Wool-fibre Crimp Part I: The Effects of Microfibrillar Geometry

Microfibrils differ in their geometrical arrangement between the orthocortex and the paracortex of a wool fibre. An investigation is reported as to whether these differences, combined with a large shrinkage perpendicular to the fibre direction as the fibre dries from an initial wet state, could account for the curvature of the fibre. The orthocortical microfibrils are characterised by ‘whorl-like’ structures, and the initial investigation models a single whorl as an assembly of uniform helices. A finite-element model is developed to extend the modelling to characterise a more realistic fibre. The model shows that, even with conservative assumptions regarding the internal geometry and shrinkage, realistic fibre curvatures are calculated, and this supports the hypothesis.