Micromechanics of Cellulose Fibres and Their Composites

Cellulose fibres such as flax, hemp, viscose and lyocell were studied with respect to their use as reinforcing agents in composites. Initially, these fibres are subjected to single fibre tensile tests, and their adhesion with polypropylene and epoxy matrices was determined by application of a microbond technique. Unidirectional epoxy composites with fibre rovings and short fibre–epoxy composites with needle punched nonwovens were manufactured by means of compression moulding. Composites were subjected to mechanical vibrations, bending and tensile tests. Interfacial adhesion was also studied at the macro-level by means of double-notch shear test and scanning electron microscopy. Lyocell fibres performed equally well in comparison with natural cellulose fibres when the dimensional variability was taken into consideration, but less well than Glass fibres at both micro- and macro-levels. The low yield strength and high failure strain observed in the stress–strain diagram of lyocell and lyocell–epoxy composites can be the critical parameter in finding new applications for these biodegradable composites.