Composites Design and Manufacture (Plymouth University teaching support materials)
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CAUTION: For the purpose of the Sustainable Composites pages, the materials described are those from natural sources, without prejudice to the results of any future Quantitative Life Cycle Analysis (QLCA) which may (or may not) make the case for these materials being more environmentally-friendly than equivalent systems manufactured from man-made fibres and synthetic resins.  The inclusion of any specific system here is not an endorsement of that product: potential users will need to fully consider each system in the context of their specific technical requirements.

The value of Eco-System Services


Natural fibres for the reinforcement of polymer matrix composites are normally the bast fibres (the structural fibres from plant stems) [1-6]. The principal plants used are flax, hemp, jute and kenaf. There is growing interest in the potential of nettle fibres.  A useful source for information on a wide variety of plants is the Crop Index at Purdue University Center for New Crops and Plant Products - crops are listed alphabetically by genus and common name.  ADAS has recently reviewed and analysed the breeding and regulations of hemp and flax varieties available for growing in the United Kingdom.

This page considers

The main advantages and disadvantages of natural fibres are listed in Table 1. 

Table 1: Main advantages and disadvantages of natural fibres  (from Stamboulis et al [7])
 ADVANTAGES  DISADVANTAGES
 Low cost  High moisture absorption
 Renewable resource  Poor dimensional stability (swelling)
 Low density  Poor microbial resistance
 High specific properties  Low thermal resistance
 High Young's modulus  Discontinuous fibre
 Good tensile strength  Anisotropic fibre properties
 Non-abrasive to tooling and moulds  Low transverse strength
 No skin irritations  Low compressive strength
 Low energy consumption  Local and seasonal quality variations
 CO2 neutral  Demand and supply cycles
 No residues when incinerated  
 Biodegradable (±)  

The main chemical constituents of natural fibres are listed in Table 2 [8].  The fibres themselves can be considered to be a composite with cellulose fibrils in a matrix of hemicelluloses, with lignin accumulating in the matrix as the plant ages [9], and pectin as the cementing/adhesive materials at the interface between the cellulosic and non-cellulosic substances [10].  The thermal degradation of natural fibres occurs in two stages: between 220-280°C mass loss is associated with degradation of the hemicelluloses (~28 kcal/mol), while between 280-300°C the lignin is lost (~35 kcal/mol) [9].  The carbohydrates (cellulose and hemicelluloses) are degraded by biological organisms.  The lignicellulosics undergo photochemical degradation due to the ultraviolet frequencies in sunlight [9].

Table 2:  The main chemical constituents of natural fibres, with relative abundance of the lignin components
(from S Laurichesse and L Avérous [8]).
Letterconstituentchemical natureformula   
 cellulose β-D-glucopyranose (Fig. 1)C6H10O5  
 hemicelluloses xylans, e.g D-xylopyranose   
  lignin: monolignol basic structures hardwood softwood grasses
G   coniferyl alcohol guaiacyl major

major

major
H   p-coumaryl alcohol p-hydroxyphenyl trace minor

minor

S   sinapyl alcohol siringyl major - major
 pectins complex polyscaccharides with
α-(1,4) linked D-galacturonic acid backbone [10]
   

Figure 1:  The chemical structure of cellulose (image source)

cellulose

The properties of natural fibres referenced to those of man-made fibre are shown in Table 3.

Table 3: Properties of natural fibres referenced to those of man-made fibre
(see PowerPoint for comparative bar-graphs of density, moduli and strengths)
  Density Modulus Elongation Strength Diameter Reference
  kg/m3 GPa % MPa μm  
Animal            
 Silk 1340 10 18-20 600   12
Grass            
 Bagasse 1250  17   290   13
 Miscanthus giganteus 190-240 3.1-3.7 - 23-28 - 14
Seed            
 Coir 1150 4-6 15-40 131-175 100-450 15
 Cotton 1520 27 6-12 200-800   12
Leaf            
 Abaca (manila hemp) 1500 [16]     980 [16] 25-40 [17] 16, 17
 Sisal 1450 10-22 3-7 530-640 50-300 15
 Pineapple 1440 35-82 1.6 413-1627 20-80 15
Bast (stem)            
 Jute 1520 60 2.0 860 200 [15] 12
 Hemp 1520 70 1.7 920   12
 Flax 1520 100 1.8 840   12
 Flax ariane 1530 58 ± 15 3.27 ± 0.4 1339 ± 486 17.8 ± 5.8 18
 Flax agatha 1530 71 ± 25 2.1 ± 0.8 1381 ± 419 15 ± 0.6 19
 Nettle (Urtica dioica)   87 ± 28 2.11 ± 0.81 1594 ± 640 19.9 ± 4.4 20
 Ramie (Boehmeria nivea) 1500 24.5 2.5 560 34 21
Man-made            
 E-glass 2550 71 3.4 3400   11
 S-glass 2500 85 4.6 4580   11
 Aramid (K49) 1440 124 2.5 2760 11.9 11
 High strain carbon 1820 200 1.3 2550 8.2 11
 High modulus carbon 2020 379 0.5 1720 11 11

However, the cross-section of natural fibres is normally neither circular nor within a tight distribution of apparent diameters.  A revised rule-of-mixtures has been proposed to recognise these differences from the case for man-made fibres:

VHS ROM equation

where the two new parameters are:

Table 4:  Fibre Area Correction Factors (FACF) for bast (and other) natural fibres sorted by increasing FACF.
Fibre Apparent diameter (μm) FACF Source
Flax 17.3±2.1 1.12 Brierley [24]
Curaua (leaf) 92.3 1.27 Terasaki et al [25]
Jute 58.6 1.297 Virk et al [23]: diameter from geometric mean projected width for 50 intervals through 180°
Jute 58.6 1.303 Virk et al [23]: median diameter from projected width for 50 intervals through 180°
Jute 58.6 1.375±0.485 Virk et al [23]: diameter from arithmetic mean projected width for 50 intervals through 180°
Jute 58.61.42 Virk et al [23]: diameter from measurements normal to the Grafil testcard
Kenaf 96.8 1.47 Terasaki et al [25]
Bamboo (grass) 136.1 1.60 Terasaki et al [25]
Sisal (leaf) 162-359 1.99 Thomason et al [26]
Flax 109-218 2.55 Thomason et al [26]
Flax  82±21 2.70 N Soatthiyanon [27, 28]

Manufacture of natural fibre reinforced polymer matrix composites

The manufacture of natural fibre reinforced thermoplastic matrix composites is constrained by the degradation temperautre of the fibres being similar to the melting point of many matrix systems.  To avoid damage to the fibres, in-situ polymerisation for liquid composite moulding (LCM) processes may be appropriate.

Modelling the manufacture of natural fibre composites is more complex than for the usual synthetic reinforcements due to absorption of the resin system, and consequent swelling of the fibre.  This then affects liquid composite moulding processes (e.g. RTM or RIFT) due to changes in the permeability of the reinforcement stack.

Deterioration of natural fibres

Various authors [31-36] have reviewed the fungal deterioration of cellulosic textiles.  Montegut et al [35] conclude that water that is physically bound to the fibres appears to be a controlling factor with both bacteria and actinomyceti needing a water activity reading a(w) of at least 0.90 (water has a(w) = 1.0).  Few species of fungus can grow below a(w) of 0.8, but severely low relative humidity can lower the a(w) below 0.4 and cause direct damage to the textile.   While humidity and temperature are the strongest influences on colony growth, there are subtle interactions between other factors such as a(w), pH, oxygen and light which determine the overall activity of the microorganisms.  The enzymes can continue to degrade fibre after the organism that produced them has been destroyed.

Simoncic et al [36] used an antimicrobial finish based on AgCl in combination with an organic-inorganic reactive binder (RB) and water- and oil-repellent finishes to control biodegradation of cellulosic (cotton) textiles.  AgCl/RB resulted in excellent microbial reduction and hence strong inhibition of biodegradation in soil burial tests.

References

  1. Caroline Baillie, Green Composites: polymer composites and the environment, Woodhead Publishing Limited, Cambridge, 2004. ISBN 1-85573-739-6.  PU CSH Library.
  2. R R Franck (editor), Bast and other plant fibres, Woodhead Publishing Limited, Cambridge, March 2005.  ISBN 1-85573-684-5.  PU CSH Library
  3. AK Mohanty, M Misra and LT Drzal, Natural Fibers, Biopolymers and Biocomposites, CRC Press/Taylor & Francis Group, Boca Raton FL, 2005.  ISBN 0-8493-1741-X.  PU CSH Library
  4. Richard Wool and X Susan Sun, Bio-Based Polymers and Composites, Elsevier, August 2005. ISBN 0-12-763952-7.  Overview.
  5. J Summerscales, N Dissanayake, W Hall and AS Virk, A review of bast fibres and their composites. Part 1: fibres as reinforcements, Composites Part A: Applied Science and Manufacturing, October 2010, 41(10), 1329-1335.
  6. J Summerscales, N Dissanayake, W Hall and AS Virk, A review of bast fibres and their composites. Part 2: composites, Composites Part A: Applied Science and Manufacturing, October 2010, 41(10), 1336-1344.
  7. A Stamboulis, CA Baillie and T Peijs, Effects of environmental conditions on mechanical and physical properties of flax fibers, Composites Part A: Applied Science and Manufacturing, 2001, A32(8), 1105-1115.
  8. S Laurichesse and L Avérous, Chemical modification of lignins: Towards biobased polymers, Progress in Polymer Science, July 2014, 39(7), 1266–1290.
  9. DN Saheb and JP Jog, Natural fiber polymer composites: a review, Advances in Polymer Technology, 1999, 18(4), 351-363.
  10. A Madhu and JN Chakraborty, Developments in application of enzymes for textile processing, Journal of Cleaner Production, 1 March 2017, 145, 114–133.
  11. NL Hancox, Fibre Composite Hybrid Materials, Elsevier Applied Science, Barking, 1981. ISBN 0-85334-928-2.  PU CSH Library
  12. TJ Reinhart, Engineered Materials Handbook 1: Composites, ASM International, 1987. ISBN 0-87170-279-7.  PU CSH Library
  13. A Balaji, B Karthikeyan and C Sundar Raj, Bagasse fiber - the future biocomposite material: a review, International Journal of ChemTech Research, 2014-2015, 7(01), 223-233.
  14. Richard Mark Johnson, Innovations and applications in the usage of miscanthus grass: executive summary, Dissertation submitted in partial fulfilment for the degree of Doctorate of Engineering, Warwick Manufacturing Group - School of Engineering - University of Warwick, September 2006 (reproduced here with the permission of Kerry Kirwan).
  15. N Chand, RK Tiwary and PK Rohatgi, Resource structure properties of natural cellulosic fibres - an annotated bibliography, Journal of Materials Science, 1988, 23(2), 381-387.
  16. WD Brouwer, Natural Fibre Composites in Structural Components: Alternative Applications for Sisal?, Seminar: Common Fund for Commodities - Alternative Applications for Sisal and Henequen, Food and Agriculture Organization of the UN (FAO) and the Common Fund for Commodities (CFC), Rome, 13 December 2000.
  17. RM Rowell, AR Sanadi, DF Caulfield and RE Jacobson, Utilization of Natural Fibers in Plastic Composites: Problems and Opportunities,
    http://www.fpl.fs.fed.us/documnts/pdf1997/rowel97d.pdf, accessed 22 December 2006 at 12:23.
  18. C Baley, Analysis of the flax fibres tensile behaviour and analysis of the tensile stiffness increase, Composites Part A: Applied Science and Manufacturing, July 2002, 33(7), 939-948.
  19. K Charlet, JP Jernot, M Gomina, J Bréard, C Morvan and C Baley, Proceedings of the 12th European Conference on Composite Materials (ECCM-12), Biarritz - France, August/September 2006.
  20. E Bodros and C Baley, Study of the tensile properties of stinging nettle fibres (Urtica dioica), Materials Letters, 15 May 2008, 62(14), 2143-2145.
  21. Koichi Goda, MS Sreekala, Alexandre Gomes, Takeshi Kaji, Junji Ohgi, Improvement of plant based natural fibers for toughening green composites - effect of load application during mercerization of ramie fibers, Composites Part A: Applied Science and Manufacturing, December 2006, 37(12), 2213-2220.
  22. AS Virk, W Hall and J Summerscales, Modulus and strength prediction for natural fibre composites, Materials Science and Technology, 2012, 28(7), 864-871.
  23. AS Virk, W Hall and J Summerscales, Physical characterisation of jute technical fibres: fibre dimensions, Journal of Natural Fibres, 2010, 7(3), 216-228.
  24. MJ Brierley, Fibre area correction factor (FACF) for flax fibre reinforcements, BEng (honours) Mechanical Engineering with Composites project report, University of Plymouth, April 2014.
  25. Y Terasaki, J Noda and K Goda, Strength evaluation of green composite with variation in cross-sectional area of plant-based natural fibers, Advanced Materials Research, August 2009, 79-82, 235-238 [Special issue on Multi-Functional Materials and Structures II edited by Y Yin and X Wang].
  26. JL Thomason, J Carruthers, J Kelly and G Johnson, Fibre cross-section determination and variability in sisal and flax and its effects on fibre performance characterisation, Composites Science and Technology, 04 May 2011, 71(7), 1008–1015.
  27. Niphaphun Soatthiyanon, Separation and characterisation of elementary kenaf fibres as reinforcement in high-density polyethylene-matrix composites and tensile behaviour of flax fibres as reinforcement in vinyl ester-matrix composites, PhD thesis, University of New South Wales, 2014 (restricted until July 2016).
  28. N Soatthiyanon, A Crosky, and MT Heitzmann, Comparison of experimental and calculated tensile properties of flax fibres, In D Fernando, J-G Teng and JL Torero (editors), Proceedings of the Second International Conference on Performance-based and Life-cycle Structural Engineering (PLSE 2015), Brisbane QLD, Australia, 9-11 December 2015, 116-120.
  29. J Summerscales, W Hall and AS Virk, A fibre diameter distribution factor (FDDF) for natural fibre composites, Journal of Materials Science, September 2011, 46(17), 5876-5880.
  30. RGG Siu, Microbial Decomposition of Cellulose, Reinhold Press, New York, 1951.
  31. JW Howard and FA McCord, Cotton quality study IV: resistance to weathering, Textile Research Journal, February 1960, 30(2), 75-117.
  32. RS Mahomed, Chapter IX in H Mark, NS Wooding and SM Atlas (editors), Chemical Aftertreatment of Textiles, Wiley-Interscience, New York, 1971.
  33. TL Vigo,, Protection of textiles from biological attack, in Lewin and Sello, Handbook of Fiber Science and Technology: Volume II: Chemical Processing of Fibers and Fabrics. Functional Finished. Part A, Marcel Dekker, New York, 1983, 367-427.
  34. D Montegut, N Indictor and RJ Koestler, Fungal deterioration of cellulosic textiles: a review, International Biodeterioration, 1991, 28(1-4), 209-226.
  35. B Simoncic, B Tomsic, B Orel and I Jerman, Biodegradation of Cellulose Fibers, Nova Science Publishers, 18 Aug 2010. ISBN-13: 978-1-61668-154-8.

Flax (Linum usitatissimum L.) fibres

Flax (grown for fibre) and linseed (grown for seed oil) are cultivars: varieties of the same plant bred with an emphasis on the required product.  In the UK the flax plant is normally sown in March-May and may grow to one-metre high dependent on the variety (there are 180 species [F1]).  The Growing Flax page of the Flax Council of Canada (FCC) website [F2] is an especially useful resource giving comprehensive details of the husbandry of this plant:

The life cycle of the plant consists of a 45 to 60 day vegetative period, a 15 to 25 day flowering period and a maturation period of 30 to 40 days and is illustrated in Turner [F3] and the following images from Turner are accessible below via the respective links from the FCC website [F2].  There are 12 distinct growth stages in the flax plant (Table 5):

Table 5: Growth stages and characteristics for flax
Growth Stage  Characteristics
1 & 2  cotyledon to growing point emerged
3 & 4  1st pair of true leaves unfolded to third pair of true leaves unfolded
5  stem extension
6, 7, & 8  buds visible to full flower
9, 10 & 11  late flower to brown capsule
12  seed ripe

The typical production cycle for flax fibres [F3] is:

A similar route is followed for the other bast fibres.  Subsequent treatments may be applied to natural fibre textiles to promote physical and/or chemical adhesion to the matrix for composites.  Similar enhancements may be achieved by modification of the matrix, e.g. poly(propylene-co-maleic anhydride) instead of PP, or by the inclusion of compatibilising agents in the matrix to bridge the properties of the hydrophilic fibre and the hydrophobic matrix.

The hierarchy of flax fibres from nano- to micro-scale is shown in Figure 2 with typical dimensions indicated in Table 6.

flax fibre hierarchy

Figure 2: The hierarchy of flax fibres.  Fibre bundles, known as technical fibres, are produced by mechanical decortication (breaking, scutching and hackling) and are ~1 m long and consist of ~10–40 elementary fibres, known as single fibres.
The elementary fibres have lengths of between 20-50 mm and diameters between 5-35 μm.  (reproduced from Harriëtte Bos, Jörg Müssig and Martien JA van den Oever in Composites Part A).

Table 6: Dimensions of the elements of plant fibres [11]
Element "Diameter" (nm)
Cellulose microfibril 2-4 nm
Cellulose mesofibril 200 nm
Cellulose macrofibril 100-200 nm
P 200-500 nm
S1 500-2000 nm
S2 5000-10000 nm
S3 500-1000 nm
P+S1+S2+S3 6200-13500 nm

The elementary fibre is normally considered to be a series of contiguous concentric tubes [F12, F13]:

At the end of life, there is potential for controlled degradation of cellulose fibres by composting or other methods.

Kvavadze et al [F14a/b] found bast fibres in clay in the Dzudzuana cave in Georgia.  The specific layer where 488 fibres were found was 14C radiocarbon dated to 32,000-26,000 years (before present).  Kvavadze et al used optical and electron microscopy to charactetise the fibres as flax, but Bergfjord et al [F14c] suggested they could be a different bast fibre given that only flax or cotton were used as comparators.  Kvadadze responded that specific traits associated with flax were evident in the analysed fibres.

In 1941, flax fibres (and hemp) were used in resin matrix composites for the bodywork of a Henry Ford car [F1].  Flax is amongst the natural fibres now finding use in thermoplastic matrix composite panels for internal structures (door panels, parcel shelves and boot linings) in the car industry.

References (F-series)

  1. Anna Lewington, Plants for People, Eden Project Books/Transworld Publisher, London, 2003.  ISBN 1-903-91908-8.  PU CSH Library.
  2. Flax Council of Canada
  3. John Anthony Turner “Linseed Law: A handbook for growers and advisers”, BASF (UK) Limited, Hadleigh - Suffolk, June 1987.  ISBN 0-9502752-2-0.  PU CSH Library.
  4. HSS Sharma, PC Mercer and AE Brown, Review of recent research on the retting of flax in Northern Ireland, International Biodeterioration, 1989, 25(5), 327-342.
  5. A Bezazi, A Belaadi, M Bourchak, F Scarpa and K Boba, Novel extraction techniques, chemical and mechanical characterisation of Agave americana L. natural fibres, Composites Part B: Engineering, November 2014, 66, 194-203.
  6. Lifang Liu, Qianli Wang, Zhaopeng Xia, Jianyong Yu and Longdi Cheng, Mechanical modification of degummed jute fibre for high value textile end uses, Industrial Crops and Products, January 2010, 31(1), 43-47.
  7. Du Bing and Zheng Laijiu, Bio-degumming process on jute fiber for textile, Journal of Biotechnology, October 2008, 136 supplement, S474.
  8. R Harwood, V Nusenbaum and J Harwood, Cottonisation of flax, International Conference on Flax and Other Bast Plants (Fiber Foundations - Transportation, Clothing and Shelter in the Bioeconomy), Saskatoon (Saskatchewan), CANADA, 21-23 July 2008, Paper ID #22, pages 118-128. ISBN 978-0-9809664-0-4.
  9. CA Farnfield and PJ Alvey, Textile Terms and Definitions - seventh edition, The Textile Institute, Manchester, 1975.  ISBN 0-900739-17-7.
  10. L Yan, Potentials of plant fibre reinforced composites in views of mechanical and physical performances, First International Conference on Advanced Composites in Marine Engineering (ICACME 2013), Beijing, 11 September 2013.
  11. C Baley, A Le Duigou, A Bourmaud, P Davies, M Nardin and C Morvan, Reinforcement of polymers by flax fibers: role of interfaces, Chapter 6 in W Smitthipong, R Chollakup and M Nardin (editors), Bio-Based Composites For High-Performance Materials: from strategy to industrial application, CRC Press, Boca Raton FL, 2015, pp 87-112. ISBN 978-1-4822-1448-2.
  12. DU Shah, Developing plant fibre composites for structural applications by optimising composite parameters: a critical review, Journal of Materials Science, September 2013, 48(18), 6083-6107.
  13. M George, M Chae and DC Bressler, Composite materials with bast fibres: structural, technical, and environmental properties, Progress in Materials Science, October 2016, 83, 1-23.
  14. (a)  E Kvavadze, O Bar-Yosef, A Belfer-Cohen, E Boaretto, N Jakeli, Z Matskevich and T Meshveliani, 30,000 years old wild flax fibers - testimony for fabricating prehistoric linen, Science, 11 September 2009, 325(5946), 1359-1361.
    (b)  Corrections and Clarifications, Science, 16 October 2009, 326(5951), 366.
    (c)  C Bergfjord, S Karg, A Rast-Eicher, M-L Nosch, U Mannering, RG Allaby, BM Murphy, B Holst, Comment on “30,000-Year-Old Wild Flax Fibers”, Science, 25 June 2010, 328(5986), 1634.
    (d)  E Kvavadze, O Bar-Yosef, A Belfer-Cohen, E Boaretto, N Jakeli, Z Matskevich and T Meshveliani, Response to Comment on “30,000-Year-Old Wild Flax Fibers”, Science, 25 June 2010, 328(5986), 1634.

Background material includes:

For review papers on flax fibres follow the link.
Published papers on natural fibres ~ flax


Hemp (Cannabis sativa L.) fibres

Hemp is an annual plant native to central Asia and known to have been grown in China over 4500 years ago [H1].  It probably reached central Europe in the Iron Age (circa 400 BC) and there is evidence of growth in the UK by the Anglo-Saxons (800-1000 AD).  It does not require fertiliser, herbicides or pesticides to grow well (and hence is potentially of great interest in the context of sustainability).  In suitable warm conditions, it can grow to 4 metres in just 12 weeks.

In 1941, hemp fibres (and flax) were used in resin matrix composites for the bodywork of a Henry Ford car which was able to withstand ten-times the impact on an equivalent metal panel [H1].  Hemp is amongst the natural fibres now finding use in thermoplastic matrix composites for internal structures (door panels, parcel shelves and boot linings) in the car industry.

H1. Anna Lewington, Plants for People, Eden Project Books/Transworld Publisher, London, 2003. ISBN 1-903-91908-8.

Background material includes:

EYH logo

Jute (Corchorus capsularis. L. - white jute or C. olitorius L. - Tossa jute) fibres

Jute is the second most common natural fibre (after cotton) cultivated in the world.  It is an annual plant that flourishes in monsoon climates and grows to 2.5-4.5 m [J1].  It is primarily grown in Bangladesh, Brazil, China, India and Indonesia.  Jute-based thermoplastic matrix composites find a substantial market in the German automotive door-panel industry (growing from 4000 tons in 1996 to over 21000 tons in 1999 and rising) [J1].

J1. Anna Lewington, Plants for People, Eden Project Books/Transworld Publisher, London, 2003. ISBN 1-903-91908-8.

Background material includes:

For review papers on jute fibres follow the link.


Hibiscus (kenaf: H. cannabinus L. and roselle (H.sabdariffa L.) fibres

Kenaf is a fibre plant native to east-central Africa, and a common wild plant of tropical and subtropical Africa and Asia.  It has been grown for several thousand years for food and fibre.  The plant has a unique combination of long bast with short core fibres in place of the hollow core.  Strong interest is being shown in this plant in Malaysia as it is fast growing and hence can yield two crops/year in the local climate.

Roselle bast fibres have potential as the reinforcement for composites (see the review papers link below).

Background material includes:

For review papers on kenaf fibres follow the link.
For review papers on roselle fibres follow the link.
Published papers on natural fibres ~ kenaf


Nettle (Urtica dioica) fibres

Nettles yield ~ 8-10 tonnes fibre/acre [N1] and are far stronger than cotton but finer than other bast fibres such as hemp.  They are a much more environmentally friendly fibre crop than cotton, which requires more irrigation and agrochemical input.

Merilä [N2] has reported elastic moduli and strengths for nettle fibre composites as in Table 7:

Table 7: Characteristics of nettle fibre composites [N2]
 Composite Modulus Strength
 24 v/o nettle/epoxy 9 GPa 91 MPa
 23 v/o nettle/phenolic 5 GPa 13 MPa

whereas 21 v/o flax/epoxy was reported to have “strength and stiffness are more than twice as high”.

Lewington [N3] states that "during the Second World War ... Britain's Ministry of Aircraft Production experimented with the use of a very strong, high-grade paper made from nettle fibre for reinforcing plastic aircraft panels as well as gear wheels and other machine parts".

N1. http://jacksonsrow.topcities.com/tikun_olam/nettle.html
N2. Ann-Jeanette Merilä, Stinging nettle fibres as reinforcement in thermoset matrices, MSc Engineering/Materials Technology, Luleå University of Technology, 2000.
N3. Anna Lewington, Plants for People, Eden Project Books/Transworld Publisher, London, 2003. ISBN 1-903-91908-8.  PU CSH Library.
N4. J Dreyer and G Edom, Chapter 9.5: Nettle, In RR Franck, Bast and other Plant Fibres, Woodhead Publishing, Cambridge, 2005.  ISBN 1-85573-684-5.   PU CSH Library
N5.  IGP Agus Suryawan, NPG Suardana, IN Suprapta Winaya, IW Budiarsa Suyasa and TG Tirta Nindhia [27 references], Study of stinging nettle (urtica dioica l.) fibers reinforced green composite materials: a review, 2017 IOP Conference Series: Materials Science and Engineering, 2017, 201, 012001, 1-7.  7th International Conference on Key Engineering Materials (ICKEM 2017), Penang - Malaysia, 11-13 March 2017.

For review papers on nettle fibres follow the link.


Other potential natural reinforcement fibres

Animal fibres:

Shah et al asked whether silk might become an effective reinforcing fibre, and made property comparisons between silk, flax and glass reinforced composites [A1].

Bamboo fibre:

BEWARE of fibres marketed as "bamboo".  Whilst some naturally retted bamboo fibre is commercially available (albeit scarce), the significant majority should be labelled as "bamboo viscose" as it is chemically processed to solution (similar to Lyocel, Modal®, Tencel® made from wood) before re-spinning into regenerated cellulosic fibre. The processing can significantly compromise any "green" claims for the regenerated fibre [B1].

Cereal crops:

Mamun et al have consdered the use of maize, oat, barley and rye fibres as reinforcements in composites [C1].

References

A1. DU Shah, D Porter and F Vollrath, Can silk become an effective reinforcing fibre? A property comparison with flax and glass reinforced composites, Composites Science and Technology, 12 September 2014, 101, 173-183.

B1. Anon., Bamboo and the FTC, https://oecotextiles.wordpress.com/category/fibers/bamboo/ accessed on 04 November 2014.

C1: AA Mamun, HP Heim and AKBledzki, The use of maize, oat, barley and rye fibres as reinforcements in composites Chapter 15 in Biofiber Reinforcements in Composite Materials, 2015, 454-487.


Further reading

  1. RR Franck, Bast and other plant fibres, Woodhead Publishing, Cambridge, March 2005.  ISBN 1-85573-684-5.  PU CSH Library
  2. AK Mohanty, M Misra and LT Drzal, Natural fibers, biopolymers, and biocomposites, Taylor and Francis, Boca Raton FL, 2005. ISBN 978-0-8493-1741-5.  PU CSH Library
  3. AD Muir and ND Westcott, Flax: the genus linum, CRC Press, London, 2003.  ISBN: 978-0-415-30807-6.  PU CSH Library.
  4. K Pickering, Properties and performance of natural-fibre composites, Woodhead Publishing, Cambridge, 2008. ISBN-13: 978 1 84569 267 4.
  5. HSS Sharma and CF van Sumere - The biology and processing of flax, M Publications, Belfast, 1992. ISBN 0-951996-30-4.  PU CSH Library
  6. JA Turner, Linseed law: a handbook for growers and advisers, BASF, Hadleigh, 1987. ISBN 0-950275-22-0.  PU CSH Library.
  7. FT Wallenberger and N Weston, Natural fibers, plastics and composites, Springer, 2004,  ISBN 978-1-4020-7643-5.
  8. SV Joshi, LT Drzal, AK Mohanty and S Arora - Are natural fiber composites environmentally superior to glass fiber reinforced composites?, Composites Part A: Applied Science and Manufacturing, 2004, 35(3), 371-376.
  9. A Stamboulis, CA Baillie and T Peijs, Effects of environmental conditions on mechanical and physical properties of flax fibers, Composites Part A: Applied Science and Manufacturing, August 2001, 32(8), 1105-1115.
  10. Peter Zugenmaier - Conformation and packing of various crystalline cellulose fibers, Progress in Polymer Science, 2001, 26(9), 1341-1417.
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Updated by John Summerscales on 25-Sep-2018 10:37. Terms and conditions. Errors and omissions. Corrections.