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Flexural and impact properties of flax woven, knitted and sequentially stacked knitted/woven preform reinforced epoxy composites
Journal of Reinforced Plastics and Composites
Abstract
In this article, plain woven, rib knitted and sequentially stacked rib knitted/plain woven, flax fabric reinforced epoxy composites are investigated for their flexural and impact properties. The effect of lay-up angle and the number of preform layers on the above-mentioned properties are also studied. The composite laminates were processed by hand lay-up technique using 2 and 4 mm thick spacers and cured under pressure of 3 bar for 2 h at 50°C, followed by curing in an oven at 120°C for 1 h. Specimen preparation and testing were carried out as per ASTM standards. The results indicate that the woven preform reinforced laminates perform better in both flexural and impact properties for all the lay-up angles and thicknesses investigated in this study. Among the sequentially stacked knitted/woven preform reinforced laminates, specimen with knitted preform as the skin layers exhibited better flexural and impact properties. The data obtained show a tendency of lower flexural and impact values with increase in number of preform layers for all lay-up angles with the exception of lay-up angle [0°/ + 45°/−45°/0°]. At low fibre volume fraction, the sequentially stacked knitted/woven preform reinforced laminates were found comparable to woven preform laminates.
... The overall impact toughness of all manufactured samples in this study is attributed to the higher volume fraction of vinyl ester matrix in composite. Since the volume fractions of woven hemp fabric in all the fabricated composites are similar (refer Table 3), the impact properties are not to be influenced by this factor but to fabric layering orientation instead [18,35]. Typical impact responses in Figure 5 show the similar trend for all samples fabricated in this study and the differences between them were only the intensity of the peaks which indicate the level of energy absorptions. ...
... This makes the samples less rigid internally, creates some kind of cushioning effect while the hammer hit the specimen thus the impact forces was absorbed not only by the matrix but also the fibres [10]. Therefore, sample HVE[0] could withstand the impact energy higher than all other samples [35] in their work implied that there is no obvious effect of lay-up angle on the impact properties of woven perform reinforced composite laminate. However, although the difference between the samples was quite insignificant in this work, the trend was obviously related to the fabric layer orientation and this matter is worth to discuss in order to justify the slight differences in their impact properties. ...
... That is the reason of the lowest flexural properties of the sample HVE[S]. Flexural properties of the composites made by[35] was lower in 0° orientation in comparison with their 90° orientation samples.Most of their results were contradicted from the fabricated composites in this study. The only reason is, with the similar size of yarn in their fabric, the fabric density in warp direction (0°) was lower than in the weft direction. ...
Hemp is a common natural bre which has reliable properties and is available in the forms of staple bres, yarns and fabrics. However, less works were done by using woven hemp fabric in composite materials, especially for an alternative to wood products. In this work, woven hemp fabrics in different fabric layering orientations have been used to reinforce vinyl ester resin by employing hand lay-up method. The properties of hemp fabric were used to investigate how these properties can affect the physical and mechanical behaviour of the fabricated composites. The results show that fabric properties and layering orientations contribute to the tensile, exural and impact properties of the composites. Based on the comparison to wood and engineered wood products’ properties, the mechanical properties of composites are found to be comparable. The comparison also shows that the woven hemp fabric reinforced vinyl ester can be an alternative for wood and engineered wood products in building industries especially in low-load bearing applications.
... Nowadays, natural fibers are considered as an effective alternative material to man-made/synthetic materials owing to exceptional properties such environmental friendliness, high strength to weight ratio, ease of fabricating their composites with less energy consumption, and nontoxicity (Rajini et al. 2013;Venkateshwaran and ElayaPerumal 2012). These impressive properties have fascinated aviation, automobile, marine, civil, and packing industries for low and medium applications, yet challenging to employ for high load applications (Muralidhar, Giridev, and Raghunathan 2012). Among the natural fibers, flax fiber is the promising reinforcement member which is reported as a substitute to synthetic fibers (glass and carbon) due to its several advantages such as low density, non-abrasiveness, good mechanical properties, renewable and nontoxic nature, and simplicity of processing (Muralidhar, Giridev, and Raghunathan 2012;Smeder and Liljedahl 1996). ...
... These impressive properties have fascinated aviation, automobile, marine, civil, and packing industries for low and medium applications, yet challenging to employ for high load applications (Muralidhar, Giridev, and Raghunathan 2012). Among the natural fibers, flax fiber is the promising reinforcement member which is reported as a substitute to synthetic fibers (glass and carbon) due to its several advantages such as low density, non-abrasiveness, good mechanical properties, renewable and nontoxic nature, and simplicity of processing (Muralidhar, Giridev, and Raghunathan 2012;Smeder and Liljedahl 1996). But due to the hydrophilic nature of vegetable fibers, they uptake high moisture content resulting in poor wettability leading to the deterioration of the interfacial properties of fiber and matrix (Chandramohan et al. 2019;Goriparthi, Suman, and Rao 2012) though they have potential to replace manmade fibers. ...
Nowadays, natural plant fibers are being explored and employed for various industrial applications owing to their attributes such as low weight to strength ratio, cost effectiveness, biodegradability and environment-friendliness. In this work, alkali and trimethoxymethyl silane (ATS) treated plain derived irregular basket woven flax fabric-reinforced epoxy composites (F-E) namely 0-TFE (Neat epoxy), 25-TFE, 35-TFE and 45-TFE with 0, 25, 35 and 45 wt.% fiber contents respectively were prepared by compression molding at room temperature, and studied for their abrasive wear and thermal degradation characteristics as per the standard procedures. Abrasive test was performed on pin on disc with a track diameter of 80 mm (ASTM G-99-05) for varying applied load and different abrasive grits condition for a constant speed of the disc. Wear outcome revealed that wear loss, specific wear rate (SWR) and coefficient of friction (COF) were influenced by the combined effect of applied load and abrasive grits. The composite 45-TFE exhibited better tribological properties amongst the prepared lot. Furthermore, thermal analysis revealed that the fabricated F-E composites are sufficiently thermally stable for structural applications and ATS treated- plain derived flax woven reinforcement enhanced the thermal stability. Scanning electron microscopy (SEM) was used to understand the wear mechanisms of composites.
... As shown in Table 3.3, most of the works done have used longer durations (more than 24 h) while working at room temperature. However, some authors used comparably short durations (1-2 h) but with temperatures higher than 50°C (Jacob et al. 2006;Jiang et al. 2009;Muralidhar et al. 2012;Muralidhar 2013;Li et al. 2015a;Rohen et al. 2015;Pushparaja et al. 2017;Boutin et al. 2020;Mishra et al. 2020). After analyzing the compression molding parameters for thermoplastic and thermoset composites, and the data presented in Tables 3.2 and 3.3, it was noticed that usually the molding duration for thermoplastic composites is much less than that for thermosets. ...
... As for flax fiber composites, 60% reinforced epoxy composites exhibited tensile strength and modulus of elasticity equal 205.56 ± 8.14 MPa and 22.67 ± 0.47 GP, respectively(Li et al. 2015a). However, lower fiber volume fraction rendered lower tensile strength results in the range between 80 and 150 MPa (DiBella et al. 2010;Muralidhar et al. 2012;Muralidhar 2013;Boutin et al. 2020;Hassan et al. 2020). ...
Selecting the proper composite fabrication technique in the automotive industry is key to fulfilling the performance criteria and economic feasibility of the manufactured parts. While there are several standard techniques that are commonly used with carbon and glass fibers, only few of those techniques are suitable for use with natural fiber reinforcements. This chapter will discuss the different natural fiber composite (NFC) manufacturing techniques used in the literature as well as those techniques used by leading automotive parts manufacturers. Compression molding, resin transfer molding, and vacuum-assisted resin transfer molding techniques are described with details on processing parameters and procedures. Hand layup technique as well as extrusion and injection molding is also discussed. Comparison between processing parameters of NFC with thermoplastic and thermoset matrices is summarized in addition to comparison of the mechanical properties of NFC manufactured using selected techniques.
... As shown in Table 3.3, most of the works done have used longer durations (more than 24 h) while working at room temperature. However, some authors used comparably short durations (1-2 h) but with temperatures higher than 50°C (Jacob et al. 2006;Jiang et al. 2009;Muralidhar et al. 2012;Muralidhar 2013;Li et al. 2015a;Rohen et al. 2015;Pushparaja et al. 2017;Boutin et al. 2020;Mishra et al. 2020). After analyzing the compression molding parameters for thermoplastic and thermoset composites, and the data presented in Tables 3.2 and 3.3, it was noticed that usually the molding duration for thermoplastic composites is much less than that for thermosets. ...
... As for flax fiber composites, 60% reinforced epoxy composites exhibited tensile strength and modulus of elasticity equal 205.56 ± 8.14 MPa and 22.67 ± 0.47 GP, respectively(Li et al. 2015a). However, lower fiber volume fraction rendered lower tensile strength results in the range between 80 and 150 MPa (DiBella et al. 2010;Muralidhar et al. 2012;Muralidhar 2013;Boutin et al. 2020;Hassan et al. 2020). ...
The new race in the automotive industry is no longer speed, but rather lightweighting and sustainability. Major automakers and component suppliers are now shifting to natural fiber reinforcements for their composite components as a sustainable and lightweight alternative to the manmade reinforcements. However, there is a gap between academic literature and the actual practices in the industry. Therefore, the main objective of this book is to bridge this gap and to provide a comprehensive and integrated review on recent practices on natural fiber composites (NFC) in the automotive industry from composites fabrication to recycling.
Manufacturing Automotive Components from Sustainable Natural Fiber Composites book acts as a body-of-knowledge or handbook for researchers and industrialists interested in this field. It provides a historic context of the adoption of NFC in the automotive industry and provides technical data on the materials used, with up-to date statistics on global production. Moreover, it discusses the process of materials qualification between material suppliers and automakers and the major challenges facing the use of NFC in the industry. Further, it provides a critical review on the manufacturing techniques used, including processing parameters and procedures. Afterward, it combines and tabulates the major manufactured NFC auto parts, with
details on major performance requirements. The book also evaluates the sustainability of NFC, by comparing the life cycle assessments and carbon footprints of different components made with different natural fibers. Finally, it provides future prospects and trends in NFC and the use of all-cellulose composites.
This book can help both researchers and practitioners by removing the hindrance of having to search several studies. It provides academic researchers with a better understanding of recent practices of NFC in the automotive industry and help them spot the research gaps on Which they will build their future research studies. Moreover, it is intended to help practitioners determine how to use NFC in producing new sustainable and innovative auto parts.
... Also, there is no health hazard like skin irritation by using natural fibres. The natural fibre mechanical properties are comparable with glass fibre and in some cases, these natural fibres have shown better specific properties compared to synthetic fibres [2]. The use of natural fibres is rapidly increasing not only in textiles, paper and home furniture; these are also used in high value added products such as functionalised fibres and reinforcing materials in composites [3]. ...
... Fibrous materials such as fibres, yarns and fabrics are specifically assembled as textile preforms in an unconsolidated manner (i.e., no matrix added) [6]. Due to their distinctive mechanical characteristics, such as enhanced transverse modulus, strength, enhanced shear resistance, damage tolerance, intra and interlaminar strength, reduced price, and flexible design potential properties, make them a prime reinforcement material for the composite applications [2,7,8]. The preforms of textiles are split into three different kinds. ...
In this study natural fibre 3D braided yarn plain woven fabric (NFBF) and natural fibre simply twisted yarn plain woven fabric (NFSF) are prepared and tensile tests are conducted on braided yarn, simply twisted yarn, NFBF and NFSF. Then the tensile results of braided yarn compared with simply twisted yarn and NFBF results with NFSF. The composites are manufactured by reinforcing prepared fabrics (NFBF and NFSF) with the epoxy resin. On these composites tensile and flexural properties characterisation is carried out in warp and weft directions of the fabrics. SEM analysis is used for fractured surface study. The test results showed that, simply twisted yarn and its fabrics (NFSF) are presented better strength than that of the braided yarn and its fabric (NFBF). The NFSF/epoxy composite in warp direction loading received higher tensile strength and flexural strength of about 67.12 MPa and 131 MPa.
... The findings from Haller et al. (2006) proved that knitted textiles show high potential for reinforcement in engineering applications, particularly as results proved that maximum load tripled and stiffness strength doubled when the wood was reinforced with the biaxial knit structure. Muralidhar et al. (2012) characterised the flexural and impact behaviour of textile composites made from laminates of knitted and woven preforms stacked together. The Plate 4. Surface view of plain Jersey with warp and weft insertion; spiral disc of biaxial knitted reinforcement; and placement of reinforcement in wooden test specimen (Haller et al., 2006) Plate 3. Carbon and Kevlar composite pipe (Pamuk, 2014, by the kind permission of G Pamuk) RJTA 21,4 composite achieved higher impact strength when the knitted preforms were placed on the outside with the woven preforms in the middle. ...
... The research shows similarities to Hu et al. (2010), who investigated composites structured with outer woven layers with two inner weft knitted layers, stitched together with Kevlar yarns, similar to that schematically shown in Figure 6. Contrary to Muralidhar et al. (2012) findings, Hu et al. (2010 suggested mechanical properties were superior when the woven layers were on the outside. The outer woven layers would transmit stress waves along the fabric plane, while the knitted structures in the core would enable large amounts of energy to be absorbed in the thickness direction. ...
Purpose
This paper aims to provide an overview of the current manufacturing methods for three-dimensional textile preforms while providing experimental data on the emerging techniques of combining yarn interlocking with yarn interlooping.
Design/methodology/approach
The paper describes the key textile technologies used for composite manufacture: braiding, weaving and knitting. The various textile preforming methods are suited to different applications; their capabilities and end performance characteristics are analysed.
Findings
Such preforms are used in composites in a wide range of industries, from aerospace to medical and automotive to civil engineering. The paper highlights how the use of knitting technology for preform manufacture has gained wider acceptance due to its flexibility in design and shaping capabilities. The tensile properties of glass fibre knit structures containing inlay yarns interlocked between knitted loops are given, highlighting the importance of reinforcement yarns.
Originality/value
The future trends of reinforcement yarns in knitted structures for improved tensile properties are discussed, with initial experimental data.
... [2][3][4] These advantages motivated several authors to study the mechanical and dynamical properties of natural fibres-reinforced composite materials. 1,2,[4][5][6][7][8][9][10][11][12][13][14][15][16] For example, Oksman 1 compared the tensile properties of high-quality long flax fibrereinforced epoxy composites with glass fibre-based materials. The mechanical characterization showed that the stiffness and strength values of the high-quality flax-epoxy composite were promising, compared to earlier works on natural fibre-reinforced composites, with in particular a stiffness of about 39 GPa which exceeds that of glass-epoxy composites (31 GPa). ...
... The results showed that hackled Fax fibre leads to the best composite properties and the twist angle should be minimal. Muralidhar et al. 5 investigated the effects of lay-up angle and the number of preform layers on the flexural and impact properties of flax fabrics-reinforced epoxy composites. They found that, for all the lay-up angles, the flax woven-reinforced laminates presented better flexural and impact properties. ...
This paper aims at comparing the mechanical behaviour of different composite materials constituted of twill flax and glass fabrics-reinforced liquid thermoplastic and thermoset resins. The main objective is to study the possibility of thermoplastic to replace thermoset matrix, and flax fibre to replace glass fibre. For this purpose, the studied composites were fabricated using the vacuum infusion technique. Next, they were subjected to several monotonic and load-unload tensile tests in order to determine their mechanical properties and their evolution with damage. Two elastic damage and elastic-plastic damage models were also considered to predict their behaviour. The obtained results show that the used thermoplastic resin could constitute an interesting alternative to the thermoset resin for the vacuum infusion process. Furthermore, the flax fibre composites, in particular those based on the thermoplastic resin, present specific tensile moduli close to those of glass composites.
... Venkateswaran et al. [26] conducted a study on Typha angustifolia-epoxy reinforced composite and noted that the weight fraction of natural fiber significantly impacts the mechanical properties of the composite. Muralidhar et al. [27] investigated the mechanical properties of flax fiber in two different forms with orientation angles of 0 • , +45 • , − 45 • , and 0 • . Sailesh et al. [28] used the Taguchi method to examine banana fiber and bamboo fiber with glass fiber and epoxy in orientation angles of 0 • , +45 • , 90 • , and 0 • . ...
In recent years, there has been a surge in the use of natural fiber polymer-based composites in various engineering fields due to their numerous advantages, including lower environmental pollution, ease of processing, high strength, and biodegradability. This study employed the Taguchi method to experimentally and statistically examine the effects of various fiber parameters on the tensile strength of a locally developed natural fiber-epoxy composite. The natural fiber used in the study was “Meriz,” a type of goat hair woven into the traditional Kurdish costume known as “Shall.” The fiber parameters examined included fiber orientation angles, weight fraction, form, and color. The results indicated that the tensile strength of the composite was improved by 100% when using the Meriz fiber with certain orientation angles, weight fraction, form, and colors, namely 0°/90°, 10 wt%, Shall, and brown, respectively. The analysis of variance also revealed that the fiber form had the most significant impact on tensile strength, contributing 40.74%. Confirmation testing demonstrated good agreement between the experimental and statistical data. Scanning electron microscopy was utilized to assess the interfacial bonding between the fiber reinforcement and the matrix and to analyze the fracture surface of the specimens with the highest and lowest tensile strength. The results indicated that the specimen with the highest tensile strength had excellent interfacial bonding compared to the specimen with the lowest tensile strength.
... They observed that hybrid knitted composites had the highest energy absorption when unsaturated polyester resin used whilst the fracture mechanism of the composites changed depending of the arrangement of glass and carbon fibres. Muralidhar et al. [27] investigated impact and flexural properties of plain woven, rib knitted and rib knitted/plain woven flax fabric reinforced epoxy composites. Their results showed that woven fabric composites had better flexural and impact properties than knitted and hybrid fabric composites whilst using knitted fabrics as the outer layers provided higher impact and flexural properties. ...
This paper investigates tensile, flexural, impact and compression after impact (CAI) performance of weft knitted fabric reinforced thermoset composites containing glass/polypropylene (PP) hybrid yarns. Glass and PP yarns were combined at three different PP ratios and converted to supreme hybrid knitted structures using a circular knitting machine. Using PP yarns helped to decrease glass fibre breakages during the knitting process. It was observed that the addition of PP yarns decreased overall density of composites up to 22%. Fabric tensile test indicated that using PP yarns enhanced ductility of the knitted fabrics. Flexural strength of composites was decreased by addition of PP yarns for both wale and course direction at 3 and 4-point bending tests. However, hybrid composites had higher specific flexural strength when they all had same glass fibre volume fraction for 3-point bending strength. Similar results were achieved for tensile properties whilst hybrid composites had higher values after normalising the same fibre volume fractions. Impact and CAI test results exhibited that the addition of PP yarns enhanced impact and damage tolerance of composites as well as reducing impact induced areas.
... The performance of knitted composites for diverse applications was examined by Leong et al. [227]. Muralidhar et al. [228] compared plain-woven composites to knitted fabric composites in terms of flexural properties. The composite with knitted-woven fabric in the outer layer had higher mechanical characteristics, according to the results. ...
... The performance of knitted composites for diverse applications was examined by Leong et al. [227]. Muralidhar et al. [228] compared plain-woven composites to knitted fabric composites in terms of flexural properties. The composite with knitted-woven fabric in the outer layer had higher mechanical characteristics, according to the results. ...
The main objective of this study is to examine the impact of reinforcements on the strength of natural fiber composites. Recent advancements in natural fiber composites have minimized the usage of man-made fibers, especially in the field of structural applications such as aircraft stiffeners and rotor blades. However, large variations in the strength and modulus of natural fiber degrade the properties of the composites and lower the safety level of the structures under dynamic load. Without compromising the safety of the composite structure, it is significant to enrich the strength and modulus of natural fiber reinforcement for real-time applications. The strength and durability of natural fiber can be enriched by reinforcing natural fiber. The reinforcement effect on natural fiber in their woven, braided, and knit forms enhances their structural properties. It improves the properties of natural fiber composites related to reinforcement with short and random-orientation fibers. The article also reviews the effect of the hybridization of natural fiber with cellulosic fiber, synthetic fiber, and intra-ply hybridization on its mechanical properties, dynamic mechanical properties, and free vibration characteristics, which are important for predicting the life and performance of natural fiber composites for weight-sensitive applications under dynamic load.
Keywords: natural fiber composite; woven natural fiber; orientation; mechanical; dynamic mechanical; vibration
... Consumption of natural resources like soil, clay and wood to manufacture different types of composites for various structural, as well as household items, has been simultaneously increasing day by day (Barman et al., 2017). To match this demand of requirements and at the same time with less consumption of natural resources to protect the environment, new ideas and feasible products can be developed by various recycling methods (Borg et al., 2016;Muralidhar et al., 2012;Spadea et al., 2015). Nowadays the demand for environmentally friendly products is higher and a necessary one is required to reduce the utilization of natural resources to protect our environment. ...
Purpose
Recycled fibres used as reinforcements are obtained from garment cut wastes of cotton, polyester and cotton/polyester fabrics to develop these composites. These composites are developed by using Epoxy resin, Kaolinite, Polypropylene sheet as matrices. Reinforcements and matrices have been used in different compositions and combinations to develop these composites. The main advantages of this type of composites are to combine the different properties of different materials to obtain unique and high-performance material.
Design/methodology/approach
Garment cut wastes from apparel industries are used for various applications in various industries. Normally, garment cut wastes and recycled fibres from garment cut wastes are used in textile, furniture, carpet, paper, automobile, construction and agricultural industries in low mechanical performance applications. In this research, composites are developed by using recycled fibres obtained from garment cut wastes as reinforcement and with different types of matrices.
Findings
Technical properties like thickness, mass per unit area, Tensile strength, Flexural strength, Impact strength, Water absorbency and Scanning Electron Microscope of developed composites were tested and analyzed. The outcome of the results demonstrates that many of the composite proportions with different blend, reinforcement and matrcies show superior mechanical performances when compared with each other, and it can be recommended for many potential applications.
Originality/value
The properties of composites are dependent on the different blend proportions of recycled fibres with reinforcement and matrices. Based on the result of tensile strength, polyester/cotton fibre reinforced composites show superior strength compared to other recycled fibre reinforced samples and it can be suitably tailored further by appropriate design of different lay-up angle and orientation with the number of different preformed layers of reinforcements to suit the intended applications.
... Fiber configuration is crucial for the impact performance of FRTCs. Muralidhar, Giridev, and Raghunathan (2012) examined the effect of different fiber configurations (rib-knitted, PW, and rib knitted/PW) on the impact performance of flax/epoxy composite. PW flax type displayed excellent impact strength compared to the other types of configurations. ...
Flax is a natural fiber that possesses excellent specific properties, low density, safe to handle, eco-friendly, and easily available. These make it exceedingly popular and a potential candidate to replace synthetic reinforcements in polymer composite applications. The thermoset polymer is used for structural application due to its excellent mechanical and interface bonding properties compared to the thermoplastic polymer. Flax-based thermoset polymer composites are becoming popular among researchers for advanced industrial applications. This article is intended to offer a review of the main results presented in the literature on flax fiber-based polymer composites, focusing the attention on the fiber structure, chemical arrangement, physical and mechanical properties. Then, the mechanical performance of pure and hybrid flax fiber reinforced epoxy or polyester composites is comprehensively analyzed.
... They observed that cross-ply and quasi-isotropic samples had less damage visible in front sides, refer Fig. 16 (b) and (d). Also, they noticed that unidirectional and sandwich layups absorbed higher impact energy than other configurations-moreover, Muralidhar et al. [158] stated that the increase of flax/epoxy composite preformed layers leads to the decline of the absorbed energy. Simultaneously, the layup angle seems to affect the impact properties of the preformed composite. ...
The importance of natural fibres over synthetic fibres have gained significant attention in the research area, due to their higher specific strength, stiffness, lightweight and inexpensive. Natural fibre composites used in various applications are often susceptible to moisture absorption and various critical loadings scenarios during their service life such as low-velocity impact damages which is a concern for structural and non-structural applications. For enhancing the toughness of natural fibres hybridisation with synthetic fibres is essential. This paper examines the essential information critically from the published literature influencing the morphological characteristics, fracture toughness, damage tolerance and impact resistance of natural fibre reinforced and their hybrid composites. Following this, this review paper critically analyses the novel improvement techniques suitable for natural fibre composites for damage tolerance and impact resistance behaviours.
... Flax fiber reinforced composites have been manufactured using this technique several times in woven and nonwoven forms. Woven flax preforms were used to reinforce epoxy (Muralidhar et al. 2012;Muralidhar 2013). Moreover, unidirectional and nonwoven flax fibers were used with epoxy resin (Santulli 2000;Di Bella et al. 2010;Bertomeu et al. 2012;Dhakal et al. 2016). ...
Natural fibers are attractive for their biodegradability and exceptional properties. Date palm as a source of fibers has many advantages over other sources of natural fibers; since date palm fiber sources are regarded as agriculture waste and the tree itself is cultivated for the fruit. Natural fibers including date palm are used as reinforcement to thermoplastics or thermosets using different manufacturing technique. This chapter discusses different composite manufacturing techniques that can be used with natural fibers. The discussed techniques are hand layup, RTM, VARTM, filament winding, pultrusion, compression molding, extrusion, injection molding and 3D printing.
... Les composites à constituants naturels ont une rigidité spécifique comparable à celle des composites à fibres de verre [14,[132][133]. C'est la raison principale de l'intérêt porté par plusieurs travaux de recherche sur l'étude de leurs propriétés mécaniques [134][135][136][137][138][139][140]. Parmi les fibres naturelles extraites des plantes, la fibre de lin est le premier choix en matière de performances structurelles [14]. ...
Durant les dernières décennies, les composites polymères renforcés par des fibres végétales ont reçu une attention importante de la part des scientifiques. L’utilisation de fibres végétales permet en effet d’améliorer les performances environnementales de ces matériaux tout en atteignant des propriétés spécifiques plus élevées. Néanmoins, un verrou majeur freine encore le développement de ces matériaux. En effet, leur sensibilité au vieillissement hydrique, due à leur caractère hydrophile, restreint leur utilisation. Dans ce contexte, nous proposons, dans le cadre de cette thèse, d’analyser l’effet du vieillissement hydrique sur le comportement statique et dynamique, d’identifier et suivre les mécanismes d’endommagement d’une structure sandwiche biosourcée et ses constituants. Les composites utilisés sont constitués d'une résine greenpoxy associée à des fibres de lin et à une âme en liège pour les sandwichs. Dans la première partie, nous avons étudié le comportement en statique et en dynamique de la résine, du composite, des âmes et des sandwichs. Cette étude a conduit d’une part à la détermination des caractéristiques mécaniques et à l’identification et le suivi des mécanismes d’endommagement par émission acoustique et observations microscopiques et d’autre part à la détermination des caractéristiques dynamiques. Dans la deuxième partie, nous avons analysé la cinétique de diffusion d'eau dans la résine, les peaux, les âmes et les sandwichs par identification de leurs paramètres de diffusion par le modèle de Fick. En suite, nous sommes intéressés à l’impact du vieillissement hydrique sur le comportement et les propriétés mécaniques des sandwichs et ses constituants.
... Ferreira et al. also highlighted a marked increase in peak load with the increase in thickness of the woven mat, while the deformation showed reduction in magnitude for the juteÀepoxy composite [31]. As per Muralidhar et al., the increase in the number of preformed layers in the flaxÀepoxy composite lead to a reduction in the absorbed energy, while the lay-up angle seems to have an influence on the impact properties of the knitted preformed composite [32]. According to Santulli and Caruso, hemp (random mat)Àepoxy composite showed a superior peak load characteristic than the jute (plain weave)Àepoxy composite in terms of magnitude of peak load [33]. ...
... Muralidhar et al. (2012) analyzed the flexural properties of woven, rib knitted and sandwich rib knitted/plain woven flax epoxy composites. Results show that sandwich composite by keeping knitted fabric as a skin layer gives better properties than individual composites. ...
Natural fiber composites with improved mechanical properties can be successfully used to replace the environmentally hazardous synthetic fiber composites in low and medium structural load applications. Detailed investigation on possibilities of improving mechanical
characteristics of woven natural fiber fabric polymer composite is very important. Main objective of the present work is to investigate effect of various important parameters such as nature of weaving architecture of a woven fabric, intra-ply hybridization of two different natural fibers in a fabric, intra-ply hybridization of synthetic and natural fibers in a fabric, chemical modification of natural fabric, nanoclay as secondary reinforcement and stacking sequence of woven fabrics with different weaving architecture on mechanical, dynamic mechanical and free vibration characteristics of the composite.
Jute woven fabrics with five different types of weaving architecture namely plain, basket, stain, twill and huckaback are considered to analyze the effect of weaving pattern of woven fabric reinforcement on mechanical, dynamic mechanical and free vibration characteristics of a polymer composite. Results revealed that weaving pattern influences the mechanical behaviour of the composite and fabric with basket type weaving pattern enhances the properties of composite material. Due to less interlace and lower crimp in the warp and weft directions of the basket type woven fabric its composite carries more load compared to the composite with other weaving patterns. Further effect of intra-ply hybridization of two different fibers in a woven fabric on mechanical behaviour of the composite has been analyzed. For this purpose, fabrics are prepared by orienting banana and jute yarn in the warp and weft direction of basket type woven fabric in different combinations. Results reveal that orienting relatively stronger
jute fiber yarns in the warp direction enhances the properties of composite material. Further synthetic-natural fiber intra-ply hybrid woven fabrics are prepared by orienting synthetic glass fiber and natural fiber such as banana and jute in the warp and weft direction in different combinations to analyze the effect on the mechanical behaviour. Results reveal that synthetic-natural fiber intra-ply hybridization can be effectively used in structural members subjected to impact loading compared to the structural members
subjected tensile or bending loads.
In order to investigate the effect of pre-surface treatment of woven fabric on mechanical behaviour of the composite basket type woven jute-banana intra-ply fabric is treated with four different chemical solutions such as alkali, potassium permanganate, benzoyl chloride and silane. Results reveal that benzoyl chloride surface treatment enhances the properties of composite material to the largest extent when compared to all other cases. It is also found that addition of nanoclay as secondary reinforcement enhances dynamic mechanical behaviour of the basket type woven jute-banana intra-ply fabric composite for the 2 weight percentage of nanoclay. From the studies on comparison of woven fabric made of conventional simply
twisted yarns and braided yarns it is found that braided yarn fabric reinforcement results in significantly higher dynamic mechanical properties of the composite due to the braided nature of yarns. However it is also observed that intra-ply hybridization of jute and banana yarns in braided fabric is not improving the dynamic mechanical behaviour. These results are compared with knitted fabric composites also which reveals that knitted fabric composites have better damping capability but very poor mechanical properties due to the higher gap naturally available between the yarns in the knitted
fabric.
Mechanical properties of the composite increases with number of layers of the fabric due to increase in the fiber loading and four layered basket type woven fabric composite has better dynamic mechanical behaviour. From the studies on sequence of layer of fabric with different weaving pattern, it is found that composites with relatively strong fabric as skin and relatively weak fabric as core have better dynamic mechanical properties due to the sandwich effect.
Buckling and free vibration characteristics of woven natural fiber laminated composite beam under the axial compression load are analyzed experimentally. Jute-plain, jute-basket and jute-herringbone fabrics are considered for the analysis on effect of number of layers and nature of weaving pattern on the buckling strength and free vibration behaviour of the beam. It is found that the buckling strength is influenced by number of layers of the fabric and nature of weaving architecture of the fabric. Natural frequency of the composite beam reduces with increase in the axial compression load while modal damping increases with axial compression load in the pre-buckled
region. However this trend in natural frequency and modal damping with increase in axial compression load changes in the post-buckled region which is clearly observed for the fundamental vibration mode.
... The primary force and rigidity and compression after impact strength of the composite material can be improved by using woven and knitted fabric in outer and inner plies, respectively (Kim & Ye, 2012). Muralidhar et al. (2012) studied flexural and impact behavior of woven, knitted, and sequentially stacked knitted/woven reinforced epoxy composites materials. They concluded that the woven reinforced laminate composites have higher flexural and impact strengths. ...
The objective of this research is to develop the woven/knitted hybrid composites for improved in plane as well as out of plane mechanical properties. Two different type of structures and two different materials were used in this study. Firstly, the woven and knitted fabrics were developed with glass and Kevlar yarn. Secondly, the laminated composites samples were fabricated with different stacking sequence of fabric plies. The epoxy resin was used as matrix. The cured samples were characterized for impact, tensile and dynamic mechanical properties. The behavior of composite materials was then analyzed with percentages of different fiber and fabric types. The samples with higher percentages of knitted reinforcement gave better impact strength but failed to provide better tensile properties. Moreover, the samples with higher percentages of woven structure and glass materials gives better modulus values.
... Even with drawbacks inherently present in natural cellulose-based fibres, such as their hydrophilic nature, wider properties variation, difficult adhesion to thermoset and especially thermoplastic resins, economical factors, etc., natural fibres are being extensively explored by automotive, aviation, marine, civil and packaging industries as an environment-friendly alternative to synthetic fibre composites. 1 Flax is probably the most commonly used bast-type fibre today. Due to its properties and availability, flax fibres have the potential to substitute glass fibres in polymer composites, even though their strength is lower. ...
In the present work damage was monitored in flax/epoxy quasi unidirectional woven laminates. Several plates with different lay-up configurations: [0°]8,[0°,90°]2s,[0°,90°,+45°,-45°]s and [+45,-45]2s were prepared in autoclave, then the damage was monitored during the tensile test using acoustic emission technique. The tensile tests show that these composites offer good mechanical properties. The acoustic emission diagrams allowed us to follow the evolution of damage and to identify several parameters: Energy, damage threshold and the number of events, however the correlation between the stress-strain curves and AE results don't show a direct relationship between the two damage indicators (E&AE): this suggests that the shape of the strain-strain curves is due predominately to another factor than AE events.
... In another study on bamboo and kenaf fibers reinforced composite, it was concluded that high mechanical strengths were observed in resin impregnated composites than alkali treated composites [2]. In another research on knitted/woven preform reinforced epoxy composites, it was concluded that the impact and flexural strengths are dependent on the lay-up angle and numbers of preform layers present in the composite [3]. Investigations on maize fiber reinforced epoxy composites reported that alkali treatment to maize fibers removed the excess lignin and improved the water absorption characteristics of the composites [4]. ...
In this study, new biodegradable composites were developed with loofah, jute and commercial E-glass as reinforcing fibers and poly ester as the resin. Loofah fibers are preheated with distilled water and alkali followed by heat treatment in order to enhance its surface properties. Four composite materials are prepared by varying the proportions of natural and glass fibers in each and maintaining the resin content as a constant. The specimens were subjected to testing of mechanical properties namely tensile strength, compressive strength, flexural strength and impact strength. The results revealed that the mechanical properties like tensile, flexural and impact strengths were high when proportions of all fibers are equal. Also, compressive strength was higher with sample containing only loofah fibers.
... Recently, in 2013 Xue and Hu [5] developed a biaxial weft-knitted flax fabric using a modified flat knitting machine. The modulus and the strength of the resulting composites are reported 4.2GPa and 161.6MPa, respectively, along the weft direction..Similarly Muralidhar et al. [6,7] made woven and rib-knitted flax reinforcement and characterized their composite material. ...
In this paper a new process to manufacture unidirectional reinforcements for eco-composite materials, made of natural fibers, is presented. Starting with flax rovings of different sizes, an apparatus was developed to feed and align the rovings over the wet-end section of a paper machine. The short kraft paper fibers are therefore mixed with the long flax roving as the machine is running, and at the end of the process, a sheet of the hybrid dry reinforcement is obtained and cut to size for impregnation with various resins, using different processes. This novel manufacturing process allows for high volume production of reinforcement. It is very flexible, and many different combinations of long and short fibers can be exploited for the production of a vast variety of dry reinforcements. In this paper, composite samples are obtained out of these reinforcements, using the resin infusion (RI) molding process with a commercial epoxy resin. The results are compared with those of usual glass fiber reinforcement. An interesting aspect is that the large variability, typical for natural fibers, is largely reduced when the short kraft fibers are present in the composite. In terms of permeability to resin, reasonably comparable values can be obtained compared to that of glass fabrics, if a low surface density of reinforcement is chosen.
... Even with drawbacks inherently present in natural cellulose-based fibres, such as their hydrophilic nature, wider properties variation, difficult adhesion to thermoset and especially thermoplastic resins, economical factors, etc., natural fibres are being extensively explored by automotive, aviation, marine, civil and packaging industries as an environment-friendly alternative to synthetic fibre composites. 1 Flax is probably the most commonly used bast-type fibre today. Due to its properties and availability, flax fibres have the potential to substitute glass fibres in polymer composites, even though their strength is lower. ...
The damage initiation and development in flax/epoxy laminates under quasi-static tension is studied. The laminates are made of quasi-unidirectional woven prepregs in different configurations [0°]8, [0°, 90°]2S, [−45°, 45°]2S and [0°, 90°, +45°, −45°]S, and processed using an autoclave. The damage was monitored during the tensile test using acoustic emission and observed by post-mortem microscopy of the samples. The stress–strain curves illustrate the ductile behaviour of the [+45°, −45°]2S composite, whereas in the other composites a more brittle behaviour was observed. Non-linearity of the stress–strain curves is explained by the intrinsic non-linearity of flax fibres in tension. The combination of the stress–strain data and the registered acoustic emission data is used to identify the damage initiation and propagation thresholds. The damage thresholds are the lowest in the [0°]8 laminate and the highest in the [+45°, −45°]2S laminate. The observed fracture zones and damage mode are cracks inside and on the boundary of technical fibres, cracks on the boundary of tows, matrix cracking, fibre pull-out and fibre breakage. A notable feature of the damage behaviour is almost full absence of transverse matrix cracks inside tows in 90° plies, which are the major damage modes in glass- and carbon-reinforced plastics. This is attributed to the low stress concentrations in transverse direction due to the low transverse modulus of flax fibres.
... During the past 10 years, polymer composites reinforced by vegetable fibers have been intensively developed not only in fundamental research but also in various industrial fields because of their enormous advantages. [1][2][3][4][5][6][7][8] These advantages involve improved mechanical properties, low cost, absence of adverse environmental effects, and these materials also represent an abundant resource. This is particularly the case with bamboo fibers (BFs). ...
Helium gas permeability and water absorption behavior of the recycled polypropylene/short bamboo fiber composite membrane were investigated. The effects of short bamboo fiber content and fiber chemical treatment on gas permeability and water absorption properties of composites have been examined. Our research showed that the solubility coefficient of helium increased as the fiber content of the bamboo increases but the diffusivity coefficient seemed to decrease with increasing amount of bamboo fiber in the composite formulation due to the poor adhesion between bamboo fiber and polymer matrix. The structure of recycled polypropylene/bamboo fibers have also investigates by X-ray diffraction technique. The chemical treatment of the bamboo fiber by alkali solution increased fiber surface roughness within the composite; in consequence, a more homogeneous dispersion of these fibers appears in the polymer matrix. The process of absorption of water was found to follow the kinetics and mechanisms described by Fick’s theory. A considerable loss in mechanical properties of the water-saturated samples after 3 months of aging in water was observed and this reduction could be delayed by fiber chemical treatment. This study provided the useful information about the behavior of recycled polypropylene/bamboo fiber composite materials during their service life time.
... Results showed that carbon fiber reinforced composite plates show the best structural behavior under low velocity impacts meanwhile carbon/glass fiber reinforced (hybrid) plates show highest strength against high impact energy. Muralidhar et al. [22] investigated flexural and impact properties of plain woven, rib knitted and sequentially stacked rib knitted/ plain woven fabric reinforced flax epoxy composites. However, the impact behavior of woven/knit fabric glass/epoxy hybrid composites has not been well understood with respect to the stacking sequence of textile fabrics. ...
In this study, the effect of stacking sequence on the impact behavior of sequentially stacked woven/knit fabric glass/epoxy hybrid composites was investigated. 2D (double layer) fabric was used as a woven fabric and rib and milano fabrics were used as knitted fabrics. Woven and knit fabric layers were sequentially stacked in six different variations to fabricate eight ply woven/knit fabric hybrid composites. The composite laminates were processed by hand lay-up technique using 3 mm thick spacers and cured under pressure of 8 MPa for 100 min. at 100 °C, followed by cooling at room temperature under same pressure. The impact and post-impact (CAI) behavior of hybrid composites at various impact energies were investigated. FEA results were compared with experimental results. Results show that specimens having outer layer of woven fabric exhibited better impact properties than that of the specimens having outer layer of knitted fabric. The worst performance in terms of impact resistance was observed in knit/knit composites. FEA analysis was in a good agreement with the experimental results.
In recent years, natural fibre polymer composites have emerged as a significant alternative to synthetic fibres, garnering considerable attention for their potential to mitigate the adverse impacts associated with their artificial counterparts. These natural fibres manifest in various forms, including short, long, and woven iterations. Of these, woven fibres stand out as a popular choice for composite fabrication, finding extensive utility across diverse domains such as structural and non-structural components, aerospace and automotive parts, household items, ballistic materials, and flooring solutions. Woven fibre-reinforced polymer composites offer a multitude of advantages, boasting enhanced stability along both warp and weft directions, consistent properties within the fabric plane, heightened comfort, superior impact resistance, increased toughness, and dimensional stability across a broad temperature spectrum. Moreover, their inherent weaving structures render them adaptable, customizable to specific requirements, and endowed with exceptional mechanical properties. This chapter provides a comprehensive overview of the myriad benefits associated with woven fibre utilization in natural fibre-reinforced polymer composites, encompassing discussions on yarn attributes, fabric characteristics, and fabrication parameters. Additionally, it delves into the attendant challenges, prospects, and diverse applications of woven fiber-reinforced composites.
Flax fibers are a viable material for creating sustainable composites since they have mechanical qualities similar to those of synthetic fibers. Because of their unique hydrophilicity and strong mechanical properties, flax fibers should be taken into specific attention while creating composite materials. Vegetable fibers like flax are highly versatile and are frequently utilized in structural composites. Additionally, flax has shown potential in a variety of other uses, including as shipping, automotive, aerospace, and construction. This study aims to provide a comprehensive overview of the state of advancement in flax fiber reinforcement composite research. The most important research on thermoset and thermoplastic composites reinforced with flax fiber is compiled and analyzed in this article. This article also summarizes the main properties of flax fibers, discusses chemically enhancing their qualities, explains the process of making and analyzing flax fiber composites, and identifies areas that require more research. The article concludes with a few critical ideas and future directions that emphasize the challenges that need to be handled in more in‐depth research and probable composites industrialization.
Highlights
Flax fibers: Structure, composition, and extraction techniques explored.
Polymer matrices in flax fiber composites: Types and processing methods.
Mechanical properties of thermoset and thermoplastic flax fiber reinforced composites.
Applications of flax fiber composites in automotive, construction, and aerospace.
Future potential of flax fiber and hybrid composites in advanced materials.
The use of naturally derived eco-friendly biocomposites became more popular due to growing environmental concerns and hunt for sustainable materials. Biocomposites can reduce the residual waste and carbon emission to the environment during their lifecycle. The present study aims to develop biocomposites by reinforcing flax fiber (F) and kenaf fiber (K) laminates with bio-epoxy matrix at four different arrangements (FFF, FKF, KFK, and KKK). The biocomposite samples were fabricated with three laminated thicknesses (3 mm, 4 mm and 5 mm) and the thermo-mechanical performance was investigated. The results showed that FFF biocomposites recorded higher tensile, flexural, and interfacial properties with lower density and absorption of water compared to KKK biocomposites due to higher cylindrical lumen diameter of flax laminates. The hybridization of flax with kenaf fiber at different stacking sequences provided greater strength, modulus, toughness, stiffness, thermal stability and degradation behaviour due to greater interfacial interaction between laminated fiber and bio-epoxy. The FKF biocomposites showed maximum impact strength (52.96 kJ/m2), tensile strength (110.21 MPa), and compressive strength (139.64 MPa) at 5 mm laminated thickness while, flexural (158.67 MPa) and shear strength (39.45 MPa) were maximum at 4 mm thickness with the highest degradation temperature (336 °C). The optimal biocomposite configuration has been identified through employability of a novel decision-making framework encompassing interval-valued intuitionistic fuzzy sets, TOmada de DecisaoInterativaMulticriterio (TODIM) and Schweizer–Sklar operations. The inclusive evaluation with regard to the applied framework has revealed that FKF and KFK biocomposites with 4 mm thickness (Lam 5 and Lam 8 ) configuration to have the optimal configuration. On the other hand, Lam 10, i.e., KKK_3 mm turned out to be inferior to all the considered biocomposite configurations.
Garment cut wastes from apparel industries are used for various applications in various industries. Normally garment cut wastes and recycled fibres from garment cut wastes are used in textile, furniture, carpet, paper, automobile, construction, and agricultural industries in low mechanical performance applications. In this research, composites are developed by using recycled fibres obtained from garment cut wastes as reinforcement and with different types of matrices. Recycled fibres used as reinforcements are obtained from garment cut wastes of cotton, polyester and cotton/polyester fabrics to develop these composites. These composites are developed by using Epoxy resin, Kaolinite, Polypropylene sheet as matrices. Reinforcements and matrices have used in different compositions and combinations to develop these composites. The main advantages of this type of composites are to combine the different properties of different materials to obtain unique and high-performance material. Technical properties like thickness, mass per unit area, Tensile strength, Flexural strength, Impact strength, Water absorbency and Scanning Electron Microscope of developed composites were tested and analyzed. The outcome of the results demonstrates that many of the composite proportions with different blend, reinforcement and matrcies show superior mechanical performances when compare it with each other, and it can be recommended for many potential applications.
The construction type of reinforcement material is a critical factor playing an essential role in the mechanical performance of composite materials. Recently, much attention has been attracted to discovering the mechanical behaviour of glass woven fabric, such as plain and different variations of twill and satin reinforced composites. In this paper, it is aimed to test the effect of a combination of unique characteristics of woven and knitted fabrics in the same matrix on the mechanical behaviour of composites. In this direction, carbon tows are fabricated into plain woven, 2/2 twill woven and interlock knitted fabrics. The effect of reinforcement construction on bending and tensile properties like strength, modulus and strain of epoxy composites manufactured in three variations as woven, knitted and woven/knitted reinforced was investigated by conducting 3-point bending and tensile tests. Experimental results indicated that hybrid composites displayed lower bending strength than woven fabric composites. However, a combination of 2/2 twill woven and knitted fabric in hybrid composites, including five fabric layers, had a higher bending modulus than 2/2 twill woven composites, including seven fabric layers. Also, it was observed that the mechanical performance of hybrid composites under tensile load was poor compared to the woven fabric composites.
Natural fiber-reinforced polymer composites (NFPCs) have gained limelight in many applications during the recent years, owing to their availability, as well as superior mechanical characteristics, cost-effectiveness, biodegradability, and lightweight. A comprehensive understanding of the manufacturing methods, proeprties and characteristics of natural fibers pave way for begetting a wide spectrum of applications for the NFPCs in automobile, aerospace, electronics, and other engineering fields. The current review article is about natural fiber-reinforced composites, the commonly used fabrication methods, including fiber pre-treatments, and numerous intermediate steps added to achieve improved bonding, processability of these composites, their properties and application prospects. Various state-of-the-art methods like additive manufacturing, vaccum bag molding, and autoclave has also been discussed. The mechanical properties obtained through various fiber reinforcements in accordance with process parameters has a substantial impact in the industrial applications of NFPCs. The tribological applications of NFPCs are becoming increasingly important in order to deal with the mechanical and chemical wear and tear during their service life in contact applications. Flammability behavior and biodegradability assessment of NFPCs are important for high-temperature and outdoor environmental applications of these materials. The review also includes a comprehensive discussion about the trending applications and future prospects for NFPCs.
Ces travaux de thèse visent à développer et caractériser des renforts tissés en fibre de sisal d’origine marocaine pour application matériaux composites. Une approche multi-échelle du comportement de renforts tissés en fibre de sisal est menée afin de comprendre et d’évaluer les différentes propriétés de renforts tissés. L’étude à l’échelle fibre montre la variabilité des propriétés morphologiques et mécaniques en traction liée à la composition de la fibre de sisal. La transformation de la fibre en fil pour le développement des renforts tissés a conduit à étudier à l’échelle fil les facteurs influençant la tissabilité du fil. La caractérisation des propriétés physiques et mécaniques du fil de sisal révèle la variabilité de ces propriétés en liaison avec les propriétés de la fibre de sisal. Les résultats montrent l’intérêt de la prise en compte des propriétés de la fibre et du fil de sisal afin de procéder au tissage des renforts fibreux. A l’échelle tissu, des renforts tissées 2D et 3D sont élaborés en se basant sur le procédé de tissage conventionnel. L’identification des propriétés physiques et mécaniques des renforts tissées 2D et 3D permet de mettre l’accent sur les différents paramètres de production influençant la performance de ces renforts. La production et la caractérisation des plaques composites à base de renforts tissées 2D et 3D montrent le potentiel des renforts tissés en fibre de sisal par rapport aux renforts tissés en fibres naturelles issus de la littérature
Due to the growing trend to promote alternative materials, the use of cellulosic fibers as filler/reinforcement in polymer composites has increased in popularity. The objective of this research is to determine the effect of flax fabric loading on the physical and mechanical properties of bio-phenolic/epoxy composites. The composites were fabricated using hand lay-up method in a mould and cured using a hot press. Bio-phenolic/epoxy blend was fabricated as control. The sample was tested for physical, tensile, flexural, impact and morphological properties. The result showed that, increasing the flax fabric loading has increased the water absorption and density of composites. The highest water absorption density was shown by the composite with 50 wt% flax fabric loading which is 3.73% and 1.23 g/cm ³ . In addition, there is no significant difference in void content for all composites. Moreover, the incorporation of flax fabric as reinforcement has improved the mechanical properties of composites. According to the morphological analysis results of the experiments, there was a good bonding interaction between the flax fabric and bio-phenolic/epoxy. The highest tensile strength, tensile modulus and impact strength was shown by composite with 50 wt% flax fabric which was 105.04 MPa, 9.10 GPa and 11.94 kJ/m ² respectively while composite with 40 wt% showed the highest flexural strength and modulus which was 150.45 MPa and 8.4 GPa respectively. It was concluded that, bio-phenolic/epoxy blend reinforced with 50 wt% flax fabric showed the best overall mechanical properties and it will be used in the future study to fabricate carbon/kevlar/flax reinforced bio-phenolic/epoxy for ballistic helmet application.
Our country is one of the world's leading walnut producers. Thousands of tons of shells that come out of walnut processing plants every year end up being used as fuel without an economic value. As walnut shell is a cellulosic base, is relatively hard and abundant in our country, it may be used as a filler for thermoset and thermoplastic matrix polymer composites. Many studies have been conducted on the use of natural materials obtained from agricultural by-products and wastes in the production of composite materials. These materials are low in environmental impact, recyclable, and easy to process. In terms of sustainable resources, the agricultural products and wastes produced in our country are attractive sources. This study; it is aimed to transform walnut shells, which are an agricultural waste and do not produce any added value to our country's economy in the form of waste, into a product that can be used in many different sectors such as maritime, automotive, aerospace, and defense industries. In the study; test samples were prepared by polymer casting method using epoxy, talc, and walnut shell. In order to determine the ideal filling ratio and whether the mixture is suitable, the test samples produced were characterized by the FT-IR method. As part of future studies, tests will be performed to determine the mechanical (tensile, bending, impact) and thermal properties of the samples (DSC, TGA, HDT). Additionally, SEM microstructure imaging will be performed.
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Composite materials are more predominant in weight-sensitive applications in a different field such as Engineering, Medicine, Military applications due to its high impact strength, easy to manufacture the intricate part, high resistance against corrosion, deformation and high thermal stability. Thus, it makes them a good alternative for weight-sensitive applications compared to the traditionally used material. Though synthetic fiber-reinforced composite offers many advantages over conventional materials, it provides weak resistance for fire, more vulnerable to rays and oxidization, uncomfortable to human health. Thus, overcomes by replacing them with natural fiber for structural applications. The low elastic modulus of the natural fiber composite makes them not suitable for many practical applications. Researchers hybridized natural fiber with a smaller amount of synthetic fiber, and filler materials such as rice husk, wood powder, clay, CNT, etc. and enhanced the elastic modulus. Also, the addition of natural fiber in the matrix enhances the energy dissipating capability along with strength. In all mechanical design, strength and modulus of the material is the most important one which influences on material selection. A property of natural fiber composites always depending on a percentage of constitutes (cellulose, hemicellulose, and lignin), fiber distribution, fiber surface roughness, etc. The present study focuses on various characterization studies such as mechanical analysis, dynamic mechanical analysis, free vibration analysis, and stability analysis of natural fiber composites. Thus, it helps better understanding of factors affecting the strength, stiffness, and stability of natural fiber composite.
This work investigates the effects of fiber content and fiber orientation on the impact behavior of flax fiber-reinforced polypropylene (PP) composites. The laminates of various fiber contents were manufactured by a vacuum bagging process; their impact properties were then measured using Charpy (i.e., in-plane impact load) and drop weight (i.e., out-of-plane impact load) impact tests. Experiments were conducted on a range of samples with different fiber volume fractions and orientations. The results show significant variations in energy absorption according to the variations in fiber orientation. Composites with differing fiber orientations exhibit different energy absorption for the in-plane and out-of-plane impact loads. The maximum Charpy energy absorption is obtained for the case of 0° fiber orientation, with the energy absorption generally lying in the range of 25–171 J/m. For the out-of-plane impact, the composites containing 30° fiber orientation absorb the highest amount of impact energy, and they can offer a better impact resistance in terms of higher peak force. The energy absorption generally lies in the range of 20–32 J. It was found that the energy absorption increases with increasing fiber content in the former (i.e., in-plane impact load) and decreases in the latter (i.e., out-of-plane impact load). Fiber orientations influence the crack propagation and failure mode of the composites. The outcomes from this study indicate that flax fiber-reinforced composite could be a commercially viable material for lightweight, crashworthy, and impact-critical structures.
Dynamic mechanical and experimental modal analysis has been performed on braided yarn woven fabric reinforced polyester composites and results are compared with those of conventional twisted yarn woven fabric and knitted woven fabric composites. The results revealed that storage modulus shows an increasing trend across conventional woven, knitted and braided woven fabric reinforcement, in that order. It is also observed that intra-ply hybridization enhances storage modulus and material loss factor of the conventional woven fabric and knitted woven fabric composites. It is also observed that knitted fabric composites have higher loss factors compared with conventional and braided fabric composites. Experimental modal analysis results reveal that the braided yarn fabric enhances the stiffness of the composite structure and hence results in higher natural frequencies while knitted fabric reinforcement enhances modal loss factor of the composite structure due the spiral orientation of yarns and large gaps associated with between the yarns in kitted fabric. POLYM. COMPOS., 2016.
Flax (Linum usitatissimum) is a blue-flowered herbaceous plant that widely grows in temperate zones as a source of both fibres and oil. While it is well known that flax fibres have been used for making linen, from a biomedical perspective, probablyone of the more important applications of flax fibres is for making surgical sutures. In addition to employing flax fibres for polymer-coated sutures, more recently, flax fibres have been proposed for reinforcing polymer composites, such as hand layup laminated scaffolds in tissue engineering. This chapter explores the mechanics of flax fibres based on recent findings from studies conducted by the authors as well as from the literature. The focus is on the effects of moisture on the mechanical properties of
yarn flax fibres as well as the possible dependence on knot geometry. The findings are applied to support arguments for the design considerations of polymer-treated flax fibre for, e.g., sutures as well as hand layup polymer composite laminates.
With the growing interest in bio-based composites as alternatives to traditional glass fibre reinforced composites (GFRPs), there has been a persistent rise in the commercial use of plant fibre composites (PFRPs). In contrast, nature’s ‘wonder-fibre’ silk has had no commercial applications, and only limited scientific investigations, as a composite reinforcement. To produce silk fibre composites (SFRPs) with useful properties, three key recommendations from our critical literature review were followed: i) a high-failure strain, low-processing temperature thermoset matrix was used to a) maximise the reinforcing effect of low-stiffness, ductile silk, and b) facilitate impregnation and avoid fibre degradation, ii) high fibre volume fractions were employed to ensure that fibres carried a larger fraction of the load, and iii) given the lack of studies investigating fracture energy dissipation mechanisms in SFRPs, interface modification was avoided due to its complex, sometimes detrimental, effects on toughness. In directly addressing the question, ‘is there a case for silks as polymer reinforcements?’, we evaluated various mechanical properties of nonwoven and plain woven SFRPs against similar flax and glass composites. In all cases, woven composites performed better than nonwoven composites. While SFRPs were weak in terms of stiffness, their flexural and tensile strength was comparable to PFRPs, but much below that of GFRPs. Notably, the low density of SFRPs, like PFRPs, made them comparable to GFRPs in terms of specific flexural properties. Woven SFRPs exhibited much higher fracture strain capacities than both flax and glass composites, making SFRPs suitable for applications where high compliance is required. The Achilles’ heels of PFRPs have been their reportedly i) inadequate interfacial properties, ii) inferior impact properties, iii) poor strength performance, and iv) high moisture sensitivity. We found that SFRPs outperformed their flax counterparts in areas i)-iii), and were more comparable to, but not better than, GFRPs. While concerns such as cost and ‘sustainability’ of silk are acknowledged, potential applications for SFRPs are discussed.
In this work, cellulose fibers from rice straw were isolated by a mechanical–high pressure steam technique, and were filled into polypropylene (PP) as a modifier. The structure and morphology of untreated and treated rice straw fibers were characterized by using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X–ray diffraction (XRD). The thermal properties, rheological behaviors and mechanical properties of the PP composites filled with untreated and treated straw fibers were investigated. The results show that the hemicelluloses and lignin can be removed from the structure of fibers by pretreatment. XRD curves reveal that this results in improving the crystallinity of the fibers. Compared with untreated rice straw fibers, PP composites filled with treated rice straw fibers exhibit higher thermal stability. The complex viscosity values of the composites decrease because of the pretreatment. Pretreatment can significantly improve tensile strength, elongation at break and impact strength of PP/rice straw fibers composites due to its enhanced interfacial adhesion between the PP matrix and rice straw fibers.
This work describes flax fibre reinforced polymeric composites with recent developments. The properties of flax fibres, as well as advanced fibre treatments such as mercerization, silane treatment, acylation, peroxide treatment and coatings for the enhancement of flax/matrix incompatibility are presented. The characteristic properties and characterizations of flax composites on various polymers including polypropylene ( PP) and polylactic acid, epoxy, bio-epoxy and bio-phenolic resin are discussed. A brief overview is also given on the recent nanotechnology applied in flax composites.
Flax reinforced tannin-based composites have a potential to be used in vehicle applications due to the environmental advantages and good mechanical properties. In this paper, the effects of fibre configuration on mechanical properties of flax/tannin composites were investigated for nonwoven and woven fabric lay-up angles (UD, [0 • , 90 • ] 2 and [0 • , +45 • , 90 • , −45 • ] 2). The tannin/flax composites were prepared by compression moulding. The manufactured specimens were then characterized for quasi-static tensile properties, dynamic mechanical properties and low-energy impact performance. Failure mechanism was further investigated using microscopy and demonstrated the need for further adhesion improvements. The study shows that the UD fabric reinforced composite performs better in tensile strength and modulus whereas [0 • , +45 • , 90 • , −45 • ] 2 composite provides the best impact energy absorption performance.
In this paper, double layered rib knitted, glass fabric-reinforced epoxy laminates made of untwisted roving and twisted ply yarns are investigated for their tensile, flexural, and impact properties. The effect of stacking sequence [0/0 and 0/90] and the introduction of inlay fiber strands on the above-mentioned properties are also studied. Introduction of inlays leads to superior mechanical properties in the coursewise direction compared to that in the walewise direction. Impact property of the 0/90 stacking sequence was found to be superior compared to that of the 0/0 sequencing. Composites reinforced with twisted ply yarns result in slightly lower mechanical properties compared to the mechanical properties of laminates reinforced with untwisted roving strands.
Knitted structures occupy a special position in composite preforming due to their inimitable characteristics. An insight into the knitted structures with respect to their composite preforming characteristics is presented in this article. Directionality of knitted structures and requirements of high performance fibers for knitting have been discussed. Contourability, net-shape preforming, high dynamic mechanical properties along with easy and rapid manufacturability are the important features of knitted structures to match the composite preform requirements. In this article, the work done in the above areas of research have been critically reviewed.
A bio-based thermoset resin was reinforced with flax fabrics and Lyocell fiber. The effect of different weave architectures was studied with four flax fabrics with different architectures: plain, twill (two different types), and dobby. The effect of the outer ply thickness was studied and characterized with flexural and impact testing. Composites manufactured with plain weave reinforcement had the best mechanical properties. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were 280 MPa, 32 GPa, 250 MPa, 25 GPa, and 75 kJ/m2, respectively. Reinforcements with twill-weave architecture did not impart appreciable flexural strength or flexural modulus even when the outer thickness was increased. Plain- and dobby (basket woven style)-weave architectures gave better reinforcing effects and the flexural properties increased with an increase in outer thickness. Water absorption properties of the composites were studied and it was observed that the hybridization wit
Partial substitution of glass fibers with natural fibers in composites to measure the effect on falling weight was performed. Flax-epoxy laminates (dimensions 250 × 25 × 10mm ) were obtained by hand lay-up using different flax thread sizes (0.2, 0.9, and 2.3 mm). Quasi-static three-point bending tests was performed on an INSTRON 4302 testing machines, using a 10 kN load cell. It was found that the flax epoxy laminates and hybrid E-glass/epoxy-flax/epoxy laminates provided a sufficient impact performance with a considerable weight reduction with respect to fiber-glass.
Most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The current work aims to develop high-performance natural fibre composite systems for structural applications using continuous textile reinforcements like UD-tapes or woven fabrics. One of the main problems in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they cannot be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g., unidirectional composites) similar to off-axis composites. Therefore, an optimum twist should be used to balance processability and mechanical properties. Subsequently, different types of fabrics (i.e., biaxial plain weaves, unidirectional fabrics and non-crimp fabrics) were produced and evaluated as reinforcement in composites manufactured by well established manufacturing techniques such as hand lay-up, vacuum infusion, pultrusion and resin transfer moulding (RTM). Clearly, as expected, the developed materials cannot directly compete in terms of strength with glass fibre composites. However, they are clearly able to compete with these materials in terms of stiffness, especially if the low density of flax is taken into account. Their properties are however very favourable when compared with non-woven glass composites.
Natural fibers are emerging as low cost, lightweight and apparently environmentally superior alternatives to glass fibers in composites. We review select comparative life cycle assessment studies of natural fiber and glass fiber composites, and identify key drivers of their relative environmental performance. Natural fiber composites are likely to be environmentally superior to glass fiber composites in most cases for the following reasons: (1) natural fiber production has lower environmental impacts compared to glass fiber production; (2) natural fiber composites have higher fiber content for equivalent performance, reducing more polluting base polymer content; (3) the light-weight natural fiber composites improve fuel efficiency and reduce emissions in the use phase of the component, especially in auto applications; and (4) end of life incineration of natural fibers results in recovered energy and carbon credits.
In this work, natural fibres (sisal, kenaf, hemp, jute and coir) reinforced polypropylene composites were processed by compression moulding using a film stacking method. The mechanical properties of the different natural fibre composites were tested and compared. A further comparison was made with the corresponding properties of glass mat reinforced polypropylene composites from the open literature. Kenaf, hemp and sisal composites showed comparable tensile strength and modulus results but in impact properties hemp appears to out-perform kenaf. The tensile modulus, impact strength and the ultimate tensile stress of kenaf reinforced polypropylene composites were found to increase with increasing fibre weight fraction. Coir fibre composites displayed the lowest mechanical properties, but their impact strength was higher than that of jute and kenaf composites. In most cases the specific properties of the natural fibre composites were found to compare favourably with those of glass.
The mechanical properties of knitted jute inlaid reinforced composites with different stacking sequences and number of layers have been studied. Flat rib knitted preforms have been produced in manual flatbed knitting machine followed by composite laminate preparation using simple hand lay-up technique. It is observed that the mechanical properties are dependant upon the stacking sequence and number of layers.
The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO2 emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84–154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on non-renewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (∼3 ton CO2 emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO2 emissions (4.3% of total USA industrial emissions) and 1.19 million m3 crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding and control moisture sensitivity in longer run.
High specific modulus and high specific strength are the most required characteristics of the materials in the aerospace structural applications. Unidirectional and multidirectional composites exhibit good properties in in-plane directions. Fibers in textile form exhibit good out-of-plane properties and good fatigue and impact resistance. Additionally, they have better dimensional stability and conformability. The variety of fabric architectures include weaves, knits, braids, stitched, and Z-pinned fabric. Vacuum assisted resin transfer molding (VARTM) is a low-cost closed molding process with the capability of producing complex parts. It is well known fact that majority of structural failures are due to fatigue. VARTM manufactured textile composites can be confidently used in the primary structures only if their fatigue performance is well understood. The biaxial braided carbon/epoxy composites with different braid angles (25°, 30°, and 45°) were investigated for primary structures of small business jet applications under tension–tension fatigue loading. Carbon/epoxy unstitched, stitched, and Z-pinned plain-woven composites were investigated for aerospace applications under tension–compression fatigue loading.
Aramid fibre–ultra-high modulus polyethylene (UHMPE) fibre interply hybrid composites were fabricated with changes in the stacking sequence. The flexural strength and modulus of hybrid composites were measured in order to investigate the effect of stacking sequence. Scanning electron microscopy (SEM) was used to examine the fracture surface of interply hybrid composites. When aramid fibre was at the compressive side and dispersion extent of fibers was small, the higher flexural strength and positive hybrid effect were observed. In addition, the different stacking sequence resulted in a change in flexural failure mechanism which had an effect on the flexural strength. As the dispersion extent of fibers decreased, the introduction of cohesive failure in aramid–aramid interface and PE–PE interface improved the flexural strength of hybrid composites.
a b s t r a c t In this paper several bidirectional flax fibers, usually used to made curtains, were employed as reinforce-ment of an epoxy matrix. Four different laminates were made by a vacuum bagging process, with varying both the areal weight and the treatment of the fabric. These structures were mechanically investigated carrying out both tensile and three point flexural tests. In order to evaluate the effect of the identified variables on the mechanical parameters (i.e. Young modulus and maximum stress) a statistical analysis was performed. Finally, by comparing the flax composite with a glass one, the convenience of the replacement of glass fiber was investigated in term of cost, weight and mechanical performances, by evaluating the structural efficiency coefficient of the cost of the material. The presence of layers with different areal weight within the structure induced a significant worsening of the flexural properties, with the start of cracks that produced a delamination failure. Also the tensile modulus got worse. Whereas the treatment on the fibers always improved the mechanical properties because the treated layer showed a behaviour of a pre-impregnated structure. For flexural stresses, the cost analysis was favourable to the substitution of the glass fibers with the flax ones. From this study, the composites reinforced with flax fibers could be used in several fields, as marine or automotive.
This study investigates the influence of the physical structure of flax fibres on the mechanical properties of polypropylene (PP) composites. Due to their composite-like structure, flax fibres have relatively weak lateral bonds which are in particular present in flax fibres that are often used in natural fibre mat reinforced thermoplastics (NMT). These weak bonds can be partly removed by combing the fibres. In order to study the influence of the physical structure of flax fibres on NMT tensile and flexural properties, uncombed and combed flax fibre reinforced PP composites were manufactured via a wet laid process. The influence of improved fibre-matrix adhesion was studied using maleic-anhydride grafted PP. Results indicated that the flax physical structure has a significant effect on flax-PP composite properties and that the flax fibre reinforced PP properties are similar to values predicted with existing micromechanical models. The tensile modulus of flax-PP composites can fairly compete with commercial glass mat reinforced thermoplastic (GMT) modulus, the strength, however, both tensile and flexural, can not. In order to rise the strength of flax fibre reinforced PP composites to the level of GMT strength, the flax fibres have to be further isolated to elementary flax fibres.
The pin-bearing strengths of eight different stacking sequences of quasiisotropic CFRP laminates were measured. The failure mechanisms were studied from scanning electron microscopy of the inside of the hole. An attempt was made to correlate the results with a simple estimate of the interlaminar normal stress distribution around the loaded half of the hole. The damage development in the presence of lateral restraint (from a torque-tightened bolt) was also examined. In general the presence of clamp-up inhibited local bearing (delamination) failure.
The design of textile composites requires a systematic approach that integrates microstructural design, preform fabrication and composite processing to produce load-bearing structural components with desired fiber architectures and mechanical properties. At the present time, an established integrated approach has yet to be realized; however, towards this end, a substantial body of research has been conducted. The purpose of this review is to detail the progress made toward realizing an integrated approach in the design and manufacture of three-dimensional textile preforms. The survey begins by identifying the recent advances in textile manufacturing with particular attention paid to new developments in multi-axial weaving, multi-axial warp knitting, stitching and braiding along with their potential advantages and limitations. A summary of the various preform manufacturing techniques corresponding to the basic load-bearing structural elements is then given. Additionally, limited examples demonstrating the geometric constraints inherent with these techniques and their associated process windows are discussed. Finally, a brief mention of some of the analytical models developed to predict the thermoelastic properties of three-dimensional textile composites is made.
Today the technical use of flax (Linum usitatissimum L.) fibres in Sweden is negligible, but there is an industrial interest in the flax fibre. To be able to concentrate further research and technical development on issues of highest importance for the development of technical uses of flax fibres, the most important properties need to be identified. The purpose of this paper was to identify the most important general properties for flax fibres in technical uses by focusing on market opinions in interesting applications and by analyzing the nature of quality criteria or desired properties.
Hemp fibre reinforced unsaturated polyester composites (HFRUPE) were subjected to low velocity impact tests in order to study the effects of non-woven hemp fibre reinforcement on their impact properties. HFRUPE composites specimens containing 0, 0.06, 0.10, 0.15, 0.21 and 0.26 fibre volume fractions (Vf) were prepared and their impact response compared with samples containing an equivalent fibre volume fraction of chopped strand mat E-glass fibre reinforcement. Post-impact damage was assessed using scanning electron microscopy (SEM). A significant improvement in load bearing capability and impact energy absorption was found following the introduction hemp fibre as reinforcement. The results indicate a clear correlation between fibre volume fractions, stiffness of the composite laminate, impact load and total absorbed energy. Unreinforced unsaturated polyester control specimens exhibited brittle fracture behaviour with a lower peak load, lower impact energy and less time to fail than hemp reinforced unsaturated polyester composites. The impact test results show that the total energy absorbed by 0.21 fibre volume fraction (four layers) of hemp reinforced specimens is comparable to the energy absorbed by the equivalent fibre volume fraction of chopped strand mat E-glass fibre reinforced unsaturated polyester composite specimens.
The impact properties of weft knitted fabric composites have been investigated based on their fracture toughness and tensile properties. The fracture toughness of knitted fabric composites was investigated by using double cantilever beam (DCB) tests. The delamination resistance of knitted fabric composites was studied by using the measured fracture toughness values in a simplified delamination model. As forces required to create a delamination are higher than the ultimate impact force, knitted fabric composites do not fail in delamination failure mode. Knitted fabric composites tend to fail in flexural mode, either in compression at the impacted area or in tension at the bottom side, opposite to the impacted area. Therefore, it is interesting to compare the impact properties of weft knitted fabric composites with their tensile properties.
This paper investigates the formability (i.e. the ability of a textile preform to conform to a 3-D shape) of weft-knit reinforced composites via the use of a composite case study (helicopter door track pocket), including the cutting plan methodology used for composite fabrication in the RTM process. The difficulties encountered during composite fabrication with specific preform types are discussed and expanded on the findings of the dry preform simulated formability results reported in part 1. The formability in the composite part was investigated through the deformation patterns of the various preform structures. The formability is specifically expressed as distributions of the preform deformation. The results of the composite case study showed that formability is influenced by the extensibility of the preform, the quality of the subsequent composite in terms of the degree of faults, and the distribution of the preform elongation in the composite.
As a result of the high cost of farm operations in Europe, there is a considerable demand for agricultural products which have a high added value. One of these potential products is linen fibre for use in both fabrics in which fine but long fibres with high moisture resorption are preferred, and in composites to produce engineered materials, for which high purity and a high Young's modulus is preferred. The production of linen from flax by traditional methods involves retting, a biochemical process which serves to remove pectins and nonstructural carbohydrates. This process, carried out in the field or in the factory, is not very easy to control and the products are of variable quality. Steam explosion treatment (STEX) of flax following dew retting can be controlled to give a well defined severity of treatment (in the range log102.9–log104.1) which leads to good fibre quality with minimum loss in fibre yield. Due to limitations on the rate of steam penetration into the fibre bundles, a minimum treatment of 2 min seems to be necessary. Through the use of NaOH pretreatments and STEX the effect of low degrees of fibre retting can be compensated for and a high yield of useful fibre obtained. The high potential of steam exploded short staple flax fibres for use in textile and technical composites has been demonstrated.