondents standards

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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

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The weight of a vehicle has always been considered an extreme important factor, because it interferes in the performance, steering, consume, environmental impact, wear of components, among the others. Because of the new demand, consume reduction aim and gases emission increased the necessity to manufacture lighter vehicles, guaranteeing the complying with the gas emission international law. Besides the legal demand, the low weight will certainly be essential for the competitiveness for the next generation of vehicles. It is with this thinking the composite materials have been introduced in the automobilist industry, because those materials show an excellent relation of strength/weight, providing a reduction of consume and the increase of load capacity. Those factors justify the increase of interest of industry and the necessity of optimization of those materials and of their process. For this research, the field of application will be the Baja SAE Project, a project that is fully developed by engineering students, where they build a prototype single seat, off-road category, for use on hilly slopes with obstacle. This research aims to study two key components of the prototype are made of composite materials, analyzing all the processing. In addition, there is the analysis of the viability of this production parts to a Baja SAE vehicle, in order to increase their performance and reduce their weight without reducing the safety and robustness of the prototype. It was possible to achieve weight reduction of the steering subsystem with manufacturing the flywheel hybrid composite (carbon/glass) and the replacement of SAE 1010 steel by hybrid composite (carbon/aramid) in CVT box. The importance of this study is to obtain a good project for the vehicle of technical and scientific manner, contributing to the know-how to the team and providing a basis for optimization for upcoming projects

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In order to study resin distribution and homogeneity of composite laminates manufactured by RTM, it was used CYCOM 890 monolithic toughened epoxy as a matrix with two different configurations of intermediated modulus (IM) carbon fibers: Satin Weave (5HS) and non crimp fabric (NCF). The injection parameters were defined based on Thermo Gravimetric Analysis (TG), Differential Scanning Calorimetry (DSC) and rheological analysis. After processing the material, the resin/fiber impregnation was studied using ultrasonic test, Thermo Gravimetric Analysis, Differential Scanning Calorimetry, Dynamic Mechanical Analysis (DMA) and flexural tests. Therefore, it was able to observe an internal residual stress during the cooling process in both laminates, higher in the composite using NCF fabric due to the lack of symmetry, although a good proportion of fiber/matrix has been verified by the lower values of flexural modulus deviation. The DMA enabled the visualization of glass transition and its association with the inter and intra molecular interaction and movement, in which the NCF composite presented better permeability due to the lowest temperature of glass transition, when compared to the Satin Weave composite

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In this work, plasma immersion ion implantation (PIII) treatments of carbon fibers (CFs) were performed in order to induce modifications of chemical and physical properties of the CF surface aimed to improve the performance of thermoplastic composite. The samples to be treated were immersed in nitrogen or air glow discharge plasma and pulsed at −3.0 kV for 2.0, 5.0, 10.0, and 15.0 min. After PIII processing, the specimens were characterized by atomic force microscopy (AFM), scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). After CFs treatments, the CF/Polypropylene (PP) composites were produced by hot pressing method. Surface morphology of as-received CFs exhibited some scratches aligned along the fibers due to the fiber manufacturing process. After both treatments, these features became deeper, and also, a number of small particles nonuniformly distributed on the fiber surface can be observed. These particles are product of CF surface sputtering during the PIII treatment, which removes the epoxy layer that covers as-received samples. AFM analyses of CF samples treated with nitrogen depicted a large increase of the surface roughness (Rrms value approximately six times higher than that of the untreated sample). The increase of the roughness was also observed for samples treated by air PIII. Raman spectra of all samples presented the characteristic D- and G-bands at approximately 1355 and 1582 cm−1, respectively. Analysis of the surface chemical composition provided by the XPS showed that nitrogen and oxygen were incorporated onto the surface. The polar radicals formed on the surface lead to increasing of the CF surface energy. Both the modification of surface roughness and the surface oxidation contributed for the enhancement of CF adhesion to the polymeric matrix. These features were confirmed ... (Complete abstract click electronic access below)

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During the retaining wall project in soil reinforced with geogrids and face milling system for segmental blocks is essential to determine the maximum connection resistance between the block and the geogrid. Thus, the aim of this study was to analyze the connection resistance based on ASTM D- 6638-01 between the segmental block model MW of Muros Terrae® company with the geogrids model Fortrac® M 35 / 20x20, Fortrac® M 55 / 30x20, Fortrac® M 80 / 30x20 and Fortrac® M 110 / 30x20 of HUESKER Synthetic GmbH using gravel 1 as a filling material. As a result, the resistance curves were obtained for the four models of geogrids and was described how it fracture. An additional investigation was the average gain connection resistance percentage when it is applied to geogrid a second layer instead of a single layer. The average percentage gains in the connection resistance to the geogrids model Fortrac® M 35 / 20x20, Fortrac® M 55 / 30x20, Fortrac® M 80 / 30x20 and Fortrac® M 110 / 30x20 were, respectively, 63.20 %, 63, 47%, 62.23 % and 51.34 %. Finally, we made a comparative analysis of the results of this study with those obtained by Guimarães (2006), Urashima et. al (2008) and Almeida and Toma (2011) to evaluate which combinations offered higher connection resistance

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Pós-graduação em Engenharia Mecânica - FEIS

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This paper refl ects on a set of themes that are part of the contemporary agenda. The article contrasts modernity and post-modernity to discuss the “new sociology” which is dedicated to interpret the world and the way of life derived from the digital revolution and an intense capitalist globalization. Accepting some of the metaphors and concepts developed by this sociology, the paper argues that the world suggests much more than the image of a “radicalized modernity”, in which the dynamics of the past collide and combine with dynamics that are coming into existence, forming a plural, uneven, and surprisingly fast system.

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The aim of the research that originated this article was the analysis of the social trajectory of students from a public preparatory course and the verification of their expectations about higher education. Data collection was based on a questionnaire with open and closed-ended questions and a semi-structured interview, based on the models used by Muzzetti (1997). Data were analyzed by the elaboration of thematic charts. Based on the researches conducted by Pierre Bourdieu (1997, 2007), this research concluded that the students understand that schooling is, besides being a viable alternative in the search for social ascension, the redeeming of social ills. Profession choice based on natural talent or divine gift generate expectations which attest the lack of knowledge about the school system by students and their parents, which is reinforced by the belief in opportunity equality.

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This article suggests the need for change in focus of studies on new instances of participation in public policy management, which emerged in the Brazilian re-democratization. Moving away from the literature that addresses the role of civil society in these instances, the author reviews studies on Participatory Budgeting (PB) indicating how such experiences are marked by the dynamics of political society. The argument is reinforced by the presentation of a survey of PB counselors in Osasco-SP, by which we perceive, in general, a role filled by political processes of representative democracy. Most councilors compose the fringes of the political society, lie on the rise in, seeking better position in the local political field, internal disputes within the parties and the municipal government. This points the limits of the democratizing potential of the PB, since the expansion of participation in budget decisions would be just within the political society.

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To compare the abrasion wear resistance and superficial roughness of different glass ionomer cements used as restorative materials, focusing on a new nanoparticulate material. Material and Method: Three glass ionomer cements were evaluated: Ketac Molar, Ketac N100 and Vitremer (3M ESPE, St. Paul, MN, USA), as well as the Filtek Z350 (3M ESPE, St. Paul, MN, USA). For each material were fabricated circular specimens (n=12), respecting the handling mode specified by the manufacturer, which were polished with sandpaper disks of decreasing grit. The wear was determined by the amount of mass (M) lost after brushing (10,000 cycles) and the roughness (Ra) using a surface roughness tester. The difference between the Minitial and Mfinal (ΔM) as well as beroughness of aesthetic restorative materials: an in vitro comparison. SADJ. 2001; 56(7): 316-20. 11. Yip HK, Peng D, Smales RJ. Effects of APF gel on the physical structure of compomers and glass ionomer cements. Oper. Dent. 2001; 26(3): 231-8. 12. Ma T, Johnson GH, Gordon GE. Effects of chemical disinfectants on the surface characteristics and color of denture resins. J Prosthet Dent 1997; 77(2): 197-204. 13. International organization for standardization. Technical specification 14569-1. Dental Materials – guidance on testing of wear resistance – PART I: wear by tooth brushing. Switzerland: ISO; 1999. 14. Bollen CML, Lambrechts P, Quirynen M. Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature. Dent Mater.1997; 13(4): 258-9. 15. Kielbassa AM, Gillmann C, Zantner H, Meyer-Lueckel H, Hellwig E, Schulte-Mönting J. Profilometric and microradiographic studies on the effects of toothpaste and acidic gel abrasivity on sound and demineralized bovine dental enamel. Caries Res. 2005; 39(5): 380-6. 16. Tanoue N, Matsumara H, Atsuta M. Wear and surface roughness of current prosthetic composites after toothbrush/dentifrice abrasion. J Prosthet Dent. 2000; 84(1): 93-7. 17. Heath JR, Wilson HJ. Abrasion of restorative materials by toothpaste. J Oral Rehabil. 1976; 3(2): 121-38. 18. Frazier KB, Rueggeberg FA, Mettenburg DJ. Comparasion of wearresistance of class V restorative materials. J Esthet Dent. 1998; 10(6): 309-14. 19. Momoi Y, Hirosakil K, Kohmol A, McCabe JF. In vitro toothebrushdentifrrice abrasion of resin-modified glass ionomers. Dent Mater. 1997; 13(2): 82-8. 20. Turssi CP, Magalhães CS, Serra MC, Rodrigues Jr.AL. Surface roughness assessment of resin-based materials during brushing preceded by pHcycling simulations. Oper Dent. 2001; 26(6): 576-84. 21. Wang L, Cefaly DF, Dos Santos JL, Dos Santos JR, Lauris JR, Mondelli RF, et al. In vitro interactions between lactic acid solution and art glassionomer cements. J Appl Oral Sci. 2009; 17(4): 274-9. 22. Carvalho FG, Fucio SB, Paula AB, Correr GM, Sinhoreti MA, PuppinRontani RM. Child toothbrush abrasion effect on ionomeric materials. J Dent Child (Chic). 2008; 75(2): 112-6. 23. Coutinho E, Cardoso MV, De Munck J, Neves AA, Van Landuyt KL, Poitevin A, et al. Bonding effectiveness and interfacial characterization of a nano-filled resin-modified glass-ionomer. Dent Mater. 2009; 25(11): 1347-57. tween Rainitial and Rafinal (ΔRa) were also used for statistical analysis (α=0.05). Results: Except for the composite, significant loss of mass was observed for all glass ionomer cements and the ΔM was comparable for all of them. Significant increase in roughness was observed only for Vitremer and Ketac N100. At the end of the brushing cycle, just Vitremer presented surface roughness greater than the composite resin. Conclusion: All glass ionomer cements showed significant weight loss after 10,000 cycles of brushing. However, only Vitremer showed an increase of roughness greater than the Z350 resin, while the nanoparticulate cement Ketac N100 showed a smooth surface comparable to the composite.

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This study assessed the surface microhardness of compound resins cured by different light sources. Methods Three micro hybrid (Vit-l-escence, Amelogen Plus, Opallis) and one nanoparticle (Filtek Z350, 3M ESPETM Dental Products, St. Paul, USA) compound resins were selected. The resins were polymerized by a halogen light unit (Ultralux, Dabi Atlante, Ribeirão Preto, Brasil) with two tips, one semi-guided made of glass and another of painted acrylic and a LED-based source (UltraLume 2, Ultradent®, South Jordan, USA). Specimens constructed from a circular aluminum matrix were photopolymerized for 40 second after they received the compound resin and stored dry for 24 hours. After this period, a Vickers surface microhardness assay was performed, measuring the top (hardness 1) and base (hardness 2) surfaces four times each. Variance analyses were complemented by Newman-Keuls method, with significance set at 5%. Results The Opallis (FGM, Santa Catarina, Brasil) resin subjected to UltraLume 2 (Ultradent®, South Jordan, USA) obtained the lowest mean hardness values for the top surface. The Vit-l-escence (Ultradent®, South Jordan, USA) compound cured by Led UltraLume 2 (Ultradent®, South Jordan, USA) and by Ultralux PCP (Dabi Atlante, Ribeirão Preto, Brasil) halogen light obtained the highest mean hardness, followed by the Filtek Z350 (3M ESPETM Dental Products, St. Paul, USA) resin subjected to UltraLume 2 (Ultradent® South Jordan, USA). The Opallis (FGM, Santa Catarina, Brasil) resin cured by LED UltraLume 2 (Ultradent®, South Jordan, USA) also obtained the lowest mean hardness for the base surface and the Vit-L-Escence (Ultradent®, South Jordan, USA) resin obtained the highest value, followed by Amelogen Plus, when cured by Ultralux (Dabi Atlante, Ribeirão Preto, Brasil) using the semi-guided tip. Conclusion The polymerization and, consequently, the microhardness achieved by the LED unit was equivalent to those achieved by conventional halogen units for three of the four composites tested.