Structural evaluation of elastic core-spun yarns and fabrics under tensile fatigue loading

Nowadays the application of elastic core-spun yarns in fabric manufacturing and the clothing industry has increased tremendously. These yarns undergo tensile fatigue loading, a common phenomenon which occurs on some part of apparel such as the knee during wearing and use. In this research, cotton covered spandex filament core-spun yarns with 5 different draw ratios on the core part were subjected to 500, 1000 and 1500 tensile fatigue cyclic loads using a purpose-built instrument for fatigue behavior assessment. Also, the woven fabrics of these yarns were produced and underwent the same cyclic loadings. Tensile properties of fatigued yarns were measured by a tensile tester. The yarn deformation and displacement of core and sheath parts was traced via a microtomy technique and scanning electron microscopy (SEM) studies. Finally, the surface of the fatigued fabrics was studied by image processing to see any surface roughness and pilling due to straining. The results revealed the pronounced effect of draw ratio on the breaking strength and breaking elongation after cyclic loading. The obtained results showed that the samples produced by a 2.9 and 3.9 draw ratio of the core part had the highest and lowest level of breaking strength after 1500 tensile cyclic loading, respectively. The samples produced by a 2.9 draw ratio showed the highest decrease of breaking elongation after 1500 tensile cyclic loading. The likely mechanism of buckling behavior of core-spun yarns after experiencing strain energy is proposed. The results showed that after 1000 cyclic loads, the highest number of pills was countable on the fabric surface.