Four cotton covered cotton/polyester yarns were produced using both filaments and staple polyester fibers in the core. Three different spinning systems ( ring, friction, and tandem spinning processes) were used to produce the cotton covered yarns. For comparison, a 100% cotton yarn and a polyester/cotton random blend yarn were also made on a rotor spinning system. The six different yarns were then incorporated as filling yarns in a medium weight denim fabric which used 100% cotton rotor yarn in the warp direction. The fabrics were stone washed in the presence of a softener. The experimental yarns and the washed fabrics were evaluated for the whole range of quality and performance properties.

Major differences were observed in the stress-strain behavior of the experimental yarns. The breaking elongation of the tandem spun yarn was found to be higher than that of 100% cotton, ring spun filament-core, and friction spun staple-core yarns, while its work of rupture was found to be higher than that of 100% cotton, and friction spun staple-core yarns. Tandem spun yarn also showed the lowest initial tensile modulus among the six yarns. The friction spun staple-core yarn showed the lowest average breaking elongation and an unusually high variation in strength and elongation. Compared to the friction spun filament-core yarn, the ring spun filament-core yarn showed higher tensile strength but lower elongation and lower work of rupture. All the six yarns exhibited a near simultaneous rupture behavior under axial loading. Comparison of yarn evenness properties revealed that the yarns containing staple fibers in the core were in general more even compared to the filament-core yarns. Between the two staple-core yarns (friction and tandem), the tandem spun yarn showed lower CV% values over a wide range of cut lengths. This yarn also gave the minimum imperfection count.

The yarns posed no major weaving problems except that the tandem spun yarn caused excessive lint shedding on the loom. As expected, the two fabrics which used the filament-core yarns in the filling direction showed the highest tensile and tear strengths in the filling direction. However, the fillingwise tensile strength of the tandem spun yarn fabric was very close to that of the two fabrics that used the filament-core filling yarns and the fillingwise tear strength of the tandem spun yarn fabric fell between that of the fabrics representing the filament-core yarns and other all staple yarns.

Comparison of the low-stress mechanical behavior of the stone-washed denim fabrics showed that the fabric containing the tandem spun filling yarn gave not only the maximum compressive softness but also minimum bending and shear rigidities. This fabric, therefore, represented the best tactile quality and mechanical comfort performance among the experimental fabrics. Fabrics made from cotton covered filling yarns received better hand ratings from a panel of young judges compared to the fabrics made from the conventional rotor spun filling yarns.