Mechanical properties of composites reinforced with lignocellulosic fibers have been researched in recent decades. Jute and mallow fibers are reinforcement alternatives, as they can contribute to increase the mechanical strength of composite materials. The present work aims to predict the Young’s modulus with application of continuous and aligned lignocellulosic fibers to be applied as reinforcement in polyester matrix. Fibers were manually separated and then arranged and aligned in the polyester matrix. Composites with addition 5, 15, and 25 vol% jute and mallow fibers were produced by vacuum-assisted hand lay-up/vaccum-bagging procedure. Samples were tested in tensile and the tensile strength, elasticity modulus, and deformation were determined. Results showed that the intrinsic Young’s modulus of the fibers was set at values around 17.95 and 11.72 GPa for jute and mallow fibers, respectively. Statistical analysis showed that composites reinforced with 15 and 25 vol% jute and mallow presented the highest values of tensile strength and Young’s modulus. The incorporation of 25 vol% of jute and mallow fibers increased the matrix Young’s modulus by 534% and 353%, respectively, effectively stiffening the composite material. Prediction models presented similar values for the Young’s modulus, showing that jute and mallow fibers might be used as potential reinforcement of polymeric matrices

The development of wind turbines for regions with low wind speeds imposes a challenge to the expansion of the corresponding energy generation capacity. The present work consists of an evaluation of the potential carded jute fiber and jute yarn to be used in the construction of a wind blade for regions of low wind intensity. The fibers used were supplied by Company Textile of Castanhal (Castanhal-Para-Brazil) and used in the study without chemical treatment in the form of single-filament fibers and yarns with a surface twist of 18.5°. The composites were produced through the resin infusion technique and underwent tensile and shear tests using 120-Ohm strain gauges and a blade extensometer to obtain the Young’s modulus. In the analysis of the results, the ANOVA test was applied with a 0.05 significance level, followed by Tukey’s test. The results showed that long, aligned jute fibers can be a good option for laminated structures applied in composites for small wind turbine blades.

In this work, composite materials of polyester matrix reinforced by short sisal fibers, were produced using the minimum stages of technology processing in the productive step, with views to produce a composite material technically easy to produce. The polyester matrix used was a pre-accelerated tereftalic with cobalt naftenat and cured at room temperature with methyl ethyl ketone peroxide (MEK) in different proportions in relation to the resin, 0.33%, 1.66%, 3.33% and 5.00% by volume in order to evaluate the influence on mechanical properties. The sisal fibers were manually cut in lengths of 5, 10 and 15 mm and used in the way purchased and surface untreated. Mechanical properties were evaluated by tests of traction and Charpy impact. The results showed that the increase in the length of the sisal fiber, tensile strength and impact of composites has been increased, reaching the composite of sisal fibers, 15 mm, the best performance with the specimen series tested.

RESUMO O desenvolvimento de compósitos reforçados com fibras naturais se alia à nova lógica do desenvolvimento sustentável e potencializa a produção de materiais ambientalmente corretos. A chave para tornar economicamente viável e ambientalmente favoráveis estes novos materiais passa pela adaptação de técnicas consagradas de fabricação de compósitos às propriedades peculiares e intrínsecas das fibras naturais, como o processo de infusão, que por se tratar de um processamento em molde fechado contribui para a redução das emissões de voláteis ao meio ambiente na etapa de fabricação. Neste trabalho estudaram-se como as principais variáveis do processo de infusão afetam as propriedades do compósito quando são utilizadas fibras naturais como reforço de uma matriz de poliéster insaturado. Produziram-se placas reforçadas com fibras de curauá, juta e palha da costa arranjadas na forma de fios alinhados ou tecido em estilo plano sob diferentes níveis de vácuo no processamento. A elevação do nível de vácuo altera a condição de compactação das fibras modificando sua porosidade, interface fibra/matriz e consequentemente as propriedades do compósito. Os compósitos foram caracterizados quanto à sua resistência à tração, módulo de elasticidade, impacto Charpy e porosidade. Os resultados mostraram que o processo de infusão possibilitou a fabricação de compósitos com até 45% de fração volumétrica de fibra, com porosidade em torno de 2% e excelente estabilidade dimensional. Verificou-se ainda que, no geral, a elevação do nível de vácuo alterou significativamente as condições de compactação dos reforços, alterando, a depender da estrutura da fibra utilizada, a eficiência da interface matriz/reforço.