1. Natural fibres as reinforcements for composites
Richard Cullen
and John Summerscales
Flax Field, Providence by Hazel Barker
From

2. Natural fibre properties
Natural Density Modulus Elongn Strength Diameter
(kg/m3) (GPa) (%) (MPa) (μm)
Animal
Silk
Seed
Coir
Cotton
Leaf
Sisal
Pineapple
Stem (bast)
Flax
Hemp
Jute
Kenaf
Man-made fibres
E-glass
S-glass
Aramid (K49)
High-strain CF
High-mod CF

3. Flax/Linseed (Linum usitatissimum L.)
Cultivars bred with an emphasis on either:
fibre (flax), or
seed (linseed)
Mike Felstead: Flax and linseed fibres as reinforcement for epoxy composites, BEng Composites, June 1995:
Materials
E-modulus (GPa)
UTS
(MPa)
Elongation (%)
Q: Queens flax
134±55
141±66
1.14±0.4
S: Silsoe flax
117±78
93±53
1.23±0.51
H: Seale-Hayne linseed
79±53
71±50
1.36±0.49

4. Growth stages (GS) 12 distinct growth stages in the flax plant:
cotyledon to growing point emerged
Growth stages 3 & 4
1st pair of true leaves unfolded to third pair of true leaves unfolded
Growth stage 5
stem extension
Growth stages 6, 7, & 8
buds visible to full flower
Growth stages 9, 10 & 11
late flower to brown capsule
Growth stage 12
seed ripe

5. Growth stages Life cycle of the flax 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
From J A Turner “Linseed Law” BASF (UK) Limited, 1987
via

6. Key resources Flax Council of Canada http://www.flaxcouncil.ca/
Interactive European Network for Industrial Crops and their Applications
Flax (Linen)

7. Hemp (Cannabis sativa L.)
Physical , Chemical and Pulping Characteristics of Hemp
Michael Karus: European hemp industry 2001: cultivation, processing, and product lines
Marianne Leupin: New processing with hemp

8. Jute (Corchorus) Corchorus capsularis. L. - white jute
Corchorus olitorius L. - Tossa jute.
second most common natural fibre, next to cotton, cultivated in the world
grown in Bangladesh, Brazil, China, India, Indonesia

9. Jute Corchorus capsularis. L. - white jute C. olitorius L. - Tossa jute.
The Golden Fibre
Biotechnology in jute fibre processing

10. Kenaf (Hibiscus cannabinus L.)
fibre plant native to east-central Africa.
common wild plant of tropical and subtropical Africa and Asia
grown for several thousand years for food and fibre
unique combination of long bast and short core fibres
two crops/year in Malaysia

11. Kenaf
PJ LeMahieu, ES Oplinger and DH Putnam Alternative Field Crops Manual: Kenaf, April
Charles S Taylor Kenaf: an emerging new crop industry, 1993 (in New Crops, 1993)
Daniel E Kugler Kenaf commercialisation: (in Progress in New Crops, 1996)
T Sellers, GD Miller, MJ Fuller, JG Broder and RR. Loper Lignocellulosic-Based Composites Made of Core From Kenaf: An Annual Agricultural Crop

12. Nettle (Urtica dioica)
Nettles yield ~ 8-10 tonnes fibre/acre
far stronger than cotton but is finer than other bast fibres such as hemp
much more environmentally friendly fibre crop than cotton, which requires more irrigation and agrochemical input

13. Nettle 24 v/o nettle/epoxy E/σ’ = 9 GPa/91 MPa
23 v/o nettle/phenolic E/σ’ = 5 GPa/13MPa
21 v/o flax/epoxy “strength and stiffness are more than twice as high”
Ann-Jeanette Merilä, Stinging nettle fibres as reinforcement in thermoset matrices, MSc Engineering/Materials Technology, Luleå University of Technology

14. STING Sustainable Technology In Nettle Growing
STING is a three and a half year LINK project sponsored by Defra through the Sustainable Technologies Initiative
Co-ordinated by De Montfort University

15. Crop Index
Purdue University Center for New Crops and Plant Products crops are listed alphabetically by genus and common name

16. From plant to fibre Harvest (combining or pulling)
Retting (dew-, wet-, stand- or enzyme-retting)
enzymes (e.g. pectinase digests pectin binder)
Decortication (scutching)
Hammer mill
Fluted rollers
Willower
Cleaning (removal of shive)
Carding (brushing/combing to align fibres)
product is known as sliver
Spinning (twisting to bind the fibres)
product is known as yarn or filaments

17. Environmental issues Economic issues
Depletion of soil nutrients/fertiliser
Competition from weeds/herbicides
Competition from animals/pesticides
Economic issues
Agricultural subsidies
Dependence on weather
Market price vs other producers

18. The future ? Extracting fibre without damage Effective coupling agents
cellulose chemistry instead of silanes
Environmental durability
barriers to prevent moisture absorption
sterilise fibres to prevent biodeterioration
Other issues ?