999 resultados para Compósitos híbridos
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Ps-graduao em Odontologia - FOAR
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Fundao de Amparo Pesquisa do Estado de So Paulo (FAPESP)
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Fundao de Amparo Pesquisa do Estado de So Paulo (FAPESP)
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Ps-graduao em Cincia e Tecnologia de Materiais - FC
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Ps-graduao em Aquicultura - FCAV
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Ps-graduao em Agronomia (Gentica e Melhoramento de Plantas) - FCAV
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The fracture surfaces express the sequence of events of energy release due to crack propagation by linking the relief of the fracture to the loading stresses. This study aims to evaluate the heterogeneity of the critical zone for the advancement of the crack along its entire length in a thermoset composite carbon fiber and epoxy matrix, fractured in DCB testing (Double Cantilever Beam) and ENF (End-Notched Flexure). Investigations were made from image stacks obtained by optical reflection of extended depth from focus reconstruction. The program NIH Image J was used to obtain elevation map and fully focused images of the fracture surface, whose topographies were quantitatively analyzed. The monofractal behavior for DCB samples was assessed as being heterogeneous along the crack front and along the crack for all the conditionings. For the samples fractured in ENF test, there was a strong positive correlation to the natural condition, considering the fibers at 0 for the monofractal dimension and structural dimension (Df and Ds). For fibers at 90 to crack propagation, there was a moderate positive correlation for the textural dimension of natural condition. However, for the samples under ultraviolet condition and those subjected to thermal cycles, there was no correlation between the fractal dimension and fracture toughness in mode II
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Sistemas de liberao controlada so formas farmacuticas que visam aumentar a eficcia teraputica, a segurana do tratamento e a adeso dos pacientes. Neste contexto, as matrizes polimricas, que buscam controlar o perfil de liberao de um frmaco, surgem como opo. Assim surge a necessidade de desenvolver e analisar materiais multifuncionais, que apresentem caractersticas superiores a dos materiais polimricos comuns, como os híbridos orgnico-inorgnicos. Esse projeto teve como objetivo analisar a capacidade de incorporao e liberao in vitro dos frmacos cloridrato de pramoxina e acetato de dexametasona em sistemas híbridos orgnico-inorgnicos. As amostras foram preparadas utilizando misturas em diferentes propores de materiais híbridos ureasil-polioxietileno (POE-1900) que possui um carter altamente hidroflico e ureasil-polioxipropileno (POP-400) com carter altamente hidrofbico. A partir dessas misturas pode-se controlar o balano hidroflico/hidrofbico das matrizes hbridas, permitindo avaliar o comportamento desses sistemas, frente a incorporao de frmacos tanto hidroflicos, como hidrofbicos. Os testes de incorporao revelaram a capacidade desses materiais de incorporar os frmacos cloridrato de pramoxina e acetato de dexametasona em concentraes relativamente altas (20% m/m e 3% m/m, respectivamente) se comparado a formulaes hoje presentes no mercado. Utilizando as diferentes propores dos precursores POE-1900 e POP-400 foi possvel modular o perfil de liberao dos frmacos, sendo que as amostras com maiores propores do POP-400 tiveram uma liberao mais retardada, devido hidrofobicidade do material. As amostras contendo a dexametasona (hidrofbico) apresentaram uma liberao mais lenta, constante e gradual se comparado a pramoxina (hidroflico).
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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
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In this work were studied associations of ZnO with the natural products caffeic and feluric acids. Two preparation methods were used, that is, the sol-gel and a reflux procedure. In the sol-gel method, ZnO is produced by the basics hydrolysis of precursors in the presence of the organic filters (caffeic and feluric acids), which results in 30 nm (or less) ZnO particles with the organic filters (in dissociated form) bonded to the surface of ZnO. In the reflux method, a dispersion of ZnO in a water/ethanol mixture was kept under reflux (50oC/4h) in the presence of the organic acids. The ZnO particles used in the reflux method have a higher diameter than sol-gel ZnO particles, but the prepared associated product ZnO/Organic acids were similar. Despite of the difference in relation to crystallinity between the products, the preparation methods resulted in analogous associations with respect to the interaction of the organic filters with the ZnO surface. The caffeic/ZnO associations presented low photostability, which lead to the degradation of the organic filter. The other associations (feluric acid/ZnO) presented satisfactory results. The FT-IR spectroscopy confirmed the formation of the association, and the nature of the bond formed compared with the Zn-O bond in Zn2+/Felutic acid complexes. The isolated organic and inorganic filters, along with the associations were analyzed by diffuse reflectance spectroscopy and Uv-vis spectroscopy. The absorption edges and the critical wavelengths were analyzed and the effects of Zn-O bonds in feluric acid/ZnO associations described as a function of the relative position of the /* system of the organic filter. Finally the performance of the hybrid filters were investigated in terms of the absorption of UVA and UVB radiations, with the UVA/UVB ratio, an efficiency parameter largely used in the description of solar filters, sunscreen and suncare products
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A aterosclerose uma doena caracterizada pela perda de elasticidade e espessamento da parede arterial, sendo iniciada pelo acmulo de lpides, clulas inflamatrias e elementos fibrosos na parede das artrias. Esses elementos, ao longo do tempo, daro origem a placas aterosclerticas ou ateromas que podem por ventura se romper, ocasionando no extravasamento de seu contedo lipdico central. Tal situao promover a adeso e a agregao plaquetria com conseqente formao de trombo. As doenas cardiovasculares (DCVs) so a principal causa de morte no mundo, sendo por isso bastante estudadas. Entre os recursos teraputicos disponveis se podem citar os antiagregantes plaquetrios. A terapia com antiagregantes plaquetrios apresenta alguns inconvenientes, que vo desde a ineficcia teraputica em alguns indivduos at efeitos adversos deletrios, como hemorragia e transtornos gastrointestinais. devido a esses fatores, acrescidos elevada prevalncia dessas doenas, que se busca a sntese de novos antiagregantes plaquetrios, mais efetivos e menos txicos para a preveno e o tratamento das DCVs, sendo o cido acetilsaliclico (AAS) um dos frmacos de primeira escolha para tratamento. Nesse projeto, usando a hibridao como estratgia de modificao molecular, planejou-se compostos derivados do AAS espaados pela subunidade N-acilhidrazona contendo ainda uma subunidade doadora de xido ntrico representado pelos furoxanos e benzofuroxanos. Esses híbridos constituem uma alternativa resistncia ao AAS por atuarem em diferentes vias bioqumicas potenciais para inibio da agregao plaquetria
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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
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O cncer uma patologia crescente entre a populao atual e segundo a Organizao Mundial da Sade (OMS) est entre as principais causa de morte mundialmente. A relevncia do perfil epidemiolgico dessa doena desperta interesse em desenvolver materiais que forneam qualidade de diagnstico e tratamento. Na busca pela qualidade da sade, o desenvolvimento de materiais que possam liberar frmacos de forma controlada e em um stio alvo, tem se tornado cada vez mais intensa, pois estes materiais podem diminuir os efeitos colaterais alm de aumentar a porcentagem do medicamento em ao direta com o stio alvo. Neste contexto, materiais polimricos híbridos orgnico-inorgnicos do tipo ureasil-politer que so biocompatveis, transparentes e flexveis permitem a incorporao de uma srie de compostos, dentre os quais, nanopartculas e frmacos. Com base nestes argumentos, neste trabalho foi desenvolvido dispositivo de liberao controlada de frmacos formado por materiais polimricos ureasil-politer contendo nanopartculas de ZnO dopadas com cobalto. A conjugao destes diferentes materiais teve como objetivo conferir as propriedades individuais de cada componente no mesmo material: o cobalto devido as suas propriedades magnticas pode guiar o dispositivo de liberao de frmaco at o rgo doente; o ZnO devido s propriedades luminescentes permite monitorar a posio do dispositivo dentro do corpo humano.
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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)
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