Analysis of Spun Yarn Failure. Part I: Tensile Failure of Yarns as a Function of Structure and Testing Parameters

Abstract

The phenomenon of spun yarn failure is strongly dependent on the yarn structure namely, the configuration, alignment and packing of the constituent fibers in the yarn cross-section. The structure of yarn is solely determined by the methods of consolidating the fibers into yarns. In the present study, ring, rotor, air-jet and open-end friction spun yarns were produced from identical fibers and their structural parameters; namely, mean fiber extent, spinning-in-coefficient, helix angle of the fibers, percentage of different hooks and their extents, number of fibers in yarn cross-section and yarn diameter were measured. These yarns were subjected to uniaxial loading on the tensile testers with a large range of gauge lengths (0 to 500 mm) and strain rates (5 to 400 m/min). The results showed that the strength of yarns largely depends on the structure of the yarns, gauge lengths and strain rates. A combined effect of fiber extent in the yarn and gauge length influences the yarn strength. At high strain rates the yarn failure is dominated by the breakage of fibers rather than the slippage of fibers. Furthermore, the analysis of the region of yarn failure provides more direct evidences of the influence of yarn structure and testing parameters on the strength of different spun yarns.