Investigation of fatigue behaviour of warp knitted fabrics under cyclic tension

Abstract In this investigation, the relationships between the warp knitted fabric fatigue behaviour and its structural parameters are examined as these are important factors influencing the mechanical properties of the fabric. For the experimental work, a uniaxial tensile fatigue tester with a single station has been designed and constructed. Cycling was continuously variable to a maximum of 115 cycles min-1, and the maximum stroke was adjustable up to 10 cm. A series of experiments was conducted to study the effect of stroke on the performance of various warp knitted structures with a view to changing the underlap length of the front guide bar or back guide bar (Tricot, Locknit, Reverse Locknit, Satin and Sharkskin) under cyclic tension. During fatiguing at different cycles and for various strokes, it was found that only insignificant differences were produced in the breaking tenacity of the polyester yarns and fabric samples, whereas their deformation and tensile modulus values increased and breaking extension decreased. The increase in front guide bar underlap, and simultaneously the increase in the underlap angle to the tensile direction, cause an increase in fabric deformation. In most samples, with the increase in underlap length in the front guide bar or back guide bar, the percentage of tensile modulus and the breaking extension % variations are greater than in Tricot fabric, but this change is more pronounced for samples with a longer front guide bar. These variations were attributed to the existence of space for yarn movement inside the fabric structure as the main fabric structural parameter, and also to the underlap length as the other parameter.