Elastic behavior of twisted impregnated yarns

Textile composites are made using reinforcements in the form of straight strands or twisted yarns. In this paper, a mathematical model is proposed to model the elastic behavior of twisted impregnated yarns. The variation of twist in the filaments at different radial locations along the impregnated yarn has been considered. The model is based on treating the yarn as a continuum of an anisotropic elastic material with the local axis oriented along the helical lines of-twist. Elastic constants of a twisted impregnated yarn have been predicted by transforming the compliance matrix of a strand via a generalised transformation matrix to obtain the compliance matrix of an impregnated filament at a particular twist angle. The compliance values have then been integrated over the cross-section ofthe yarn by dividing the yarn into infinitesimal cylindrical elements to obtain the elastic properties of the yarn. The effects of migration and microbuckling on the elastic properties of twisted impregnated yarns have also been considered by using equivalent twist values.