The application of cellulose nanocrystal has lately been investigated as polymer composites reinforcement owing to favorable characteristics of biodegradability and cost effectiveness as well as superior mechanical properties. In the present work novel nanocomposites of unsaturated polyester matrix reinforced with low amount of 1, 2, and 3 wt% of cellulose nanocrystals obtained from conifer fiber (CNC) were characterized. The polyester matrix and nanocomposites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), bending test, and thermogravimetric analysis (TGA). The result showed that the addition of only 2 wt% CNC increased the nanocomposite flexural strength by 159%, the ductility by 500% and the toughness by 1420%. Fracture analyses by SEM revealed a uniform participation of the CNC in the polyester microstructure. The resistance to thermal degradation of the CNC reinforced nanocomposites was improved in more than 20 °C as compared to neat polyester. No significant changes were detected in the water absorptions and XRD pattern of the neat polyester with incorporations up to 3 wt% CNC. These results reveal that the 2 wt% CNC nanocomposite might be a promising more ductile, lightweight and cost-effective substitute for conventional glass fiber composites in engineering applications.

Natural lignocellulose fibers have been extensively investigated and applied as a reinforcement of polymer composites in industrial applications from food packing to automotive parts. Among the advantages of natural fibers stands their relatively low cost and sustainable characteristics. These are accentuated in the case of residual fibers such as those obtained from coffee husks, an agribusiness waste, usually burnt or disposed into the environment. As composite reinforcement, hydrophilic natural fibers display adhesion problems to the most hydrophobic polymer matrices. This adhesion might be improved with distinct types of fibers surface treatments. In the present work, the effectiveness of three surface treatments applied to coffee husk fiber wastes (CHFW) were investigated, aiming to improve the tensile performance of castor oil-based polyurethane (COPU) biocomposites. The effects of treatments associated with (i) chemical with sodium hydroxide, (ii) physical by temperature and pressure and hydrothermic treatment, and (iii) biological by fermentation with Phanerochaete Chrysosporium fungus were evaluated by means of Fourier transformed infrared spectroscopy, X-ray diffraction, thermal analyses and morphology by scanning electron microscopy for different concentration of NaOH, different hydrothermic times at 121 °C/98 kPa and exposition to P. chrysosporium. The most effective treatment was the hydrothermal one at 121 °C and 98.06 kPa for 30 min. Preliminary tensile tests were performed in COPU biocomposites reinforced with 20% CHFWs subjected to the optimized conditions for each distinct type of treatment. The results indicated that the hydrothermal treatment promoted significant enhancement in the fiber/matrix interfacial bond, increasing the tensile strength up to 60% compared to COPU reinforced with in natura CHFWs fibers. It is important to mention that these composites can be applied as plastic wood for household items’ internal parts and in the automobile industry.

In a recent paper, novel polyester nanocomposites reinforced with up to 3 wt% of cellulose nanocrystals (CNCs) extracted from conifer fiber were characterized for their crystallinity index, water absorption, and flexural and thermal resistance. The use of this novel class of nanocomposites as a possible substitute for conventional glass fiber composites (fiberglass) was then suggested, especially for the 1 and 2 wt% CNC composites due to promising bending, density, and water absorption results. However, for effective engineering applications requiring impact and tensile performance, the corresponding properties need to be evaluated. Therefore, this extension of the previous work presents additional results on Izod and tensile tests of 1 and 2 wt% CNC-reinforced polyester composites, together with a comparative cost analysis with fiberglass. The chemical effect caused by incorporation of CNCs into polyester was also investigated by FTIR. In comparison to the neat polyester, the Izod impact energy increased 50% and 16% for the 1 and 2 wt% composites, respectively. On the other hand, the tensile strength and Young’s modulus remained constant within the ANOVA statistical analysis. FTIR analysis failed to reveal any chemical modification caused by up to 2 wt% CNC incorporation. The present impact and tensile results corroborate the promising substitution of a polyester composite reinforced with very low amount of CNCs for common fiberglass in engineering application.

Neste trabalho objetiva-se avaliar a microestrutura e as propriedades mecânicas de um aço ARBL microligado recebida na condição laminada e após recozimento a 950 ºC e 1150 ºC. A microestrutura foi analisada por meio da técnica de microscopia confocal e as micrografias foram utilizadas para análise quantitativa do tamanho dos grãos. As propriedades mecânicas obtidas foram determinadas por meio de ensaios de tração. Foi observado que em todas condições a microestrutura é constituída de ferrita e perlita, mas que os tamanhos de grãos ferríticos são diferentes e que os tratamentos térmicos promoveram a queda da tensão de escoamento e da resistência à tração. No entanto, verificou-se que um dos tratamentos térmicos resultou num tamanho de grão mais próximo ao tamanho de grão encontrado na condição recebida.Palavras-chave: Aço microligado; Recozimento; Microestrutura; Propriedades Mecânicas.

Neste artigo foi feita análise da falha e do projeto construtivo de um vaso de pressão germinado, que sofreu uma trinca transversal na região do anel de reforço e solda de interligação da parede horizontal do vaso com a vertical. Primeiramente foi feito ensaio não destrutivo por líquido penetrante para revelar da trinca e o ensaio de ultrassom para medição de espessura da parede do vaso. Para análise dos materiais, inicialmente foram retiradas amostras dos cilindros vertical e horizonal distantes da solda a fim de realizar análise química e microestrutural da seção transversal do material de cada cilindro e determinação de dureza Vickers. As mesmas análises foram realizadas na região soldada trincada a fim de verificar se as mudanças metalúrgicas ocasionadas pelo processo de soldagem foram responsáveis pela formação da trinca. A análise do projeto utilizado foi realizada a partir do cálculo de espessura mínima admissível, pressão máxima de trabalho admissível (PMTA) e as dimensões necessárias para o anel de reforço ideal de acordo com as condições de operação estabelecidas pelo fabricante, empregado de acordo com o código de projeto internacional ASME Section VIII, Divisão 1. Também foi verificado se o ajuste da seção soldada na qual foi encontrada a trinca apresentava um desalinhamento dentro das tolerâncias estabelecidas pelo código. Após análise dos resultados, verificou-se que a falha foi ocasionada por um procedimento mal executado, que poderia ter sido evitado caso as recomendações do código tivessem sido acatadas.