Strength variability of single flax fibres

Abstract

Due to the typical large variability in the measured mechanical properties of flax fibres, they are often employed only in low graded composite applications. The present work aims to investigate the reasons for the variability in tensile properties of flax fibres. It is found that the inaccuracy in the determination of the cross sectional area of the fibres is one major reason for the variability in properties. By applying the 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. The 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 behaviour (linear and nonlinear) of the fibres are found to be correlated with the amount of defects. The linear stress-strain curves tend to show higher tensile strength, higher Young's modulus, and 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. Revision of manuscript submitted to Journal of Materials ScienceReference Number JMSC22209 "Strength Variability of Single Flax Fibres" by Aslan et al. Dear EditorThe authors would like to thank the two referees for their constructive comments. The authors have now carefully considered each of the referees' reports which are shown in italic and have taken them into account as described below. Reviewer #1 This is a well-written paper which presents important results with clarity. It complements two papers I have recently seen in refereeing:(1) We have modified the fibre information accordingly at page 3, line 9-13. (1) Thomason et al on 'fibre cross section determination and variability in sisal and flax and its effect on fibre performance characterization' (Composites Science and Technology CSTE-D-11- Response to Reviewer Comments (3) Reference 8 should be Virk AS, Hall W, Summerscales J (not Amandeep, Wayne and Summerscales).This has been changed. (4)There are a few phrases which would benefit from sub-editing by a native English speaker.The manuscript has been corrected by a native English speaker, resulting in a number of grammatical corrections. Reviewer #2 This is a useful contribution to this subject area. There is little doubt that there are issues surrounding the variability in fibre properties and this study is a useful contribution to the debate.(1) It is for this reason that studies of textile fibres use the linear density method of measurement rather than relying upon the dubious notion of a regular (and circular) cross section. This needs to be mentioned in the text.The authors believe that the linear density method whi...

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