Opening Behavior of Lockstitch Seams in Woven Fabrics Under Cyclic Loading Conditions

The opening behavior of lockstitch seams (seam type 1.01.01, SSa-1, stitch type 301 ) under cyclic loading conditions has been analyzed, using models of the slippage of yarns in the fabric and the deformation of the stitch itself. The extension properties of the sewing thread under constant cyclic loading conditions were included by using an empirical formula to predict the maximum strain in terms of the applied load and its number of repetitions. Similarly, an empirical formula was used to predict the amount of yarn slippage in woven fabric, in terms of the applied load and its number of repetitions. This formula was obtained from experiments in which the sewing threads in a lockstitch seam were replaced by pins. These results were combined to provide a method for predicting the deformation of a stitch under cyclic loading conditions. The amount of seam opening actually occurring was measured experimentally under different conditions and compared with the calculated values. Reasonable agreement was obtained, with the model explaining the influence of thread properties, stitch density, thread consumption, applied load, and the number of loading cycles. The model was therefore effective in predicting seam opening behavior under cyclic loading conditions.