Fibre cross-section determination and variability in sisal and flax and its effects on fibre performance characterisation

The results of a study on the measurement of fibre cross-section and its variability in flax and sisal fibres are presented. Cross-section values obtained from fibre “diameter” measurements were more than double the values obtained from actual observation of cross-sections of the same individual fibres. The overall conclusion is that fibre “diameter” measurement is not an attractive method for accurate estimation of cross-sectional area of these natural fibres. This conclusion is significant for researchers engaged in micromechanical investigation of natural fibre composites since differences in fibre cross-section translate directly into differences of the same magnitude in the values obtained for the fibre modulus and strength. The error in fibre cross-section introduced by the “diameter” method scales with the average fibre “diameter” which may also result in erroneous observations of fibre modulus and strength scaling inversely with natural fibre “diameter”. The difference in average cross-section observed from fibre to fibre was significantly greater than the variation along the length of each individual fibre. The minimum to maximum cross-section variability of individual flax fibres was found to be approximately twice that observed for sisal fibres.