Some microrheological aspects of wood-pulp fibres subjected to fatigue loading

Wood-pulp fibres are recognized as concentrically-layered, laminated composite tubes of structural reinforcing material, the cellulose microfibrils, embedded in a cementing matrix of hemicellulose and lignin. When the single fibres are subjected to cyclic mechanical action, their morphological behaviour is characterized by the fatigue growth of micro-voids and surface damage which individually and collectively give rise to stress concentrations, and eventually crack development. The progressive damage phenomena, evinced by the surface imaging and optical sectioning techniques through utilizing confocal laser scanning microscopy, are understood to be consequences of the cumulative material micromechanical degradation and subsequent microstructural breakdown of the cellulose microfibrillar framework. This structural breakdown is believed to effect the fibrillation and flexibilization of the fibres.