Caracterização da preparação superficial de substratos metálicos por meio de um jateamento rotativo / Description of the surface preparation of metallic substrates by rotating blaster

A preparação superficial possui significativa influência sobre a eficácia da pintura. Esta visa remover a camada superficial de oxidação, bem como proporcionar uma rugosidade superficial que favoreçam o desempenho de tintas e revestimentos. Neste sentido, este trabalho visa avaliar a preparação superficial obtida por um método alternativo, o jateamento rotativo. A preparação superficial foi realizada disco rotativo denominado Perago, da marca Tercoo, sendo avaliado o grau de limpeza superficial, a rugosidade proporcionada, bem como se estes possibilitaram obter uma adesão satisfatória. O grau de limpeza superficial foi classificado segundo a ISO 8501 por meio de uma avaliação superficial. A rugosidade superficial (parâmetros Ra e Rz) foi avaliada por meio de um rugosímetro da Mitutoyo, modelo SJ-201P. A adesão foi mensurada conforme a ASTM D4541, por meio de um aparelho da Defelsko e modelo PosiTest AT. Por meio deste trabalho foi possível caracterizar o tratamento superficial, sendo observado o grau de limpeza mais elevado (SA.3), bem como os parâmetros de rugosidade Ra (5,06 ± 0,34 µm) e Rz (igual a 50,93 ± 0,75 µm). Por fim, segundo os resultados obtidos no ensaio de adesão, pode-se considerar este tratamento superficial satisfatório para o revestimento utilizado

Influência da incorporação de resíduos na permeabilidade ao vapor de água de compósitos de matriz epoxídica / Influence of the incorporation of waste on the water vapor permeability of epoxide matrix composites

Seja um revestimento ou uma embalagem, a permeabilidade ao vapor de água é uma caracterização importante para verificar a eficácia dos mesmos. Neste sentido, este trabalho avalia o efeito da incorporação de resíduos, chamote e pó da casca de coco, na permeabilidade de compósitos de matriz epoxídica. O sistema epóxi utilizado neste trabalho foi o DGEBA/TETA, na estequiometria de 20 phr. A quantidade de carga foi igual a 20% do volume, sendo avaliadas formulações sem carga, reforçadas somente com chamote, reforçadas somente com pó da casca de coco e reforçados com ambos os resíduos. O ensaio de permeabilidade foi realizado conforme a ASTM D1653 por meio do método B, na condição C à uma temperatura de 23°C. Os resultados deste trabalho indicaram que a adição de chamote favorece a uma redução na permeabilidade ao vapor de água, enquanto a adição de pó da casca de coco tende a elevar a permeabilidade ao inserir descontinuidades na matriz

Analysis of the properties of piassava fiber and castor oil polyurethane for application in polymeric composite materials / Análise das propriedades da fibra de piassava e resina poliuretana de óleo de mamona para aplicação em materiais compósitos poliméricos

This work aims to characterize the waste from a broom factory located in the city of Campos dos Goytacazes-RJ, Brazil. The company uses the natural fiber popularly known as "Piaçava Nova", from the south of Bahia, of the species Attalea Funifera Martius. Fibers are used to make brooms that are sold in the city. A large amount of waste generated daily and rendered unusable when discarded irregularly in landfills. Approximately 10m³ of waste per month is created from this small factory. Therefore, this underutilized material can prove to be a quality raw material when used combined with natural resins for development of a polymeric composite floor be used in construction. In addition to the objective, this project sustains the responsibility of the academic society towards the environment, in order to minimize the use of synthetic fibers when there is possibility of using the natural ones

Weibull analysis of the tensile strength dependence with fiber diameter of giant bamboo

The fibers extracted from the stem of the giant bamboo plant have been investigated as possible composite reinforcement due to their relatively high tensile strength. A dimensional characterization of the distribution and the effect of diameter on the mechanical resistance of bamboo fiber of the species Dendrocalmus giganteus has not yet been performed. The present work characterized the distribution of a bundle of this bamboo fiber. Based on this characterization, diameter intervals were set and the dependence of the tensile strength of these fibers with a corresponding diameter was analyzed by the Weibull method. The results indicated an inverse dependence, in which the highest tensile strength was obtained for the thinnest fibers. Moreover, a mathematical hyperbolic relationship was found to adjust well this inverse correlation. An investigation of the microstructure by means of scanning electron microscopy revealed a potential mechanism for this correlation. Keywords: Giant bamboo, Fiber diameter, Tensile strength, Weibull analysi

Properties of Luffa Cylindrica Mats Reinforced Castor Oil-Based Polyurethane Composite as an Alternative for Oriented Strand Board

The main objective of this work was to produce and characterize a novel ecofriendly castor oil-based polyurethane (COPU) matrix composite reinforced by Luffa cylindrica mats, luffa for short, to be used as panels, as an alternative to oriented strand board (OSB). To do so, the mechanical behavior was evaluated by tree point flexural, perpendicular o surface tensile, screw pullout, and impact tests that were carried on the novel composite along with the neat matrix. Furthermore, the physical characteristics, the thermomechanical behavior, and the functional groups of the materials were observed by water absorption and thickness swelling tests along with dilatometry and Fourier transform infrared spectroscopy (FTIR). A comparison with commercialized OSB was also performed for control. The luffa/COPU composite was prepared by hand lay-up with 48 vol% of luffa mats incorporated as the maximum allowed by the mold under the available resources for manufacturing. The luffa fibers acted as a good reinforcement for the COPU matrix, where the flexural strength and modulus of elasticity were increased by more than 23 and 10 times, respectively, and the other mechanical properties more than doubled for the composites compared to the neat COPU resin. In general, the composite presented a lower performance compared to the commercial OSB, with the impact results being the exception. The water absorption and thickness swallowing results showed an already-expected behavior for the studied materials, where the better performance was found for the hydrophobic neat resin. The FTIR revealed that there was little interaction between luffa and COPU resin, which can be translated to a weak interface between these materials. However, the mechanical behavior, together with the other results presented by the luffa/COPU composite, confirm it is more than enough to be used as civil construction panels such as OSB

Toughness of polyester matrix composites reinforced with sugarcane bagasse fibers evaluated by Charpy impact tests

The fibers extracted from the sugarcane bagasse have been investigated as possible reinforcement for polymer matrix composites. The use of these composites in engineering applications, associated with conditions such as ballistic armor, requires information on the impact toughness. In the present work, Charpy tests were performed in ASTM standard specimens of polyester matrix composites, reinforced with 10, 20 and 30 vol% of continuous and aligned sugarcane bagasse fibers, in order to evaluate the impact energy. Within the standard deviation, the composite absorbed impact energy increased with the volume fraction of sugarcane bagasse fiber. This toughness performance was found by scanning electron microscopy to be associated with the fiber/matrix delamination. Keywords: Sugarcane bagasse fiber, Polyester composites, Charpy test, Impact toughnes

High temperature work hardening stages, dynamic strain aging and related dislocation structure in tensile deformed AISI 301 stainless steel

The development of dislocation structures associated with work hardening stages and dynamic strain aging (DSA) is investigated in an AISI 301 austenitic stainless steel plastically deformed in tension at 500 and 600 °C. In the first work hardening stage, up to 22% of plastic strain at 500 °C and 18% at 600 °C, incipient dislocation cells begin to be formed and are observed in association with {1 0 0} TEM diffraction pattern. At the transition point from first to second stage, the cells are well consolidated with a maximum dislocation density typical of DSA in stainless steels. The sharp decrease in work hardening rate after the transition point discloses a reduction in cell size together with evidence of dynamic recovery without sub-boundaries formation due to DSA. Keywords: 301 stainless steel, Work hardening stages, Dislocation structure, Dynamic strain agin

Mechanical and microstructural characterization of geopolymeric concrete subjected to fatigue

Cements from alkali-activated reactions are unleashing opportunities for the future application of inorganic polymers, known as geopolymers. These materials are eco-friendly, since their manufacturing process does not involve carbon dioxide (CO2) emission and it makes possible the use of industrial waste as raw material. In this work, a geopolymeric cement concrete (GCC) was developed through adequate portions of geopolymer components. Its characteristics were compared with Portland cement concrete (PCC), through the establishment of some parameters of design such as consumption of binders, water/aggregates ratio and cement content. The mechanical performance of these concretes was evaluated with emphasis on the fatigue behavior. The results showed a better fatigue performance of CCG in comparison with PCC in several parameters. Better matrix/aggregate adhesion in the CCG in comparison with PCC was also observed in the microstructural analysis, which may explain its superior fatigue performance. Keywords: Geopolymer, Concrete, Fatigu

Evaluation of the physical properties of composite panels with eucalyptus sawdust waste and castor oil-based polyurethane

Natural fibers have several advantages over synthetic fibers, and due to this, they are being increasingly used in various applications. Industrial waste generated during the production chain of different types of sectors is becoming a major environmental problem. The objective of this work was to produce and evaluate the physical properties of composite panels produced with waste from the wood industry, eucalyptus sawdust, and also with another waste, this time from the red ceramic industry, chamotte, and matrix polyurethane resin based on of castor oil. The composite panels were produced in volumetric fractions of 70, 75, 80, 85 and 90% of eucalyptus sawdust, and a variation of 0, 5 and 10% of chamotte. The tests to evaluate the physical properties were: Density, Moisture Content, Water Absorption and Thickness Swelling. The results showed that as the volumetric fraction of chamotte was incorporated into the composite, the higher the density value was obtained, and that this value decreased as the eucalyptus fiber fraction increased in the formulation. The SEM images revealed that chamotte provided a reduction in the amount of bubbles present in the resin. The moisture content, water absorption and swelling increased as the volumetric fraction of fiber increased, and decreased as the volumetric fraction of chamotte incorporation increased. It is concluded that there is technical feasibility for the use of eucalyptus residue, together with chamotte and castor oil-based polyurethane resin for the manufacture of composites. The perspective after this research is make a partner with a wood panels industry and create a new line of green composites panels made by recycled waste from industry

Fique Fabric: A Promising Reinforcement for Polymer Composites

A relatively unknown natural fiber extracted from the leaves of the fique plant, native of the South American Andes, has recently shown potential as reinforcement of polymer composites for engineering applications. Preliminary investigations indicated a promising substitute for synthetic fibers, competing with other well-known natural fibers. The fabric made from fique fibers have not yet been investigated as possible composite reinforcement. Therefore, in the present work a more thorough characterization of fique fabric as a reinforcement of composites with a polyester matrix was performed. Thermal mechanical properties of fique fabric composites were determined by dynamic mechanical analysis (DMA). The ballistic performance of plain woven fique fabric-reinforced polyester matrix composites was investigated as a second layer in a multilayered armor system (MAS). The results revealed a sensible improvement in thermal dynamic mechanical behavior. Both viscoelastic stiffness and glass transition temperature were increased with the amount of incorporated fique fabric. In terms of ballistic results, the fique fabric composites present a performance similar to that of the much stronger KevlarTM as an MAS second layer with the same thickness. A cost analysis indicated that armor vests with fique fabric composites as an MAS second layer would be 13 times less expensive than a similar creation made with Kevlar™