A Three-component Model of the Wool Fibre – Effects of Morphology, Elasticity and Intermediate Filament Arrangement on Fibre Stiffness

The contributing effects of wool fibre morphology have been ignored in early mechanical behavioural models, in which the wool fibre has been treated as a two-phase composite with parallel constituents. Here, the stiffness of wool cells and fibres are modelled in terms of their morphological characteristics and the stiffness of all phases. The stiffness of a wool fibre is derived from the stiffnesses of three components – the cuticle, orthocortex, meso/paracortex – and their proportions within the fibre. The mesocortex and paracortex are treated as one component due to their similar location within the fibre and structural similarity. The stiffness of the cuticle is calculated from the stiffnesses of the exocuticle and endocuticle on the basis of earlier experimental data. The stiffnesses of the orthocortices and meso/paracortices are modelled with respect to intermediate filament (IF or microfibril) angles, stiffnesses and the volume fractions of IFs and matrix. Although the addition of a fourth component could be a simple extension to the model, this three-component model gives the essential properties for the simulation of the mechanical behaviour of wool fibres. The developed model may give new insight into the relevance of internal fibre structure to single fibre behaviour affecting fibre assemblies in yarns and may provide guidance for sheep breeding programmes designed to improve properties such as wool prickle, resilience and bulk characteristics.