Flax Fibre Reinforced Epoxy Composites Research Articles

Towards greener wind power: Nanodiamond-treated flax fiber composites outperform standard glass fiber composites in impact fatigue tests

Wind energy is facing two major problems, recyclability of wind turbine blades, primarily made from fiberglass, and rain erosion on the blade’s leading edges. Here, we show that flax fiber reinforced epoxy composites have less impact fatigue damage than glass fiber (GF) composites made with the same resin. The novel treatment of flax with non-toxic nanodiamonds even boosts its outstanding performance. Nanodiamond-treated flax fiber (FFND) composites exhibit a damage incubation period up to 17 times as long as GF composites and have at least 74% less mass loss. This is connected to lower initial impact pressure, less shock wave reflections and better impact absorption of flax composites. The nanodiamonds act as fiber sizing, strengthening the fibers and their matrix interface. This delays fracturing and results in less erosion, making the biodegradable FFND a promising replacement for GF towards a fabrication of more sustainable and longer lasting wind turbine blades.

Modeling and analysis of TiO2 filler's impact on specific wear rate in flax fiber-reinforced epoxy composite under abrasive wear using Taguchi approach

PurposeThis study explores how titanium oxide (TiO2) filler influences the specific wear rate (SWR) in flax fiber-reinforced epoxy composites (FFRCs) through a Taguchi approach. It aims to boost abrasive wear resistance by incorporating TiO2 filler, promoting sustainable and eco-friendly materials.Design/methodology/approachThis study fabricates epoxy/flax composites with TiO2 particles (0–8 wt%) using hand layup. Composites were tested for wear following American Society for Testing and Materials (ASTM) G99-05. Statistical analysis used Taguchi design of experiments (DOE), with ANOVA identifying key factors affecting SWR in abrasive sliding conditions.FindingsThe study illuminates how integrating TiO2 filler particles into epoxy/flax composites enhances abrasive wear properties. Statistical analysis of SWR highlights abrasive grit size (grit) as the most influential factor, followed by normal load, wt% of TiO2 and sliding distance. Grit size has the highest effect at 43.78%, and wt% TiO2 filler contributes 15.61% to SWR according to ANOVA. Notably, the Taguchi predictive model closely aligns with experimental results, validating its reliability.Originality/valueThis paper integrates TiO2 filler and flax fibers to form a novel hybrid composite with enhanced tribological properties in epoxy composites. The use of Taguchi DOE and ANOVA offers valuable insights for optimizing control variables, particularly in natural fiber-reinforced composites (NFRCs).

Wear, morphological and thermal behavior of flax fibre reinforced epoxy composites

Wear, morphological and thermal behavior of flax fibre reinforced epoxy composites

Optimization of dry sliding wear performance of TiO2 filled bamboo and flax fiber reinforced epoxy composites using Taguchi approach

Purpose This paper aims to report the effect of titanium oxide (TiO2) particles on the specific wear rate (SWR) of alkaline treated bamboo and flax fiber-reinforced composites (FRCs) under dry sliding condition by using a robust statistical method. Design/methodology/approach In this research, the epoxy/bamboo and epoxy/flax composites filled with 0–8 Wt.% TiO2 particles have been fabricated using simple hand layup techniques, and wear testing of the composite was done in accordance with the ASTM G99-05 standard. The Taguchi design of experiments (DOE) was used to conduct a statistical analysis of experimental wear results. An analysis of variance (ANOVA) was conducted to identify significant control factors affecting SWR under dry sliding conditions. Taguchi prediction model is also developed to verify the correlation between the test parameters and performance output. Findings The research study reveals that TiO2 filler particles in the epoxy/bamboo and epoxy/flax composite will improve the tribological properties of the developed composites. Statistical analysis of SWR concludes that normal load is the most influencing factor, followed by sliding distance, Wt.% TiO2 filler and sliding velocity. ANOVA concludes that normal load has the maximum effect of 31.92% and 35.77% and Wt.% of TiO2 filler has the effect of 17.33% and 16.98%, respectively, on the SWR of bamboo and flax FRCs. A fairly good agreement between the Taguchi predictive model and experimental results is obtained. Originality/value This research paper attempts to include both TiO2 filler and bamboo/flax fibers to develop a novel hybrid composite material. TiO2 micro and nanoparticles are promising filler materials, it helps to enhance the mechanical and tribological properties of the epoxy composites. Taguchi DOE and ANOVA used for statistical analysis serve as guidelines for academicians and practitioners on how to best optimize the control variable with particular reference to natural FRCs.

Investigation on the effect of castor‐oil based bio‐resins on mechanical, visco‐elastic, and water diffusion properties of flax fiber reinforced epoxy composites

AbstractDue 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.

Effect of Water Absorption on the Mechanical Properties of Alkaline Treated Bamboo and Flax Fiber Reinforced Epoxy Composites

Untreated and alkaline treated bamboo and flax fiber reinforced epoxy composites are processed using a hand layup process. The effect of alkaline treatment on the mechanical properties of the composites has been analysed. Alkaline treatment of the fiber has enhanced the mechanical properties of the developed composites. Composite reinforced with 5 % NaOH treated fiber show better performance when compared with untreated fiber reinforced composites. Alkaline treatment of the bamboo and flax fiber with 5 % NaOH has improved the hardness by 3.57 and 2.43 %, tensile strength by 47 and 20.72 % and flexural strength by 7.36 and 13.85 % in bamboo and flax fiber reinforced composites, respectively. The increase in the percentage NaOH in the alkaline treatment of the fibers resulted in weakening of fiber resulting in a drop in the properties of the developed composites. Water absorption tests of the developed composites were conducted as per ASTM D570 by immersion in distilled water at room temperature. The influence of water absorption on mechanical properties of developed composites is also examined. The quantity of water absorption and diffusion coefficient are reduced with alkaline treatment of fiber. Mechanical properties of the composite were found to decrease by the water absorption, which can be controlled by alkaline treatment of fiber and thereby reducing water absorption rate and improve the mechanical properties of the composites.
 HIGHLIGHTS
 
 Reinforcing natural fiber in polymer resin is highly beneficial because it helps to improves the strength and toughness of the polymer
 Moisture absorption rate and lack of interfacial adhesion between the polymer and natural fiber made natural fiber reinforced composites less attractive compared to synthetic fiber reinforced composites
 Alkaline treatment of the natural fiber increases the fiber surface roughness, which results in improved mechanical interlock between fiber and matrix, resulting in improved mechanical and water resistance properties of the developed composites
 
 GRAPHICAL ABSTRACT

Investigation into the fatigue properties of flax fibre epoxy composites and hybrid composites based on flax and glass fibres

Natural fibre reinforced composites (NFRCs) offer a sustainable and environmentally friendly alternative to composites made from synthetic reinforcements, with their response to dynamic loading phenomena being of utmost importance for structural applications. Herein, flax fibre reinforced epoxy composites and their glass fibre reinforced hybrid counterparts were developed benefiting from synergic effects of hybridisation between flax and glass fibres with the aim of achieving optimised fatigue behaviour. In order to study the fatigue behaviour, three different types of composite laminates comprised of flax fibres only, and two hybrid flax-glass configurations were fabricated, with alternating flax/glass reinforced layers. The hybrid effects on the fatigue behaviour of all the composite laminates were investigated by using constant ratio R under a tension–tension fatigue loading. The investigated fatigue behaviour showed promising performance in the hybrid laminates, with a great effect of the hybrid configuration on the fatigue life. The hybrid laminate with alternating layers of flax and glass demonstrated the best performance under fatigue, showing a good damage accumulation indicator; about 7 times greater, as compared to the other two laminates. The statistical analysis performed indicated that the aforementioned laminate has a less probability of failure, i.e. it will fail in a greater number of fatigue cycles, as compared to the other two laminates. The influence of various parameters such as fabrication induced defects, fibre matrix interface on the fatigue life has been further characterised using imaging techniques. The findings of this study significantly contribute towards the exploitation of natural fibre reinforced composites and their hybrids to understand the damage mechanisms that take place during fatigue loadings and how the fabrication-related defects have an influence on the overall performance of those structures in load-bearing applications.

Influence of Environmental Conditions on the Mechanical Properties of Flax Fiber Reinforced Thermoset Composites

A new type of flax fiber-reinforced bio-sourced thermoset composites is investigated to explore their usage in hot and humid conditions and is compared with flax fiber reinforced epoxy composites. Hygrothermal aging of composites is carried out for 40 days at 50 °C and 90%RH. The influence of moisture uptake of composites during aging is evaluated in terms of physical parameters (i.e., swelling and weight gain) and mechanical properties. The deterioration of the mechanical properties during aging is mainly attributed to the presence of flax fibers, especially the fiber-matrix interface. The evolution of flexural properties induced by aging is similar for both synthetic epoxy composites and bio-based benzoxazine composites and is described using an analytical model. The mechanical test results show that after 40 days of aging, flax/benzoxazine composites lose about 20% of their flexural properties whereas flax/epoxy composites lose about 32% of properties. The recovery of flexural properties after drying is higher for flax/benzoxazine composites than for flax/epoxy composites, which demonstrates the potential of this bio-sourced thermoset composite material.

Influence of reinforcement architecture on static and dynamic mechanical properties of flax/epoxy composites for structural applications

Weave architecture of the reinforcement in polymeric composite structures affects macroscopic mechanical properties of the developed composites significantly along with many other factors. In present article, nine different but systematic weave architectures were obtained by changing the number of simultaneous yarns moving in warp and weft direction of flax (Linum usitatissimum) woven fabric. Static and dynamic mechanical properties (Tensile, Flexural, Impact, loss modulus, storage modulus and damping factor) of flax fiber reinforced epoxy composites were investigated. The effect of weave configurations on failure mechanism of the developed composites has also been studied morphologically. Scanning electron microscopy (SEM) was performed to investigate the failure mechanism of the developed composites. Tensile strength and modulus was found to be significantly affected by the number of simultaneous load sharing fibers weaved in loading direction and crimp of the fabric respectively. Interlacing points of the fabric seems to control the flexural strength and modulus of the developed composites. Reinforcement architecture was also found to be responsible for the changes in impact strength of developed composites. Consistent with Young’s modulus, storage modulus and loss modulus were also affected by weave parameters such as unevenness in the architecture of reinforcement.

Fatigue monitoring of flax fibre reinforced epoxy composites using integrated fibre-optical FBG sensors

We demonstrated the applicability of integrated Fibre Bragg Grating (FBG) sensors in the case of flax fabric reinforced epoxy matrix composites produced by resin transfer moulding (RTM). FBG sensors were integrated between the reinforcing layers of the composites. We verified the robustness of FBG-based strain measurement by comparing it to strain gauge strain measurement, optical fine strain measurement and deflection measurement from crosshead displacement during four-point flexural tests. After the extensive characterization of the static properties of the composite material, fatigue tests were performed in the same setup on the specimens with integrated FBG sensors. We demonstrated that with the integrated optical fibres, the cyclic creep strain of the composites could be monitored, which could be used as a criterion to predict the fatigue failure of the composites. The proposed technique can provide an effective and robust way for periodic condition monitoring of composite structures, especially in natural fibre reinforced composites, where creep is more pronounced than in the case of synthetic fibre reinforced composites.

Interface modification and the influence on damage development of flax fibre – Epoxy composites when subjected to hygroscopic cycling

The moisture sensitivity of natural fibre composites limits their use in structural applications. Degradation of the fibre–matrix interface is likely to occur when the material is subjected to variable moisture conditions. This study investigates the damage development in unidirectional flax fibre reinforced epoxy composites during hygroscopic cycling. It is expected that the insertion of a silicone interphase increases interfacial toughness and therefore postpones or avoids interface degradation. Various silicones and a silane coupling agent were used in an attempt to enhance the long-term behavior of the composite. Hygroscopic cycling was performed by varying the relative humidity between approximately 25 and 80% at 80 °C. When examining the flax-epoxy reference composite, regression analysis showed a significant decline of the transverse strength during six consecutive wet-dry cycles. The degradation of the mechanical properties is attributed to fibre–matrix debonding and to cohesive failure in the fibre bundles. Both damage mechanisms are visualized in a unique three-dimensional model. Contrary to the hypothesis, the insertion of a silicone interphase led to an accelerated decrease of the transverse strength. Computed tomography analysis confirmed the weakening of the fibre–matrix interphase. Although the damage development was altered, the composites having a thin silicone interphase did not show a significant decrease in longitudinal stiffness and strength. This result is promising as it suggests that stress transfer is not significantly hindered.

Experimental investigation of mechanical and morphological properties of flax fiber reinforced epoxy composites incorporating SiC and Al2O3

The present research work investigates the influence of SiC and Al2O3 on the mechanical and morphological properties of flax dispersed epoxy composites. Composites were fabricated via compression moulding by adding ceramic fillers like SiC and Al2O3 in different proportions for improving tensile, flexural and impact properties of flax fiber incorporated with ceramics filler epoxy composites. Scanning Electron Microscopy is performed to analyse the microstructure and modes of failure of the composites. A tensile strength of 44.56 MPa, flexural strength of 112.56 MPa and impact strength of 28.57 kJ/m2 are the results for 20 wt% of flax fiber and 8 wt% of SiC and were the maximum values. The increase of SiC upto 8 wt% had a significant influence on the mechanical properties of the composites.

Enhancing Mode I and Mode II interlaminar fracture toughness of flax fibre reinforced epoxy composites with nano TiO2

The present study seeks to examine the effect of matrix modification on the interlaminar properties of flax fibre reinforced epoxy composites with nano Titanium dioxide (nano TiO2) particle addition. Mode I and Mode II interlaminar fracture toughness is evaluated using (double cantilever beam) DCB and (end-notched flexure) ENF test specimens. Nano TiO2 (50 nm size) is mixed in the epoxy by mechanical stirring followed by sonication process at a loading rate of 0, 0.3, 0.4 and 0.5 wt%. Compression moulding is the fabrication procedure followed. The results indicate that nanoparticle addition improves the interlaminar fracture toughness values. Mode I and Mode II interlaminar fracture toughness values improved by 52% (for 0.4 wt% TiO2) and 73% (for 0.5 wt% TiO2) respectively. Structural properties are studied using Fourier transform infrared spectroscopy. Scanning electron microscopy images are observed to evaluate the fibre matrix interface and failure mechanisms.

Flax/Epoxy Composite Beams - Simulation of Flexural Stresses

Bio-based fibre reinforcements (hemp, jute, flax) derived from agricultural waste and forestry are increasing its potential towards advanced composites, promoting environmental benefits and thermal recycling (including a reduction in CO2 emissions and the fossil fuel depletion). Currently, there is a growing interest of natural fibres due to its lower density, and higher modulus-to-density ratioscompared to glass and carbon fibre reinforcements. The present work was intended to understand how the flax fibre layups and orientation affect the behaviour of laminated composites in bending. Unidirectional [00]2S, cross-ply [0/90]S, and angle-ply [+45/-45]S laminates made up of flax fibre reinforced epoxy composites are considered to study flexural stresses and mid-span deflections. Basic principles of the classical beam theory (CBT) are applied for obtaining analytical solutions, which were also compared with the finite element simulation results.

Investigation of mechanical, thermal and water absorption properties of flax fibre reinforced epoxy composite with nano TiO2 addition

The present study aims at exploring the influence of nano TiO2 in enhancing the mechanical, thermal and water absorption properties of the flax fibre reinforced epoxy composites. The composites were prepared using the compression moulding technique. Epoxy was modified using nano titanium dioxide (50 nm size) at a loading rate (percentage by weight of the composite) of 0%, 0.5%, 0.7% and 0.9% by mechanical stirring and sonication process. The morphological characterisation was done by Scanning electron microscopy and the structural properties by Fourier transform infrared spectroscopy. The results indicate a significant improvement in strength of the composite system with the addition of TiO2. The optimum weight percentage for maximum performance was obtained as 0.7. The increase in tensile, flexural, impact and interlaminar shear strength values were observed as 10.95%, 20.05%, 10.45% and 18.80% respectively. Water diffusion coefficient was reduced by 31.66% by the addition of nano particles.

Experimental design of the bearing performances of flax fiber reinforced epoxy composites by a failure map

Abstract This paper represents the first effort aimed to the investigation of the pin/hole contact stress and failure mechanisms of epoxy composites reinforced with woven flax fabrics, underwent to tensile bearing tests. In particular, the maximum loads and failure modes are evaluated at varying the laminate geometrical configuration. In order to optimize the use of polymer composites reinforced with flax fibers in structural applications, an experimental failure map, identifying main failure modes of mechanically fastened joints, is obtained as function of hole diameter, distance of the hole from the free edge of the laminate and laminate width. Moreover, a theoretical approach based on the observation that a particular fracture mechanism occurs when its threshold fracture load is lower than the loads of the other competitive ones, is proposed. Main goal of this paper is to give a simple experimental methodology to support the joining design of natural composite laminates reinforced with woven flax fabrics.

Tensile and compressive damaged response in Flax fibre reinforced epoxy composites

Composite reinforcement by natural fibres like Flax do not enjoy the same popularity in engineering design as Carbon or Glass fibres on account of the relatively immature mechanical data on Flax-composites. Tensile and compressive mechanical properties are determined for Flax-fibre-reinforced-Epoxy composite. Damaged response is followed through SEM observations and by measuring evolving stiffness and permanent deformation. Specimens are repeatedly loaded-unloaded at progressively increasing maximum loads until failure, allowing a quantitative description of in-plane modulus and inelasticity evolution. Stiffness degradation rates do not necessarily correlate with inelastic straining rates, and modulus may remain unchanged while still accumulating inelastic strains – therefore both modulus and inelastic strain need evaluating to fully describe the material damaged response. Damage initiates within the fibre or at fibre-matrix interface; matrix-related damage appears not critical to damage initiation and progression. The reported data is valuable for the development of predictive models of damaged-condition response in Flax-epoxy structures.

Mechanical behavior of palm oil–based composite foam and its sandwich structure with a flax–epoxy composite

ABSTRACTEmpty fruit bunch fiber (EFB), an abundant biomass waste from the palm oil industry, is used to reinforce palm oil–based polyurethane foam (POPU), and the mechanical properties of the composite foams are also assessed. The fiber–foam interfacial adhesion is also investigated by SEM images and Fourier transform infrared spectrometry. The results show that the composite foam reinforced by 15–30% EFB volume fractions could be enhanced by up to 10 times in flexural strength and twice in compressive strength compared to neat POPU. The composite foams with 20% and 30% volume fraction of EFB are exploited as a core in a sandwich construction with unidirectional flax fiber–reinforced epoxy composites (as face sheets). Sandwiches using EFB/POPU composite foam cores exhibited better toughness and achieved higher flexural energy at break compared to that using a commercial poly(ethylene terephthalate (PET) foam core. Furthermore, the failure mechanisms occurred under a combination of flexural and shear deformation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43977.

Effects of surface grafting of copper nanoparticles on the tensile and bonding properties of flax fibers

Abstract In the present work, functionalized copper nanoparticles (FCuNPs) were grafted onto flax fibers, and the effects on the tensile properties, bonding strength to an epoxy resin, as well as the properties of the flax fiber-epoxy model composites were investigated. The copper nanoparticles were synthesized at ambient temperature by a chemical reduction method. The reduction of solution of copper chloride salt in the polyvinylalcohol medium was done by using sodium borohydrate. Ultraviolet-visible spectroscopy, transmission electron microscopy, and X-ray diffraction studies were used to characterize the size of the synthesized particles. The synthesized copper nanoparticles were applied to saturate the unidirectional flax natural fibers, whose surfaces were previously tailored with the cationic agent triethylammonium chloride. A remarkable improvement in the tensile strength by 75% and modulus by 50% for FCuNPs grafted flax fibers was found. Thermo-mechanical properties of the flax fiber reinforced epoxy composites were studied using DMTA. Finally, the anti-microbial analysis for composites was also conducted against Aspergillus niger spores, and enhanced anti-microbial performance was observed for treated fiber-based composites.

The voids formation mechanisms and their effects on the mechanical properties of flax fiber reinforced epoxy composites

Unidirectional flax fiber reinforced composites (FFRC) were made by hot press. Effects of processing parameters, including curing pressure, time and temperature on the distribution, shape and content of the voids formed during the manufacturing process of FFRC were investigated. The voids were characterized with the aid of ultrasonic C-scan and optical microscopy. Tensile and interlaminar shear properties of FFRC containing different content and shape of the voids were tested. The results showed that the voids were easily trapped in both the intralaminar and inside the flax yarns of FFRC due to the distinct structural characteristics of flax fibers. The relationships between voids and mechanical properties of the composites were established.