Flax Fibre Composites Research Articles

Fluid-Structure Interaction on The Design of Fully Assembled Shell Eco-Marathon (SEM) Prototype Car

To achieve high fuel efficiency, vehicles designs are inclined to choose lightweight materials and structures. However, these structures are generally weak, and structural integrity is a common concern. The purpose of this paper is to carry out fluid-structure interaction (FSI) study in one-way coupling analysis on a Shell Eco Marathon (SEM) prototype car which travels in a low-speed range to analyse its structural response. A new set of economical materials is proposed and analysed with the concern on self-fabrication process. The Flax fibre composite is introduced as a part of the proposed material set due to its environmental and economic advantages. The study herein is purely a numerical simulation work as a first approach to design a sustainable SEM prototype car. The fully assembled SEM prototype car was analysed with the proposed materials with ANSYS Workbench in the coupling of the fluid (ANSYS Fluent) and structural solver (ANSYS Mechanical) in a one-way FSI. Even with a thin shell design, the proposed material only experiences minimum deformations. The simulations also reveal that the maximum von-Mises stress experienced, after considered the safety factor, is still several order lower than the yield strength. This study has confirmed that the car design has fulfilled its structural requirements to operate at the design speed.

Drilling performance of flax fibre epoxy composites: Induced thrust force and delamination damage analyses

Abstract Drilling of fibre reinforced composites is challenging because it causes severe damage that can deteriorate the mechanical performance of the composites. In this experimental study, flax natural fibre reinforced epoxy composites were used as samples for assessment of drilling parameters on drilling thrust force and delamination damage. Drill diameter, spindle speed and feed rate were the drilling parameters used for analyses of delamination damage and thrust force. Taguchi method of L18 orthogonal array was implemented as the experimental design layout. The elucidation of delamination damage was carried out using delamination factor whereas the acquisition of thrust forces were completed using a Kistler force dynamometer. Results showed that the tool diameter had the greatest influence on the thrust force. It is suggested that lower feed rate should be able to minimise the peel up delamination at the entrance and push out delamination at the exit surface of the composites. Thereupon, larger feed rate resulted in the excessive thrust force that induced higher delamination damage on flax fibre composites.

Exploration of mechanical properties of flax fibre and GFRP hybrid composites

In recent years, the flax fibers are used as a reinforcement material to enhance the mechanical properties of the composite material. Flax fibres are bio degradable, economical and exhibits unique mechanical properties compared to glass fibres reinforced polymers (GFRP). In contrast, the flax fibers are combined with thermoset, biodegradable and thermoplastic matrices have shown excellent mechanical properties. In this article, the hybrid composite of flax fibers and GFRP (F-GFRP) composites are made with various proportions like 15:55, 25:45, 35:35, 45:25 and 55:15. The various mechanical properties like tensile, impact and flexural strengths of the composites are evaluated by investigating the tensile, impact and flexural tests.

Wear Analysis, mechanical properties and Analysis of Variance of Jute/Glass/flax fibers and their barium sulphate as filler composites

Natural fibers give strength to polymer composite for making very low cost materials and are very good market now a days. Therefore the researcher’s main attention is to apply appropriate technology by utilizing these natural fibers as efficient and economically in order to produce very good quality fiber reinforced polymer composites for different engineering applications. In our research work, the experiments like tensile, flexural and impact tests were carried out for different natural fibers like, woven Jute, glass and flax hybrid-reinforced epoxy composites with filler of barium sulphate and without filler composite. Therefore the best, cheap and efficient process called hand layup technique was applied to prepare composite material. The surface morphology of the composites was examined through scanning electron microscope, due to the low density and high specific properties of glass, flax fiber composites, it offer cost savings when compared with synthetic fibers. Therefore this king of composite materials can be used in automobile industry. Fro the study, the hybrid composites with barium sulphate filler as composite was used by us to provide good and improved mechanical properties such as tensile, flexural and impact strength. And also the good reduced wear property analyzed on filler composite.

Investigation of Alkaline Surface Treatment Effected on Flax Fibre Woven Fabric with Biodegradable Polymer Based on Mechanical Properties

Biodegradable polymers such as polylactic acid (PLA) are used nowadays due to their degradability, durability and environmentally friendly properties. Alkaline surface treatment of natural fibres is used to increase the flexural properties of composites. This research investigated the flexural properties of dry compressed PLA, wet mix PLA, untreated flax/PLA and treated flax/PLA composites. The flax fibre was first treated with NaOH. The wet mix PLA was prepared via solvent casting with chloroform and dried at room temperature overnight followed by post-drying in an oven. The flax/PLA composites were fabricated using a hot press for 6 minutes. The wet mix PLA showed higher flexural strength compared to the dry compressed PLA. The treated flax fibre composite showed higher flexural strength compared to the untreated flax fibre. The flexural strength and elongation at break of the treated flax fibre composite was increased by 4.79% and 27.76%, respectively, while the flexural modulus decreased by 0.79% compared with the untreated flax composite. The treated flax composite also showed an improvement in impact properties, increasing its impact strength by about 3% and 10% at energy levels of 10 J, 15 J, and 17.5 J compared with the untreated flax fibre. Therefore, the investigation of the surface treatment of flax in a PLA matrix based on its mechanical properties revealed better properties compared to untreated flax/PLA composite.

Mechanical and Interfacial Properties of Flax Fiber-reinforced Plastic Composites Based on a Chemical Modification Method

Due to growing interest in environmental protection, eco-friendly fibers with high specific strength and low cost are widely used to reinforce matrix materials. Flax fiber is a natural renewable plant fiber that originates from the phloem of flax. Flax fibers not only have the characteristics of other natural fibers but also have the outstanding mechanical properties of natural fibers. However, due to the large amount of hydrophilic hydroxyl groups on the surface, the hydrophilic absorption of flax fibers is large, and the wet-heat durability of the composite is poor, which limits the use of flax fiber as a reinforcement material in civil engineering applications. In this study, based on the research results of flax fiber, a flax fiber sheet was grafted with multiwalled carbon nanotubes, a silane coupling agent and nano-TiO2 particles. The effect of different treatment methods and process parameters on the mechanical and interfacial properties of flax fiber-reinforced plastic (FFRP) composites materials was studied. The results show that the FFRP composites grafted with multiwalled carbon nanotubes have higher tensile strength and interlaminar shear strength than those grafted with the same content of nano-TiO2 particles. Flax fiber composites with improved interfacial properties can be obtained by grafting flax fiber sheets, but the content of particles on the flax fiber surface should not exceed 2.0 wt.% of nano-TiO2 and multiwalled carbon nanotubes. Under this treatment, the FFRP composites have improved properties, such as tensile strength, interlaminar shear strength and glass transition temperature.

Experimental evaluation of stiffness predictions of multiaxial flax fibre composites by classical laminate theory.

Despite the good mechanical properties of natural fibre composites, their use in load-bearing components is still limited, which may be due to lack of knowledge and confidence in calculating the performance of the composites by mechanical models. The present study is providing an experimental evaluation of stiffness predictions of multiaxial flax fibre composite by classical laminate theory (CLT). The experimental base is (i) multiaxial flax fibre composites fabricated with two types of biaxial non-crimp fabrics, having a nominal yarn orientation of ±45°, and (ii) uniaxial flax fibre composites fabricated with the same flax yarn as used in the fabrics. The fabricated composites are characterised by volumetric composition, yarn orientation and tensile properties. A fast and easy operational Fast Fibre Orientation (FFO) method is developed to determine the actual yarn orientation in fabrics and composites. It is demonstrated that the FFO method is a robust method, giving repeatable results for yarn orientations, and it can be used both on fabrics and composites. CLT predictions of stiffness of the multiaxial flax fibre composites are shown to be in good agreement with the measured stiffnesses of the composites in three testing directions (0°, 45°, and 90°). The use of the actual yarn orientations measured by the FFO method, instead of the nominal yarn orientations of ±45°, is shown to result in improved CLT predictions of stiffness with a mean deviation between predictions and measurements on 0.2 GPa. Altogether, it is demonstrated that stiffness of multiaxial flax fibre composites can be accurately predicted by CLT, without any fitting constants, based on independently determined stiffness parameters of the related uniaxial flax fibre composite, and based on measured yarn orientations in the flax fibre fabric.

Environmentally Friendly Surface Modification Treatment of Flax Fibers by Supercritical Carbon Dioxide

The present work investigates the effects of an environmentally friendly treatment based on supercritical carbon dioxide (scCO2) on the interfacial adhesion of flax fibers with thermoset matrices. In particular, the influence of this green treatment on the mechanical (by single yarn tensile test), thermal (by TGA), and chemical (by FT-IR) properties of commercially available flax yarns was preliminary addressed. Results showed that scCO2 can significantly modify the biochemical composition of flax fibers, by selectively removing lignin and hemicellulose, without altering their thermal stability and, most importantly, their mechanical properties. Single yarn fragmentation test results highlighted an increased interfacial adhesion after scCO2 treatment, especially for the vinylester matrix, in terms of reduced debonding and critical fragment length values compared to the untreated yarns by 18.9% and 15.1%, respectively. The treatment was less effective for epoxy matrix, for which debonding and critical fragment length values were reduced to a lesser extent, by 3.4% and 3.7%, respectively.

Experimental evaluation on comparative mechanical properties of Jute - Flax fibre Reinforced composite structures

In the modern era, the world is facing unprecedented challenges in form of environmental pollution and international agencies are forcing scientists and materialists to look for green materials and structures to counter this problem. Composites based on renewable sources like plant based fibres, vegetable fibres are finding increasing use in interior components of automobile vehicles, aircraft, and building construction. In the present study, jute and flax fibre based composites were developed and tested for assessing their suitability for possible applications in interior cabin and parts of automobile and aerospace vehicles. Matrix system involves epoxy as resin and fibre weight fractions used were 45% and 55% respectively. Composites samples were prepared as per American society for testing and materials (ASTM) standard and were tested for individual fiber tensile strength, composite tensile strength, and flexural strength to analyse its behavior under various loading conditions. The results revealed that the Jute fibre composites possess enhanced mechanical properties over Flax fibre composites.

Tensile creep behaviour of unidirectional flax fibre reinforced bio-based epoxy composites

Abstract Composites made of natural fibres are promising in applications of structural components. Their creep resistance is a very important characteristic to be evaluated but is not well understood. This work investigates creep response of a unidirectional flax fibre reinforced bio-based epoxy under various tensile stress levels. Acoustic emission detection and fracture surface morphology analysis were utilized to analyse the creep mechanisms. In addition, a flax fibre pre-treatment using a green chemical (furfuryl alcohol) was applied in order to reduce to creep deformation. The results show that unidirectional flax fibre composites exhibit perceivable creep at low stress levels and have a relatively short creep rupture life at high stress levels. The creep deformation at low stress can be ascribed to the time-dependent shear deformation of matrices at interface area (hemicellulose/pectin matrix at fibrils interface and the epoxy at fibres interface). Creep at high stress are characterized with a development of extensive damage events and doesn't show typical three-stage creep deformation behaviour over creep life. Composites with furfuryl alcohol treated flax fibres displayed a reduced creep deformation of about 30% than their untreated counterparts at the same creep stress, proving that treating flax fibres with furfuryl alcohol is efficient to improve the creep resistance of flax fibre composites.

Enhancement of Mechanical Properties of Flax-Epoxy Composite with Carbon Fibre Hybridisation for Lightweight Applications.

The effect of unidirectional (UD) carbon fibre hybridisation on the tensile properties of flax fibre epoxy composite was investigated. Composites containing different fibre ply orientations were fabricated using vacuum infusion with a symmetrical ply structure of 0/+45/−45/90/90/−45/+45/0. Tensile tests were performed to characterise the tensile performance of plain flax/epoxy, carbon/flax/epoxy, and plain carbon/epoxy composite laminates. The experimental results showed that the carbon/flax fibre hybrid system exhibited significantly improved tensile properties over plain flax fibre composites, increasing the tensile strength from 68.12 MPa for plain flax/epoxy composite to 517.66 MPa (670% increase) and tensile modulus from 4.67 GPa for flax/epoxy to 18.91 GPa (305% increase) for carbon/flax hybrid composite. The failure mechanism was characterised by examining the fractured surfaces of tensile tested specimens using environmental scanning electron microscopy (E-SEM). It was evidenced that interactions between hybrid ply interfaces and strain to failure of the reinforcing fibres were the critical factors for governing tensile properties and failure modes of hybrid composites.

Evaluation of delamination damage and surface roughness in end milling flax fibre composites

Flax fibre reinforced composites have been very attractive in numerous applications such as wall and automotive panels. With chemical treatments and modifications, their mechanical competent can be at par with the existing synthetic fibre composites. The flax fibre composites are normally fabricated to near-net shape, but very often these composites require a secondary cutting process such as milling to attain final geometrical and dimensional tolerances. Due to the continuous contact of the milling tool on the composite material during cutting process, several undesirable damage such as delamination, matrix cracking, fibre pull-out; existed which may lead to deterioration of their mechanical strength. In this study, parametric effects of milling parameters, namely; feed rate, spindle speed, and number of end mill flutes on delamination damage and surface roughness, were investigated. Taguchi L18 orthogonal array was used to design the experimental plan. Signal to Noise (S/N) ratio and response tables were implemented to analyse the experimental data. It was found that spindle speed and feed rate had equal effects on delamination damage and surface roughness, whereas the number of end mill flute had a marginal influence on the aforementioned machining outputs.

Low velocity impact and compression after impact damage responses on flax/basalt fiber hybrid composites

The aim of this research is to study the low velocity impact and compression after impact responses of woven flax and basalt fiber reinforced polyester composite. The basalt and flax fibers are arranged with varying stacking orders and composites were fabricated through compression molding technique. This research also focuses on the utilization of natural and synthetic fiber combinations for some impact related applications. The low velocity impact test was carried out with 12 J of energy to explore the composite load bearing capacity. The impact affected area was calculated with the help of Liquid Penetrant test (LPT), the minimum affected area noticed on pure basalt fiber composite. Compression after impact (CAI) showed better results for composite which has more stacking of flax fiber. From the overall observation the alternate arrangement of basalt and flax fiber composite shows the better performance for low velocity impact and compression after impact studies.

Heat and smoke production of flax fibre reinforced composites under horizontal and vertical orientations

In this research, the effects of horizontal and vertical orientations on the fire reaction of flax fibre reinforced composites were investigated in the cone calorimetry tests. It was interesting to note that both short and long flax fibre composites under vertical orientation ignited later and released less heat/smoke than horizontally oriented samples due to thin pyrolysis layer and short combustion time. The addition of flame retardant reduced the flammability, but irregular char formation under the vertical orientation led to the higher heat and smoke production. Moreover, composite's structure and material system influenced the heat release rate trends depending on the orientation. Finally, Fire Dynamics Simulator numerically simulated the heat release rate and visualised heat/smoke flows in the horizontal and vertical set-ups of the cone calorimeter.

Basic modeling of the visco elastic behavior of flax fiber composites

Basic modeling of the visco elastic behavior of flax fiber composites

Thermal effect on the tribo-mechanical behavior of natural fiber composites at micro-scale

This paper aims to explore the thermal influence on the micro-tribo-mechanical behavior of natural fiber composites. Nanoindentation and scratch-test are used to characterize flax fibers reinforced polypropylene (PP) composites. Results show a different thermo-mechanical behavior between flax fibers and PP matrix. While the stiffness of PP matrix decreases by increasing the sample temperature, the stiffness of flax fibers shows an increase then a decrease by changing the sample temperature from 25 °C to 100 °C with a maximum at 60 °C. This attests to a modification of the chemical composition of flax fibers when increasing the temperature. The specific thermo-mechanical behavior of flax fibers affects their friction comportment at a high sliding speed which demonstrates that the tribology of NFRP composites is thermo-mechanical-dependent.

Improving moisture durability of flax fibre composites by using non-dry fibres

Non-dry flax fibre and polyester resin that has low sensitivity to moisture were used in the production of composites and the effects on flexural and moisture sorption properties of composites under wet-dry cycling were determined. Results showed that composites made of non-dry fibre have lower moisture sorption and degree of swelling and shrinking compared to composites made of dried fibre. Mean strength and modulus of composites made of non-dry fibre are 4–12% and 13–14% respectively, higher than composites made of dried fibre in longitudinal direction. Mean strength and modulus of composites made of non-dry fibre are 18–22% and 11–21% respectively, higher than composites made of dried fibre in transverse direction after the wet-dry cycling. The results suggest that composites made of non-dry fibre could be used for enhancing moisture durability of composites and lessen the time, cost and embodied energy to produce the composites, by omitting the step of drying the fibres.

Tailoring of tensile and dynamic thermomechanical properties of interleaved chemical-treated fine almond shell particulate flax fiber stacked vinyl ester polymeric composites

Natural fiber and particulates are being exploited to attain eco-friendly products for construction and automotive sectors. These sectors are moving towards the use of high damping characteristic natural biofibers and particulate-reinforced polymer composite as part of the structural components. In this work, woven flax fiber (0° and 90°) and almond shell particulates were used. They were subsequently treated with alkaline and acetylene chemical solution separately. Polymer composite laminates were prepared using a vinyl ester resin as matrix and by stacking flax fibers and almond particulates interleaved in an alternative sequence using the hand layup technique. This was followed by hydraulic pressing. Composite laminates were fabricated by varying the almond shell particulate weight fraction of 0%, 5%, 10%, and 15%. Mechanical properties such as tensile and flexural strength were experimentally measured. Dynamic thermomechanical analysis was conducted on the alkaline-treated and untreated composites with different frequencies for the assessment of the damping characteristics. The alkaline-treated interleaved almond shell and flax fiber composite showed considerably higher damping characteristics. This could be due to the improved adhesion between the matrix and reinforcements. An addition of almond shell particulate positively increased the strength and stiffness of composites.

Experimental investigation on the response of unidirectional flax fiber composites to low-velocity impact with after-impact tensile and compressive strength measurement

This study investigated the low-velocity impact tolerance of flax fiber/epoxy composite reinforced by unidirectional fibers. Visual inspection and ultrasonic scanning were employed to assess the external and internal damage under impact, and to investigate their dependencies to the impactor shape as well as the impact energy. The results show that impacted specimens experience various types of fracture, matrix cracking, fiber breakage and delamination, where the impact shape shows a clear effect on the damage extent. Tensile tests show a significant effect of the residual damage, which decreases the residual strength by 41% at 5J. The impact-induced damage did not affect significantly the compressive behavior for an impact energy less than 3J. Depending on the damage extent, high impact energy shows a significant strength reduction. The effect of pre-existing damage under compressive load, monitored by the DIC system, has shown a substantial effect on the buckling mode and both residual cracks and delamination development.

The effects of water ageing on the tensile static and fatigue behaviors of greenpoxy–flax fiber composites

This work presents the experimental results of the effect of water ageing in flax fibers reinforced greenpoxy resin matrix composite materials. The experimental study was carried out on two cross-ply laminates ([0/90]s and [+45/−45]s). First, the water uptake of the two composite materials was studied. Second, the mechanical properties were identified as a function of the immersion time. The results obtained show that the Young's modulus of composites decreases progressively to 26% for [0/90]s specimens and 46.36% for [+45/−45]s specimens after 30 days of ageing. Finally, the effects of interactions between water ageing and cyclic fatigue behavior were studied. We consider stiffness loss, hysteresis curves, energy dissipation and loss factor versus number of cycles as a function of different immersions time. A significant decrease in the mechanical characteristics of the composites as a function of the immersion time is observed. [+45/−45]s specimens are more sensitive to both fatigue and water ageing phenomena.