Properties of bamboo fibres produced using an environmentally benign method

The properties of bamboo fibres extracted from raw bamboo plants in an environmentally benign manner were investigated. To reduce environmental impacts of the manufacturing process, microwave, ultra-sonication and enzyme were used to extract the bamboo fibres, avoiding the use of hazardous chemicals. The new method enabled the extraction of single fibres while retaining a certain quantity of lignin in fibre. The retained lignin allowed the fibre to possess UV absorption and antibacterial properties, which will be advantageous for many textile applications.

Bond properties of rubber modified epoxy

In this paper, the bond integrity of unmodified and rubber-modified epoxy used for bonding the carbon fibre sheets to the hosting steel surface was investigated. The rigidity of the bonding agent is one of the factors that have a significant role in the premature failure (debonding) of this application. In order to overcome this issue, a series of experiments were conducted on the steel plates using the epoxy resin modified by CTBN and ATBN reactive liquid polymers, in addition to the unmodified epoxy resin. The interface between the carbon fibre matrix and the hosting surface is subjected to a longitudinal shear force for which the corresponding displacement is recorded. The shear stress-strain relationship for the tested specimen is plotted. The result shows that, the bond behaviour of modified epoxy using CTBN and ATBN reactive liquid polymers was improved in terms of ductility and toughness.

Qualitative spectroscopic characterization of the matrix-silane coupling agent interface across metal fibre reinforced ion exchange resin composite membranes

The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier transform infrared spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol-gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metal-polymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metal-polymer interface was investigated with scanning electron microscopy and Fourier transform infrared micro-spectroscopy. Fourier transform infrared mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infrared micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed.

Intrinsic tensile properties of cocoon silk fibres can be estimated by removing flaws through repeated tensile tests

 ilk fibres from silkworm cocoons have lower strength than spider silk and have received less attention as a source of high-performance fibres. In this work, we have used an innovative procedure to eliminate the flaws gradually of a single fibre specimen by retesting the unbroken portion of the fibre, after each fracture test. This was done multiple times so that the final test may provide the intrinsic fibre strength. During each retest, the fibre specimen began to yield once the failure load of the preceding test was exceeded. For each fibre specimen, a composite curve was constructed from multiple tests. The composite curves and analysis show that strengths of mass-produced Muga and Eri cocoon silk fibres increased from 446 to 618 MPa and from 337 to 452 MPa, respectively. Similarly, their toughness increased from 84 to 136 MJ m(-3) and from 61 to 104 MJ m(-3), respectively. Composite plots produced significantly less inter-specimen variations compared to values from single tests. The fibres with reduced flaws as a result of retests in the tested section have a tensile strength and toughness comparable to naturally spun dragline spider silk with a reported strength of 574 MPa and toughness of 91-158 MJ m(-3), which is used as a benchmark for developing high-performance fibres. This retesting approach is likely to provide useful insights into discrete flaw distributions and intrinsic mechanical properties of other fatigue-resistant materials.

Prestressed natural fibre spun yarn reinforced polymer-matrix composites

Abstract We report that a prestressing technique similar to that traditionally used in prestressed concrete can improve the mechanical performance of flax fibre spun yarn reinforced polymer-matrix composites. Prestressing a low twist yarn not only introduces tension to the constituent fibres and compressive stress to the matrix similar as in prestressed concretes, but also causes changes to the yarn structure that lead to the rearrangement of fibres within the yarn. Prestressing increases the fibre packing density in yarn, causes fibre straightening, and reduces fibre obliquity in yarn (improved fibre alignment along yarn axis). All these changes contribute positively to the mechanical properties of the natural fibre yarn reinforced composites. Crown

A systematic study of carbon fibre surface grafting via in situ diazonium generation for improved interfacial shear strength in epoxy matrix composites

A recently established means of surface functionalization of unsized carbon fibres for enhanced compatibility with epoxy resins was optimised and evaluated using interfacial shear stress measurements. Interfacial adhesion has a strong influence on the bulk mechanical properties of composite materials. In this work we report on the optimisation of our aryl diazo-grafting methodology via a series of reagent concentration studies. The fibres functionalised at each concentration are characterised physically (tensile strength, modulus, coefficient of friction, and via AFM), and chemically (XPS). The interfacial shear strength (IFSS) of all treated fibres was determined via the single fibre fragmentation test, using the Kelly-Tyson model. Large increases in IFSS for all concentrations (28-47%) relative to control fibres were observed. We show that halving the reagent concentration increased the coefficient of friction of the fibre and the interfacial shear strength of the composite while resulting in no loss of the key performance characteristics in the treated fibre.

Experimental investigation on bonding properties of reactive liquid rubber epoxy in CFRP retrofitted concretet members

The load bearing capacity of aging reinforced concrete structures, such as bridges, is increasingly extended with the use of Carbon Fibre Reinforced Polymer (CFRP). Premature failure, which is attributed to the rigid behaviour of the bonding agent (epoxy resin) and the high stresses at the interface region, can occur because of the debonding of CFRP sheets from host surfaces. To overcome the debonding issue, the epoxy resin is modified by different reactive liquid polymers to improve its toughness, flexibility, adhesion, and impact resistance. This study reports the usage of two reactive liquid polymers, namely, liquid Carboxyl-Terminated Butadiene-Acrylonitrile (CTBN) and liquid Amine-Terminated Butadiene-Acrylonitrile (ATBN), to improve the mechanical properties of the commercially available MBrace saturant resin when added to a ratio of 100:30 by weight. The neat and modified epoxies were analysed using the Dynamic Mechanical Thermal Analysis (DMTA) to determine and compare the storage modulus and glass transition temperatures of these materials. Moreover, the bonding strength of neat and modified epoxies was evaluated through single-lap shear tests on CFRP sheets bonded to concrete prisms. The results indicate that the modified resins exhibited improved ductility and toughness and became reasonably flexible compared with the neat epoxy resin. The improved properties will help delay the premature debonding failure in CFRP retrofitted concrete members.

Understanding key wet spinning parameters in an ionic liquid spun regenerated cellulosic fibre

The use of ionic liquid solvents for thespinning of regenerated cellulose fibres has thepotential to produce both technical and textile graderegenerated cellulose fibres. When spinning fibres,many parameters impact the material properties of thespun fibre. In this study, key wet spinning parametershave been investigated for the development of regeneratedcellulose fibres from ionic liquid solutions. Thecoagulation and associated diffusion equilibrium werecalculated for two imidazolium-based ILs, and it wasfound that the anion largely influenced the coagulationkinetics. This was likely due to the associationbetween the anion of the IL and cellulose. Theorientation of the polymer chains is known to influencethe mechanical properties greatly; previously, hotstretching was used to orientate cellulose acetate. Herewe investigated this influence on the mechanicalproperties of regenerated cellulose fibres by applying apost stretch at different stretch ratios.

Development of a novel cellulose/duck feather composite fibre regenerated in ionic liquid

By blending cellulose and duck feather in the common solvent 1-allyl-3-methylimidazoloium chloride, a regenerated composite fibre has been developed with improved fibres over regenerated cellulose fibres (RCF). The mechanical properties of composite fibre was shown to be better than RCF with a 63.7% improvement in tensile strain. Here, we thoroughly characterise the composite fibre and show that the composite fibre has many advantages over RCFs both from a spinning perspective and as a regenerated fibre.

Interfacial characterization and reinforcing mechanism of novel carbon nanotube – carbon fibre hybrid composites

Carbon nanotube (CNT) deposition onto carbon fibre resulting in hybrid surface structures with various morphologies were successfully carried out using electrospray technique. In terms of tensile testing and Weibull analysis this process did not degrade fibre mechanical properties. When incorporated into composites, the interfacial shear strength (IFSS), as measured by single fibre fragmentation testing, increased by up to 124%. Experimental work was carried out to develop a deeper understanding of the interfacial reinforcing mechanism. Contact angle measurements demonstrated that the CNT deposition resulted in good wettability by the resin. Significant increases in roughness, friction and surface area were also found after CNT deposition, especially for the sample prepared using the parameter of 20 kV/10 cm at 100 °C. Surface energy analysis revealed that an increase in the dispersive surface energy due to the CNTs likely contributed to the improvement of interaction between fibre and matrix. Fractographic analysis revealed that the length of fibre pull-out and the size of cracks between the fibre and matrix were markedly decreased in the hybrid CNT surface structure, indicating that the stress transfer and interfacial shear strength have been improved. Finally, the potential for further improvement in interfacial composite properties by this approach was assessed.

Phytochemicals and biofunctional properties of buckwheat: a review

A growing trend for nutraceutical and gluten-free cereal-based products highlights the need for development of new products. Buckwheat is one of the potential candidates for such products and the present paper reviews the functional and nutraceutical compounds present in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). The vital functional substances in buckwheat are flavonoids, phytosterols, fagopyrins, fagopyritols, phenolic compounds, resistant starch, dietary fibre, lignans, vitamins, minerals and antioxidants, which make it a highly active biological pseudocereal. Cholesterol-lowering effects that lessen the problems of constipation and obesity are important health benefits that can be achieved through the functional substances of buckwheat.