Strength variability of single flax fibres
- 409 Downloads
Due to the typical large variability in the measured mechanical properties of flax fibres, they are often employed only in low grade composite applications. The present study aims to investigate the reasons for the variability in tensile properties of flax fibres. It is found that an inaccuracy in the determination of the cross-sectional area of the fibres is one major reason for the variability in properties. By applying a typical circular fibre area assumption, a considerable error is introduced into the calculated mechanical properties. Experimental data, together with a simple analytical model, are presented to show that the error is increased when the aspect ratio of the fibre cross-sectional shape is increased. A variability in properties due to the flax fibres themselves is found to originate from the distribution of defects along the fibres. Two distinctive types of stress–strain behaviours (linear and nonlinear) of the fibres are found to be correlated with the amount of defects. The linear stress–strain curves tend to show a higher tensile strength, a higher Young’s modulus, and a lower strain to failure than the nonlinear curves. Finally, the fibres are found to fracture by a complex microscale failure mechanism. Large fracture zones are governed by both surface and internal defects; and these cause cracks to propagate in the transverse and longitudinal directions.
KeywordsAspect Ratio Cottonized Fibre Strain Behaviour Flax Fibre Polarise Optical Microscope
The authors gratefully acknowledge Stergios Goutianos and Hans Lilholt for helpful advices and Shahid Mehmood for technical assistance, and for valuable input on fibre defects. The research has been partly funded by the European Community’s Seventh Framework Programme under grant agreement no 214467 (NATEX), and grant no 274-07-0300 (WoodFibre3D) by the Danish Agency for Science, Technology and Innovation.
- 6.Virk AS (2010) PhD thesis, University of Plymouth, United KingdomGoogle Scholar
- 11.Cierpucha W, Kozlowski R, Mankowski R, Wasko J, Mankowski T (2004) Fibres Text East Eur 47:13Google Scholar
- 12.Harwood R, Nusenbaum V, Harwood J (2008) International Conference on Flax and Other Bast Plants Saskaaton Canada, p 118Google Scholar
- 13.Reme PA, Johnsen PO, Helle T (2002) J Pulp Pap Sci 28:122Google Scholar
- 18.Mehmood S (2009) Unpublished results: Risø National Laboratory for Sustainable Energy. Technical University of Denmark, DenmarkGoogle Scholar