Processamento e caracterização de compósitos termoplásticos multifuncionais reforçados com fibras de carbono e buckypapers de nanotubos de carbono
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Data
2021-12-01
Autores
Santos, Luis Felipe de Paula [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A área de compósitos multifuncionais encontra-se em constante expansão e sua utilização permite a concepção de materiais que não tenham somente a função de suporte mecânico, mas que também apresentem melhorias térmicas, elétricas, magnéticas, dentre outras. Além disso, é essencial que o compósito obtido promova uma redução da massa e de volume do sistema aumentando, assim, sua eficiência. O presente trabalho tem como objetivo processar e caracterizar buckypapers (BPs) de nanotubos de carbono carboxilados com e sem adição de mantas de poli (éter imida) (PEI), bem como avaliar sua influência nas propriedades térmicas e mecânicas de compósitos termoplásticos reforçados com fibras de carbono. Os resultados provenientes das análises de microscopia eletrônica de varredura, porosimetria, difratometria de Raios-X (DRX) e espectroscopia Raman evidenciaram uma estrutura altamente porosa para o BP e a potência utilizada na ponteira ultrassônica, não causaram danos significativos na estrutura cristalina dos nanotubos de carbono. A partir da avaliação da influência da incorporação de BP no comportamento térmico, foi constatado que houve um aumento na estabilidade térmica do compósito de PEI/Fibra de carbono (CF). Para o poli (aril éter cetona) (PAEK)/CF, a adição de BP com manta de PEI (BP-CM) não influenciou significativamente em sua estabilidade térmica. Porém, ao se adicionar BP sem manta (BP-SM), ambos os compósitos apresentaram uma redução em suas propriedades térmicas. Considerando os compósitos de PAEK, verificou-se que os BP-SM promoveram uma redução da temperatura de fusão (Tm) e de cristalização (TC) dos laminados, enquanto que para os laminados de BP-CM foi apenas observada a redução da TC. A partir das análises dinâmico-mecânicas realizadas observou-se que a adição do BP-CM promoveu um aumento da flexibilidade em ambos os compósitos avaliados. Por fim, a adição de BP promoveu uma redução da resistência interlaminar em modo-I (GIC), logo uma menor dissipação de energia, menor rugosidade e uma menor quantidade de micro mecanismos da fratura foram observados. Por outro lado, em modo-II um aumento da resistência interlaminar (GIIC) foi observada, indicando que os nanotubos de carbono atuaram como “pontes”, gerando, assim, um aumento da energia dissipada, da formação de mecanismos de danos e da rugosidade. Este comportamento foi observado tanto em condições estáticas quanto dinâmicas.
Multifunctional composites have been expanding over the last decade, allowing the design of materials that not only have the function of mechanical support but also add thermal, electrical, and magnetic improvements to materials. In addition, it is crucial to obtain laminates that promote both a reduction in weight and volume, increasing its efficiency. This work aims to obtain and to characterize carbon nanotube buckypapers with and without poly (ether imide) (PEI) mats, as well as evaluate their influence on the thermal and mechanical properties of carbon fiber reinforced thermoplastic composites. Scanning electron microscopy, porosimetry, X-ray diffraction (XRD), and Raman spectroscopy results showed a highly porous structure for BP and the power applied to the ultrasonic tip did not cause significant damage to the crystal structure of carbon nanotubes. The thermal stability of the PEI/CF laminates showed an increase by the incorporation of the BP whereas, the addition of BP with PEI mats (BP-CM) in PAEK/CF laminate did not influence significantly its thermal stability. Although, adding only BP (BP-SM) in both laminates showed a reduction in their thermal stability. Considering the PAEK laminate, the BP-SM promoted a reduction of both melting (Tm) and crystallization (Tc) temperatures. However, for both laminates with BP-CM, only a reduction of the crystallization temperature was noted. Dynamic mechanical analysis (DMA) results revealed that the addition of BP-CM promoted an increase of the flexibility for both composites. Finally, the addition of buckypapers led to a reduction in the interlaminar strength in mode-I (GIC), which means less energy dissipation, limited roughness, and a smaller amount of micro-fracture mechanisms were observed. On the other hand, an increase of the interlaminar resistance (GIIC) was observed in mode-II, indicating the carbon nanotubes acted as “bridges” between matrix and fibers, increasing the dissipated energy, the formation of damage mechanisms, and roughness of the composites. It is crucial to mention that both modes were conducted under static and dynamic conditions
Multifunctional composites have been expanding over the last decade, allowing the design of materials that not only have the function of mechanical support but also add thermal, electrical, and magnetic improvements to materials. In addition, it is crucial to obtain laminates that promote both a reduction in weight and volume, increasing its efficiency. This work aims to obtain and to characterize carbon nanotube buckypapers with and without poly (ether imide) (PEI) mats, as well as evaluate their influence on the thermal and mechanical properties of carbon fiber reinforced thermoplastic composites. Scanning electron microscopy, porosimetry, X-ray diffraction (XRD), and Raman spectroscopy results showed a highly porous structure for BP and the power applied to the ultrasonic tip did not cause significant damage to the crystal structure of carbon nanotubes. The thermal stability of the PEI/CF laminates showed an increase by the incorporation of the BP whereas, the addition of BP with PEI mats (BP-CM) in PAEK/CF laminate did not influence significantly its thermal stability. Although, adding only BP (BP-SM) in both laminates showed a reduction in their thermal stability. Considering the PAEK laminate, the BP-SM promoted a reduction of both melting (Tm) and crystallization (Tc) temperatures. However, for both laminates with BP-CM, only a reduction of the crystallization temperature was noted. Dynamic mechanical analysis (DMA) results revealed that the addition of BP-CM promoted an increase of the flexibility for both composites. Finally, the addition of buckypapers led to a reduction in the interlaminar strength in mode-I (GIC), which means less energy dissipation, limited roughness, and a smaller amount of micro-fracture mechanisms were observed. On the other hand, an increase of the interlaminar resistance (GIIC) was observed in mode-II, indicating the carbon nanotubes acted as “bridges” between matrix and fibers, increasing the dissipated energy, the formation of damage mechanisms, and roughness of the composites. It is crucial to mention that both modes were conducted under static and dynamic conditions
Descrição
Palavras-chave
Compósitos termoplásticos, Nanotubos de carbono, Propriedades térmicas, Resistência à fratura interlaminar, Mecanismos da fratura, Thermoplastic composites, Carbon nanotubes, Thermal properties, Interlaminar fracture strength, Failure mechanisms, Nanocompósitos (Materiais), Termoplásticos, Nanotubos, Propriedades térmicas.