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Authors
Abstract(s)
Os compósitos têm vindo a ser cada vez mais utilizados com o intuito de aumentar a vida
útil dos equipamentos. Os compósitos podem ser constituídos por uma de três matrizes:
cerâmicas, poliméricas e metálicas. As matrizes poliméricas são as mais empregues, em
virtude da sua facilidade de fabrico e resistência específica. Por esta razão, existem cada
vez mais estudos com o intuito de melhorar as propriedades das matrizes constituintes
dos compósitos, para desta forma poder melhorar as propriedades finais dos materiais e
suas aplicações. Por outro lado, os nanomateriais à base de carbono possibilitam novas
aplicações, uma vez que as suas propriedades físicas são únicas, melhorando as
propriedades mecânicas, elétricas, térmicas, entre outras.
Neste trabalho apresenta-se um estudo das propriedades mecânicas, elétricas e
eletromecânicas de compósitos de matriz epóxi reforçada com várias percentagens de
nanoplaquetas de grafeno (GNP) (0,25; 0,5; 0,75 e 1 wt. %). O compósito com 0,75 wt. %
apresentou a melhor resistência mecânica (tensão máxima, módulo de elasticidade e
dureza) e o compósito com 1 wt. % apresentou os piores. Pois, com maiores frações de
reforço cria-se uma saturação e maior dificuldade de homogeneização, ou seja, existe
uma maior probabilidade de formação de aglomerados provocando imperfeições na
interface.
Constatou-se que estes compósitos apresentam uma resistividade elevada, não sendo
possível a realização do estudo das propriedades eletromecânicas. Por esta razão
recorreu-se ao fabrico de laminados com tecido de carbono e reforço de nanoplaquetas
de grafeno (GNP). As propriedades mecânicas melhoraram em relação aos compósitos,
mas de forma pouco significativa. Relativamente às propriedades elétricas, os laminados
apresentam uma condutividade elétrica na gama dos semicondutores, permitindo assim
a realização de ensaios piezoresistivos. Desta forma realizou-se ensaios de caracterização
eletromecânica com avaliação simultânea da resposta elétrica durante ciclos de carga e
descarga. O comportamento da variação de resistência mostrou-se linear inverso sem
nanoreforço e linear direto com nanoreforço.
Lately, composites have been increasingly used to boost the life span of engineering equipment. Composites can be comprised of one of three following matrices, i.e., ceramic, polymeric, and metallic. Nevertheless, polymeric matrices are reported to be the most widely used by the scientific community, due to their ease of manufacture and specific strength. Therefore, numerous studies can be found in the literature aiming to improve the properties of the polymeric matrixes that form composites, ultimately, enhancing the final properties of the materials and their respective applications. Furthermore, carbon-based nanomaterials, owing to their physical properties, which are quite distinctive, have namely the capability to enable new applications, by improving the mechanical, electrical, and thermal properties. In In this dissertation work, a study of the mechanical, electrical, and electromechanical properties of epoxy composites reinforced with various percentages of graphene nanoplatelets GNP – 0.25, 0.5, 0.75, and 1 wt. % – is presented. From the experimental tests conducted, considering mechanical properties, the composite with 0.75 wt. % showed promising results, whilst, at the opposite extreme, the composite with 1 wt. % depicted the severest experimental data achieved. For the latter, it is possible to assume that the composite with more reinforcement is induced to the saturation phenomenon, that is, there is a higher probability of agglomerates formation which cause imperfections in the interfaces. Moreover, it was found that these composites have considerably high resistivity, which prevents the study of the electromechanical properties from being achieved. Within this framework of thought, the fabrication of laminates with carbon fabric and GNP nanoreinforcement was thereafter used. Broadly, the overall mechanical properties improved compared to the composites. Lastly, regarding electrical properties, the laminates have been found to possess an electrical conductivity in the semiconductor range, allowing this way piezoresistive tests performance. On top, it was also determined that the laminate reinforced without GNP showed a negative behavior of resistance variation, whereas the laminate reinforced with PNG presented a positive behavior.
Lately, composites have been increasingly used to boost the life span of engineering equipment. Composites can be comprised of one of three following matrices, i.e., ceramic, polymeric, and metallic. Nevertheless, polymeric matrices are reported to be the most widely used by the scientific community, due to their ease of manufacture and specific strength. Therefore, numerous studies can be found in the literature aiming to improve the properties of the polymeric matrixes that form composites, ultimately, enhancing the final properties of the materials and their respective applications. Furthermore, carbon-based nanomaterials, owing to their physical properties, which are quite distinctive, have namely the capability to enable new applications, by improving the mechanical, electrical, and thermal properties. In In this dissertation work, a study of the mechanical, electrical, and electromechanical properties of epoxy composites reinforced with various percentages of graphene nanoplatelets GNP – 0.25, 0.5, 0.75, and 1 wt. % – is presented. From the experimental tests conducted, considering mechanical properties, the composite with 0.75 wt. % showed promising results, whilst, at the opposite extreme, the composite with 1 wt. % depicted the severest experimental data achieved. For the latter, it is possible to assume that the composite with more reinforcement is induced to the saturation phenomenon, that is, there is a higher probability of agglomerates formation which cause imperfections in the interfaces. Moreover, it was found that these composites have considerably high resistivity, which prevents the study of the electromechanical properties from being achieved. Within this framework of thought, the fabrication of laminates with carbon fabric and GNP nanoreinforcement was thereafter used. Broadly, the overall mechanical properties improved compared to the composites. Lastly, regarding electrical properties, the laminates have been found to possess an electrical conductivity in the semiconductor range, allowing this way piezoresistive tests performance. On top, it was also determined that the laminate reinforced without GNP showed a negative behavior of resistance variation, whereas the laminate reinforced with PNG presented a positive behavior.
Description
Keywords
Compósitos de Matriz Polimérica Efeito Piezoresistivo Híbrido Laminado Nanoplaquetas de Grafeno Resina Epóxi Viscoelasticidade