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Geopolymer composites reinforced with flax fabrics (FF) and nanoclay platelets are synthesised and studied in terms of physical and mechanical properties. X-Ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM) techniques are used for phase and microstructure characterisation. The nanoclay platelets are added to reinforce the geopolymer matrices at 1.0%, 2.0%, and 3.0% by weight. It is found that 2.0 wt.% nanoclay enhances the density, decreases the porosity and subsequently improves the flexural strength and toughness. The microstructural analysis results indicate that the nanoclay behaves not only as a filler to improve the microstructure of the binder, but also as an activator to support the geopolymeric reaction producing higher content of geopolymer gel. This enhances the adhesion between geopolymer matrix and flax fibres, which improves the mechanical properties of the geopolymer nanocomposites reinforced with flax fabrics. [ABSTRACT FROM AUTHOR]

Despite their scarce resistance to humid or wet conditions, natural fiber reinforced composites (NFRCs) seem to be able to partially recover their performances under discontinuous exposition to marine environment. To investigate this peculiarity, flax fiber reinforced composite was at first subjected to salt-fog spray condition at 35 °C for 15 and 30 days, respectively, and then stored in "dry" condition (i.e., 50% R.H. and 22 °C) between 0 and 21 days. The performances evolution was evaluated through flexural tests, water uptake and contact angle measurements. Moreover, the morphology of fractured mechanical samples was examined by using 3D optical microscope and scanning electron microscope (SEM). Flax fiber reinforced composite experienced phenomena of both reversible and irreversible degradation during the wet phase thus evidencing a relevant mechanical recovery thanks to the drying. Quite interestingly, the laminate showed an almost complete recovery of the flexural strength, meaning that this property is more strictly related to mainly reversible aging phenomena whereas the greater stiffness loss is more probably due to irreversible ones. • Natural Fiber Reinforced Composites were aged under alternated salt-fog and dry steps. • Flexural tests, water uptake and water contact angle measurements were performed. • NFRCs experienced reversible and irreversible degradative phenomena. • Due to the drying, NFRCs showed an almost complete recovery of flexural strength. • A topological map discriminating reversible and irreversible aging zones was created. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effect of water absorption on the cutting behavior of biocomposites using flax fiber reinforced polylactic-acid (PLA) and the orthogonal cutting process. Different immersion times have been considered from 1 to 150 days in order to investigate both transient and saturated hygrometric regimes. Machining forces are measured during the cutting process and the machined surfaces are analyzed using a scanning electron microscope and an optical interferometer. The in-situ removed chip morphologies are captured by a high-speed camera. Results show a functional relationship between the multiscale hygro-mechanical properties of flax fiber composites and their shear mechanisms that are controlled by the water content. The water uptake modifies the cellulosic structure of natural flax fibers in the transient regime and damages the fiber/matrix interfaces in the saturated regime, which affects considerably the cutting mechanisms and the machinability of the biocomposite structure at different scale levels. • Flax fibers reinforced biocomposites are machined under different hygrometric conditions. • Chip morphology, cutting forces, and surface analysis are considered to investigate the machinability. • Cutting mechanisms differ when switching from transient to saturated hygrometric regime. • Cutting behavior of biocomposites is related to their multiscale hygro-mechanical properties. [ABSTRACT FROM AUTHOR]