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

Figures & data

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.

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).

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 cm^3 g^−1)	σ (MPa)	σ/ρ (MPa cm^3g^−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].

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].

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.

Table 5. Equilibrium moisture content of various plant fibres at 100% RH (unless indicated).

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].

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).

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.

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.

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.

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	vf, flax fibre (%)	vf, 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].

Faruk O, Bledzki AK, Fink H-P, et al. Progress report on natural fiber reinforced composites. Macromol Mater Eng. 2014;299(1):9–26.

 Web of Science ®Google Scholar

Bismarck A, Burgstaller C, 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.

 Web of Science ®Google Scholar

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

 Google Scholar

Lee K-Y, Delille A, Bismarck A. Greener surface treatments of natural fibres for the production of renewable composite materials. In: Kalia S, et al., editors. Cellulose fibers: bio- and nano-polymer composites. Berlin: Springer-Verlag; 2011. p. 155–178.

 Google Scholar

Bismarck A, Mishra S, Lampke T, et al. Plant fibers as reinforcement for green composites. In: Mohanty AK, et al., editors. Natural fibers, biopolymers and biocomposites. Boca Raton (FL): CRC Press; 2005. p. 37–108.

 Google Scholar

Thomason JL, Carruthers J, Kelly J, 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.

 Web of Science ®Google Scholar

Lee K-Y, Bharadia P, Blaker JJ, et al. Short sisal fibre reinforced bacterial cellulose polylactide nanocomposites using hairy sisal fibres as reinforcement. Compos A. 2012;43(11):2065–2074.

 Web of Science ®Google Scholar

Karnani R, Krishnan M, Narayan R. Biofiber-reinforced polypropylene composites. Polym Eng Sci. 1997;37(2):476–483.

 Web of Science ®Google Scholar

Mishra S, Tripathy SS, Misra M, 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.

 Web of Science ®Google Scholar

Lee K-Y, Ho KKC, Schlufter K, et al. Hierarchical composites reinforced with robust short sisal fibre preforms utilising bacterial cellulose as binder. Compos Sci Technol. 2012;72(13):1479–1486.

 Web of Science ®Google Scholar

Roulson D, Sain M, Couturier M. 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.

 Web of Science ®Google Scholar

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

 Web of Science ®Google Scholar

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

 Web of Science ®Google Scholar

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

 Web of Science ®Google Scholar

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

 Web of Science ®Google Scholar

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

 Google Scholar