Impact of stretchable weft yarn with varied configuration on the tensile properties of the seam of denim fabrics

Purpose The purpose of this study is to investigate the influence of different weft yarn types, elastane content and sewing thread linear densities on the seam-level tensile behaviour of stretch denim fabrics. While previous research has focused on the tensile behaviour of stretch denim, this study examines the mechanical response of seams, addressing a gap in understanding seam performance during body movements and its effect on wear comfort. Design/methodology/approach Three weft yarn types – cotton core spun, polyester core spun and polyester air-covered yarn – with varying elastane levels were used to create denim samples. Lapped seams were constructed and evaluated to assess their tensile behaviour. Findings The results of this study showed that seams constructed on fabrics made with polyester core spun and polyester air-covered yarns exhibited a noticeable decrease in modulus with increasing elastane content, thereby enhancing wear comfort. In contrast, seams of cotton core spun yarn fabric showed minimal change. Breaking loads were lower for seam fabrics than for those without seams, with polyester air-covered yarn fabric showing the highest breaking load among the others. Fabric type had the greatest impact on seam performance, followed by elastane content. The impact of sewing thread linear density was found to be less because of seam slippage. Originality/value This study provides a comparative analysis of how different weft yarn types and elastane content affect the tensile behaviour of seams in stretch denim, contributing valuable insights for optimising seam durability and comfort in stretch garments.