Metodologia de curvatura de bambu laminado colado (BLAC) para fabricação de mobiliário: diretrizes para o design

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da Espessura nas Propriedades Mecânicas de Compósitos Híbridos Interlaminares de Curauá/Vidro/Poliéster

The interest in the use of vegetable fibers (e.g. jute, sisal and curaua) for more noble applications, such as reinforcement in polymeric composite materials, has increased over the years due to a variety of aspects, especially those related to environmental legislation and community awareness regarding the life cycle of products. In this context, the aim of this work is to develop hybrid interlaminate curaua/glass/insaturated polyester composites by hot compression molding and to analyze their mechanical properties as a function of the thickness of the laminate. The short beam strength of the thickest sample decreased due to its higher void content. Furthermore, the thinnest sample showed lower hardness, and lower impact, tensile and Iosipescu shear strength, partly attributed to its lower fiber volumetric fraction. Thus, in general, the most adequate laminate was the one comprising eight layers, four of which were of glass fiber and four of curaua fiber, but only if flexural loading is not critical.

Estudo in vitro do comportamento de facetas confeccionadas com artglass e targis quando submetidas à inserção e remoção de grampos circunferenciais em cromo-cobalto

Aiming to investigate in vitro the behavior of esthetic veneers placed in crows and made of the laboratory resins Artglass and Targis when submitted to insertion and removal of circunferential cobalt-chromium clasps, 24 veneer crowns were made (twelve with Artglass (Heraeus Kulzer) and twelve with Targis (Ivoclar Vivadent)), as well as the respective cobalt-chromium clasps. The crowns were then submitted to five thousand cycles of clasps insertion and removal, using a proper device. Using the verification of the force necessary to remove the clasps over the crowns during the experiment, the clasps and crowns mass variation, and the macroscopic inspection of the veneers, one may conclude that the veneers did not show a significant variation of the force required to remove the clasps over the crowns; they show a little amount of abrasion, possible to detect using a visual inspection and they show a little and variable amount of mass loss, less for that made with Artglass (average of 0,002g) and greater for that made with Targis (average of 0,006g)

Effect of fiber orientation on the shear behavior of glass fiber/epoxy composites

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

Repair Technique for Fractured Implant-Supported Metal-Ceramic Restorations: A Clinical Report

The fracture of porcelain structures have been related in either natural dentition or implant-supported restorations. Techniques using a composite resin or indirect methods can be used. This article presents a porcelain fracture on implant-supported metal-ceramic restoration. IPS Empress e.max laminate veneer restoration was used to repair the fracture. With this technique, it was possible to restore aesthetics and function, combined with low cost and patient satisfaction.

Caracterização física e mecânica de compensado produzido com dois diferentes adesivos em duas variações de pressão de prensagem

The adhesives used in the production of engineered boards have been object of study over the years in order to improve the properties of the boards with less energy consumption, lower production costs and reduced environmental impact. In addition to that, process variables may affect the properties of the board. The present study aimed to characterize sheets of plywood, manufactured with two types of adhesives, under two different pressing conditions. The adhesives used for the study were Phenol-formaldehyde and Polyurethane castor oil based. The pressure of pressing was varied in a range from 75 to 160 Bar, in order to verify how they influence the physical and mechanical properties of the board. The tests performed resulted in a conclusion that shows that the moister content of the veneers interferes on the physical and mechanical tests. In general, boards produced with polyurethane resin showed superior physical and mechanical results; although the ones produced with phenol formaldehyde at a pressure of 75 Bar had always equal or higher values, compared to what is found in literature

Comparação de compósitos obtidos via RTM de resina epóxi e fibra de carbono com e sem descontinuidade nos tecidos

Technology is growing interest in the use of composites, due to the requirement of lighter materials and more resistant, factors essential to meet the project specifications and reduce the operational cost. In the production of high performance structural composites, considering the aerospace criteria, the domestic industry has shown interest in the process of resin transfer molding (RTM) for reproducibility and low cost. This process is suitable for producing components of polymeric composites with relatively simple geometries, consistent thicknesses, high quality finish with no size limitations. The objective of this work was machined carbon steel to make a matched-die tooling for RTM and produce two composite plates of epoxy resin and carbon fiber fabric with and without induced discontinuities, which were compared towards their impregnation with ultrasound, their properties via tensile tests and thermal analysis. In ultrasonic inspection, it was found good impregnation of the preform of both composites. In the thermal analysis it was possible to check the degradation temperature of the composites, the glass transition temperature and it was found that the composites showed no effective cure cycles, but presented good performance in the tensile test when compared with aluminum alloy 7050 T7451 . The results showed that the injection strategy was appropriate since the laminate exhibited a good quality for the proposed application

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)

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

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

Influência do condicionamento ambiental sobre as propriedades viscoelásticas de compósitos aramida/epóxi

The increasing application of structural composites in the aerospace industry is mainly due to its low specific weight coupled with its excellent mechanical properties when in service. As a result of climatic variations that pass the aircraft is of paramount importance to study the influence of weathering on this type of material when subjected to such changes. The purpose of this work is to evaluate the mechanical behavior of specimens of kevlar fiber /epoxy matrix composites, by dynamic mechanical thermal analysis (DMA) and interlaminar shear strength tests (ILSS), after passing through three environmental conditioning: saline fog, hygrothermal and ultraviolet radiation. From the results, we concluded that the laminate was molded supplied homogeneously, not presenting problems such as porosity, delaminations or cracks inside. After a period of 625 hours of exposure to hygrothermal conditioning, we observed a 1,2% maximum of absorption of moisture. Samples subjected to the conditioning by UV irradiation (600 hours) and salt spray showed a reduction of about 24,30% and 32,30%, respectively, on the shear strength (ILSS). In DMA analysis is not observed significant changes on the glass transition temperature. However, when considering the storage modulus of the samples conditioned by UV radiation (1200 hours), salt spray and hygrothermal conditioning there is an increase of 5,34% , 7,19% and 5,57% respectively

Avaliação dos efeitos ambientais nas propriedades do compósito de poliamida 6,6/fibras de carbono

This graduation work done study of polyamide 6.6/composite carbon fibres, since its processing, characterization of the main properties. Besides the influence of temperature, UV radiation, salt spray and moisture on the mechanical and viscoelastic behavior. To achieve this goal, the first composite was processed from the heat compression molding using known variables of the process and using the empirical method to find the best value for other parameters. The method processing molding was chosen because it common in composites processing in order to evaluate the influence of crystallinity of the properties that influence the mechanical and viscoelastic behavior laminates. From the obtained laminate specimens were evaluated in weathering, such as: in hygrothermal chamber, UV, salt spray and thermal shock. In another step, the effect produced by these constraints were evaluated by optical microscopy, ultrasound, dynamic mechanical analysis and vibration tests. This project was conducted at the Department of Technology and Materials of UNESP in Guaratingueta, where all the equipment and techniques for the implementation of this project met available. After the tests proved the applicability of the composite polyamide 6.6/carbon fibers in aeronautical applications with resistance the main climatic influences

Sistemas cerámicos puros parte 2: materiales, propiedades ópticas y consideraciones clínicas

While dentistry continues to advance, the aesthetic techniques have evolved in proceedings more effective, functional and biocompatible. Meanwhile, cosmetic dentistry has become a bit more complex and technically difficult. With improvement of the properties (physical and optical) of the ceramics and the establishment of a working protocol, ceramic restorations have become increasingly popular. Currently there are several ceramic systems have excellent optical properties such as opalescence, fluorescence, translucency, chromaticity, which allow the restoration to mimic the tooth structure. From the physical point of view has restored biomechanical integrity and strengthening the remaining tooth structure. All this has led the profession to experience the use of new ceramic systems ranging from conventional feldspathic ceramics to modem ceramic reinforced, injected or computer-aid made. The material selection should be based on clinical need, aesthetic and functional requirements, restoration site, prosthetic design and laboratory techniques. In this article we will deal with the characteristics of the materials, their optical properties and clinical considerations for proper selection.

Reabilitação estética do sorriso por meio do sistema cerâmico dissilicato de lítio: relato de caso

The reestablishment of a harmonious smile through dental ceramics, when properly conducted and with specific indications, can achieve extremely predictable results. For aesthetic and functional rehabilitation, many ceramic materials can be used such as zirconia, leucite, alumina, feldspar, and lithium disilicate. Among these materials the lithium disilicate stands out due to the following characteristics: its resistance to wear, to chemical attack, high temperatures and oxidation; low electrical conductivity; near zero thermal expansion; good optical properties and biocompatibility with periodontal; excellent esthetics; color stability and reinforcement of tooth structure. The indications for the use of lithium disilicate are not limited to multiple facets of teeth in cases where there was no favorable response to tooth whitening, and also comprehend teeth with multiple restorations, diastema closure, shape alteration, and dental contouring, replacement of missing or fractured teeth, among others. The versatility of lithium disilicate ceramics allows its utilization in several clinical situations. The concomitant use of lithium disilicate for veneers and over metal has satisfactory aesthetic results, as reported in the present studying cases that require both aesthetics and resistance.

O impacto do preparo, da cerâmica e do contato oclusal na distribuição de tensões em facetas

Pós-graduação em Odontologia Restauradora - ICT