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Oxidised nanocelluloses have previously shown promise for the production of extruded filaments with high tensile strength properties. However, they also exhibit poor wet strength due to swelling upon immersion in water. This has resulted in the use of chemical cross-linkers, or co-extrusion with multivalent cations, or cationic polymers, to inhibit this. Here, we report on the effect of incorporating sugar alcohols (glycerol, sorbitol and maltitol) in an oxidised nanocellulose gel before extrusion. Whilst their presence weakens the initial gel, they enable the continuous wet spinning of filaments that are stable in aqueous media without the need for post extrusion processing. We conclude that the relative hydrophilicity of the sugar alcohol and its ability to protonate surface carboxyl groups upon drying are key parameters regarding the physicochemical effects observed. [ABSTRACT FROM AUTHOR]

X-ray diffraction is an important tool for studying multiphase materials because it can resolve parameters from each phase independently. When coupled with a high-flux, microfocussed x-ray beam, scanning microdiffraction experiments are possible. This letter reports on the use of this technique to image a fiber reinforced composite with a complex woven lamina geometry. These systems are difficult to study with other experimental techniques because the fibers are inaccessible and the matrix is often opaque. However, microfocused x-ray diffraction reveals how macroscopic load affects the weave microgeometry by reorienting the embedded fibers. [ABSTRACT FROM AUTHOR]

Growing environmental concerns and stringent waste-flow regulations make the development of sustainable composites a current industrial necessity. Natural fibre reinforcements are derived from renewable resources and are both cheap and biodegradable. When they are produced using eco-friendly, low hazard processes, then they can be considered as a sustainable source of fibrous reinforcement. Furthermore, their specific mechanical properties are comparable to commonly used, non-environmentally friendly glass-fibres. In this study, four types of abundant natural fibres (jute, kenaf, curaua, and flax) are investigated as naturally-derived constituents for high performance composites. Physical, thermal, and mechanical properties of the natural fibres are examined to evaluate their suitability as discontinuous reinforcements whilst also generating a database for material selection. Single fibre tensile and microbond tests were performed to obtain stiffness, strength, elongation, and interfacial shear strength of the fibres with an epoxy resin. Moreover, the critical fibre lengths of the natural fibres, which are important for defining the mechanical performances of discontinuous and short fibre composites, were calculated for the purpose of possible processing of highly aligned discontinuous fibres. This study is informative regarding the selection of the type and length of natural fibres for the subsequent production of discontinuous fibre composites. [ABSTRACT FROM AUTHOR]

The molecular deformation and crystal orientation of a range of next generation regenerated cellulose fibers, produced from an ionic liquid solvent spinning system, are correlated with macroscopic fiber properties. Fibers are drawn at the spinning stage to increase both molecular and crystal orientation in order to achieve a high tensile strength and Young’s modulus for potential use in engineering applications. Raman spectroscopy was utilized to quantify both molecular strain and orientation of fibers deformed in tension. X-ray diffraction was used to characterize crystal orientation of single fibers. These techniques are shown to provide complimentary information on the microstructure of the fibers. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm −1 , emanating from the backbone structure of the cellulose polymer chains was followed under tensile deformation. It is shown that the shift rate of this band with respect to strain increases with the draw ratio of the fibers, indicative of an increase in the axial molecular alignment and subsequent deformation of the cellulose chains. A linear relationship between the Raman band shift rate and the modulus was established, indicating that the fibers possess a series aggregate structure of aligned crystalline and amorphous domains. Wide-angle X-ray diffraction data show that crystal orientation increases with an increase in the draw ratio, and a crystalline chain slip model was used to fit the change in orientation with fiber draw ratio. In addition to this a new model is proposed for a series aggregate structure that takes into better account the molecular deformation of the fibers. Using this model a prediction for the crystal modulus of a cellulose-II structure is made (83 GPa) which is shown to be in good agreement with other experimental approaches for its determination. [ABSTRACT FROM AUTHOR]

Sustainability of fibre reinforced polymer composites has become vital for reaching the global sustainable development goals. Natural fibres, particularly flax, and bioderived matrices are possible sustainable solutions for the composites industry, due to the constituents' embedded environmental impact reduction. According to the circular economy paradigm, sustainability can also be achieved by delaying the disposal of materials. This work reports the interfacial properties of flax fibres with three potentially sustainable advanced matrices, i.e., a vitrimer that combines the beneficial properties of both thermosets and thermoplastics, an entirely bio-based thermoset, and an advanced thermoplastic resin. Each of the selected matrices offers the potential for either recyclability, repairability, reusability, or the use of renewable sources and a reduction in the emissions of volatile organic compounds. Microbond tests were used to evaluate the interfacial shear strength and critical fibre length. It was found that the vitrimer and the bio-based thermoset matrices had a higher level of adhesion with flax fibres (∼ 20 and ∼ 24 MPa, respectively) compared to a traditional epoxy matrix (∼ 12 MPa); the advanced thermoplastic resin (∼ 6 MPa) shows the poorest adhesion. The vitrimer matrix was selected as a candidate for a sustainable and repairable discontinuous flax fibre reinforced composite. Mechanical and low-temperature rapid repair performance of an aligned discontinuous flax fibre composite, produced using the HiPerDiF method, were investigated. End-to-end and single patch repair methods were performed: vitrimer matrix composites show the potential for a mechanical strength recovery (∼ %50-70) that would allow them to be reused over several life cycles, enabling a circular economy. • The interfacial shear strengths of flax fibre with three matrices: advanced thermoplastic, bio-based, and vitrimer, were reported and compared with standard epoxy. • Vitrimer and bio-based thermoset matrices showed higher levels of adhesion compared to standard epoxy and advanced thermoplastic matrices. • A rapid and low-temperature repair performance of aligned discontinuous flax fibre reinforced vitrimers were mechanically and physically investigated. [ABSTRACT FROM AUTHOR]

The textile industry is resource-intensive, which has a significant impact on global emissions and waste pollution. To meet the demand of textiles over a third of fibres used in manufacturing are sourced from fossil fuels. As the global demand for textiles continues to grow, manufacturers are having to seek innovative approaches to providing sustainable and regenerative cellulose fibres. However, the latest climate change pressures on the textile industry have uncovered grave environmental issues associated with traditional regenerative cellulose production, such as the viscose manufacturing process. The viscose process requires intensive use of hazardous chemicals which leads to water pollution and ecotoxicity. In addition, if forestry products are unsustainably sourced for this process, this can lead to resource scarcity and deforestation. To provide a holistic solution for mitigating these challenges this study uses the by-products of paper manufacturing dissolved in an ionic liquid to produce regenerated cellulose filaments. Paper mill sludge (PMS) is a cellulosic by-product typically used on animal bedding and land spreading. The material has been dissolved in an ionic liquid - 1-ethyl-3-methylimidazolium diethyl phosphate - with the aid of a co-solvent dimethyl sulfoxide (DMSO) - and spun into continuous filaments for textile production. The mechanical properties of paper sludge filaments are found to be competitive with commercial viscose, which is promising for their drop-in replacement. It is also demonstrated that by increasing the concentration of the PMS from 9% to 12.4%, an improvement of the filament properties can be achieved; an increase in modulus from ∼19 GPa to ∼26 GPa and strength from ∼223 MPa to ∼282 MPa. These values are shown to be competitive with other commercial, less sustainable, regenerated cellulose fibres. Image 1 [ABSTRACT FROM AUTHOR]

The effect of electrospun cellulose nanocrystals (CNCs)-polyetherimide (PEI) hybrid nanofibrous mats on Mode I and Mode II interlaminar fracture toughness of unidirectional carbon/epoxy composite laminates is demonstrated. It is shown that the CNCs reinforced PEI nanofibrillar interleaves result in a ~28% increase in Mode I initial fracture toughness values compared to neat PEI nanofibrous interleaves. Specifically, the interrelated micro- and nano-scale toughening mechanisms including carbon fibre bridging, fibre necking, fibre rupture with CNCs aggregates, and nanofibre rupture contributed to the fracture toughness improvements under Mode-I loading. Nano-scale mechanisms of shear hackles, and crack pinning by CNCs aggregates increased the Mode II fracture toughness up to ~3 kJ/m2 as a result of a 6 wt% CNCs reinforced PEI nanofibrillar mat interleave. Interleaving laminated composites with electrospun CNCs-PEI hybrid nanofibrillar mats has been demonstrated as a novel and prospective strategy to strengthen and toughen interlaminar zones of carbon/epoxy composite laminates. [ABSTRACT FROM AUTHOR]