ECT - Artigos publicados em periódicos
URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/2969
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Navegando ECT - Artigos publicados em periódicos por Assunto "Accelerated aging"
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Artigo Accelerated aging effects on carbon fiber/epoxy composites(Elsevier, 2017-02-01) Barbosa, Ana Paula Cysne; Fulco, Ana Paula Pereira; Guerra, Érick Stéfano Silveira; Arakaki, Franscisco K.; Tosatto, Marcio; Nascimento, Maria Carolina Burgos Costa do; Melo, José Daniel DinizThe influence of operational environments on the long-term durability of structural components fabricated with carbon fiber reinforced composites is an ongoing concern. Exposures to ultraviolet radiation, temperature cycles and moisture are known to degrade the polymeric matrix. In this work, carbon-epoxy composites were subjected to accelerated aging in an aging chamber with controlled conditions of temperature, humidity and UV-radiation. Changes within the material are evaluated by Fourier-Transform Infrared (FTIR) Spectroscopy, Dynamic Mechanical Analysis (DMA), interlaminar shear strength and compressive strength, Scanning Electron Microscopy (SEM), and also in terms of mass variation. Although significant changes in mechanical properties were not observed, the effects of accelerated aging on the composite material were evidenced by mass loss, fiber exposure, chemical alterations, increased crack density in interlaminar shear tests and fiber buckling in fractured specimens after compression testinArtigo Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC(Springer, 2011-02-14) Bicudo, Tatiana de Campos; Candeia, R. A.; Sinfrônio, F. S. M.; Queiroz, N.; Barros Filho, A. K. D.; Soledade, Luiz Edmundo Bastos; Santos, I. M. G.; Souza, A. L.; Souza, A. G.Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by basecatalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME