The Investigation of Knitted Materials Bonded Seams Behaviour upon Cyclical Fatigue Loading

In this research uniaxial tension behaviour of knitted materials with bonded seams is analysed. The objects of the investigation were two types of knitted materials, having the same fibre composition (93 % PES, 7 % EL), but different in knitting pattern, i. e. plain single jersey and 1 × 1 rib. Bonded overlap seams were formed by changing the orientation of knitted materials strips, i. e. parallel/parallel, parallel/bias, parallel/perpendicular, bias/bias and bias/perpendicular. The strips of each knitted material were joined by two types of thermoplastic polyurethane (PU) films different in thickness (75 m and 150 m). Mechanical characteristics of bonded seams were defined in longitudinal tension direction direction. During uniaxial tension such parameters as maximal force Fmax (N) and maximal elongation ɛmax (%) were recorded from typical tension diagrams. The changes of tested specimens' strength and deformation were compared before and after cyclical fatigue tension the conditions of which were 50 cycles up to tension force F equal 24.5 N. The results have shown that changes before and after cyclical fatigue tension are mostly determined by knitting pattern of materials, the orientation of knitted materials strips in bonded seam, but not effected by thermoplastic polyurethane film