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Highlights Three dimensional (3D) textiles are preferable reinforcing materials for composites with lightweight and higher mechanical properties. In this study, a 3D woven flax fiber reinforced PLA composite with better flexural and tensile properties was developed. Four hybrid yarns with varied PLA contents were prepared as warp, weft and z‐yarns to weave the 3D preform and then changed to composites through compression molding technology without additional fillers and matrixes. The composite's flexural and tensile properties were studied and an optimum value of 78.0 and 140.0 MPa respectively were found. Stress strain properties were also discussed which implies the flexural elongation is higher than those of tensile values. The microstructure was analyzed using optical microscope and SEM equipment's showed composites with higher PLA content were more brittle due to the PLA inimitable behavior. The thermal properties of the 3D composites made with different Flax/PLA combinations have closer and comparable values. One way ANOVA statistical analysis was done to show the significancy of PLA /Flax mass ratio, which has a significant effect on composite's properties. This study could bring a novel procedural approach for an advanced 3D woven composites for load bearing applications. 3D woven flax /PLA composite was developed using Flax/PLA hybrid yarns Tensile and flexural properties were studied Flexural strength increases with PLA, but, slightly lower in its strain PLA/Flax mass ratio has a significant effect on composite's properties The mechanical strengths were improved compared to the related findings [ABSTRACT FROM AUTHOR]

This research aims to study the effect of injection parameters on the mechanical properties of the developed green composites. Natural flax fibre and biodegradable polymer, polylactic acid was chosen to develop the green composites. The flax fibre was chemically treated using sodium hydroxide to fabricate the green composite by injection moulding. The injection parameters namely (i) injection pressure (bar), (ii) injection speed (mm/s), and (iii) injection temperature (°C) was considered to investigate their effect on the mechanical properties of developed polylactic acid/flax green composites. The mechanical properties, such as (a) tensile strength (TS), (b) tensile modulus (TM), (c) percentage elongation under tensile loading (PET), (d) flexural strength (FS), (e) flexural modulus (FM), (f) percentage elongation under flexural loading (PEF), (g) compressive strength (CS), and (h) shear strength (SS) was evaluated under different injection conditions. Furthermore, the morphology of the mechanically tested specimens was investigated using a scanning electron microscope. Grey relational analysis was performed to find the optimal injection condition. The optimum injection condition depicting superior mechanical properties was found at injection parameters combination of 90 bar (injection pressure), 60 mm/s (injection speed), and 165 °C (injection temperature). [ABSTRACT FROM AUTHOR]

Due to the depletion of petro‐based sources and environmental consciousness, researchers are striving to replace synthetic fibers and resins in composites with bio‐sourced ones without compromising their properties. In this regard, the present study investigates the effect of partially replacing epoxy moieties with castor oil based bio‐resins on various properties of epoxy resin and its flax fiber reinforced composite system to achieve sustainable materials, thereby encouraging the bio‐based theme. Base‐catalyzed transesterification was used to synthesize epoxy methyl ricinoleate (EMR) as a low viscous reactive green monomer derived from epoxidized castor oil (ECO). The influence of both ECO and EMR bio‐resin on various mechanical, thermo‐mechanical properties, free mode vibration, and water absorption of epoxy and its composites were studied. The composition with 20% of ECO and EMR was optimized based on stiffness‐toughness balance. The inclusion of 20% EMR significantly escalated the tensile, impact, and fracture toughness properties of epoxy composites by 6.45%, 12.8%, and 14.2%, respectively. The strong fiber‐matrix interface was confirmed by increased pullout adhesion by 21% and 35.1% due to the addition of ECO and EMR, respectively. Dynamic mechanical analyzer revealed a 12% higher storage modulus for EMR modified composites than ECO counterparts. Scanning electron microscope morphology revealed superior interfacial adhesion between fiber and matrix in case of EMR modified bio‐composite, which resulted in a lower water diffusion coefficient than ECO modified bio‐composite. These results showed that the 20% EMR customized epoxy composite is dimensionally stable with improved mechanical properties and may act as a green alternative to petro‐sourced epoxy composites in automotive and semistructural applications. Highlights: Effects of castor oil based bio‐resins on epoxy composites are studied.Composites with significant bio‐content (~50 wt%) are developed.EMR modified epoxy composites exhibited improved mechanical properties.A strong fiber‐matrix interface was confirmed by increased pullout adhesion.Reduction in pot life of epoxy was observed on adding ECO and EMR. [ABSTRACT FROM AUTHOR]

The present work is an attempt to study the effect of different surface treatments of flax fiber on the mechanical properties of the natural fiber reinforced natural rubber (NR) composites. In this study, flax fiber was chopped to 1, 1.25, and 1.5 cm in length and mixed with NR in two roll mill. The composite of 20%, 30%, 40%, and 50% fiber loading was prepared from each fiber length. Tensile analysis showed that a 1.25 cm fiber length composite of volume 40% has higher tensile strength compared to others. Hence, this optimized the fiber length and loading has opted for further study. Flax fiber was treated with NaOH and laccase and reinforced into an NR matrix. Properties like tensile strength, hardness, relative density, water diffusion, scanning electron microscope (SEM) and Fourier‐transform infrared spectroscopy (FTIR) for surface treated and untreated natural fiber‐reinforced NR composites have been investigated and compared. The reduction in the hydrophilic characteristics of the NaOH and laccase treated fiber was evident from FTIR analysis and increase in the crystallinity index of the fiber depicted by X‐ray diffraction (XRD) results. SEM analysis showed the enhanced interfacial interaction of treated flax fiber NR composite compared to untreated composite due to the removal of non‐cellulosic contents in fiber and an increase in the surface roughness after treatments. Further, an increase of 9% and 27.4% in tensile and tear strength was found in NaOH treated flax fiber reinforced NR composite. [ABSTRACT FROM AUTHOR]

In this research work, the natural fiber reinforced hybrid epoxy composites were fabricated using the hand lay‐up method. The flax and kevlar are used as a reinforcement and epoxy as a binding material. This study aims to analyze the influence of stacking sequence and hybridization on the mechanical, water absorption, and morphological properties of polymer composites. The results reveal that the neat kevlar reinforced composite achieved a maximum tensile strength, modulus, and impact strength of 189.94 MPa, 2345.35 MPa and 37.16 kJ/m2 respectively with less water absorption behavior. Whereas, the hybrid composite with kevlar as an outer layers and flax as core layers was exhibited a maximum flexural strength, modulus, and inter laminar shear strength of 360.76, 37124.2, and 213.51 MPa, respectively. The water absorption percentage was more in neat natural flax reinforced epoxy composite due to its more hydrophilic nature. The scanning electron microscope analysis reveals the proper bonding and adhesion of both kevlar and flax fabrics with the epoxy matrix. [ABSTRACT FROM AUTHOR]

The protein‐based superabsorbent composite FCP‐g‐PAA/Kaolinite is prepared by grafting acrylic acid (AA) into the flax cake protein (FCP) using free radical polymerization in this study. The chemical structure, thermal stability, and the morphology of the FCP‐g‐PAA/Kaolinite are characterized by Fourier transform infrared, Thermogravimetric analysis, and scanning electron microscope. The results show that AA was grafted successfully into FCP. And, it has the maximum swelling capacity where the MBA concentration, APS concentration, Kaolinite concentration, FCP concentration, neutralization degree, and reaction time was 0.13%, 1.4%, 8%, 9%, 70% and 2 h, respectively. The swelling capacity reaches 860 g/g in distilled water, 238 g/g in tap water and 78 g/g in 0.9% NaCl. In addition, its water absorbency can still reach 60% after reuse for six times and the water retention rate of the material was 70% after 12 h. Therefore, FCP has a broad application prospect as a material for preparing superabsorbent composite. [ABSTRACT FROM AUTHOR]