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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. ABSTRACTFibre metal laminates (FMLs) have been widely used to manufacture airframe components. This work describes novel sisal fibre reinforced aluminium laminates (SiRALs) that have been prepared by cold pressing techniques and tested under tensile, flexural and impact loading. The pristine sisal fabric and the sisal fibre reinforced composites (SFRCs) were also tested to understand the difference in mechanical performance of the sisal fibre metal laminates. The SiRALs achieved not only the highest modulus and strength, but also the highest specific properties. The mean specific tensile strength and modulus of the SIRALs reached increases of 132% and 267%, respectively, when compared to the sisal fibre reinforced composites (SFRCs). Moreover, the mean specific flexural strength and modulus of the SiRALs were significantly higher than SFRCs, revealing increases of 430% and 973%, respectively. A delamination fracture mode was noted for SiRALs under bending testing. The SiRALs can be considered promising and sustainable composite materials for structural and multifunctional applications.

A full factorial design (2 2 3 1) has been used to investigate the effect of the use of sodium hydroxide fibre treatment, Portland cement and uniaxial pressure on the physical and mechanical properties of hybrid short coir fibre reinforced composites (HSCoirFRCs). The response variables considered in this work were the apparent density, porosity, tensile and flexural strength, the modulus of elasticity and the Charpy impact resistance. The alkali treatment contributed not only to reduce the apparent porosity, but also to increase the mechanical properties of the HSCoirFRCs. A reduction of the impact resistance and an increase of the apparent density was also identified after treatment. Cold pressing significantly affected the physical and mechanical properties of the HSCoirFRCs. Higher pressure levels enhanced the wettability of the fibres and, consequently, the mechanical performance of the composites. The incorporation of cement microparticles as a second reinforcement phase was however not effective, leading to decreased strength and an increased apparent density of the materials. The HSCoirFRC structure can be considered an economical and sustainable alternative for future secondary structural parts in lightweight transport applications.

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In recent years, studies of composite materials have focused on the use of natural fibres as an alternative to synthetic ones. Their attractive mechanical properties, sustainability, low cost and low weight have leveraged research in this area, with the potential of a variety of applications in the engineering field. In this paper, a Full Factorial Design (2¹6¹) experiment was performed to identify the effect of silica microparticle inclusions and the stacking sequence of glass fibre cross-ply fabric and short sisal fibre layers on the apparent density, tensile and flexural strength and modulus of hybrid epoxy composites. In general, the hybrid composites with higher number of glass fibre layers achieve higher values of tensile and flexural strength (348 MPa and 663.28 MPa), tensile and flexural modulus (22 GPa and 2.50 GPa) and higher apparent density (2.02 g/cm³). It is, however, noteworthy that the incorporation of silica particles improves the mechanical performance of composites containing larger amounts of sisal fibres.

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The progress in establishing new classes of biocomposites has led to potential applications in the automotive, aerospace, and construction industries because of their life cycle properties, low cost, lightweight, nonabrasive, and moderate mechanical strength. The heterogeneity of natural fibers plays an important role in the fiber-matrix adhesion, therefore affecting the mechanical performance and the durability of the composites. This work has described the manufacturing, characterization, and testing of hybrid composites reinforced with sisal fibers and silica nanoparticles. A full factorial design was performed to identify the effects of fiber treatment, fiber orientation and nanosilica inclusion factors on the physical and mechanical properties of hybrid composites. Composites made with unidirectional untreated fibres and silica nanoparticles (2 wt%) provided higher impact resistance. In contrast, the highest strength and stiffness values and the lowest overall porosity were achieved when unidirectional treated fibres with 2 wt% of silica inclusions were considered. POLYM. COMPOS., 39:146-156, 2018.

The knowledge about anisotropy of wood possibility more security design of structures and structural members designed. Therefore, there are little quantity of results knowledge about shrinkage and anisotropy coefficients of Wood species, motivating the development of new researches. The aim of research is evaluate the possibility of estimate the full shrinkage (radial; tangential; volumetric), anisotropy coefficient and shrinkage coefficient (radial; tangential; volumetric), using polynomial regression models (linear; quadratic; cubic) and exponential, by density of five Wood species (Cedro Doce [C20]; Canafístula [C30]; Angelim Araroba [C40]; Mandioqueira [C50]; Angelim Vermelho [C60]), properly classifieds in five strength classes for dicotyledonous according Brazilian Standard ABNT NBR 7190:1997. The better results were from tangential and volumetric retractions both using exponentials functions, justified by lower values of variation coefficients, with coefficients values of determination adjusted ranging from 51 and 54%. Even considered significant to the regressions for the tangential and volumetric shrinkage by analysis of variance, but with adjusted coefficients of determination lower than 70%, news researches should realized with other Wood species, enabling find general expressions for estimating such properties using the knowledge of the density.