A multi-scale study of the interface between natural fibres and a biopolymer (original) (raw)
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Polymers
The complete flax stem, which contains shives and technical fibres, has the potential to reduce the cost, energy consumption and environmental impacts of the composite production process if used directly as reinforcement in a polymer matrix. Earlier studies have utilised flax stem as reinforcement in non-bio-based and non-biodegradable matrices not completely exploiting the bio-sourced and biodegradable nature of flax. We investigated the potential of using flax stem as reinforcement in a polylactic acid (PLA) matrix to produce a lightweight, fully bio-based composite with improved mechanical properties. Furthermore, we developed a mathematical approach to predict the material stiffness of the full composite part produced by the injection moulding process, considering a three-phase micromechanical model, where the effects of local orientations are accounted. Injection moulded plates with a flax content of up to 20 V% were fabricated to study the effect of flax shives and full straw ...
Macroscopic analysis of interfacial properties of flax/PLLA biocomposites
Composites Science and Technology, 2010
This study presents results from a study of the mechanical behaviour of flax reinforced Poly(L-Lactic Acid) (PLLA) under in-plane shear and mode I interlaminar fracture testing. Slow cooling of the unreinforced polymer has been shown to develop crystalline structure, causing improvement in matrix strength and modulus but a drop in toughness. The in-plane shear properties of the composite also drop for the slowest cooling rate, the best combination of in-plane shear performance and delamination resistance is noted for an intermediate cooling rate, (15.5°C/min). The values of G Ic obtained at this cooling rate are higher than those for equivalent glass/polyester composites. These macro-scale results have been correlated with microdroplet interface debonding and matrix characterization measurements from a previous study. The composite performance is dominated by the matrix rather than the interface.
Is the low shear modulus of flax fibres an advantage for polymer reinforcement?
Materials Letters, 2016
Flax fibres are increasingly used as polymer reinforcement as an alternative to glass fibres. Indeed, flax has attractive assets (low density, low environmental footprint, high tensile mechanical properties, etc.) but also some limits that need to be investigated. This study gives a comparison between the in-plane shear behaviour of flax/epoxy and glass/epoxy unidirectional laminates. For equivalent volume fractions, the shear stiffness of biocomposites is significantly lower than glass ones. This result is explained by the microstructure and anisotropic properties of flax fibres wall components. However, the micromechanical analytical model of in-plane shear strength demonstrates that the low shear modulus of flax fibres (Gf LT =2500 and 29700 MPa for flax and glass fibre, respectively) is an advantage since it limits strain concentration within plies by reducing potential cracking. Finally, due to the low failure strain of flax composites, our study show that a 2% strain limit must be chosen for a suitable comparison of flax and glass composites shear strength.
Mechanical characterization and damage events of flax fabric-reinforced biopolymer composites
Polymers and Polymer Composites
Natural fibre-reinforced biopolymer composites are of special interest because they are entirely bioresourced, recyclable and biodegradable. Poly(lactic acid) (PLA), poly(hydroxybutyrate- co-hydroxyvalerate) (PHBV) and poly(butylene succinate) (PBS) are among the most known environment-friendly biodegradable thermoplastics. Unfortunately, they present unbalanced mechanical characteristics when they are taken separately. The aim of this work is to overcome this problem using a blending process accompanied with fibre reinforcement. For this purpose, entirely biodegradable composite materials were fabricated and characterized. These biocomposites are based on two different ternary PLA/PHBV/PBS blends reinforced with twill flax fabrics and fabricated using extrusion and film-stacking techniques. Monotonic and cyclic load–unload tensile tests followed by acoustic emission and scanning electron microscopy observations were performed. In particular, the obtained biocomposites present inter...
Variability of mechanical properties of flax fibres for composite reinforcement. A review
Industrial Crops and Products, 2020
Flax fibres are a promising reinforcement in the development of biocomposites and are finding new applications in transport structures. However, there is a perceived problem with plant fibres related to the variability of the properties of these natural materials. This paper describes the factors which affect variability, from plant growth conditions to fibre sampling and testing. A large number of test results are presented (characterization of elementary fibres, bundles, assemblies of bundles, and unidirectional composites), and it is shown that provided fibre supply is carefully controlled, characterization procedures are appropriate, and manufacturing processes are optimal then excellent composite properties can be achieved with low variability.
Biomechanism and Bioenergy Research, 2022
Measurement of mechanical properties of biocomposites is a good method for evaluating their effectiveness of adhesion between fiber and polymer matrix. In this research, the effects of four different chemical treatments of flax fiber on some mechanical properties of their biocomposites was investigated. Initially, the flax fiber was soaked in alkaline, silane, benzoyle and peroxide solution and the fiber were dried in an air-cabinet drier at 70°C. After grinding, each group were separately mixed with HDPE powder at a ratio of 10% flax fiber and 90% HDPE. From these mixture, composite plates were prepared through extruding, pelleting, and rotational molding. The resulting composites were tested for their various mechanical properties using tensile tests. The test results indicated the maximum strain was 6.22%, maximum supported load at yield point was 582 N, maximum stress at yield pint was 20.26 MPa and maximum modulus of elasticity was 467.75 MPa all for alkaline treatment. It was found that all tested mechanical properties for HDPE were significantly lower than the composites made from fiber containing biocomposites. However there was no significant difference between the mechanical strength of composites produced from various chemical treatments.
Polymers
This research aimed to evaluate, at different scales (technical flax fiber, fiber band and flax composites, bio-based composites), the effect of retting and processing parameters on the biochemical, microstructural, and mechanical properties of flax-epoxy bio-based materials. On the technical flax fiber scale, a biochemical alteration of the fiber was observed as the retting increased (a decrease of the soluble fraction from 10.4 ± 0.2 to 4.5 ± 1.2% and an increase of the holocellulose fractions). This finding was associated with the degradation of the middle lamella, favoring the individualization of the flax fibers observed at retting (+). A direct link was established between the biochemical alteration of technical flax fibers and their associated mechanical properties (decrease of the ultimate modulus 69.9 to 43.6 GPa and maximum stress from 702 to 328 MPa). On the flax band scale, the mechanical properties are driven by the interface quality between the technical fibers. The hi...
Polymer Engineering & Science, 2020
This study aimed at investigating the reinforcement effect of milkweed (MW) floss, a smooth and homogeneous natural fiber with a wide hollow lumen, on bio-based polymer composites. First, MW floss was thoroughly characterized in terms of morphology, surface roughness, and tensile and thermal resistance. Then, MW floss was compared to flax fibers, one of the most widely used natural fibers in the composite industry. Subsequently, bio-based composites made of polylactic acid (PLA) and 1 wt% MW floss were produced by injection molding and compared to composites reinforced with 1 wt% of flax fibers. Finally, thermal behavior, mechanical properties, and impact resistance of composites were determined. Results showed that MW floss, with respect to flax fibers, exhibits lower tensile modulus, ultimate tensile strength, surface roughness as well as a shorter critical length. Nonetheless, and despite the lower intrinsic properties of MW floss, UTS and impact resistance of MW/PLA composites were found to be 60% and 15% higher than those of Flax/PLA composites, respectively. In addition, micrographs of MW/PLA interface revealed a lack of adhesion in MW/PLA, which should be overcome by surface treatment in upcoming work.
Numerical and Experimental Analyses of Biocomposites Reinforced with Natural Fibres
International Journal of Materials Engineering, 2012
In the last decades the biocomposites have been widely used in the construction, automobile and aerospace industries. Not only the interface transition zone (ITZ) but also the heterogeneity of natural fibres affects the mechanical behaviour of these composites. This work focuses on the numerical and experimental analyses of a polymeric co mposite fabricated with epo xy resin and unidirectional sisal and banana fibres. A three -d imensional model was set to analyze the composites using the elastic properties of the individual phases. In addition, a two-dimensional model was set taking into account the effective composite properties obtained by micro mechanical models. A tensile testing was performed to validate the numerical analyses and evaluating the interface condition of the constitu tive phases.
Biocomposites reinforced with natural fibers:thermal, morphological and mechanical characterization
Materia-rio De Janeiro, 2017
This study evaluates the thermal, morphological and mechanical behavior of polypropylene (PP) composite with different natural fibers. The fibers used were wood, sugarcane, bamboo, babassu, coconut and kenaf with and without coupling agent. The thermal, morphological and mechanical properties were evaluated, and a composite PP+GFPP (glass fiber) was used as reference. The interaction at the interface fiber-polymer matrix was studied by scanning electron microscopy (SEM) at the fractured surface of the composites, as expected the presence of maleic anhydride (MA) as coupling agent increasedthe interaction at the interface. The influence of natural fiber in the degree of crystallinity of the composites was evaluated by DSC analysis. The samples of PP+GFPP and PP+(PP-MA)+WF (wood flour) showed better temperature stability. PP+GF also presented superior flexural modulus. The thermal dynamic mechanical behavior was evaluated by DMA, a decrease in storage modulus with increasing temperature was observed, the PP+GF and the composite containing maleic anhydride and sugarcane fiber showed higher modulus. The natural fiber biocomposites studied, consistently presented lower flexural modulus and tensile strength than the reference composite, with and without the use of coupling agent. As expected the use of natural fibers lowered the density compared to the reference material.