Tensile testing of single fibres

Abstract

Glass, flax and aramid fibres are used widely in making composites. These fibres have diameter between 10-20 µm and these are converted to yarn/roving to make woven preforms. Similarly, paper is made from individual cellulose fibres, but in the form of nonwoven mat. Fibres such as flax, jute, viscose and hair are widely used in textile products. These fibres differ greatly in chemical composition, homogeneity and degree of crystallinity. Fibres are solid in nature, but some of them are partly hollow having lumen (flax, pulp) or medulla (hair) in their central axis. Tensile testing of these short length fibres is crucial for many applications, but it is tedious due to their small diameters (>100 µm) and small loads (mN) required for fracture. Paper frame technique adopted to test these single fibres is discussed and corresponding stress-strain diagrams are compared between glass, hair and cellulose fibres. Fractography of these fibres were also carried out using scanning electron microscopy. Nanoindentation was also performed on single fibre cross-sections to measure the modulus. Since the fibres chosen have different packing geometry and crystallinity in different directions, indentation modulus revealed different value compared to tensile modulus. But glass fibre revealed 70 GPa of modulus in both tensile and nanoindentation tests, because it is a isotropic fibre. Tested fibres have strength from anywhere between 200-3000 MPa and elongation ranging from 4% to 45 %. Weibull statistics was also performed and weibull modulus was found to be low for natural fibres compared to man made fibres.