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Abstract

This article reviews the tensile properties of various plant fibre-reinforced polymers reported in literature. We critically discuss the use of plant fibres as reinforcement for the production of bio-based, renewable or green polymer composites. The tensile properties of these composites are compared against various (non-)renewable engineering/commodity polymers and commercially available randomly oriented glass fibre-reinforced polymers (GFRP). Composites containing random short plant fibres possess similar properties to randomly oriented GFRP at a lower overall part weight. Unidirectional plant fibre-reinforced polymers offer better performance than randomly oriented GFRP and have the potential to be adapted in applications requiring better mechanical performance, especially in applications where the use of costly synthetic fibres might be less attractive. Plant fibres can also be regarded as fillers to replace the more expensive polymers and improve the green credentials of the final composite parts. These features may motivate the industry to move towards plant fibre-based products.

Introduction

The ever-growing problem associated with global waste, the public’s growing awareness on sustainability, environmental legislative pressures such as the EU end-of-life vehicle [1], landfill of waste products [2] and waste electrical and electronic equipment directives [3], as well as the growing demand for more environmental friendly products have reinvigorated the interest in bio-based materials in the consumer industry [4,5]. Polymer manufacturers are required to consider the lifecycle of their materials and evaluate the environmental impact of their products starting from sourcing of raw materials over processing to disposal of the final product. As a result, numerous research efforts have been poured into the synthesis, manufacturing and production of bio-derived polymers [6–9]. While there are some commercial successes in bio-derived polymers, their applications in our everyday life still remain somewhat limited. Take poly(lactic acid) (PLA) for example, a commercially available and fully bio-derived and biodegradable polymer with tensile moduli and strengths in the range of ∼4 GPa and ∼70 MPa, respectively [10,11]. PLA can be regarded as one of the best performing bio-derived polymers [12] and has already found commercial applications in the textile [13] and food packaging industries [14]. Nevertheless, its engineering applications are still lacking due to its low heat distortion temperature (∼60°C) and limited melt strength [15]. Poly(hydroxyl butyrate) (PHB) is another bio-derived polyester that is synthesised by microorganisms, such as Ralstonia eutropha [16]. The high production cost associated with the synthesis of PHB and its brittle nature [17] limits its applications in everyday use.

To ensure a sustainable future, we need to produce bio-derived materials that can compete with or potentially replace the ‘big four’ polymers – polypropylene (PP), polystyrene (PS), polyethylene (PE) and polyvinyl chloride (PVC) [18]. However, the performance of bio-derived polymers still trails traditional petroleum-based engineering polymers. To address this challenge, a composite strategy, i.e. combining bio-derived polymers with bio-based reinforcements could be used to bridge this property-performance gap. In this context, plant fibres are seen as an ideal reinforcement for bio-based polymer matrices due to their renewability and wide availability [19]. In fact, plant fibre-reinforced polymer composites are already widely used in the automotive industry. More than 98% of plant fibre-reinforced polymer composites produced in the European Union in the year 2012 were used in the automotive industry [20]. Daimler AG replaced the door panels of the Mercedes-Benz E-class with flax and sisal fibre mat-reinforced epoxy resin [21]. A weight reduction of 20% and an improvement in the mechanical performance of the door panels were achieved. In 2005, Rieter Automotive won the JEC Composites Award for their plant fibre-reinforced thermoplastic under-floor module with integrated thermal, aerodynamic and acoustic functions [22]. Jute fibre-reinforced polyesters are used as construction materials in India but the market size is relatively small [23]. Table 1 summarises the applications of plant fibre-reinforced polymer composites in the automotive industry [24]. It is also worth mentioning at this point that the total usage of plant fibre-reinforced polymers exceeds that of wood fibre-reinforced polymers (90 000 versus 60 000 t in the European Union 2012) [20] in the automotive industry as plant fibre-reinforced polymers are stiffer compared to wood fibre-reinforced counterparts.

Table 1.

Current applications of plant fibre-reinforced polymer composites.

Manufacturer	Model	Components
Audi	A2, A3, A4, A4 Avant, A6, A7, Roadstar, Coupe	Seat back, side and back door panel, boot lining, spare tire lining
BMW	3, 5 and 7 series	Door panels, headliner panel, boot lining, seat back, noise insulation panels, moulded foot well linings
Citroen	C5	Interior door panel
Daimler-Benz	Mercedes A, C, E, S class, trucks, EvoBus	Door panels, windshield/dashboard, business table, piller cover panel, glove box, instrumental panel support, insulation, moulding rod/apertures, seat backrest panel, trunk panel, seat surface/backrest, internal engine cover, engine insulation, sun visor, bumper, wheel box, roof cover
Fiat	Punto, Brava, Marea, Alfa, Romeo 146, 156	Door panel
Ford	Mondeo CD 162, Focus, Freestar	Floor trays, door panels, B-piller, boot liner
General Motors	Cadillac Deville, Chevrolet, Trailblazer	Seat backs, cargo area floor
Honda	Pilot	Cargo area
Lotus	Eco Elise	Body panels, spoiler, seats, interior carpets
Mitsubishi	Space star, Colt	Cargo area floor, door panels, instrumental panels
Opel	Astra, Vectra, Zafira	Instrumental panel, headliner panel, door panels, pillar cover panel
Peugeot	406	Front and rear door panels
Rover	2000	Insulation, rear storage shelf/panel
Renault	Clio, Twingo	Rear parcel shelf
Saturn	L3000	Package trays, door panel
Toyota	Raum, Brevis, Harrier, Celsior	Door panels, seat backs, floor mats, spare tire cover
Volvo	C70, V70	Seat padding, natural foams, cargo floor tray
Volkswagen	Golf A4, Passat Variant, Bora	Door panel, seat back, boot lid finish panel, boot liner

Adapted from Faruk et al. [24] with kind permission from Wiley.

The use of plant fibres not only can address the aforementioned property-performance gap between bio-derived and petroleum-derived polymers but also serve as alternative to existing synthetic fibres, such as glass fibres [25,26], as some plant fibres are available at potentially lower cost but possess a tensile stiffness similar to glass fibres (Table 2) [27,28]. As a result, the research into plant fibre-reinforced polymers started to re-emerge in the field of composite science and engineering over the last 25 years (see Figure 1) [29]. Over this period, numerous researchers have been studying the use of plant fibres to produce fully or partially bio-based composites, also known as green or renewable composites. This article reviews the use of plant fibres as reinforcement for polymers. The mechanical properties of plant fibre-reinforced polymer composites reported in the literature were collated, juxtaposed and compared to the mechanical performance of commercially available commodity and engineering polymers, as well as commercially available glass fibre-reinforced polymer composites (GFRP).

Figure 1.

The number of scientific publications in the field of plant fibres and plant fibre-reinforced composites. Adapted from Bismarck et al. [29] and further updated using an abstract-title-keyword search of ‘natural fib* AND composite*’ on Scopus.

Table 2.

Estimated cost of various plant fibres in its loose form and E-glass fibres.

Fibres	Price (US$ kg⁻¹)^a
Sisal	0.5–2.8
Hemp	0.5–5
Kenaf	0.4–0.6
Jute	0.3–0.9
Coir	0.3–0.4
E-glass fibre tow	0.9–1.5

^aThe price was estimated from wholesalers listed online (http://www.alibaba.com).

Plant fibres – a brief introduction

Plant fibres are a subset of natural fibres, which also includes animal fibres (wool, feathers and silk) and mineral fibres (asbestos and basalt). Animal and mineral fibres have also been explored as reinforcement for composite materials [30–33]. Silk fibres, for example, were shown to be effective reinforcements for epoxy resins. Plain woven silk fibre-reinforced epoxy composites were found to possess tensile stiffness and strength of up to 6.5 ± 0.1 GPa and 111 ± 2 MPa, respectively [34]. The tensile performance of these silk fibre-reinforced epoxy are comparable to flax fibre-reinforced epoxy composites. The impact strength of silk fibre-reinforced epoxy, however, exceeds those of flax fibre-reinforced epoxy composites, indicating the suitability of silk fibre-reinforced polymers for toughness-critical applications.

The various classifications of plant fibres are shown schematically in Figure 2 [35,36]. Plant fibres can further be divided into wood-based and non-wood-based fibres. Wood-based fibres are produced from either softwood, such as pine and spruce, or hardwood, such as oak and beeches. These fibres are widely used to produce papers and paper-based products but also as fillers or reinforcements for polymers, mainly in wood plastic composites (WPC) or wood fibre composites (WFC). In fact, the market of WPC or WFC in the European Union in 2012 exceeded 260 000 t [20,37]. For recent developments in WPC/WFC, the readers are referred to reviews by Najafi [38], Ashori [39], Faruk et al. [40] and Kumar et al. [41] Non-wood-based plant fibres, on the other hand, can be further categorised into four different categories: bast, leaf, stalk and seed fibres [35]. Selected physical and (specific) tensile properties of various plant, natural and synthetic fibres are summarised in Table 3 [42]. On a ‘per weight’ basis, jute, flax and hemp fibres have higher tensile moduli than E-glass fibres [43,44] due to their lower density (∼1.5 g cm⁻³) compared to E-glass (∼2.5 g cm⁻³). This is particularly important in applications where weight reduction is a priority.

Figure 2.

Classification of plant fibres and some exemplary (fibrous) products. Adapted from Mohanty et al. [36].

Table 3.

Mechanical performance of plant fibres compared to other types of natural and synthetic fibres. ρ, E, σ and ε denote fibre density, tensile modulus of the fibre, tensile strength of the fibre and fibre elongation-at-break, respectively.

Fibre	ρ (g cm⁻³)	E (GPa)	E/ρ (GPa cm³ g⁻¹)	σ (MPa)	σ/ρ (MPa cm³g⁻¹)	ε (%)
Flax	1.5	50–70	33–47	345–1500	230–1000	2.7–3.2
Hemp	1.47	70	47	690	469	1.6
Jute	1.3–1.49	13–26.5	9–20	393–800	264–615	1.16–1.5
Ramie	1.55	61.4–128	40–83	400–938	258–605	1.2–3.8
Sisal	1.45	9.4–22	7–15	468–700	323–483	3–7
Cotton	1.5–1.6	5.5–12.6	3–8	287–800	179–533	7–8
Silk	1.31	10	8	600	458	20
Spider silk	1.31	7.2–9.2	6–7	800–1000	611–763	30–60
Basalt	2.66	92.5	35	3050	1147
Asbestos	2.0–2.8	1.0–3.5	0.4–2	550–750	196–375
E-glass	2.55	73	29	3400	1333	2.5

Adapted from Lee et al. [42].

Chemical composition of plant fibres

Plant fibres consist of three major components; cellulose, hemicellulose and lignin, with cotton being the exception (see Table 4) [35]. Cotton is composed of nearly pure cellulose (95.3 wt-% cellulose, 1.0 wt-% protein, 0.8 wt-% wax, 1.0 wt-% pectic substances, 0.9 wt-% ash and 1.1 wt-% of sugars, organic acids) [45]. Cellulose is a linear homopolymer consisting of d-glucopyranose units linked together by β(1→4) glycosidic bonds. The degree of polymerisation (DP) of native cellulose has been a subject of interest over many years. DP of native cellulose has been reported to vary between 2400 and 21 000, with claims of cellulose being mono-disperse to highly polydisperse [46–53]. Such high discrepancy between DP of native cellulose is postulated to be due to difficulties in preparing pristine (non-degraded) cellulose for molecular weight determination. Cellulose in plant fibres (such as cotton, flax and ramie) typically has a degree of crystallinity of between 65 and 70% [54].

Table 4.

The chemical composition of various plant fibres.

Fibre	Cellulose (wt-%)	Hemicellulose (wt-%)	Lignin (wt-%)	Pectin (wt-%)	Wax (wt-%)
Flax	71	18.6–20.6	2.2	2.3	1.7
Hemp	70–74	17.9–22.4	3.7–5.7	0.9	0.8
Jute	61–71.5	13.6–20.4	12–13	0.2	0.5
Kenaf	45–57	21.5	8–13	3–5
Ramie	68.6–76.2	13.1–16.7	0.6–0.7	1.9	0.3
Nettle	86			10
Sisal	66–78	10–14	10–14		2
Henequen	77.6	4–8	13.1
PALF	70–82		5–12.7
Banana	63–64	10	5
Abaca	56–63		12–13	1
Oil palm EFB	65		19
Oil palm mesocarp	60		11
Coir	32–43	0.15–0.25	40–45	3–4
Cereal straw	38–45	15–31	12–20	8

Adapted from Bismarck et al. [35].

Hemicelluloses are a heterogeneous group of polysaccharides consisting of 5- and 6-ring polysaccharides [55,56]. They are characterised by having β(1→4) glycosidic bonds that are neither cellulose or pectin chemically. Hemicelluloses are hydrophilic in nature and can easily be hydrolysed by acids and are soluble in alkali [57]. The role of hemicelluloses in plant fibres is to strengthen the cell wall of the fibres by interacting with cellulose and in some cases, lignin [56]. Lignin is a phenolic compound that provides rigidity to the plant cell wall [55] and acts as a binder holding the polysaccharide (cellulose) fibres together [58]. However, the true chemical structure of lignin is still not well understood [59]. Lignin possesses a high carbon-to-hydrogen content, implying that it is highly aromatic or unsaturated. It contains hydroxyl (–OH), methoxyl (–O–CH₃) and carbonyl (C = O) groups. Ethylenic and sulphur containing groups have also been found in lignin [60]. Lignin is hydrophobic and amorphous in nature, with a softening temperature of about 90°C [57].

Challenges associated with utilising plant fibres in composites

Variability in tensile properties of single plant fibres

Plant fibres seem to be a suitable reinforcement to produce structural composites but they do suffer from drawbacks stemming from the inherent nature of plant fibres [35]. We can see from Table 3 that the tensile properties of plant fibres vary significantly, even within the same type of fibres. This variability is due to (i) the inherent scatter of the materials properties and (ii) experimental methods used to determine the tensile properties of single fibres. The tensile properties of a plant fibre type can vary between fibres harvested from the same cultivation [35,61]. This is due to the structural variations of the plant fibres themselves, affecting crystallinity, composition, microfibrillar angle and luminal porosity as a result of different growth conditions [62–64]. Furthermore, plant fibres often go through a retting process to separate or loosen the fibres from its non-fibrous plant components [65]. Water-retting is conducted by immersing the harvested fibre crops in water for a period of time. Water penetrates the stalk and swells the inner cells of the plant materials, causing the outermost layers of the plant materials to burst. Water-retting is able to produce high quality fibres but it produces large amount of waste water [66] and this process is banned in many countries (apart from China and Hungary) [67]. Dew-retting is another fibre retting method relying on fungi to colonise harvested plant materials in the fields. The combination of air, sun, dew and bacteria and fungi leads to fermentation, which digest much of the stem materials surrounding the fibre bundles [65]. This retting method, however, requires appropriate moisture and temperature conditions for the retting process to work [65]. This is a parameter that is very difficult to control as it is highly dependent on the region and the weather. The fibres extracted by dew-retting possess lower quality compared to water-retted fibres [65,68].

Another major contribution to the variability of the tensile properties is variability in plant fibre diameter [35,69], as well as the determination of a fibre’s cross-sectional fibre area (see Figure 3 for the traced perimeter of a ‘single’ plant fibre) [70,71]. This ‘single’ plant fibre (Figure 3) is in fact composed of an assembly of elementary fibres. The difficulty in accurately determining the cross-sectional area of plant fibres translates to a significant scatter in the measured tensile moduli and strengths of the same plant fibres. The calculated tensile modulus of a ‘single’ plant fibre decreases with increasing ‘assumed’ fibre diameter [72], showing the importance of the determination of the fibre diameter. Furthermore, the mechanical processing of natural fibres, such as decortication, scutching and hackling in which the stems of the fibres are broken by mechanical action to separate the technical fibres from fibre bundles, often induces defects usually in the form of kink bands [73,74]. These defects reduce the tensile properties of plant fibres [75] and to increase the probability of fibre breakage during processing, leading to plant fibres with lengths shorter than their respective critical length [76].

Figure 3.

Cross-sections of a sisal fibre and a flax fibre determined by scanning electron micrography (a) and (c), and optical microscope (b) and (d), respectively. The drawn outlines show the perimeter of the fibres. Obtained from Thomason et al. [71] with kind permission from Elsevier.

Moisture uptake of plant fibres

Plant fibres have poor resistance to moisture absorption due to the presence of large amounts of hydroxyl groups. The equilibrium moisture content at room temperature of selected plant fibres at various relative humidity (RH), evaluated using simple weight gain measurements, is shown in Table 5. It can be seen that the equilibrium moisture content of different plant fibres is around 7 wt-% when stored for an extended period of time in a desiccator containing distilled water with RH of 100%. In some cases, the equilibrium moisture content of plant fibres can be as high as 30 wt-% in high (95%) relative humidity (RH) environments (measured using dynamic vapour sorption) [77]. By de-waxing plant fibres (e.g. in a mixture of ethanol and benzene [78] or Soxhlet extraction in acetone [79,80]), it is possible to increase the equilibrium moisture content (see Table 5 for sisal fibres – 5.8 wt-% before de-waxing to 6.5 wt-% after de-waxing). It is also possible to reduce the moisture uptake of plant fibres; Bismarck et al. [81] studied the moisture uptake of different flax fibres; namely green flax, dew-retted flax and Duralin flax. The Duralin process was developed by CERES B.V., which uses deseeded flax straw as raw material. A description of the Duralin process can be found in the literature [81–83]. During the fibre treatment hemicellulose and lignin are depolymerised into lower molecular weight compounds, which subsequently cure into a water resistant resin [82]. As a result, Duralin flax exhibited the lowest moisture uptake among the studied flax fibres.

Table 5.

Equilibrium moisture content of various plant fibres at 100% RH (unless indicated).

The poor moisture resistance of plant fibres will also affect the mechanical properties of plant fibre-reinforced polymers. The absorbed water could plasticise the polymer matrices or cause de-bonding at the plant fibre–polymer matrix interface [84,85]. Numerous researchers have studied the influence of moisture uptake of plant fibres incorporated into polymers on the mechanical performance of the resulting plant fibre-reinforced polymers [82,86–88]. Stamboulis et al. [82] studied the effect of moisture on the tensile properties of green and Duralin flax fibre-reinforced PP composites. The moisture content of the composites was tailored by immersing the composites in water for various periods of time. The authors found that the tensile moduli and strength of the composites decreased by as much as 40 and 20%, respectively, as the moisture content of the composites increased from 0 to 13 wt-%. The decrease in tensile moduli and strength of Duralin flax-reinforced PP was slightly less than that of green flax-reinforced PP, indicating that the moisture absorption of hydrophilic reinforcing fibres does play a major role even though they were embedded in a hydrophobic polymer. This decrease in tensile properties of the flax-fibre composites was postulated to be due to a decrease in the tensile properties of the flax fibres as a result of moisture ingress, which was hypothesised to reduce the rigidity of cellulose within the flax fibres. Assarar et al. [86] studied the effect of water aging on the mechanical properties of flax fibre-reinforced epoxy composites compared to glass fibre-reinforced epoxy composites. After immersing the composites in water for 10 days, the tensile moduli of glass fibre-reinforced epoxy and flax fibre-reinforced epoxy composites decreased by 9 and 30%, respectively and the tensile strength decreased by 9 and 13%, respectively. The authors also found that the equilibrium moisture uptake of flax fibre-reinforced epoxy composites after immersion in water was 13.5 wt-% while glass fibre-reinforced epoxy composites had an equilibrium moisture content of only 1.05 wt-%.

Adhesion between plant fibres and polymer matrices

Hydrophilic plant fibres are often postulated to be poorly compatible with hydrophobic polymer matrices, such as polypropylene or polylactide [89]. As a result, numerous efforts have been poured into improving the fibre–matrix adhesion between plant fibres and hydrophobic polymer matrices [90–93]. Mercerisation of plant fibres is often conducted to improve the compatibility between plant fibres and polymer matrices [94–96]. Mercerisation is one of the oldest treatment methods for cellulosic fibres and often used in the cotton industry. During mercerisation native crystalline cellulose-I is converted to more thermodynamic favourable cellulose-II by swelling the cell wall of plant fibres in an alkaline solution [97]. It is worth mentioning at this point that a complete transformation of cellulose-I to cellulose-II is difficult to achieve in plant fibres [98]. Nevertheless, the mercerisation of plant fibres often leads to a more polar and rougher plant fibre surface [94]. The higher surface energy of plant fibres improves wettability of the fibres with various polymer matrices and the rougher fibre surface further enhances the fibre–matrix adhesion by mechanical interlocking [99].

Chemical coupling of plant fibres to polymers using a reactive copolymer, such as maleic anhydride grafted polypropylene (MAH-PP), has also been widely studied [100–102]. Upon heating, MAH-PP will covalently bind to the hydroxyl groups of plant fibres (the fibres could be pre-treated to expose more hydroxyl groups for reaction). Gassan and Bledzki [103] studied the effectiveness of MAH-PP compared to neat polypropylene (PP) to improve the performance of woven jute fibre-reinforced (MAH-) PP composites. The authors observed an increase in flexural strength of up to 40% for jute-reinforced MAH-PP compared to jute-reinforced PP (from 60 to 100 MPa). This was also accompanied by the observation of a reduced number of jute fibres being pulled out from a MAH-PP matrix, an indication of improved fibre–matrix adhesion. Other surface chemical modifications of plant fibres aiming to improve the compatibility between plant fibres and polymer matrices, as well as reducing the moisture absorption of the fibres have also been explored. These include acetylation [104], silylation [105–108] and isocyanate treatment [109] to name a few. Although these modification methods altered the wettability of natural fibres, large quantities of hazardous chemicals are usually involved in the process of hydrophobising the fibres and the chemical waste must be handled and disposed of appropriately. This adds extra cost to the production of plant fibre-reinforced composites, making chemical fibre treatments much less attractive. Therefore, the chemical modification of plant fibres and the use of chemically modified fibres as reinforcement for polymers are not covered in this article. The readers are referred to review articles by Li et al. [110] and John et al. [111], which summarise recent developments in the chemical modification of plant fibres and their applications in composites.

Furthermore, chemical treatments of plant fibres do not always result in improved composite performance. The main reason for the lack of improvements over virgin fibres is the anisotropy of plant fibres. The transverse moduli of natural fibres are an order of magnitude lower than their axial moduli [112,113]. Cichocki et al. [112] showed that the axial modulus of jute fibres is 38.4 GPa but its transverse modulus is only 5.5 GPa and Baley et al. [113] showed that the axial modulus of flax fibres is seven times larger than its transverse modulus (axial modulus: 59 GPa, transverse modulus: 8 GPa). It is also worth mentioning that anisotropy exists in synthetic fibres as well; for instance the axial fibre moduli of carbon fibres are between 230 and 640 GPa while the transverse moduli of these fibres ranges from 10 to 30 GPa [114,115]. In addition to this, Thomason [116] attributed the failure of natural fibres to deliver the desired performance in composites to the high linear thermal coefficient of expansion (LTCE) of natural fibres. The interfacial shear stress between the fibre and the matrix is the product of residual compressive stress σ _r and the static friction coefficient at the fibre/matrix interface. Due to the high LTCE of natural fibres, σ _r will be lowered, which translates to poor interfacial shear strength between the fibres and the matrix. This challenge could potentially be addressed by coating plant fibres with highly crystalline nanocellulose derived from bacteria (see Figure 4), which possesses low LTCE (0.1 × 10⁻⁵K⁻¹) [117], to bridge the gap which often exists between the fibre and the matrix [79,89,118–120].

Figure 4.

Scanning electron images showing (a) neat sisal fibres, (b) sisal fibres coated with a dense layer of BC and (c) ‘hairy’ sisal fibres produced using a novel slurry dipping method. A dense layer of BC on sisal fibres was obtained by drying the slurry-dipped fibres under vacuum 80°C. ‘Hairy’ sisal fibres were obtained by partially drying the slurry-dipped fibres between filter papers, followed drying in an air oven held at 40°C. Obtained from Lee et al. [120].

Processing and manufacturing of plant fibre-reinforced polymer composites

The production volume of plant fibre-reinforced polymers for the automotive industry reached 60 000 t in 2012 and is forecasted to reach 80 000 t by 2020 [20]. Approximately 90% of these plant fibre composites are anticipated to be converted into parts by compression moulding. Nevertheless, plant fibre-reinforced polymer composites can be manufactured using a variety of methods depending on the length of the plant fibres to be used as filler/reinforcement. The length of plant fibres can be broadly defined as either ‘endless’ in terms of composite micromechanics, i.e. at least several centimetres long, therefore bridging at least one main dimension in composites, or ‘short’. Short fibres are loosely defined as fibres with a length of less than 1 cm. Plant fibres that are several centimetres long are often used as reinforcement in the form of fabrics, yarns or fibre strands for thermosetting matrices, such as epoxy resins or polyesters. In this context, resin transfer moulding (RTM) is often used to produce plant fibre-reinforced polymer composites [121,122] or composites with in-plane reinforcement [123–126]. While using thermosetting resins as the matrix for plant fibres results in high performance and solvent-resistant composites, the manufacturing process itself is rather laborious and produces waste associated with the consumables required for the RTM processes. Therefore, research and development has also focused on the use of thermoplastic polymer matrices for plant fibre composites [127]. To produce plant fibre mat-, fabric- or roving-reinforced thermoplastic composites, film stacking and compression moulding methods are often used [128,129]. These composites can also be reprocessed or recycled [24]. Plant fibres can be combined with thermoplastic polymer fibres in processes used to manufacture fibre preforms, for instance when producing fibre fleeces by carding or slivering. These commingled fibre preforms can be converted into final composite parts by heat consolidation [130–132]. However, the use of thermoplastic matrices for the production of plant fibre composites creates other problems, such as thermal degradation of plant fibres during processing and consolidation [133]. Furthermore, thermoplastic long plant fibre-reinforced composites often have (rather) high porosity as in these composites the fibres are not easily impregnated thoroughly by the melt due to the lack of shear and pressure, which are the driving forces to bring the matrix in between the fibres [134].

Short plant fibres, on the other hand, are typically processed using melt mixing techniques, whereby the short fibres are dosed into a mixer, such as high-speed mixers [135,136], single [137] or twin screw extruders [135,137–139] to disperse the fibres within the matrix – the product of this process is called compound – ready for use for the next processing step. This compound is further processed using conventional polymer processing techniques, such as extrusion, compression or injection moulding to produce three-dimensional parts, such as hollow chamber profiles for terraces and automotive interior parts, just to mention a few examples. While compounding is cost effective, the main challenge is the processability of the fibres throughout the whole manufacturing process. To ensure processability, the fibres have to be very short (about 1 mm) [37] because the longer the fibres, the more difficult it becomes to distribute them homogeneously in the matrix within injection moulded parts and the higher the tendency to block or plug the dosing equipment [140]. However, the shorter the fibre length, the lower the reinforcing potential of plant fibres, as the fibres become too short for effective stress transfer (see the section ‘Comparison of the tensile performance of plant fibre-reinforced polymer composites with engineering/commodity polymers’). One possible solution to address the challenge of processability of short plant fibres is to use a cable-coating or pultrusion technique, whereby yarns of short plant fibres can be impregnated or coated with a thermoplastic matrix [141]. Long plant fibres can also be processed in this manner. These pre-impregnated plant fibre yarns can then be fed into melt mixers, followed by extrusion to produce final composite parts. Nevertheless, this adds additional cost and effort to the manufacturing process [141]. Another approach to solving the challenge of processability of plant fibres is to coat the yarn or roving consisting of long plant fibres with a sizing (an aqueous solution of various chemical compounds) containing a film former, which coats the fibres and ‘glues’ them together, followed by chopping them into several millimetre long fibre bundles, which can be dosed using standard screw dosing equipment and fed properly into the intake zones of extruders [142].

Plant fibres as reinforcement for polymers

The concept of introducing plant fibres into polymers dates as far back as 1920s, where plant fibre (cotton) fabrics were used to reinforce phenolic resins. These composites, known as Cord Aerolite, containing 90% fibres and possessed tensile moduli and strengths of up to and 14 GPa and 180 MPa, respectively [143]. An improved version, known as Gordon Aerolite, which was made from unidirectional flax fibre-reinforced phenolic resin possessed tensile modulus and strength of up to 40 GPa and 310 MPa, respectively [144]. In 1940s, Henry Ford introduced soybean fibres into phenol formaldehyde resin and used it for the body panel and the chassis of a car [145,146]. This concept was further extended by VEB Sachsenring in the former German Democratic Republic who manufactured the car Trabant starting in the late 1950s. The doors, roof, boot lid, bonnet and fenders of the Trabant were made from waste cotton-reinforced phenolic resin, also known as Duroplast. The waste cotton was imported from the former Soviet Union and this made Trabant the first ever car made from recycled materials.

Numerous papers about plant (natural) fibre composites were published since then. Figure 5 summarises the tensile properties of UD and randomly oriented plant fibre-reinforced polymers reported by various authors [28,95,119,124,125,129,134,136,147–362]. Shah [37] also tabulated selected data in his recent publication. Plant fibre-reinforced polymers with tensile moduli and strengths of up to 40 GPa and 450 MPa, respectively, were produced (Figure 5). These high-performance composites typically contain loading fractions (w _f) of 40–60 wt-%. UD high-performance plant fibre composites can be produced from endless hemp [215], flax [125,134,149,163,174,179,181,198,216,234], ramie [325], kenaf [176,308], sisal [309], isora [321], pineapple leaf [159], Napier grass [180], Alfa [317] and jute fibres [158,229,255,322], as well as plant fibre mats [129,149,203,275,304,316]. Figure 5 contains a vast number of data extracted from literature including some of the earlier developments in plant fibre-reinforced polymers. However, it should be considered that not all reported mechanical properties of these composites is optimal due to non-optimised processing of fibres and composites. The spread of the data also demonstrates the variability of plant fibre composite properties caused by processing, which can also be found synthetic fibres, e.g. glass fibres, whereby the length of the fibre will be affected depending on processing routes used. This variability in length leads to variability in measured tensile performance (see the section ‘Comparison of the tensile performance of plant fibre-reinforced polymer composites with engineering/commodity polymers’).

Figure 5.

Reported tensile properties of plant fibre-reinforced polymer composites [28,95,119,124,125,129,134,136,147–362]. E and σ denote tensile modulus and strength, respectively. The data used for the non-renewable engineering polymers include PP, LLDPE, HDPE, PBT, PA6, PA12 and PC. The data used for the renewable polymers PLA, CA, CAB, CAP, PHBV and PHA. These data were obtained from MatWeb (www.matweb.com).

We also compared the literature data of plant fibre-reinforced polymer composites with commercially available (non-)renewable commodity and engineering polymers (Figure 5). For comparison we chose PP, linear low density polyethylene (LLDPE), high-density polyethylene (HDPE), polybutylene terephthalate (PBT), polyamide 6 (PA6), polyamide 12 (PA12) and polycarbonate (PC) as our non-renewable commodity or engineering polymers and PLA, cellulose acetate (CA), cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP), poly(hydroxy butyrate-co-valerate) (PHBV) and poly(hydroxy alkanoate) (PHA) as renewable polymers. These are indicated by red circular dots and green triangles, respectively, in Figure 5.

Comparison of the tensile performance of plant fibre-reinforced polymer composites with engineering/commodity polymers

Figure 6 depicts the tensile performance of various plant fibre-reinforced polymers as a function of fibre loading fraction (w _f). The dotted red lines in Figure 6 denote the tensile modulus and strength of our chosen benchmark, e.g. the bio-based polymer with the highest best mechanical properties, PLLA, measured to be ∼4 GPa and ∼70 MPa, respectively [10,11]. It can be seen from this figure that the tensile moduli of most randomly oriented short plant fibre-reinforced polymers are around (or below) the benchmark PLLA, even at w _f> 50 wt-%. The tensile strengths of plant fibre-reinforced polymers also showed a similar trend, whereby most of the data are around (or below) our benchmark PLLA, including those of composites containing a high w _f of plant fibres. This can be attributed to the random orientation of plant fibres within the polymers, which is the reason for the low tensile properties of the resulting composites. This situation is worsened when using (or creating during the processing) very short fibres, which results in less effective stress transfer from the matrix to the fibres. Nevertheless, it can be concluded from Figure 6 that plant fibres are an excellent stiffening agent. Plant fibre composites with tensile moduli exceeding those of commodity/engineering polymers were realised, which is apparent by a larger number of data points above the benchmark region for tensile modulus compared to the tensile strength of the plant fibre-reinforced polymer composites.

Figure 6.

Comparison of reported tensile moduli (E) and strengths (σ) of plant fibre-reinforced polymer composites [28,95,119,124,125,129,134,136,147–362] as a function of fibre loading fraction (w _f). The red dotted line shows the properties of PLLA. The filled green and hollow blue icons represent UD plant fibre-reinforced polymers and randomly oriented plant fibre-reinforced polymers, respectively.

Effective fibre reinforcement is achieved if the length of the fibre exceeds the critical fibre length, which depends on the fibre–matrix combination (and method of manufacturing, see the section ‘Processing and manufacturing of plant fibre-reinforced polymer composites’), the fibre tensile strength at the critical length and the fibre diameter [363]. This can be better understood using an exemplarily calculation of the critical length of plant fibres. The interfacial shear strength τ between sisal fibres and PLA [79] or CAB [89] obtained by single fibre pull-out tests was reported to be 12.1 and 1.02 MPa, respectively. For hemp fibres pulled-out from CAB, an interfacial shear strength of 0.76 MPa was reported [89]. The tensile strengths (σ_f ) of technical sisal and hemp fibres were measured to be 342 and 286 MPa, respectively. From these data, the minimum critical length (L_C ) of the fibres¹ in CAB and PLA matrices can be calculated using the following equation:(1)

The critical length of sisal fibres in PLA was estimated to be 1.4 mm but for sisal and hemp fibres in CAB this is already 17–19 mm. For effective fibre reinforcement, the length of the reinforcing fibre should exceed the critical length L >> L _c (normally >15L _c) [363]. While this could be achieved for the sisal–PLA combination, the effect of composite processing (compounding, extruding, pelletising and injection moulding) will no doubt lead to a decrease of the fibre length to less than L _c for hemp fibre-PLA or CAB combinations. Nevertheless, plant fibres do add value when compounded into polymers; plant fibres are regarded as cheaper filler than conventional engineering (polymer, glass or carbon) fibres, replacing some portion of the more expensive polymers, leading to a reduction in the overall cost while increasing the renewable fraction of the resulting composites.

It can also be seen from Figure 6 that the tensile moduli of UD plant fibre-reinforced polymers exceeds that of PLLA at w _f as low as 20 wt-% when UD plant fibre composites are used. These observations are consistent with recent investigations [364]; the tensile moduli of UD jute and flax fibre-reinforced epoxy composites increased linearly with increasing v _f. However, a critical v _f at which the tensile properties of UD outperform neat epoxy resin exists at around 10 vol.-% (corresponding to w _f ∼13 wt-%). This critical v _f corresponds to the transition from a matrix-dominated failure to a fibre-dominated failure. Below this critical v _f, a brittle failure of the composites was observed and at v _f>10 vol.-%, a more serrated fracture surface, with increased occurrence of fibre pull-out, was observed. The authors also calculated the maximum theoretical fibre volume fraction v _f to be 60 vol.-% (corresponding to w _f ∼65 wt-%) for twisted flax and jute fibre yarns.

Comparison of the mechanical performance of plant fibre-reinforced polymers with glass fibre-reinforced polymers

Plant fibres are valuable alternative reinforcing fibres for commodity composite applications [25,26]. In order to assess whether plant fibres could be used to produce structural composites with properties on par with conventional glass fibre-reinforced polymers (GFRP), we have plotted the tensile moduli and strengths of commercially available GFRP as a function of w _f (Figure 7) along with the collected tensile properties of plant fibre-reinforced polymers reported by various authors in the literature. Recent publications also compared selected plant fibre-reinforced polymers with GFRPs in an Ashby plot [365,366]. Although we are aware, that the mechanical properties of composites should be correlated with the respective fibre volume fractions, we adhere to w _f due to the fact, that most papers dealing with plant fibre composites use this parameter and the lack of information to convert it to v _f. It can be seen in Figure 7 that plant fibres can be used to produce composites with tensile moduli on par with and even outperforming commercially available glass fibre-reinforced polymer composites, indicating the potential of plant fibres as an alternative reinforcement to glass fibres in load bearing or structural applications. Similar observations can also be made for the tensile strength of plant fibre-reinforced polymer composites.

Figure 7.

Comparison between the reported tensile moduli (E) and strengths (σ) of plant fibre-reinforced polymer composites [28,95,119,124,125,129,134,136,147–362] and glass fibre-reinforced polymers as a function of fibre loading fraction (w _f). The data for glass fibre-reinforced polymers were obtained from MatWeb (www.matweb.com). The green and blue hollow icons represent UD plant fibre and plant fibre fabric-reinforced polymers and randomly oriented plant fibre-reinforced polymers, respectively.

In contrast to the tensile moduli of plant fibres, which are comparable to E-glass fibres (especially those of jute, flax, hemp and ramie – see Table 3), the tensile strength of glass fibres is at least twice as high as the tensile strength of plant fibres. Nevertheless, some randomly oriented plant fibre-reinforced polymer composites have very similar mechanical properties compared to randomly oriented GFRP, especially at low w _f. As w _f increases, the property-performance gap between randomly oriented plant fibre-reinforced polymers and GFRP increases. Madsen et al. [367] showed that a transition w _f exists. This transition w _f corresponds to the assembly of plant fibres has been fully compacted to its minimum volume at a given processing condition. Beyond this w _f, the mass of plant fibres within the composite stayed constant but the mass of the matrix decreases and the volume fraction of porosity increases. This transition point, a result of insufficient matrix that was added to the composites to fill the free space between the fibres or the fibre lumens, was found to occur at w _f = ∼40–50 wt-%, depending on the consolidation pressure [368], leading to the widening of the property-performance gap between plant fibre composites and GFRP.

Glass fibres are however inherently heavier than plant fibres (the density of glass fibres is 2.5 g cm⁻³ versus ca. 1.5 g cm⁻³ for plant fibres). On a ‘per weight’ basis, the specific property-performance gap between plant fibre-reinforced polymer composites and GFRP should be closer. To elucidate this further, the specific tensile properties of plant and glass fibre-reinforced polymer composites were compared in Figure 8. Herein, we used average plant and glass fibre densities of 1.5 and 2.5 g cm⁻³, respectively. It can be seen that on a ‘per weight’ basis, most plant fibre-reinforced polymers actually perform equally well compared to GFRP. Nevertheless, the tensile properties of UD flax, jute and hemp fibre-reinforced polymer composites do outperform randomly oriented plant but also glass fibre-reinforced polymer composites, signifying that UD plant fibre composites could potentially offer a valuable alternative for certain composite applications requiring intermediate mechanical properties. It should be noted that unidirectional plant [369,370] (and regenerated cellulose [371,372]) fibre-reinforced polymers exhibit a non-linear stress–strain behaviour, which offers early warning prior to final composite failure. Uniaxial tensile cyclic tests showed that the elastic limit was as low as 0.15% strain. This was hypothesised to be due to the untwisting of plant fibre yarns and the realigning of cellulose microfibrils in the plant fibres. Such observations raise the question as to what strain range should be used to evaluate the tensile moduli of UD plant fibre-reinforced polymers.

Figure 8.

Comparison between the specific tensile moduli (E/ρ) and strengths (σ/ρ) of plant fibre-reinforced polymer composites [28,95,119,124,125,129,134,136,147–362] and glass fibre-reinforced polymers as a function of fibre loading fraction (w _f). The data for glass fibre-reinforced polymers were obtained from MatWeb (www.matweb.com). The green and blue hollow icons represent UD and fabric plant fibre-reinforced polymers and randomly oriented plant fibre-reinforced polymers, respectively.

Lifecycle assessment (LCA) of plant fibre-reinforced polymers

Plant fibre-reinforced polymers are often perceived as ‘green’ or environmental friendly. It was proposed that plant fibre-reinforced polymers are likely to be more environmental friendly than GFRP because: [373] (i) plant fibre production results in lower environmental impacts compared to glass fibre production, (ii) plant fibre-reinforced polymers have higher fibre content for equivalent performance, which therefore reduces the amount of (more polluting) base polymers, (iii) plant fibre-reinforced composites are lighter, improving the fuel efficiency and reducing emissions during their use phases and (iv) plant fibre-reinforced composites can be incinerated for energy recovery at the end of their service life. To support such perception, LCA can be conducted to study the environmental impact associated with plant fibre-reinforced polymers and to elucidate how these composites compare against GFRP.

Kim et al. [374] assessed the lifecycle of kenaf fibre-reinforced PHB (w _f = 50%) and compared the environmental impact of these composites to glass fibre-reinforced PP (w _f = 37%). The authors found that the production of kenaf fibre-reinforced PHB consumes less energy compared to glass fibre-reinforced PP, with a potential energy savings of up to 23 MJ kg⁻¹. The global warming potential (GWP) of kenaf fibre-reinforced PHB was also found to be lower than glass fibre-reinforced PP (3.9–4.2 kg CO₂ eq kg⁻¹ for kenaf fibre-reinforced PHB, 4.5 kg CO₂ eq kg⁻¹ for glass fibre-reinforced PP). However, kenaf fibre-reinforced PHB contributed a heavier environmental burden in other impact categories such as photochemical smog formation, acidification and eutrophication potentials. The largest pollutant that contributes to these impact categories arises from the emission of nitrogen and phosphorus from soil during biomass cultivation associated with fertilisers. The environmental impact of flax fibre-reinforced PP was compared against glass fibre-reinforced PP in a separate study [375]. It was found that the lower tensile strength of flax fibres compared to glass fibres led to a higher environmental impact associated with flax fibre-reinforced PP when equal composite strength for flax fibre-reinforced PP and glass fibre-reinforced PP was targeted. When stiffness is used as the main design criteria for composites (assuming both composites are equally durable), flax fibres could potentially serve as a substitute for glass fibres if the w _f of flax fibres is sufficiently high.

Garkhail [376] used LCA to quantify the green credentials of compression moulded flax fibre-reinforced PP and compared against GFRP equivalent. For non-automotive applications, the environmental impact of flax fibre-reinforced PP was found to be higher than the GFRP equivalent. Two reasons were proposed: (i) the need of pesticides and other chemicals to produce flax and (ii) extra weight of material required to achieve the property criterion. For automotive applications on the other hand, the environmental impact of flax fibre-reinforced PP was found to be lower than that of its GFRP equivalent, if stiffness was used as the main design criteria. This was due to the lower weight of flax fibre-reinforced PP compared to the GFRP equivalent, leading to reduced fuel consumption. Table 6 summarises the mass of flax fibre-reinforced PP required to achieve the same mechanical properties as 1 kg of GFRP. When tensile strength and notched impact strength were used as design criteria, flax fibre-reinforced PP perform much worse environmentally compared to the GFRP equivalent due to high mass of flax fibre-reinforced PP needed to sustain the same maximum tensile load and notched impact strength.

Table 6.

Volume fraction of flax and glass fibres, as well as the mass of flax fibre-reinforced PP (in reference with 1 kg of glass fibre-reinforced PP) required to achieve the target design criteria for automotive application.

Design criteria	Target value	v _{f, flax fibre} (%)	v _{f, glass fibres} (%)	Mass of flax fibre-PP (kg)
Tensile strength	45 MPa	35	8	1.04
Stiffness	3 GPa	10	5	0.97
Impact strength (notched Charpy)	20 kJ m⁻²	25	13	2.96^a

^aThe thickness of this composite is 3.2 times that of GFRP to achieve the desired impact strength.

Adapted from Garkhail [376].

Outlook

Research into the use of plant fibres as reinforcement for polymers has gained renewed interest over the past 40 years due to the possibility of producing high-performance, renewable and sustainable (green) composites that could potentially bridge the property-performance gap between renewable polymers and petroleum-derived polymers. Plant fibres are also regarded as alternative reinforcing fibres in composite applications. In this review, we discussed the various chemical and physical properties of plant fibres as well as the manufacturing routes to produce plant fibre-reinforced polymer composites. We have also evaluated the possibility of using plant fibres as alternative reinforcement to produce (high-performance) green composites. The tensile properties of plant fibre-reinforced polymers reported by various authors have been compiled and compared in this article. It was found that plant fibres serve as excellent reinforcement for polymers when the orientation of the fibres is unidirectional to the loading direction and the fibres are long. Tensile moduli and strengths of up to 40 GPa and 450 MPa, respectively, were reported for UD plant fibre composites containing between 40–60 wt-% flax, hemp, jute or ramie fibres. These are some of the highest values reported so far for plant fibre-reinforced polymers in the literature.

The tensile properties of plant fibre-reinforced polymers were also compared against commercially available randomly oriented short GFRP. It was found that green composites containing random short plant fibres do have similar properties as GFRP at a lower overall part weight, while UD plant fibre-reinforced polymers offer the potential to be adapted in applications requiring better mechanical performance. UD plant fibre composites provide composite designers with materials where the application of synthetic fibres might be less attractive (for cost-to-performance reasons). Plant fibres also can be regarded as ‘effective fillers’ as they could replace the more expensive polymers, increase the biomass fraction, improve the tensile modulus and reduce the overall cost of the final product. Furthermore, the thermal and impact properties of the final product can be improved by the incorporation of plant fibres. Falling weight impact tests showed plant fibre-reinforced polyesters and PLA exhibited higher energy absorption compared to neat polyester and PLA, respectively [154,377]. This may further motivate industry to replace their petroleum-derived materials with plant fibre-reinforced polymers in various commercial applications.

Footnotes

Acknowledgements

We would like to thank the reviewers for their constructive comments that helped to improve the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Alexander Bismarck

Koon-Yang Lee

1

Here we quote the minimum critical length because the studies by Pommet et al. [89] and Juntaro et al. [] measured the tensile strengths of natural fibre ‘bundles’. If the fibre ‘bundles’ could be broken up to individual technical fibres, the measured tensile strength of the fibres could potentially be higher, leading to longer critical fibre lengths.

ORCID

Alexander Bismarck

Koon-Yang Lee

References

Directive 2000/53/EC of the European Parliament and of the Council of 18 September 2000 on End-of-life Vehicles.

Directive 1999/31/EC of the European Parliament and of the Council of 26 April 1999 on the Landfill of Waste.

Directive 2002/96/EC of the European Parliament and of the Council of 4 July 2012 on Waste Electrical and Electronic Equipment (WEEE).

Meier

MAR.

Metathesis with oleochemicals: new approaches for the utilization of plant oils as renewable resources in polymer science. Macromol Chem Phys. 2009;210(13–14):1073–1079.

Flaris

Singh

Recent developments in biopolymers. J Vinyl Addit Technol. 2009;15(1):1–11.

Ragauskas

Williams

Davison

et al. The path forward for biofuels and biomaterials. Science. 2006;311(5760):484–489.

Datta

Henry

Lactic acid: recent advances in products, processes and technologies - a review. J Chem Technol Biotechnol. 2006;81(7):1119–1129.

Philip

Keshavarz

Roy

Polyhydroxyalkanoates: biodegradable polymers with a range of applications. J Chem Technol Biotechnol. 2007;82(3):233–247.

Raquez

Deleglise

Lacrampe

et al. Thermosetting (bio)materials derived from renewable resources: a critical review. Prog Polym Sci. 2010;35(4):487–509.

10.

Lee

K-Y

Tang

Williams

et al. Carbohydrate derived copoly(lactide) as the compatibilizer for bacterial cellulose reinforced polylactide nanocomposites. Compos Sci Technol. 2012;72(14):1646–1650.

11.

Montrikittiphant

Tang

Lee

K-Y

et al. Bacterial cellulose nanopaper as reinforcement for polylactide composites: renewable thermoplastic NanoPaPreg. Macromol Rapid Commun. 2014;35(19):1640–1645.

12.

Lee

K-Y

Aitomäki

Berglund

et al. On the use of nanocellulose as reinforcement in polymer matrix composites. Compos Sci Technol. 2014;105:15–27.

13.

Gupta

Revagade

Hilborn

Poly(lactic acid) fiber: an overview. Prog Polym Sci. 2007;32(4):455–482.

14.

Jamshidian

Tehrany

Imran

et al. Poly-lactic acid: production, applications, nanocomposites, and release studies. Compr Rev Food Sci Food Safety. 2010;9(5):552–571.

15.

Dorgan

Braun

Wegner

et al. Poly(lactic acids) – a brief review. In: Khemani

et al., editors. Degradable polymers and materials: principles and practice. Washington (DC): American Chemical Society; 2006. p. 102–125.

16.

Ackermann

Muller

Losche

et al. Methylobacterium rhodesianum cells tend to double the DNA content under growth limitations and accumlate PHB. J Biotechnol. 1995;39(1):9–20.

17.

Verhoogt

Ramsay

Favis

BD.

Polymer blends containing poly(3-hydroxyalkanoates). Polymer. 1994;35(24):5155–5169.

18.

Blaker

Lee

Bismarck

Hierarchical composites made entirely from renewable resources. J Biobased Mater Bioenergy. 2011;5:1–16.

19.

Morton

Hearle

JWS.

Physical properties of textile fibres. Manchester: The Textile Institute; 1993.

20.

Carus

Eder

Dammer

et al. Wood-plastic composites (WPC) and natural fibre composites (NFC): European and Global Markets 2012 and future trends in automotive and construction. Germany: nova-Institut GmbH; 2015.

21.

Schuh

TG.

Renewable materials for automotive applications. Stuttgart: Daimler-Chrysler AG; 2005.

22.

Anon . Ten Alps Communications Ltd t/a Sovereign Publications. Rieter Automotive Systems; 2008. [cited 2016 Dec 16]. Available from: http://www.compositesworld.com/articles/jec-composites-2005-show-review

23.

Winfield

AG.

Jute reinforced polyester projects for unido-government of India. Plast Rubber Int. 1979;4(1):23–28.

24.

Faruk

Bledzki

Fink

H-P

et al. Progress report on natural fiber reinforced composites. Macromol Mater Eng. 2014;299(1):9–26.

25.

Wambua

Ivens

Verpoest

Natural fibres: can they replace glass in fibre reinforced plastics?. Compos Sci Technol. 2003;63(9):1259–1264.

26.

Corbiere-Nicollier

Gfeller-Laban

Lundquist

et al. Life cycle assessment of biofibres replacing glass fibres as reinforcement in plastics. Resour Conserv Recy. 2001;33(4):267–287.

27.

Gindl

Keckes

Tensile properties of cellulose acetate butyrate composites reinforced with bacterial cellulose. Compos Sci Technol. 2004;64(15):2407–2413.

28.

Karnani

Krishnan

Narayan

Biofiber-reinforced polypropylene composites. Polym Eng Sci. 1997;37(2):476–483.

29.

Bismarck

Burgstaller

Lee

K-Y

et al. Recent progress in natural fibre composites: selected papers from the 3rd international conference on Innovative Natural Fibre Composites for Industrial Applications, Ecocomp 2011 and BEPS 2011. J Biobased Mater Bioenergy. 2012;6(4):343–345.

30.

Sergeev

Chuvashov

Galushchak

et al. Basalt fibers - a reinforcing filler for composites. Powder Metal Metal Ceram. 1994;33(9–10):555–557.

31.

Hardy

Scheibel

TR.

Composite materials based on silk proteins. Prog Polym Sci. 2010;35(9):1093–1115.

32.

Hong

Wool

RP.

Development of a bio-based composite material from soybean oil and keratin fibers. J Appl Polym Sci. 2005;95(6):1524–1538.

33.

Shubhra

QTH

Saha

Alam

AKMM

et al. Effect of matrix modification by natural rubber on the performance of silk-reinforced polypropylene composites. J Reinf Plast Compos. 2010;29(22):3338–3344.

34.

Shah

Porter

Vollrath

Can silk become an effective reinforcing fibre? A property comparison with flax and glass reinforced composites. Compos Sci Technol. 2014;101:173–183.

35.

Bismarck

Mishra

Lampke

et al. Plant fibers as reinforcement for green composites. In: Mohanty

et al., editors. Natural fibers, biopolymers and biocomposites. Boca Raton (FL): CRC Press; 2005. p. 37–108.

36.

Mohanty

Misra

Drzal

et al. Natural fibers, biopolymers, and biocomposites. In: Mohanty AK, Misra M, Drzal LT, editors. An introduction. London: CRC Press; 2005. p. 1–36.

37.

Shah

DU.

Developing plant fibre composites for structural applications by optimising composite parameters: a critical review. J Mater Sci. 2013;48(18):6083–6107.

38.

Najafi

SK.

Use of recycled plastics in wood plastic composites - a review. Waste Manage. 2013;33(9):1898–1905.

39.

Ashori

Wood-plastic composites as promising green-composites for automotive industries!. Bioresour Technol. 2008;99(11):4661–4667.

40.

Faruk

Bledzki

Matuana

LM.

Microcellular foamed wood-plastic composites by different processes: a review. Macromol Mater Eng. 2007;292(2):113–127.

41.

Kumar

Tyagi

Sinha

Wood flour-reinforced plastic composites: a review. Rev Chem Eng. 2011;27(5–6):253–264.

42.

Lee

K-Y

Delille

Bismarck

Greener surface treatments of natural fibres for the production of renewable composite materials. In: Kalia

et al., editors. Cellulose fibers: bio- and nano-polymer composites. Berlin: Springer-Verlag; 2011. p. 155–178.

43.

Riedel

Nickel

Natural fibre-reinforced biopolymers as construction materials - new discoveries. Angew Makromol Chem. 1999;272:34–40.

44.

Saheb

Jog

JP.

Natural fiber polymer composites: a review. Adv Polym Technol. 1999;18(4):351–363.

45.

Tripp

Rollins

ML.

Morphology and chemical composition of certain components of cotton fiber cell wall. Anal Chem. 1952;24(11):1721–1728.

46.

Holt

Mackie

Sellen

DB.

Degree of polymerization and polydispersity of native cellulose. J Poly Sci C Polym Sympos. 1972;1973(42):1505–1512.

47.

Holtzer

Benoit

Doty

The molecular configuration and hydrodynamic behavior of cellulose trinitrate. J Phys Chem. 1954;58(8):624–634.

48.

Hunt

Newman

Scheraga

et al. Dimensions and hydrodynamic properties of cellulose trinitrate molecules in dilute solutions. J Phys Chem. 1956;60(9):1278–1290.

49.

Levi

Sellen

DB.

The degree-of-polymerization and polydispersity of cellulose in beechwood, and its radial variation across fibre cell-walls. Carbohydr Res. 1967;5(3):351–355.

50.

Schurz

Tritthart

Supermolecular gels in cellulose nitrate solutions. Polymer. 1966;7(9):475–477.

51.

Sellen

Levi

MP.

A light scattering and viscosity study of polydispersity changes in the cellulose of wood when subjected to fungal attack. Polymer. 1967;8(C):633–642.

52.

Huque

Goring

DAI

Mason

SG.

Molecular size and configuration of cellulose trinitrate in solution. Can J Chem. 1958;36(6):952–969.

53.

Segal

Fractionation of cellulose trinitrates by gel permeation chromatography. J Pol Sci B Poly Lett. 1966;4(12):1011–1018.

54.

Franco

PJH

Valadez-González

Fiber-matrix adhesion in natural fiber composites. In: Mohanty

et al., editors. Natural fibers, biopolymers and biocomposites. Boca Raton (FL): CRC Press; 2005. p. 177–230.

55.

Bismarck

Mishra

Lampke

et al. Plant fibers as reinforcement for green composites. In: Mohanty

et al., editors. Natural fibers, biopolymers and biocomposites. Boca Raton (FL): CRC Press; 2005. p. 37–108.

56.

Scheller

Ulvskov

Hemicelluloses. Ann Rev Plant Biol. 2010;61:263–289.

57.

Olesen

Plackett

DV.

Perspectives on the performance of natural plant fibres. Copenhagen: Plant Fibre Laboratory, Royal Veterinary and Agricultural University.

58.

Kumar

MNS

Mohanty

Erickson

et al. Lignin and its applications with polymers. J Biobased Mater Bioenergy. 2009;3(1):1–24.

59.

Duval

Lawoko

A review on lignin-based polymeric, micro- and nano-structured materials. React Funct Polym. 2014;85:78–96.

60.

Mohanty

Misra

Hinrichsen

Biofibres, biodegradable polymers and biocomposites: an overview. Macromol Mater Eng. 2000;276(3–4):1–24.

61.

Koronis

Silva

Fontul

Green composites: a review of adequate materials for automotive applications. Compos B Eng. 2013;44(1):120–127.

62.

McLaughlin

Tait

RA.

Fracture mechanism of plant fibres. J Mater Sci. 1980;15(1):89–95.

63.

Mukherjee

Satyanarayana

KG.

An empirical evaluation of structure-property relationships in natural fibres and their fracture behaviour. J Mater Sci. 1986;21(12):4162–4168.

64.

Nishino

Natural fibre sources. In: Baillie

, editor. Green composites: polymer composites and the environment. Cambridge: Woodhead Publishing; 2004. p. 49–80.

65.

Dodd

Akin

DE.

Recent developments in retting and measurement of fiber quality in natural fibers: pros and cons. In: Mohanty

et al., editors. Natural fibers, biopolymers and biocomposites. Boca Raton (FL): CRC Press; 2005. p. 141–158.

66.

Sharma

HSS

Sumere

CFv.

Enzyme treatment of flax. Genet Eng Biotechnol. 1992;12(2):19–23.

67.

USDA. Industrial hemp in the United States: status and market potential. Washington (DC): Department of Agriculture; 2000. Available from: http://www.globalhemp.com/Archives/Government_Research/USDA/ages001Ee.pdf

68.

Akin

Foulk

Dodd

et al. Enzyme-retting of flax and characterization of processed fibers. J Biotechnol. 2001;89(2–3):193–203.

69.

Shah

Nag

Clifford

MJ.

Why do we observe significant differences between measured and ‘back-calculated’ properties of natural fibres?. Cellulose. 2016;23(3):1481–1490.

70.

Thomason

Carruthers

Natural fibre cross sectional area, its variability and effects on the determination of fibre properties. J Biobased Mater Bioenergy. 2012;6(4):424–430.

71.

Thomason

Carruthers

Kelly

et al. Fibre cross-section determination and variability in sisal and flax and its effects on fibre performance characterisation. Compos Sci Technol. 2011;71(7):1008–1015.

72.

Lamy

Baley

Stiffness prediction of flax fibers-epoxy composite materials. J Mater Sci Lett. 2000;19(11):979–980.

73.

Hänninen

Michud

Hughes

Kink bands in bast fibres and their effects on mechanical properties. Plast Rubber Compos. 2011;40(6/7):307–310.

74.

Hänninen

Thygesen

Mehmood

et al. Mechanical processing of bast fibres: the occurrence of damage and its effect on fibre structure. Ind Crop Prod. 2012;39:7–11.

75.

Baley

Influence of kink bands on the tensile strength of flax fibers. J Mater Sci. 2004;39(1):331–334.

76.

Duc

Vergnes

Budtova

Polypropylene/natural fibres composites: analysis of fibre dimensions after compounding and observations of fibre rupture by rheo-optics. Compos A Appl Sci Manuf. 2011;42(11):1727–1737.

77.

Hill

CAS

Norton

Newman

The water vapor sorption behavior of natural fibers. J Appl Polym Sci. 2009;112(3):1524–1537.

78.

Bismarck

Mohanty

Aranberri-Askargorta

et al. Surface characterization of natural fibers; surface properties and the water up-take behavior of modified sisal and coir fibers. Green Chem. 2001;3(2):100–107.

79.

Juntaro

Pommet

Kalinka

et al. Creating hierarchical structures in renewable composites by attaching bacterial cellulose onto sisal fibers. Adv Mater. 2008;20(16):3122–3126.

80.

Mukherjee

Satyanarayana

KG.

Structure and properties of some vegetable fibers. Part 1 sisal fiber. J Mater Sci. 1984;19(12):3925–3934.

81.

Bismarck

Aranberri-Askargorta

Springer

et al. Surface characterization of flax, hemp and cellulose fibers; surface properties and the water uptake behavior. Polym Compos. 2002;23(5):872–894.

82.

Stamboulis

Baillie

Garkhail

et al. Environmental durability of flax fibres and their composites based on polypropylene matrix. Appl Compos Mater. 2000;7(5):273–294.

83.

Stamboulis

Baillie

Peijs

Effects of environmental conditions on mechanical and physical properties of flax fibers. Compos A Appl Sci Manuf. 2001;32(8):1105–1115.

84.

Mokhothu

John

MJ.

Review on hygroscopic aging of cellulose fibres and their biocomposites. Carbohydr Polym. 2015;131:337–354.

85.

Célino

Freour

Jacquemin

et al. The hygroscopic behavior of plant fibres: a review. Front Chem. 2014;1:1–12.

86.

Assarar

Scida

El Mahi

et al. Influence of water ageing on mechanical properties and damage events of two reinforced composite materials: flax–fibres and glass–fibres. Mater Design. 2011;32(2):788–795.

87.

Dan-mallam

Abdullah

Yusoff

PSMM.

Mechanical properties of recycled Kenaf/Polyethylene Terephthalate (PET) fiber reinforced Polyoxymethylene (POM) hybrid composite. J Appl Polym Sci. 2014;131(3):39831.

88.

Dhakal

Zhang

Bennett

et al. Effects of water immersion ageing on the mechanical properties of flax and jute fibre biocomposites evaluated by nanoindentation and flexural testing. J Compos Mater. 2014;48(11):1399–1406.

89.

Pommet

Juntaro

Heng

JYY

et al. Surface modification of natural fibers using bacteria: depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites. Biomacromolecules. 2008;9(6):1643–1651.

90.

Kalia

Kaith

Kaur

Pretreatments of natural fibers and their application as reinforcing material in polymer composites – a review. Polym Eng Sci. 2009;49(7):1253–1272.

91.

La Mantia

Morreale

Green composites: a brief review. Compos A Appl Sci Manuf. 2011;42(6):579–588.

92.

Dittenber

GangaRao

HVS.

Critical review of recent publications on use of natural composites in infrastructure. Compos A Appl Sci Manuf. 2012;43(8):1419–1429.

93.

Shahzad

Hemp fiber and its composites – a review. J Compos Mater. 2012;46(8):973–986.

94.

Bledzki

Fink

Specht

Unidirectional hemp and flax EP- and PP-composites: influence of defined fiber treatments. J Appl Polym Sci. 2004;93(5):2150–2156.

95.

Mishra

Tripathy

Misra

et al. Novel eco-friendly biocomposites: biofiber reinforced biodegradable polyester amide composites – fabrication and properties evaluation. J Reinf Plast Compos. 2002;21(1):55–70.

96.

Wang

Panigrahi

Tabil

et al. Effects of chemical treatments on mechanical and physical properties of flax fiber-reinforced rotationally molded composites. ASAE Annual International Meeting, 2004. p. 6745–6755.

97.

Heß

Trogus

Ljubitsch

et al. Ueber Quellungserscheinungen an Zellulosefasern. Kolloid-Zeitschrift. 1930;51(1):89–96.

98.

Mukherjee

Woods

HJ.

Mercerization of jute. Nature. 1950;165(4203):818–819.

99.

Wang

Pattarachaiyakoop

et al. A review on the tensile properties of natural fiber reinforced polymer composites. Compos B Eng. 2011;42(4):856–873.

100.

Bledzki

Gassan

Composites reinforced with cellulose based fibres. Prog Polym Sci. 1999;24(2):221–274.

101.

Bledzki

Sperber

Faruk

Rapra review report: natural and wood fiber reinforcement in polymers. Shrewsbury: Smithers Rapra; 2002.

102.

Mishra

Naik

Patil

YP.

The compatibilising effect of maleic anhydride on swelling and mechanical properties of plant-fiber-reinforced novolac composites. Compos Sci Technol. 2000;60(9):1729–1735.

103.

Gassan

Bledzki

AK.

The influence of fiber-surface treatment on the mechanical properties of jute-polypropylene composites. Compos A Appl Sci Manuf. 1997;28(12):1001–1005.

104.

Tserki

Zafeiropoulos

Simon

et al. A study of the effect of acetylation and propionylation surface treatments on natural fibres. Compos A. 2005;36(8):1110–1118.

105.

Valadez-Gonzalez

Cervantes-Uc

Olayo

et al. Chemical modification of henequen fibers with an organosilane coupling agent. Compos B Eng. 1999;30(3):321–331.

106.

Mehta

Drzal

Mohanty

et al. Effect of fiber surface treatment on the properties of biocomposites from nonwoven industrial hemp fiber mats and unsaturated polyester resin. J Appl Polym Sci. 2006;99(3):1055–1068.

107.

Ganan

Garbizu

Llano-Ponte

et al. Surface modification of sisal fibers: effects on the mechanical and thermal properties of their epoxy composites. Polym Compos. 2005;26(2):121–127.

108.

Pothan

Thomas

Groeninckx

The role of fibre/matrix interactions on the dynamic mechanical properties of chemically modified banana fibre/polyester composites. Compos A. 2006;37(9):1260–1269.

109.

George

Janardhan

Anand

et al. Melt rheological behaviour of short pineapple fibre reinforced low density polyethylene composites. Polymer. 1996;37(24):5421–5431.

110.

Tabil

Panigrahi

Chemical treatments of natural fiber for use in natural fiber-reinforced composites: a review. J Polym Environ. 2007;15(1):25–33.

111.

John

Anandjiwala

RD.

Recent developments in chemical modification and characterization of natural fiber-reinforced composites. Polym Compos. 2008;29(2):187–207.

112.

Cichocki

Thomason

JL.

Thermoelastic anisotropy of a natural fiber. Compos Sci Technol. 2002;62(5):669–678.

113.

Baley

Perrot

Busnel

et al. Transverse tensile behaviour of unidirectional plies reinforced with flax fibres. Mater Lett. 2006;60(24):2984–2987.

114.

Miyagawa

Mase

Sato

et al. Comparison of experimental and theoretical transverse elastic modulus of carbon fibers. Carbon. 2006;44(10):2002–2008.

115.

Maurin

Davies

Baral

et al. Transverse properties of carbon fibres by nano-indentation and micro-mechanics. Appl Compos Mater. 2008;15(2):61–73.

116.

Thomason

JL.

Why are natural fibres failing to deliver on composite performance?

Conference Proceedings of the 17th International Conference of Composite Materials, Edinburgh; 2009.

117.

Nishino

Matsuda

Hirao

All-cellulose composite. Macromolecules. 2004;37(20):7683–7687.

118.

Juntaro

Pommet

Mantalaris

et al. Nanocellulose enhanced interfaces in truly green unidirectional fibre reinforced composites. Compos Interfaces. 2007;14(7–9):753–762.

119.

Lee

K-Y

KKC

Schlufter

et al. Hierarchical composites reinforced with robust short sisal fibre preforms utilising bacterial cellulose as binder. Compos Sci Technol. 2012;72(13):1479–1486.

120.

Lee

K-Y

Bharadia

Blaker

et al. Short sisal fibre reinforced bacterial cellulose polylactide nanocomposites using hairy sisal fibres as reinforcement. Compos A. 2012;43(11):2065–2074.

121.

Van de Weyenberg

Ivens

De Coster

et al. Influence of processing and chemical treatment of flax fibres on their composites. Compos Sci Technol. 2003;63(9):1241–1246.

122.

Rong

Zhang

Liu

et al. The effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites. Compos Sci Technol. 2001;61(10):1437–1447.

123.

Rouison

Sain

Couturier

Resin transfer molding of natural fiber reinforced composites: cure simulation. Compos Sci Technol. 2004;64(5):629–644.

124.

Roulson

Sain

Couturier

Resin transfer molding of hemp fiber composites: optimization of the process and mechanical properties of the materials. Compos Sci Technol. 2006;66(7–8):895–906.

125.

Oksman

High quality flax fibre composites manufactured by the resin transfer moulding process. J Reinf Plast Compos. 2001;20(7):621–627.

126.

Hautala

Pasila

Pirila

Use of hemp and flax in composite manufacture: a search for new production methods. Compos A. 2004;35(1):11–16.

127.

Faruk

Bledzki

Fink

H-P

et al. Biocomposites reinforced with natural fibers: 2000–2010. Prog Polym Sci. 2012;37(11):1552–1596.

128.

Oksman

Mechanical properties of natural fibre mat reinforced thermoplastic. Appl Compos Mater. 2000;7(5–6):403–414.

129.

Garkhail

Heijenrath

RWH

Peijs

Mechanical properties of natural-fibre-mat-reinforced thermoplastics based on flax fibres and polypropylene. Appl Compos Mater. 2000;7(5–6):351–372.

130.

Van de Velde

Kiekens

Effect of Flax/PP panel process parameters on resulting composite properties. J Thermoplast Compos Mater. 2003;16(5):413–431.

131.

Wielage

Lampke

Utschick

et al. Processing of natural-fibre reinforced polymers and the resulting dynamic-mechanical properties. J Mater Process Technol. 2003;139(1–3):140–146.

132.

Zampaloni

Pourboghrat

Yankovich

et al. Kenaf natural fiber reinforced polypropylene composites: a discussion on manufacturing problems and solutions. Compos A. 2007;38(6):1569–1580.

133.

Wielage

Lampke

Marx

et al. Thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene. Thermochim Acta. 1999;337(1–2):169–177.

134.

Madsen

Lilholt

Physical and mechanical properties of unidirectional plant fibre composites – an evaluation of the influence of porosity. Compos Sci Technol. 2003;63(9):1265–1272.

135.

Bledzki

Letman

Viksne

et al. A comparison of compounding processes and wood type for wood fibre – PP composites. Compos A. 2005;36(6):789–797.

136.

Sain

Suhara

Law

et al. Interface modification and mechanical properties of natural fiber-polyolefin composite products. J Reinf Plast Compos. 2005;24(2):121–130.

137.

Yang

H-S

Wolcott

Kim

H-S

et al. Properties of lignocellulosic material filled polypropylene bio-composites made with different manufacturing processes. Polymer Testing. 2006;25(5):668–676.

138.

Balasuriya

Mai

YW.

Mechanical properties of wood flake-polyethylene composites. Part I: effects of processing methods and matrix melt flow behaviour. Compos A. 2001;32(5):619–629.

139.

Wang

Chan

Lai

et al. Twin screw compounding of PE-HD wood flour composites. Int Polym Process. 2001;16(2):100–107.

140.

Burgstaller

A comparison of processing and performance for lignocellulosic reinforced polypropylene for injection moulding applications. Compos B Eng. 2014;67:192–198.

141.

Ganster

Fink

Pinnow

High-tenacity man-made cellulose fibre reinforced thermoplastics – injection moulding compounds with polypropylene and alternative matrices. Compos A. 2006;37(10):1796–1804.

142.

Fink

Ganster

Uihlein

et al. Rieselfähige pellets auf basis cellulosischer spinnfasern, verfahren zu deren herstellung und deren verwendung. Google Patents; 2006.

143.

De Bruyne

NA.

Plastic materials for aircraft construction. J Royal Aeronaut Soc. 1937;41(319):523–590.

144.

De Bruyne

NA.

Plastic progress: some further developments in the manufacture and use of synthetic materials for aircraft constructions. In: Flight and the aircraft engineer. Waterloo: Royal Aero Club; 1939. p. 41–43.

145.

Shurtleff

Aoyagi

Henry Ford and his researchers – history of their work with soybeans, soyfoods and chemurgy (1928-2011): extensively annotated bibliography and sourcebook. Lafayette (CA): Soyinfo Center; 2011.

146.

Ford

Automobile chassis construction. Google Patents; 1942.

147.

Chi

et al. Mechanical, thermal expansion, and flammability properties of co-extruded wood polymer composites with basalt fiber reinforced shells. Mater Des. 2014;60:334–342.

148.

Yam

RCM

Mak

DMT.

A cleaner production of rice husk-blended polypropylene eco-composite by gas-assisted injection moulding. J Clean Prod. 2014;67:277–284.

149.

Zimniewska

Stevenson

Sapieja

et al. Linen fibres based reinforcements for laminated composites. Fibres Text East Eur. 2014;22(3):103–108.

150.

Arao

Fujiura

Itani

et al. Strength improvement in injection-molded jute-fiber-reinforced polylactide green-composites. Compos B Eng. 2015;68:200–206.

151.

Mihai

Chapleau

Denault

Processing-formulation-performance relationships of polypropylene/short flax fiber composites. J Appl Polym Sci. 2015;132(9):41528.

152.

Nabinejad

Sujan

Rahman

et al. Effect of oil palm shell powder on the mechanical performance and thermal stability of polyester composites. Mater Des. 2015;65:823–830.

153.

Paul

Kanny

Redhi

GG.

Mechanical, thermal and morphological properties of a bio-based composite derived from banana plant source. Compos A. 2015;68:90–100.

154.

Siengchin

Reinforced flax mat/modified Polylactide (PLA) composites: impact, thermal, and mechanical properties. Mech Compos Mater. 2014;50(2):257–266.

155.

Singh

Palsule

Coconut fiber reinforced chemically functionalized high-density polyethylene (CNF/CF-HDPE) composites by Palsule process. J Compos Mater. 2014;48(29):3673–3684.

156.

Tawakkal

ISMA

Cran

Bigger

SW.

Effect of Kenaf fibre loading and thymol concentration on the mechanical and thermal properties of PLA/Kenaf/thymol composites. Ind Crop Prod. 2014;61:74–83.

157.

Toupe

Trokourey

Rodrigue

Simultaneous optimization of the mechanical properties of postconsumer natural fiber/plastic composites: phase compatibilization and quality/cost ratio. Polym Compos. 2014;35(4):730–746.

158.

Virk

Hall

Summerscales

Microstructural characterisation of jute/epoxy quasi-unidirectional composites. Appl Compos Mater. 2014;21(6):885–903.

159.

Wisittanawat

Thanawan

Amornsakchai

Mechanical properties of highly aligned short pineapple leaf fiber reinforced – nitrile rubber composite: effect of fiber content and bonding agent. Polym Test. 2014;35:20–27.

160.

C-S

Hsu

Y-C

Liao

H-T

et al. Characterization and biocompatibility of chestnut shell fiber-based composites with polyester. J Appl Polym Sci. 2014;131(17):40730.

161.

Perez-Fonseca

Robledo-Ortiz

Ramirez-Arreola

et al. Effect of hybridization on the physical and mechanical properties of high density polyethylene-(pine/agave) composites. Mater Des. 2014;64:35–43.

162.

Piekarska

Piorkowska

Krasnikova

et al. . Polylactide composites with waste cotton fibers: thermal and mechanical properties. Polym Compos. 2014;35(4):747–751.

163.

Poilane

Cherif

Richard

et al. Polymer reinforced by flax fibres as a viscoelastoplastic material. Compos Struct. 2014;112:100–112.

164.

Prabu

Uthayakumar

Manikandan

et al. Influence of redmud on the mechanical, damping and chemical resistance properties of banana/polyester hybrid composites. Mater Des. 2014;64:270–279.

165.

Puglia

Santulli

Sarasini

et al. Thermal and mechanical characterisation of Phormium tenax-reinforced polypropylene composites. J Thermoplast Compos Mater. 2014;27(11):1493–1503.

166.

Raghavendra

Ojha

Acharya

et al. Jute fiber reinforced epoxy composites and comparison with the glass and neat epoxy composites. J Compos Mater. 2014;48(20):2537–2547.

167.

Riyapan

Riyajan

S-A

Tangboriboonrat

Preparation of polymer composite: low natural rubber, cassava starch and palm fiber. In: Nakason

Thitithammawong

Wisunthorn

, editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2014. p. 314–317.

168.

Sarifuddin

Ismail

Ahmad

Incorporation of Kenaf core fibers into low density polyethylene/thermoplastic sago starch blends exposed to natural weathering. Mol Cryst Liq Cryst. 2014;603(1):180–193.

169.

Sathishkumar

Navaneethakrishnan

Shankar

et al. Investigation of chemically treated randomly oriented sansevieria ehrenbergii fiber reinforced isophthallic polyester composites. J Compos Mater. 2014;48(24):2961–2975.

170.

Oumer

Bachtiar

Modeling and experimental validation of tensile properties of sugar palm fiber reinforced high impact polystyrene composites. Fiber Polym. 2014;15(2):334–339.

171.

Moothoo

Ouagne

Allaoui

et al. Vegetal fibre composites for semi-structural applications in the medical environment. J Reinf Plast Compos. 2014;33(19):1823–1834.

172.

Monteiro

Margem

Altoe

et al. Tensile strength of polyester composites reinforced with thinner buriti fibers. 20th Brazilian Conference on Materials Science and Engineering, Joinville, Brazil; 2012.

173.

Merkel

Rydarowski

Kazimierczak

et al. Processing and characterization of reinforced polyethylene composites made with lignocellulosic fibres isolated from waste plant biomass such as hemp. Compos B Eng. 2014;67:138–144.

174.

Marrot

Bourmaud

Bono

et al. Multi-scale study of the adhesion between flax fibers and biobased thermoset matrices. Mater Des. 2014;62:47–56.

175.

Mahmoudi

Hebbar

Study of mechanical properties of a composite-based plant fibre of the palm and thermoplastic matrices (PP). J Compos Mater. 2014;48(3):291–299.

176.

Mahjoub

Yatim

Sam

ARM

et al. Characteristics of continuous unidirectional Kenaf fiber reinforced epoxy composites. Mater Des. 2014;64:640–649.

177.

Gacoin

et al. Experimental investigation on the mechanical performance of starch-hemp composite materials. Constr Build Mater. 2014;61:106–113.

178.

Kumar

SMS

Duraibabu

Subramanian

Studies on mechanical, thermal and dynamic mechanical properties of untreated (raw) and treated coconut sheath fiber reinforced epoxy composites. Mater Des. 2014;59:63–69.

179.

Kong

Park

Lee

Study on structural design and analysis of flax natural fiber composite tank manufactured by vacuum assisted resin transfer molding. Mater Lett. 2014;130:21–25.

180.

Kommula

Reddy

Shukla

et al. Mechanical properties, water absorption, and chemical resistance of napier grass fiber strand-reinforced epoxy resin composites. Int J Polym Anal Chem. 2014;19(8):693–708.

181.

Khalfallah

Abbes

et al. Innovative flax tapes reinforced Acrodur biocomposites: a new alternative for automotive applications. Mater Des. 2014;64:116–126.

182.

Kern

Kim

Argento

et al. Mechanical behavior of microcellular, natural fiber reinforced composites at various strain rates and temperatures. Polym Test. 2014;37:148–155.

183.

Kengkhetkit

Amornsakchai

A new approach to “Greening” plastic composites using pineapple leaf waste for performance and cost effectiveness. Mater Des. 2014;55:292–299.

184.

Kang

Park

Kim

SH.

Improvement in the adhesion of bamboo fiber reinforced polylactide composites. J Compos Mater. 2014;48(21):2567–2577.

185.

Kalapakdee

Amornsakchai

Mechanical properties of preferentially aligned short pineapple leaf fiber reinforced thermoplastic elastomer: effects of fiber content and matrix orientation. Polym Test. 2014;37:36–44.

186.

Islam

Miao

Optimising processing conditions of flax fabric reinforced Acrodur biocomposites. J Compos Mater. 2014;48(26):3281–3292.

187.

Tan

Yang

et al. Hot compaction and mechanical properties of ramie fabric/epoxy composite fabricated using vacuum assisted resin infusion molding. Mater Des. 2014;56:852–861.

188.

Mechanical and biodegradable properties of L-lactide-grafted sisal fiber reinforced polylactide composites. J Reinf Plast Compos. 2014;33(22):2034–2045.

189.

Benyahia

Merrouche

Effect of chemical surface modifications on the properties of alfa fiber-polyester composites. Polym-Plast Technol Eng. 2014;53(4):403–410.

190.

Benyahia

Merrouche

Rahmouni

ZEA

et al. Study of the alkali treatment effect on the mechanical behavior of the composite unsaturated polyester-Alfa fibers. Mech Ind. 2014;15(1):69–73.

191.

Bin Saiman

Bin Wahab

Bin Wahit

MU.

The effect of yarn linear density on mechanical properties of plain Woven Kenaf reinforced unsaturated polyester composite. In: Ismail

Mohd Nor

Mohd Ali

et al., editors. Applied mechanics and materials. Zurich: Trans Tech Publications Ltd; 2014. p. 962–966.

192.

Bodur

Bakkal

Savas

et al. A new approach for the development of textile waste cotton reinforced composites (T-FRP): laminated hybridization vs. coupling agents. J Polym Eng. 2014;34(7):639–648.

193.

Crossley

Schubel

Stevenson

Furan matrix and flax fibre as a sustainable renewable composite: mechanical and fire-resistant properties in comparison to phenol, epoxy and polyester. J Reinf Plast Compos. 2014;33(1):58–68.

194.

Dan-Mallam

Abdullah

Yusoff

PSMM.

The effect of hybridization on mechanical properties of woven Kenaf fiber reinforced polyoxymethylene composite. Polym Compos. 2014;35(10):1900–1910.

195.

El-Sabbagh

AMM

Steuernagel

Meiners

et al. Effect of extruder elements on fiber dimensions and mechanical properties of bast natural fiber polypropylene composites. J Appl Polym Sci. 2014;131(12):40435.

196.

El-Shekeil

Sapuan

Jawaid

et al. Influence of fiber content on mechanical, morphological and thermal properties of Kenaf fibers reinforced poly(vinyl chloride)/thermoplastic polyurethane poly-blend composites. Mater Des. 2014;58:130–135.

197.

Ahmed

Islam

Hassan

et al. Impact of succinic anhydride on the properties of jute fiber/polypropylene biocomposites. Fiber Polym. 2014;15(2):307–314.

198.

Baets

Plastria

Ivens

et al. Determination of the optimal flax fibre preparation for use in unidirectional flax-epoxy composites. J Reinf Plast Compos. 2014;33(5):493–502.

199.

Baghaei

Skrifvars

Rissanen

et al. Mechanical and thermal characterization of compression moulded polylactic acid natural fiber composites reinforced with hemp and lyocell fibers. J Appl Polym Sci. 2014;131(15):40534.

200.

Sathishkumar

Navaneethakrishnan

Shankar

et al. Investigation of chemically treated longitudinally oriented snake grass fiber-reinforced isophthallic polyester composites. J Reinf Plast Compos. 2013;32(22):1698–1714.

201.

Sharma

Kumar

Studies on properties of banana fiber reinforced green composite. J Reinf Plast Compos. 2013;32(8):525–532.

202.

Thakur

Singha

Thakur

MK.

Ecofriendly biocomposites from natural fibers: mechanical and weathering study. Int J Polym Anal Chem. 2013;18(1):64–72.

203.

Xue

Mechanical properties of biaxial weft-knitted flax composites. Mater Des. 2013;46:264–269.

204.

Paukszta

Mankowski

Kolodziej

et al. Polypropylene (PP) composites reinforced with stinging nettle (Utrica dioica L.) fiber. J Nat Fiber. 2013;10(2):147–158.

205.

Popa

Pernevan

Sirghie

et al. Mechanical, thermophysical and fire properties of sansevieria fiber-reinforced polyester composites. J Chem. 2013;2013:343068.

206.

Ramanaiah

Prasad

AVR

Reddy

KHC.

Mechanical, thermophysical and fire properties of sansevieria fiber-reinforced polyester composites. Mater Des. 2013;49:986–991.

207.

Ramanaiah

Prasad

AVR

Reddy

KHC.

Mechanical and thermo-physical properties of fish tail palm tree natural fiber-reinforced polyester composites. Int J Polym Anal Chem. 2013;18(2):126–136.

208.

Robertson

N-LM

Nychka

Alemaskin

et al. Mechanical performance and moisture absorption of various natural fiber reinforced thermoplastic composites. J Appl Polym Sci. 2013;130(2):969–980.

209.

Rozite

Varna

Joffe

et al. Nonlinear behavior of PLA and lignin-based flax composites subjected to tensile loading. J Thermoplast Compos Mater. 2013;26(4):476–496.

210.

Sarasini

Puglia

Fortunati

et al. Effect of fiber surface treatments on thermo-mechanical behavior of poly(lactic acid)/phormium tenax composites. J Polym Environ. 2013;21(3):881–891.

211.

Sathishkumar

Navaneethakrishnan

Shankar

et al. Mechanical properties of randomly oriented snake grass fiber with banana and coir fiber-reinforced hybrid composites. J Compos Mater. 2013;47(18):2181–2191.

212.

Kannan

Cheng

et al. Effect of reinforcement on the mechanical and thermal properties of flax/polypropylene interwoven fabric composites. J Ind Text. 2013;42(4):417–433.

213.

Karaduman

Gokcan

Onal

Effect of enzymatic pretreatment on the mechanical properties of jute fiber-reinforced polyester composites. J Compos Mater. 2013;47(10):1293–1302.

214.

Khan

GMA

Shams

MSA

Kabir

et al. Influence of chemical treatment on the properties of banana stem fiber and banana stem fiber/coir hybrid fiber reinforced maleic anhydride grafted polypropylene/low-density polyethylene composites. J Appl Polym Sci. 2013;128(2):1020–1029.

215.

Kobayashi

Takada

Processing of unidirectional hemp fiber reinforced composites with micro-braiding technique. Compos A. 2013;46:173–179.

216.

Lebrun

Couture

Laperriere

Tensile and impregnation behavior of unidirectional hemp/paper/epoxy and flax/paper/epoxy composites. Compos Struct. 2013;103:151–160.

217.

Maheswari

Reddy

Muzenda

et al. Mechanical properties and chemical resistance of short tamarind fiber/unsaturated polyester composites: influence of fiber modification and fiber content. Int J Polym Anal Chem. 2013;18(7):520–533.

218.

Martin

Mouret

Davies

et al. Influence of the degree of retting of flax fibers on the tensile properties of single fibers and short fiber/polypropylene composites. Ind Crop Prod. 2013;49:755–767.

219.

Mir

Nafsin

Hasan

et al. Improvement of physico-mechanical properties of coir-polypropylene biocomposites by fiber chemical treatment. Mater Des. 2013;52:251–257.

220.

Bisanda

ETN

Ansell

MP.

Properties of sisal-cnsl composites. J Mater Sci. 1992;27(6):1690–1700.

221.

Deng

Beehag

Hillier

et al. Kenaf-polypropylene composites manufactured from blended fiber mats. J Reinf Plast Compos. 2013;32(16):1198–1210.

222.

Fernandes

Correlo

Mano

et al. Natural fibres as reinforcement strategy on cork-polymer composites. In: Pinto

AMP

et al., editors. Advanced materials forum VI, Pts 1 and 2. Zurich: Trans Tech Publications Ltd; 2013. p. 373–378.

223.

Fernandes

Mano

Reis

RL.

Hybrid cork-polymer composites containing sisal fibre: morphology, effect of the fibre treatment on the mechanical properties and tensile failure prediction. Compos Struct. 2013;105:153–162.

224.

Gunning

Geever

Killion

et al. Mechanical and biodegradation performance of short natural fibre polyhydroxybutyrate composites. Polymer Testing. 2013;32(8):1603–1611.

225.

Hussein

Rozman

Tay

GS.

The effect of Kenaf fibre loadings on the properties of UV-cured unsaturated polyester composites. J Reinf Plast Compos. 2013;32(14):1062–1071.

226.

Jayaramudu

Reddy

GSM

Varaprasad

et al. Preparation and properties of biodegradable films from Sterculia urens short fiber/cellulose green composites. Carbohydr Polym. 2013;93(2):622–627.

227.

Kaiser

Anuar

Samat

et al. Effect of processing routes on the mechanical, thermal and morphological properties of PLA-based hybrid biocomposite. Iran Polym J. 2013;22(2):123–131.

228.

Chen

Porter

RS.

Composite of polyethylene and Kenaf, a natural cellulose fiber. J Appl Polym Sci. 1994;54(11):1781–1783.

229.

Costa

D'Almeida

JRM.

Effect of water absorption on the mechanical properties of sisal and jute fiber composites. Polym Plast Technol Eng. 1999;38(5):1081–1094.

230.

Dash

Rana

Mishra

et al. Novel, low-cost jute-polyester composites. Part 1: processing, mechanical properties, and SEM analysis. Polym Compos. 1999;20(1):62–71.

231.

Devi

Bhagawan

Thomas

Mechanical properties of pineapple leaf fiber-reinforced polyester composites. J Appl Polym Sci. 1997;64(9):1739–1748.

232.

Wollerdorfer

Bader

Influence of natural fibres on the mechanical properties of biodegradable polymers. Ind Crop Prod. 1998;8(2):105–112.

233.

Bourmaud

Ausias

Lebrun

et al. Observation of the structure of a composite polypropylene/flax and damage mechanisms under stress. Ind Crop Prod. 2013;43:225–236.

234.

Coroller

Lefeuvre

Le Duigou

et al. Effect of flax fibres individualisation on tensile failure of flax/epoxy unidirectional composite. Compos A. 2013;51:62–70.

235.

Reddy

KRN

Rao

DKN

Rao

KGK

et al. Studies on woven century fiber polyester composites. J Compos Mater. 2012;46(23):2919–2933.

236.

Sathishkumar

Navaneethakrishnan

Shankar

Tensile and flexural properties of snake grass natural fiber reinforced isophthallic polyester composites. Compos Sci Technol. 2012;72(10):1183–1190.

237.

Seki

Sarikanat

Ezan

MA.

Effect of siloxane treatment of jute fabric on the mechanical and thermal properties of jute/HDPE. J Reinf Plast Compos. 2012;31(15):1009–1016.

238.

Venkateshwaran

Elayaperumal

Sathiya

GK.

Prediction of tensile properties of hybrid-natural fiber composites. Compos B Eng. 2012;43(2):793–796.

239.

Wang

Cui

Zhang

et al. Effects of methyl methacrylate grafting and polyamide coating on the interfacial behavior and mechanical properties of jute-fiber-reinforced polypropylene composites. J Vinyl Addit Technol. 2012;18(2):113–119.

240.

Wei

Preparation and mechanical properties of cotton stalk bast fibers reinforced polypropylene composites. In: Chen

Liu

Dai

et al., editors. Advanced materials research. Zurich: Trans Tech Publications; 2012. p. 929–932.

241.

Wei

Tian

Preparation and mechanical properties of cotton stalk bast fibers reinforced polylactic acid biodegradable composites. In: Zeng

Kim

Y-H

Chen

, editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2012. p. 1367–1371.

242.

Yang

Murakami

Hamada

Molding method, thermal and mechanical properties of jute/PLA injection molding. J Polym Environ. 2012;20(4):1124–1133.

243.

Fischer

Werwein

Graupner

Nettle fibre (Urtica dioica L.) reinforced poly(lactic acid): a first approach. J Compos Mater. 2012;46(24):3077–3087.

244.

Haque

Ali

Hasan

et al. Chemical treatment of coir fiber reinforced polypropylene composites. Ind Eng Chem Res. 2012;51(10):3958–3965.

245.

Jiang

HW.

Study on the bio-composite from sisal fiber reinforced cellulose acetate. In: Cui

Yuan

, editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2012. p. 2301–2306.

246.

Khan

Zaman

et al. Fabrication and characterization of jute fabric-reinforced PVC-based composite. J Thermoplast Compos Mater. 2012;25(1):45–58.

247.

Lopez

Vilaseca

Barbera

et al. Processing and properties of biodegradable composites based on Mater-Bi (R) and hemp core fibres. Resour Conserv Recy. 2012;59:38–42.

248.

Swan

Jr. Ferguson

Composition, structure, and mechanical properties of hemp fiber reinforced composite with recycled high-density polyethylene matrix. J Compos Mater. 2012;46(16):1915–1924.

249.

Nascimento

DCO

Ferreira

Monteiro

et al. Studies on the characterization of piassava fibers and their epoxy composites. Compos A. 2012;43(3):353–362.

250.

Porras

Maranon

Development and characterization of a laminate composite material from polylactic acid (PLA) and woven bamboo fabric. Compos B Eng. 2012;43(7):2782–2788.

251.

Rachini

Mougin

Delalande

et al. Hemp fibers/polypropylene composites by reactive compounding: Improvement of physical properties promoted by selective coupling chemistry. Polym Degrad Stabil. 2012;97(10):1988–1995.

252.

Ramanaiah

Prasad

AVR

Reddy

KHC.

Thermal and mechanical properties of waste grass broom fiber-reinforced polyester composites. Mater Des. 2012;40:103–108.

253.

Reddy

Shukla

Maheswari

et al. Evaluation of mechanical behavior of chemically modified Borassus fruit short fiber/unsaturated polyester composites. J Compos Mater. 2012;46(23):2987–2998.

254.

Tran Huu

Ogihara

Kobayashi

Interfacial, mechanical and thermal properties of coir fiber-reinforced poly(lactic acid) biodegradable composites. Adv Compos Mater. 2012;21(1):103–122.

255.

Tran Huu

Ogihara

Nakatani

et al. Mechanical and thermal properties and water absorption of jute fiber reinforced poly(butylene succinate) biodegradable composites. Adv Compos Mater. 2012;21(3):241–258.

256.

Arrakhiz

Elachaby

Bouhfid

et al. Mechanical and thermal properties of polypropylene reinforced with Alfa fiber under different chemical treatment. Mater Des. 2012;35:318–322.

257.

Bajpai

Singh

Madaan

Comparative studies of mechanical and morphological properties of polylactic acid and polypropylene based natural fiber composites. J Reinf Plast Compos. 2012;31(24):1712–1724.

258.

Christian

Billington

SL.

Mechanical response of PHB- and cellulose acetate natural fiber-reinforced composites for construction applications. Compos B Eng. 2011;42(7):1920–1928.

259.

Dani

Reddy

JPD

Rajulu

et al. Green composites from wheat protein isolate and hildegardia populifolia natural fabric. Polym Compos. 2011;32(3):398–406.

260.

De Rosa

Santulli

Sarasini

Mechanical characterization of untreated waste office paper/woven jute fabric hybrid reinforced epoxy composites. J Appl Polym Sci. 2011;119(3):1366–1373.

261.

El-Shekeil

Sapuan

Abdan

et al. Influence of fiber content on the mechanical and thermal properties of Kenaf fiber reinforced thermoplastic polyurethane composites. Mater Des. 2012;40:299–303.

262.

El-Shekeil

Sapuan

Khalina

et al. Effect of alkali treatment on mechanical and thermal properties of Kenaf fiber-reinforced thermoplastic polyurethane composite. J Therm Anal Calorim. 2012;109(3):1435–1443.

263.

Elzubair

Miguez Suarez

JC.

Mechanical behavior of recycled polyethylene/piassava fiber composites. Mater Sci Eng A Struct Mater Prop Microstruct Process. 2012;557:29–35.

264.

Farahani

Ahmad

Mosadeghzad

Effect of fiber content, fiber length and alkali treatment on properties of Kenaf fiber/UPR composites based on recycled PET wastes. Polym-Plast Technol Eng. 2012;51(6):634–639.

265.

Gohil

Shaikh

AA.

Cotton-epoxy composites: development and mechanical characterization. Key Eng Mater. 2011;471–472:291–296.

266.

Khalili

SMR

Farsani

Rafiezadeh

An experimental study on the behavior of PP/EPDM/JUTE composites in impact, tensile and bending loadings. J Reinf Plast Compos. 2011;30(16):1341–1347.

267.

Prasad

AVR

Rao

KM.

Mechanical properties of natural fibre reinforced polyester composites: Jowar, sisal and bamboo. Mater Des. 2011;32(8–9):4658–4663.

268.

Reddy

Yang

Biocomposites developed using water-plasticized wheat gluten as matrix and jute fibers as reinforcement. Polym Int. 2011;60(4):711–716.

269.

Reddy

Yang

Completely biodegradable soyprotein-jute biocomposites developed using water without any chemicals as plasticizer. Ind Crop Prod. 2011;33(1):35–41.

270.

Suardana

NPG

Abdalla

Yoon

et al. Characterization and possibility of coconut filter fibers as reinforcement for polymers. In: Mark

, editor. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2011. p. 1202–1207.

271.

Way

Dean

et al. Polylactic acid composites utilising sequential surface treatments of lignocellulose: chemistry, morphology and properties. J Polym Environ. 2011;19(4):849–862.

272.

Wirawan

Sapuan

Yunus

et al. The effects of thermal history on tensile properties of poly(vinyl chloride) and its composite with sugarcane bagasse. J Thermoplast Compos Mater. 2011;24(4):567–579.

273.

Wood

Coles

Maggs

et al. Use of lignin as a compatibiliser in hemp/epoxy composites. Compos Sci Technol. 2011;71(16):1804–1810.

274.

Yang

Ota

Morii

et al. Mechanical property and hydrothermal aging of injection molded jute/polypropylene composites. J Mater Sci. 2011;46(8):2678–2684.

275.

Zhang

Huang

Liu

ZZ.

Study on the natural fiber/pp wrap spun yarns reinforced thermoplastic composites. In: Zeng

, editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2011. p. 1470–1475.

276.

Abdrahman

Zainudin

ES.

Properties of Kenaf filled unplasticized polyvinyl chloride composites. In: SM

Sapuan

et al., editors. Composite science and technology, Pts 1 and 2. Los Angeles (CA): Sage; 2011. p. 507–512.

277.

Anuar

Hassan

Mohd Fauzey

et al. Compatibilized PP/EPDM-Kenaf fibre composite using melt blending method. In: MSJ

Hashmi

Mridha

Naher

editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2011. p. 743–747.

278.

Anuar

Zuraida

Improvement in mechanical properties of reinforced thermoplastic elastomer composite with Kenaf bast fibre. Compos B Eng. 2011;42(3):462–465.

279.

Chaudhary

Borkar

Mantha

SS.

Sunnhemp fiber-reinforced waste polyethylene bag composites. J Reinf Plast Compos. 2010;29(15):2241–2252.

280.

Deo

Acharya

SK.

Effect of moisture absorption on mechanical properties of chopped natural fiber reinforced epoxy composite. J Reinf Plast Compos. 2010;29(16):2513–2521.

281.

Ibrahim

Dufresne

El-Zawawy

et al. Banana fibers and microfibrils as lignocellulosic reinforcements in polymer composites. Carbohyd Polym. 2010;81(4):811–819.

282.

Kumar

Zhang

Aligned ramie fiber reinforced arylated soy protein composites with improved properties. Compos Sci Technol. 2009;69(5):555–560.

283.

Leao

Souza

Cherian

et al. Pineapple leaf fibers for composites and cellulose. Mol Cryst Liq Cryst. 2010;522:336–341.

284.

Liang

Pan

Zhu

et al. Mechanical and thermal properties of poly(butylene succinate)/plant fiber biodegradable composite. J Appl Polym Sci. 2010;115(6):3559–3567.

285.

Oksman

Mathew

Langstrom

et al. The influence of fibre microstructure on fibre breakage and mechanical properties of natural fibre reinforced polypropylene. Compos Sci Technol. 2009;69(11-12):1847–1853.

286.

Paul

Joseph

Mathew

et al. Preparation of polypropylene fiber/banana fiber composites by novel commingling method. Polym Compos. 2010;31(5):816–824.

287.

Phuong

Sollogoub

Guinault

Relationship between fiber chemical treatment and properties of recycled pp/bamboo fiber composites. J Reinf Plast Compos. 2010;29(21):3244–3256.

288.

Rao

KMM

Rao

Prasad

AVR.

Fabrication and testing of natural fibre composites: Vakka, sisal, bamboo and banana. Mater Des. 2010;31(1):508–513.

289.

Shubhra

QTH

Alam

AKMM

Gafur

et al. Characterization of plant and animal based natural fibers reinforced polypropylene composites and their comparative study. Fiber Polym. 2010;11(5):725–731.

290.

Singha

Thakur

VK.

Fabrication and characterization of S-cilliare fibre reinforced polymer composites. Bull Mater Sci. 2009;32(1):49–58.

291.

S-K

C-S.

The processing and characterization of polyester/natural fiber composites. Polym-Plast Technol Eng. 2010;49(10):1022–1029.

292.

Taib

Ramarad

Ishak

ZAM

et al. Properties of Kenaf fiber/polylactic acid biocomposites plasticized with polyethylene glycol. Polym Compos. 2010;31(7):1213–1222.

293.

Tasdemir

Akalin

Kocak

et al. Investigation of properties of polymer/textile fiber composites. Int J Polym Mater. 2010;59(3):200–214.

294.

Tayommai

Aht-Ong

Natural fiber/PLA composites: mechanical properties and biodegradability by gravimetric measurement respirometric (GMR) system. In: Suttiruengwong

Sricharussin

, editors. Advanced materials research. Zurich: Trans Tech Publications Ltd; 2010. p. 223–226.

295.

Wang

X-Y

Wang

Q-H

Huang

Research on mechanical behavior of the flax/polyactic acid composites. J Reinf Plast Compos. 2010;29(17):2561–2567.

296.

Acha

Marcovich

Reboredo

MM.

Lignin in jute fabric-polypropylene composites. J Appl Polym Sci. 2009;113(3):1480–1487.

297.

Alam

Ahmed

Haque

et al. Mechanical properties of natural fiber containing polymer composites. Polym-Plast Technol Eng. 2009;48(1):110–113.

298.

Ashori

Nourbakhsh

Polypropylene cellulose-based composites: the effect of bagasse reinforcement and polybutadiene isocyanate treatment on the mechanical properties. J Appl Polym Sci. 2009;111(4):1684–1689.

299.

Bax

Muessig

Impact and tensile properties of PLA/Cordenka and PLA/flax composites. Compos Sci Technol. 2008;68(7–8):1601–1607.

300.

de Farias

Farina

Pezzin

APT

et al. Unsaturated polyester composites reinforced with fiber and powder of peach palm: mechanical characterization and water absorption profile. Mater Sci Eng C Biomim Supramol Syst. 2009;29(2):510–513.

301.

El-Tayeb

NSM.

Development and characterisation of low-cost polymeric composite materials. Mater Des. 2009;30(4):1151–1160.

302.

Graupner

Application of lignin as natural adhesion promoter in cotton fibre-reinforced poly(lactic acid) (PLA) composites. J Mater Sci. 2008;43(15):5222–5229.

303.

Habibi

Ei-Zawawy

Ibrahim

et al. Processing and characterization of reinforced polyethylene composites made with lignocellulosic fibers from Egyptian agro-industrial residues. Compos Sci Technol. 2008;68(7–8):1877–1885.

304.

Hagstrand

Oksman

Mechanical properties and morphology of flax fiber reinforced melamine-formaldehyde composites. Polym Compos. 2001;22(4):568–578.

305.

Khoathane

Vorster

Sadiku

ER.

Hemp fiber-reinforced 1-pentene/polypropylene copolymer: the effect of fiber loading on the mechanical and thermal characteristics of the composites. J Reinf Plast Compos. 2008;27(14):1533–1544.

306.

Kim

S-J

Moon

J-B

Kim

G-H

et al. Mechanical properties of polypropylene/natural fiber composites: comparison of wood fiber and cotton fiber. Polym Test. 2008;27(7):801–806.

307.

Kunanopparat

Menut

Morel

et al. Reinforcement of plasticized wheat gluten with natural fibers: from mechanical improvement to deplasticizing effect. Compos A. 2008;39(5):777–785.

308.

Ochi

Mechanical properties of Kenaf fibers and Kenaf/PLA composites. Mech Mater. 2008;40(4–5):446–452.

309.

Oksman

Wallstrom

Berglund

et al. Morphology and mechanical properties of unidirectional sisal-epoxy composites. J Appl Polym Sci. 2002;84(13):2358–2365.

310.

Puglia

Terenzi

Barbosa

et al. Polypropylene-natural fibre composites. Analysis of fibre structure modification during compounding and its influence on the final properties. Compos Interfaces. 2008;15(2–3):111–129.

311.

Shibata

Takachiyo

Ozawa

et al. Biodegradable polyester composites reinforced with short abaca fiber. J Appl Polym Sci. 2002;85(1):129–138.

312.

Singha

Thakur

VK.

Synthesis and characterization of grewia optiva fiber-reinforced PF-based composites. Int J Polym Mater. 2008;57(12):1059–1074.

313.

Tragoonwichian

Yanumet

Ishida

A study on sisal fiber-reinforced benzoxazine/epoxy copolymer based on diamine-based benzoxazine. Compos Interfaces. 2008;15(2–3):321–334.

314.

Lei

et al. Natural fiber reinforced poly(vinyl chloride) composites: effect of fiber type and impact modifier. J Polym Environ. 2008;16(4):250–257.

315.

Yao

Lei

et al. Rice straw fiber-reinforced high-density polyethylene composite: effect of fiber type and loading. Ind Crop Prod. 2008;28(1):63–72.

316.

Niu

Jiao

Wang

et al. Direct manufacturing of flax fibers reinforced low melting point PET composites from nonwoven mats. Fiber Polym. 2010;11(2):218–222.

317.

Ben Brahim

Ben Cheikh

Influence of fibre orientation and volume fraction on the tensile properties of unidirectional Alfa-polyester composite. Compos Sci Technol. 2007;67(1):140–147.

318.

Bodros

Pillin

Montrelay

et al. Could biopolymers reinforced by randomly scattered flax fibre be used in structural applications?. Compos Sci Technol. 2007;67(3–4):462–470.

319.

Dhakal

Zhang

Richardson

MOW.

Effect of water absorption on the mechanical properties of hemp fibre reinforced unsaturated polyester composites. Compos Sci Technol. 2007;67(7–8):1674–1683.

320.

Lim

J-K.

Fabrication and mechanical properties of completely biodegradable hemp fiber reinforced polylactic acid composites. J Compos Mater. 2007;41(13):1655–1669.

321.

Joshy

Mathew

Joseph

Studies on interfacial adhesion in unidirectional isora fibre reinforced polyester composites. Compos Interfaces. 2007;14(7–9):631–646.

322.

Khondker

Ishiaku

Nakai

et al. A novel processing technique for thermoplastic manufacturing of unidirectional composites reinforced with jute yarns. Compos A. 2006;37(12):2274–2284.

323.

Mutje

Girones

Lopez

et al. Hemp strands: PP composites by injection molding: effect of low cost physico-chemical treatments. J Reinf Plast Compos. 2006;25(3):313–327.

324.

Mutje

Vallejos

Girones

et al. Effect of maleated polypropylene as coupling agent for polypropylene composites reinforced with hemp strands. J Appl Polym Sci. 2006;102(1):833–840.

325.

Nam

Netravali

AN.

Green composites. II. Environment-friendly, biodegradable composites using ramie fibers and soy protein concentrate (SPC) resin. Fiber Polym. 2006;7(4):380–388.

326.

Ramaraj

Mechanical and thermal properties of polypropylene/sugarcane bagasse composites. J Appl Polym Sci. 2007;103(6):3827–3832.

327.

Sastra

Siregar

Sapuan

et al. Tensile properties of Arenga pinnata fiber-reinforced epoxy composites. Polym-Plast Technol Eng. 2006;45(1):149–155.

328.

Tserki

Matzinos

Zafeiropoulos

et al. Development of biodegradable composites with treated and compatibilized lignocellulosic fibers. J Appl Polym Sci. 2006;100(6):4703–4710.

329.

Vilaseca

Mendez

Pelach

et al. Composite materials derived from biodegradable starch polymer and jute strands. Process Biochem. 2007;42(3):329–334.

330.

Ben

Kihara

Development and evaluation of mechanical properties for Kenaf fibers/PLA composites. In: JK

Kim

et al., editors. Advances in composite materials and structures, Pts 1 and 2. Zurich: Trans Tech Publications Ltd; 2007. p. 489–492.

331.

Bledzki

Jaszkiewicz

Mechanical performance of biocomposites based on PLA and PHBV reinforced with natural fibres – a comparative study to PP. Compos Sci Technol. 2010;70(12):1687–1696.

332.

Bledzki

Jaszkiewicz

Scherzer

Mechanical properties of PLA composites with man-made cellulose and abaca fibres. Compos A. 2009;40(4):404–412.

333.

Brahmakumar

Pavithran

Pillai

RM.

Coconut fibre reinforced polyethylene composites: effect of natural waxy surface layer of the fibre on fibre/matrix interfacial bonding and strength of composites. Compos Sci Technol. 2005;65(3–4):563–569.

334.

Cao

Y-q.

Evaluation of statistical strength of bamboo fiber and mechanical properties of fiber reinforced green composites. J Central South Univ Technol. 2008;15:564–567.

335.

Esteves

Estevao

Ferreira

et al. Mechanical behaviour of composite materials with long jute fibers. 15th International Conference on Experimental Mechanics; July 22–27, Porto; 2012.

336.

Foulk

Chao

Akin

et al. Analysis of flax and cotton fiber fabric blends and recycled polyethylene composites. J Polym Environ. 2006;14(1):15–25.

337.

Gouanve

Meyer

Grenet

et al. Unsaturated polyester resin (UPR) reinforced with flax fibers, untreated and cold He plasma-treated: thermal, mechanical and DMA studies. Compos Interfaces. 2006;13(4–6):355–364.

338.

R-H

Lim

J-K

Kim

C-I

et al. Biodegradable composites based on polylactic acid(PLA) and China jute fiber. In: Zhou

et al., editors. Progresses in fracture and strength of materials and structures, 1–4. Zurich: Trans Tech Publications Ltd; 2007. p. 1302–1305.

339.

Idicula

Neelakantan

Oommen

et al. A study of the mechanical properties of randomly oriented short banana and sisal hybrid fiber reinforced polyester composites. J Appl Polym Sci. 2005;96(5):1699–1709.

340.

Ismail

Awang

Sa'At

MH.

Tensile strength of natural fiber reinforced polyester composite. 2nd international conference on Solid State Science and Technology; 2006; Kuala Terengganu, Malaysia. AIP Publishing; 2007. p. 174–179.

341.

Joshy

Mathew

Joseph

Studies on short isora fibre-reinforced polyester composites. Compos Interfaces. 2006;13(4–6):377–390.

342.

Kakroodi

Bainier

Rodrigue

Mechanical and morphological properties of flax fiber reinforced high density polyethylene/recycled rubber composites. Int Polym Process. 2012;27(2):196–204.

343.

Nascimento

DCO

Lopes

FPD

Monteiro

SN.

Tensile behavior of lignocellulosic fiber reinforced polymer composites: Part I piassava/epoxy. Matéria (Rio de Janeiro). 2010;15(2):189–194.

344.

Pohl

Bierer

Natter

et al. Properties of compression moulded new fully biobased thermoset composites with aligned flax fibre textiles. Plast Rubber Compos. 2011;40(6–7):294–299.

345.

Portela

TGR

da Costa

Santos

NSS

et al. Tensile behavior of lignocellulosic fiber reinforced polymer composites: Part II buriti petiole/polyester. Materia-Rio De Janeiro. 2010;15(2):216–222.

346.

Rodriguez

Petrucci

Puglia

et al. Characterization of composites based on natural and glass fibers obtained by vacuum infusion. J Compos Mater. 2005;39(3):265–282.

347.

Singha

Kaith

Khanna

AJ.

Synthesis and characterization of cannabis indica fiber reinforced composites. BioResources. 2011;6(2):2101–2117.

348.

Singha

Thakur

VK.

Fabrication and study of lignocellulosic Hibiscus sabdariffa fiber reinforced polymer composites. BioResources. 2008;3(4):1173–1186.

349.

Wirawan

Sapuan

Abdan

et al. Tensile and impact properties of sugarcane bagasse/poly (vinyl chloride) composites. In: SM

Sapuan

et al., editors. Composite science and technology, Pts 1 and 2. Zurich: Trans Tech Publications Ltd; 2011. p. 167–172.

350.

Ren

Preparation and properties of short natural fiber reinforced poly(lactic acid) composites. Trans Nonferr Metals Soc China. 2009;19:S651–S655.

351.

Baiardo

Zini

Scandola

Flax fibre-polyester composites. Compos A. 2004;35(6):703–710.

352.

Biagiotti

Puglia

Torre

et al. A systematic investigation on the influence of the chemical treatment of natural fibers on the properties of their polymer matrix composites. Polym Compos. 2004;25(5):470–479.

353.

Gomes

Goda

Ohgi

Effects of alkali treatment to reinforcement on tensile properties of curaua fiber green composites. JSME Int J Series A-Solid Mech Mater Eng. 2004;47(4):541–546.

354.

Jayaraman

Manufacturing sisal-polypropylene composites with minimum fibre degradation. Compos Sci Technol. 2003;63(3–4):367–374.

355.

Keller

Compounding and mechanical properties of biodegradable hemp fibre composites. Compos Sci Technol. 2003;63(9):1307–1316.

356.

Sain

MM.

High stiffness natural fiber-reinforced hybrid polypropylene composites. Polym-Plast Technol Eng. 2003;42(5):853–862.

357.

Oksman

Skrifvars

Selin

JF.

Natural fibres as reinforcement in polylactic acid (PLA) composites. Compos Sci Technol. 2003;63(9):1317–1324.

358.

Sameni

Ahmad

Zakaria

Mechanical properties of Kenaf-thermoplastic natural rubber composites. Polym-Plast Technol Eng. 2003;42(3):345–355.

359.

Singleton

ACN

Baillie

Beaumont

PWR

et al. On the mechanical properties, deformation and fracture of a natural fibre/recycled polymer composite. Compos B Eng. 2003;34(6):519–526.

360.

Sreekala

Thomas

Neelakantan

NR.

Utilization of short oil palm empty fruit bunch fiber (OPEFB) as a reinforcement in phenol-formaldehyde resins: studies on mechanical properties. J Polym Eng. 1997;16(4):265–294.

361.

van den Oever

MJA

Bos

van Kemenade

Influence of the physical structure of flax fibres on the mechanical properties of flax fibre reinforced polypropylene composites. Appl Compos Mater. 2000;7(5–6):387–402.

362.

Williams

Wool

RP.

Composites from natural fibers and soy oil resins. Appl Compos Mater. 2000;7(5–6):421–432.

363.

Callister

WD.

Materials science and engineering: an introduction. New York: John Wiley & Sons; 2010.

364.

Shah

Schubel

Licence

et al. Determining the minimum, critical and maximum fibre content for twisted yarn reinforced plant fibre composites. Compos Sci Technol. 2012;72(15):1909–1917.

365.

Shah

DU.

Natural fibre composites: comprehensive Ashby-type materials selection charts. Mater Des. 2014;62:21–31.

366.

Dicker

MPM

Duckworth

Baker

et al. Green composites: a review of material attributes and complementary applications. Compos A: Appl Sci Manuf. 2014;56:280–289.

367.

Madsen

Thygesen

Lilholt

Plant fibre composites – porosity and volumetric interaction. Compos Sci Technol. 2007;67(7–8):1584–1600.

368.

Aslan

Mehmood

Madsen

Effect of consolidation pressure on volumetric composition and stiffness of unidirectional flax fibre composites. J Mater Sci. 2013;48(10):3812–3824.

369.

Shah

Schubel

Clifford

et al. The tensile behavior of off-axis loaded plant fiber composites: an insight on the nonlinear stress-strain response. Polym Compos. 2012;33(9):1494–1504.

370.

Baets

Plastria

Ivens

et al. Determination of the optimal flax fibre preparation for use in UD-epoxy composites. ICCM International Conferences on Composite Materials; 2011.

371.

Shamsuddin

Lee

Bismarck

Ductile unidirectional continuous rayon fibre-reinforced hierarchical composites. Compos A. 2016;90:633–641.

372.

Hajlane

Kaddami

Joffe

et al. Design and characterization of cellulose fibers with hierarchical structure for polymer reinforcement. Cellulose. 2013;20(6):2765–2778.

373.

Joshi

Drzal

Mohanty

et al. Are natural fiber composites environmentally superior to glass fiber reinforced composites?. Compos A. 2004;35(3):371–376.

374.

Kim

Dale

Drzal

et al. Life cycle assessment of Kenaf fiber reinforced biocomposite. J Biobased Mater Bioenergy. 2008;2(1):85–93.

375.

Duflou

Yelin

Van Acker

et al. Comparative impact assessment for flax fibre versus conventional glass fibre reinforced composites: are bio-based reinforcement materials the way to go?. CIRP Annals Manuf Technol. 2014;63(1):45–48.

376.

Garkhail

SK.

Composites based on natural fibres and thermoplastic matrices. London: Queen Mary University of London; 2001.

377.

Dhakal

Zhang

Richardson

MOW

et al. The low velocity impact response of non-woven hemp fibre reinforced unsaturated polyester composites. Compos Struct. 2007;81(4):559–567.

378.

Lee

Bismarck

Assessing the moisture uptake behavior of natural fibres. In: Zafeiropoulos

, editor. Interface engineering of natural fibre composites for maximum performance. Cambridge: Woodhead Publishing; 2011. p. 275–288.

379.

Baltazar-Y-Jimenez

Bismarck

Wetting behaviour, moisture up-take and electrokinetic properties of lignocellulosic fibres.

Cellulose. 2007;14(2):115–127.

Plant fibre-reinforced polymers: where do we stand in terms of tensile properties?

Abstract

Introduction

Current applications of plant fibre-reinforced polymer composites.

Estimated cost of various plant fibres in its loose form and E-glass fibres.

Plant fibres – a brief introduction

Mechanical performance of plant fibres compared to other types of natural and synthetic fibres. ρ, E, σ and ε denote fibre density, tensile modulus of the fibre, tensile strength of the fibre and fibre elongation-at-break, respectively.

Chemical composition of plant fibres

The chemical composition of various plant fibres.

Challenges associated with utilising plant fibres in composites

Variability in tensile properties of single plant fibres

Moisture uptake of plant fibres

Equilibrium moisture content of various plant fibres at 100% RH (unless indicated).

Adhesion between plant fibres and polymer matrices

Processing and manufacturing of plant fibre-reinforced polymer composites

Plant fibres as reinforcement for polymers

Comparison of the tensile performance of plant fibre-reinforced polymer composites with engineering/commodity polymers

Comparison of the mechanical performance of plant fibre-reinforced polymers with glass fibre-reinforced polymers

Lifecycle assessment (LCA) of plant fibre-reinforced polymers

Volume fraction of flax and glass fibres, as well as the mass of flax fibre-reinforced PP (in reference with 1 kg of glass fibre-reinforced PP) required to achieve the target design criteria for automotive application.

Outlook

Footnotes

Acknowledgements

Disclosure statement

ORCID

1

ORCID

References