Flax Fibers Research Articles

Toughened Vinyl Ester Resin Reinforced with Natural Flax Fabrics

Vinyl ester resins are widely used as thermoset matrix materials for laminated composites, particularly in naval and automotive applications, due to their strength, chemical resistance, and ease of processing. However, their brittleness limits their use, especially in cold conditions. This study investigates the toughness of core–shell rubber (CSR)-modified resins in composites with natural fibers. This research compares the properties of the neat resin matrix and the CSR-modified matrix. After optimizing the resin curing process with catalysts, various treatments were tested to analyze their mechanical and thermal properties. Using the vacuum bagging process, flax and glass fibers were used as reinforcements to assess the effects of matrix modifications. Flax fibers were chosen for their sustainability as a potential alternative to glass fibers. Mechanical testing was performed, comparing the performance of flax-based composites to those with glass fibers. Water absorption tests on flax composites followed the ISO 62 standard. Additionally, interlaminar shear strength and SEM micrography studies were conducted to examine the morphology and fiber–matrix adhesion, linking the microscopic structure to mechanical properties. Results indicate that while glass-reinforced composites have superior properties, flax composites offer a sustainable alternative, making them a promising choice for future applications.

The Influence of Alkaline Treatment on Delamination resistance of Woven Flax Fiber-Reinforced Epoxy Composite Laminates

AbstractDelamination is one of the most typical failure modes of fiber-reinforced polymer composite laminates. Thus, investigating and improving the delamination behavior of these laminates are of vital importance. The present research discovers and investigates the role of the alkaline treatment of twill-woven flax fabric on the delamination resistance of flax fiber-reinforced epoxy composite laminates. Initially, flax fibers were treated with different sodium hydroxide solution concentrations (2–5–10%) for 2 h. The influence of alkaline treatment on fiber characteristics was evaluated by performing a single-yarn tensile test, scanning electron microscopy, and Fourier transform infrared spectroscopy analysis for treated and untreated flax fibers. The appropriate treatment condition was selected based on the properties obtained from the tests conducted on the fiber level. Subsequently, to discover the role of alkaline treatment on delamination resistance, flax fabric was treated with the selected treatment condition for further composite fabrication. The treated and untreated flax fiber-reinforced epoxy composites were fabricated using a hand lay-up technique followed by hot compression. Interlaminar shear strength, double cantilever beam, and end-notch flexural tests were carried out for treated and untreated composites to determine the effect of alkaline treatment on the delamination resistance. The results proved that the alkaline treatment of flax fabric significantly improved the delamination resistance of treated composite laminates compared to untreated ones. The interlaminar shear strength, the mode I interlaminar fracture toughness (propagation), and mode II interlaminar fracture toughness were improved by 27.3%, 14%, and 24.9%, respectively, for treated composite laminates compared to untreated ones.

Application of natural fibre pultruded profiles in diverse lightweight structures and architectural scenarios

AbstractReevaluating the materials that shape our built environment holds significant importance for sustainable construction. This research introduces newly developed natural fibre pultruded profiles, composed of flax fibres and bio-resin, customised for specific properties and targeted applications. Engineered to withstand both bending and compression loads, these profiles have been subjected to rigorous mechanical testing to demonstrate their compression and flexural strength, as well as flexibility. The emphasis lies on the bottom-up design approach, guiding the creation of applications suitable for this innovative material in various lightweight structures. The paper presents a series of case studies showcasing the use of biocomposite profiles in diverse design and structural contexts. The initial focus was on active-bending structures, highlighting the material’s flexibility, showcased at a ten-metre span structure, the first large-scale demonstrator. However, given the material’s versatile properties, it is suitable for a wide range of other applications. Key case studies discussed include reciprocal, tensegrity and deployable structures, as well as modular planar or space frame systems. These profiles offer a sustainable and versatile alternative to traditional materials and composites, providing innovative and eco-friendly construction solutions while contributing to industry sustainability goals.

Extraction and characterization of bark fibers from Ethiopian Ficus thonningii tree

The growing environmental pollution issues by synthetic textile products demand sustainable natural textile alternatives. This paper aimed at extracting and characterizing a new fiber called Ficus thonningii fiber from Ficus thonningii trees found in Ethiopia to be used as a source of textile fiber for different applications. The study utilized water and chemical extraction with sodium hydroxide methods. Physical, mechanical, and chemical properties such as length, diameter, fineness, tenacity, moisture content, moisture regain, cellulose, hemicellulose, lignin, and ash content were characterized. The results revealed that Ficus thonningii fiber possesses comparable characteristics with jute, sisal, and flax fibers that can be used for different applications. The fiber exhibits tenacity of 39.65 cN, an elongation of 2.60%, a moisture content of 10.78%, and a moisture regain of 11.98% when extracted chemically. While it exhibits a tenacity of 37.83 cN, an elongation of 3.02%, a moisture content of 10.35%, and a moisture regain of 11.02% when extracted using water extraction method. Both extraction methods yield a fiber length of 101.50 mm. The chemical composition of the fiber obtained through water extraction consists of 52.35% cellulose, 19.20% hemicellulose, 17.20% lignin, and 1.20% ash. On the other hand, the chemical extraction method results in a composition of 63.57% cellulose, 16.10% hemicellulose, 12.10% lignin, and 0.83% ash. These results confirm the potential use of Ficus thonningii tree as a valuable source of coarse fibers for various technical textile applications.

Magnetic Effects in Textile Fibers Filled with Nanoconstituents Based on Iron Oxides

ABSTRACT The paper proves the possibility of providing magnetic properties in the process of saturation of textile fibers with a nanomixture of divalent and trivalent iron oxides. The mechanisms of interaction of nanostructures with natural and synthetic fibers are analyzed. The peculiarities of the introduction of magnetic components into flax, cotton, polyamide, and polyester fibers are determined. The relative number of particles with nanoscale in the total was statistically proved. To evaluate the macro effects of saturation, the relative amount of the accumulated mixture of divalent and trivalent iron oxides was determined, taking into account the previous fiber weight. Two basic constants characterizing the properties of textile fibers to magnetic interaction are proposed. It is proved that flax fibers exhibit the highest magnetic efficiency. The average size of iron oxide nanoparticles is 80–90 nanometers, which is confirmed by studies using electron microscopy. The final magnetization of the obtained textile materials provides an attractive magnetization of 20–30 mPascal. The magnetic field of magnetic textile fibers acts at a height of up to 6–7 mm. The directions of the use of fibers with magnetic properties are shown as a prospect for the development of textile smart products.

Trait Interactions and Yield Enhancement in Linseed (Linum usitatissimum L.): Insights from Correlation and Path Analysis

Linseed (Linum usitatissimum L.) is a self-pollinated (2n = 30) annual Rabi season crop mainly cultivated for flax fiber and oil due to its commercial use. The present investigation was carried out to study an association analysis among the yield and yield attributes using 75 linseed genotypes including 10 checks in a randomized block design with three replications at Oilseeds Research Farm, Kalyanpur, Chandra Shekhar Azad University of Agriculture and Technology, Kanpur, Uttar Pradesh, (India) during Rabi season of 2019-20. The correlation analysis revealed that the traits number of secondary branches per plant followed the number of primary branches per plant and number of capsules per plant at both the genotypic and phenotypic levels. The results of the path coefficient analysis revealed that traits such as the number of secondary branches per plant, number of capsules per plant, number of seeds per capsule, and plant height exhibited a strong and positive direct effect on seed yield per plant at both the genotypic and phenotypic levels. The seed yield can be improved by selecting traits such as number of primary branches per plant, number of secondary branches, number of capsules per plant, and plant height. It is recommended that the breeder focus on these traits in linseed to enhance its commercial value for the farming community.

Optimum Selection of Sisal and Flax Fiber Reinforced Composites for Experimental Investigation Utilizing VICOR Method

Optimum Selection of Sisal and Flax Fiber Reinforced Composites for Experimental Investigation Utilizing VICOR Method

Investigation of the reproducibility of the treatment efficacy of a commercial bio stimulant using metabolic profiling on flax

Introduction and objectivesSince the use of a bio stimulant should provide a response to a problem that depends on the production system implemented (crops, plant model, soil, climate, the farmer’s practices…), the agricultural sector is facing concomitant challenges of choosing the best bio stimulant that suits their needs. Thus, understanding bio stimulant-plant interactions, at molecular level, using metabolomics approaches is a prerequisite, for the development of a bio stimulant, leading to an effective exploration and application of formulations in agriculture. AGRO-K®, is commercialized as a plant-based bio stimulant that improve vigor and enhance resistance to lodging in cereal crops. A recent previous untargeted metabolomics study has demonstrated the ability of this bio stimulant to improve wheat resistance to lodging, in real open-field conditions. However, the reproducibility of the impact of this bio stimulant in other filed crops is not yet investigated.MethodsTherefore, the present study aimed to assess the changes in primary and secondary metabolites in the roots, stems, and leaves of fiber flax (Linum usitatissimum L), treated with the bio stimulant, using NMR and LC-MS-based untargeted metabolomics approach.Results and conclusionsIn addition to the previous result conducted in wheat, the present analysis seemed to show that this bio stimulant led to a similar pathway enhancement in flax. The pathways which seem to be reproducibly impacted are hydroxycinnamic acid amides (HCAAs), phenylpropanoids and flavonoids. Impacting these pathways enhance root growth and elongation and cell wall lignification, which can aid in preventing crop lodging. These results confirm that HCAAs, flavonoids, and phenylpropanoids could serve as signatory biomarkers of the impact of AGRO-K® on improving lodging resistance across various plant species.

The critical role of size effect on internal damage and mechanical properties of flax fiber reinforced composites

The effect of the size on the strength of laminated artificial fiber reinforced composites has been extensive discussed during the design of large composites structure. With the trial as the structures in aerospace, civil engineering, automobile industry, the scaling of the properties of plant fiber reinforced composite should be studied. In this paper, the size effect and failure mechanism of tensile and impact properties of flax fiber reinforced composites were valuated. The effects of different area, thickness and volume on the tensile properties of composites were explored. Additionally, the failure mechanism of size effect on tensile specimens was proposed through the damage morphologies of composites. It is found that the twist of fiber bundle plays an important role in the size effect of composite thickness. Besides, the relationship between impact properties and size effect of composites was conducted, including the size of hammer, different impact energy and sample size. The curves of different types of impact samples were normalized to verify the linear rule in response stage. The crack length after impact was measured and the size effect of crack length was discussed. The size effect of crack area was studied by calculating the crack area with ultrasonic C-scan. Different “size effects” between flax fibers and artificial fibers were explored. The results are expected to provide a theoretical basis for the structural design of plant fiber reinforced composites.

3D‐printing continuous plant fiber/polylactic acid composites with lightweight and high strength

AbstractContinuous plant yarn‐reinforced polylactic acid (PLA) composites were produced through in situ 3D printing, focusing on how plant fiber attributes influence the crystallization, mechanical, and rheological properties of the printed composites. The aim of this study was to assess the viability of plant fibers as substitutes for synthetic ones in engineering additive manufacturing. Plant fibers promoted the crystallization of PLA due to their shear induction and nucleation agent induction effects. The inherent triangular void defect during printing decreased with increasing plant fiber‐volume fraction. Rheological analysis revealed a transition to more elastic behavior post‐fiber addition, indicating solid‐like properties. The tensile strength of flax fiber‐yarn/PLA composite (volume fraction of 50.79%) was 342.37% higher than that of pure PLA, with a 22.2% lower density than pure PLA. Flax fiber demonstrated a superior reinforcement effect than carbon fiber in compressive strength for 3D printed honeycomb sheets with lower energy consumption and footprint. Optimizing fiber characteristics holds promise for high‐performance 3D‐printed natural fiber composites, particularly in vehicle applications.Highlights Plant fiber/polylactic acid (PLA) composites were in situ printed with a volume fraction of 50.79%. Plant fibers promoted the crystallization of PLA during the printing process. The tensile strength of flax fiber/PLA increased by 342.3% with a 22.2% lower density than PLA. Flax fiber showed a better reinforcement than carbon fiber in a compressive test of printed honeycomb.

Interlaminar fracture toughness of flax, carbon, and hybrid flax carbon‐woven fiber‐reinforced composites

AbstractThe effect of the asymmetric distribution of woven flax fiber on the interlaminar fracture toughness of carbon fiber‐reinforced polymer (CFRP) is investigated experimentally via a double cantilever beam test, and the results are backed by analytical and numerical analysis. Four hybrid configurations are fabricated with different stacking sequences of (CFRP) and flax fiber‐reinforced polymer (FFRP) plies. The results of hybrid specimens are compared with those of all CFRP and all FFRP specimens. The hybrid composite with one carbon/flax fiber layer at the interface requires the highest critical energy release rate, GC, to initiate cracks. A resin layer on top of the flax plies and a carbon fiber imprint in that layer are observed, thus signifying an increase in GC for the hybrid composites with dissimilar interface layers. Varying the number of carbon/flax fiber layers at the interface adversely affects GC. Mode II contribution to the GC was verified analytically for asymmetric hybrid configurations. The agreement between experimental, numerical, and analytical results is excellent. The hybridization of flax with carbon enhances the fracture toughness of CFRP while providing an opportunity to achieve lightweight, high‐performance, and eco‐friendly structures.Highlights Flax fiber is used to increase the fracture toughness (GC) of CFRP Asymmetric carbon/flax fiber hybrid composites are designed for this purpose One interface carbon/flax hybrid exhibits a 70% increase in GC Blocking the plies together results in reduced GC and mode‐II fracture as well Numerical and analytical analysis agrees well with experimental results

Hybrid Geopolymer Composites Based on Fly Ash Reinforced with Glass and Flax Fibers

This article’s aim is to analyze physical, mechanical, and fracture properties as well as the thermal investigation of geopolymer composites reinforced with flax, glass fiber, and also the hybrid combination of fibers. Two types of matrices were considered as composites matrices. The first composition was based on fly ash and river sand. The second matrix composition contained fly ash and glass spheres. The content of reinforcement was 1% by mass. Compressive strength and three-point bending fracture tests were performed. The values of fracture toughness and fracture energy were determined. The resonance method was used to verify the dynamic characteristics, such as the dynamic modulus of elasticity and the dynamic Poisson ratio. The results show that single-type fibers in composites based on fly ash and glass spheres did not affect compressive strength. However, introducing hybrid reinforcement increased compressive strength by about 10% compared to the reference specimens. Flax fibers and hybrid reinforcement ensured higher fracture toughness and energy. The results also revealed great potential for glass sphere application to geopolymer materials in terms of fracture mechanics and thermal properties. Despite the lower strength properties in relation to geopolymers based on sand aggregate, applying reinforced fibers into the composite with glass spheres enhanced the compressive strength compared to other materials. Materials modified with glass spheres have a thermal conductivity twice as low as that of materials containing river sand.

The Influence of Dew Retting on the Mechanical Properties of Single Flax Fibers Measured Using Micromechanical and Nanomechanical Approaches

The mechanical properties of single flax fibers are characterized here as a function of dew retting. The fibers are measured using micromechanical and nanomechanical techniques over a large retting period (91 days). Damage-free single flax fibers in various stages of dew retting were manually extracted from retted flax plant stems. The flexural modulus and strength of the flax fibers were determined using micromechanical methods. The effective modulus of the outer surface of the single fibers was measured using AFM-based nanoindentation. The micromechanical methods revealed that the flexural modulus and strength of the manually extracted single fibers does not vary significantly as the retting progresses. The micromechanical methods revealed two distinct values of flexural strength in the fibers attributed to different failure modes. The values of these strengths do not vary significantly with retting or over-retting. The nanomechanical methods revealed that the effective modulus of the outer surface of the single fibers does evolve with retting. The physical/chemical origin of these observations remains to be established and could be the objective of future work.

EFFECTS OF NATURAL FIBERS ON THE COMPRESSIVE STRENGTH PROPERTIES OF HDPE MATRIX COMPOSITES

The current research reveals the synergistic effect of different ratios of natural fiber concentration and maleic anhydride grafted polyethylene (PE-g-MA) compatibilizer on the compressive strength properties of high density polyethylene (HDPE) matrix composites. Composites containing flax (FF) and palm (PF) short fibers with different weight ratios were processed by melt blending and then compression tests were performed at a compression speed of 2 mm/min. As a result of the tests, the best compressive strength properties were observed in the composite samples using 10% flax fiber and compatibilizer.

Fabrication of Green Composite Materials Using the Weight Sum Method (WSM) Method

The quest for sustainable materials the investigation into natural fibers for composite materials has been prompted by this development., aiming to reduce the environmental impact of traditional synthetic composites. In this study, we investigate the potential of flax, hemp, jute, kenaf, and ramie fibers as reinforcements in green composites fabricated using the Water Soaking Method (WSM). The evaluation parameters considered include density (g/cm3), fiber diameter (μm), tensile strength (MPa), Young’s modulus (GPa), and elongation at break (%). Through meticulous experimentation and analysis, it is revealed that jute emerges as the frontrunner among the alternatives, exhibiting superior performance across multiple evaluation parameters. Jute-based green composites demonstrate commendable strength and stiffness properties, coupled with a moderate density, making them promising candidates for various structural applications. Conversely, kenaf fiber-based composites exhibit the lowest performance in terms of evaluated parameters, indicating potential limitations in its suitability for high-performance applications. The comparative assessment underscores the significance of material selection in composite fabrication, emphasizing the diverse mechanical properties exhibited by different natural fibers. Furthermore, the utilization of the WSM method showcases its effectiveness in producing green composites with desirable characteristics, signifying its potential as a viable manufacturing technique for sustainable materials. eco-friendly composites, highlighting the importance of considering multiple factors such as fiber type and fabrication method in achieving optimal performance and environmental sustainability in composite materials. Further research may delve into refining fabrication techniques and exploring novel fiber combinations applications.

Fatigue analysis on flax-epoxy composites: insights and implications

This study investigates the performance of flax fiber and epoxy resin composites, focusing on fatigue testing, which is scarcely reported in the literature. Fatigue behavior is evaluated under full reverse bending loading conditions: R = −1. Apart of the definition of the classic S-N curve, the analysis deeply investigated the evolution of the hysteresis leaf generated during each cycle over the entire fatigue life. This approach allows evaluating interesting parameters such as the evolution of the loss factor and the apparent modulus over life, being these informations fundamental for practical application of natural-fiber composites in engineering applications.

Analytical investigation of green composite lamina utilizing natural fiber to strengthen PLA

This work’s main goal is to investigate the effects of the natural fiber orientation angle on the lamina’s engineering constants, such as the shear modulus, major Poisson’s ratio, longitudinal and transverse Young’s moduli, and lamina level shear coupling coefficients. The PLA matrix of the three green composite laminas under study is reinforced with natural fiber. The three natural fibers under study are flax, jute, and bamboo fibers. The study assesses the performance of three PLA laminas reinforced with natural fibers for each of the previously listed engineering constants. The behavior of the green composite lamina for various fiber volume fractions is also presented in this study. This analytical investigation employs the macromechanics of lamina to do the examination. The investigation’s findings demonstrated that the volume % and fiber orientation have a considerable impact on the lamina’s engineering constants. The study offers a comprehensive variation of the lamina’s engineering constants for each fiber orientation angle between 0 and 90° and for each fiber volume fraction between 0 % (entirely matrix) and 100 % (completely fibers) in steps of 5 %. The outcomes of the presented study will help in the design of the facesheets for the composite sandwich structures. The results presented can be used to check the viability of using natural fibers to strengthen different polymer matrices. Bamboo-PLA lamina outperforms flax-PLA and jut-PLA laminae.

Adaptability of hybrid populations of Linum usitatissimum L. in conditions of the Northern Transural region

Relevance. The selection of genotypes with high adaptive properties for the conditions of the Tyumen region allows us to contribute to the development of a regional strategy for breeding and genetic work, selection and cultivation of varieties in connection with changing weather and climatic conditions.Material and methodology. The research was carried out over a three-year period (2020-2022) in the northern forest-steppe zone of the Tyumen region. Intervarietal hybridization (4x4 scheme), evaluation of the obtained material according to morphological (4 pcs.), biological (1 pc.), adaptive indicators (2 pcs.) was carried out using generally accepted methods. The objects of study were 12 combinations of fiber flax, first obtained in the region.Results. Significant differences (p<0.05*) were determined between hybrid populations of fiber flax in the influence of genotype, environment, and genotype-environment interaction on the degree of implementation of the studied traits. Correlation relationships have been identified that determine the fiber content in the stem (r=0.79-0.91*, growing season, plant height, inflorescence length, softness, camber), the number and weight of seeds per plant (r=0.79-0 ,91*, inflorescence length, number, size and crackability of the capsule). Based on the results of individual selection in the third hybrid generation (F3), early ripening (4 pieces), tall (n=4), with the maximum number of bolls (n=4) and the number of seeds in them (n=7), fiber content (n =4) in the stem of the combination.Conclusions. Hybrid combinations of fiber flax with high levels of stable properties (G1, G3, G9, G10, G11), productivity criteria (G1, G2, G4, G7, G8, G9, G11, G12) can be valuable in breeding work.

Generalisation of the yield stress measurement in three point bending collapse tests: application to 3D printed flax fibre reinforced hydrogels

This paper describes the extrusion pressure's effect on composite hydrogel inks' filaments subjected to three point bending collapse tests. The composite considered in this work consists of an alginate-poloxamer hydrogel reinforced with flax fibres. Increased extrusion pressure resulted in more asymmetrical filaments between the support pillars. Furthermore, the material and printing conditions used in the present study led to the production of curved specimens. These two characteristics implicitly limit the validity of the yield stress equations commonly used in open literature. Therefore, a new system of equations was derived for the case of asymmetrical and curved filaments. A post-processing method was also created to obtain the properties required to evaluate this yield stress. This new equation was then implemented to identify the strength of failed hydrogels without flax fibre reinforcement. A statistical analysis showed this new equation's significance, which yielded statistically higher (i.e. 1.15 times larger) strength values compared to the numbers obtained with the open literature equations. At larger extrusion pressures, longer periods were needed for the material to converge towards its final shape. Larger extrusion pressure values led to lower yield stresses within the composite hydrogel filament: a 5 kPa increase in extrusion pressure lowered the yield stress by 19%. In comparison, a 15 kPa increase led to a 29% decrease in the yield stress. Overall this study provides guidelines to standardize three point bending collapse tests and analysis comparison between different materials.

Influence of castor oil‐derived bio‐resin on mechanical and visco‐elastic properties of dynamic covalent imine bond based epoxy and its composite

AbstractThe widespread use of thermoset composites has raised significant environmental and economic concerns due to their non‐recyclable nature. This study addresses these issues by developing vitrimers and their composites featuring dynamic imine bonds synthesized from vanillin, 3,3′‐dimethyl‐4,4′‐diaminodicyclohexylmethane, and epoxy. To enhance toughness and bio‐content in the vitrimer and its composites, a green reactive monomer, epoxy methyl ricinoleate (EMR), was synthesized via the transesterification of epoxidized castor oil (ECO) and incorporated as the reactive diluent. The effect of EMR on bio‐resin mechanical, thermo‐mechanical, and relaxation times (τ) of the vitrimer was examined. The inclusion of EMR reduced the relaxation time, indicating improved dynamic bond exchange efficiency. EMR incorporation decreased the relaxation time, suggesting enhanced efficiency in the interchange of dynamic bonds. In addition, the incorporation of 20% EMR increased the impact strength of the epoxy vitrimer by 37.8%. The study also details the manufacturing and characterization of greener composites made with these vitrimers and flax fabric, which were evaluated for various mechanical and thermo‐mechanical properties. Morphological analysis using a scanning electron microscope revealed good interfacial adhesion between the fiber and matrix. Furthermore, the flax fiber vitrimer‐based composite demonstrated effective chemical recyclability. The results indicate that these composites possess mechanical and thermal‐mechanical properties well‐suited for lightweight engineering applications.Highlights Recyclable vitrimers were developed from vanillin and epoxy. Toughness and bio‐content were enhanced by adding EMR. Relaxation time was reduced by EMR, improving bond exchange efficiency. Epoxy vitrimer impact strength was increased by 37.8% with 20% EMR. Green composites with vitrimers and flax fabric were manufactured.