| Wood fibre flexibility is known to play an important role in papermaking and to affect paper properties, and therefore a number of methods have been developed to measure this property. Although a large fraction of pulps consist of damaged fibres, past methods were developed to measure ideal uniform fibres. The major focus of this thesis was to explore the effect of fibre defects on fibre flexibility.;The fibre flexibility of two synthetic fibre types and three wood pulps were measured using a cantilever approach which related the tree end deflection of a fibre to its flexibility. There was no significant effect of either fibre cell wall dislocations, nodes or pits, i.e. common wood fibre defects, on fibre deflection, and hence the measured flexibility. In addition, and contrary to past observations, none of the fibre defects, including kinks, acted as hinges and no segmental bending around these defects was observed. Black spruce kraft and TMP fibres, as well as Jack pine kraft fibres were considered in this study.;The deflection of fibres fixed at one end under viscous loading conditions (cantilever) was also considered analytically. The fibre models included fibres with and without nodes, fibres with varying diameters, and fibres with abrupt changes in diameter. The free end deflections of these fibres were most sensitive to the diameter of the fibre at the fixed end. Simulated fibre nodes had very little effect on measured deflection, i.e. measured flexibility, except when close to the clamped end. The experimental results of this thesis are in good agreement with those obtained analytically. |
