Torsional properties of staple fibre plied yarns

D.G. Phillips, C.-D. Tran, W.B. Fraser & G.H.M. van der Heijden

A mathematical analysis of the mechanical governing equations applying to the torsional behaviour of multi-ply yarns under tension has been carried out. This analysis clearly shows that there are two components, a geometric component that determines the slope or gradient of the torque due to tension and a component that determines the yarn torque at zero applied tension (intrinsic torque) that depends on the fibre number, fibre moduli and diameter as well as the strand structural geometry. The effect of the ratio of the ply twist to the spinning twist of the single strands on the torque properties has been numerically analysed for two, three and four-ply yarns prepared from single 31 tex yarns. The model has been compared with experimental torque data for a range of two-ply yarns plied at different percentages of the singles spinning twist and also with different yarn histories and test environments. The experimental data reflect the trends identified by the model.

keywords: torque, tension, governing equations, torsion, bending, multi-ply yarn, zero torque condition, fibre diameter, yarn count, yarn history, experimental data, ply twist

The Journal of the Textile Institute 101, 595-612 (2010)