Tensile Property and Fatigue Behaviour of Warp Knitted Fabrics

Several two fully threaded guide bar warp knitted structures with three different course densities (cpc) were knitted from polyester textured yarns, and their tensile properties and fatigue behavior were investigated. Tensile tests were applied to determine the tensile behaviour of the fabrics and obtain the parameters controlling fatigue behaviour. A number of cycle amplitudes, such as 2, 4, 6, 8, 10 and 12 mm, were applied in fatigue tests. The existence space for yarn movement and the length of the underlaps were considered as structural parameters influencing the corresponding mechanical behaviour. The results show that with an increase in the underlap length, the breaking strain decreases, and the breaking strain in fabrics with a longer underlap in the front guide bar is more than those with the same underlap length in the back guide bar. There is no meaningful relationship between cpc and breaking stress. Repeated extension causes stress relaxation and secondary creep and subsequent strain softening in warp knitted structures. The cyclically stabilised stress of fabrics was increased by raising the amplitude of extension and/or by increasing the length of the underlap. Also the cyclic stabilised stress of fabrics with a longer underlap in the back guide bar was higher than those with the same length of the underlap in the front guide bar. There is no distinguished trend between the cyclic stabilised stress and cpc of fabrics.

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Wykonano szereg dzianin z teksturowanej przędzy PES za pomocą maszyny z dwoma w pełni nawleczonymi grzebieniami igielnicowymi z różną gęstością rządkową a następnie badano ich właściwości wytrzymałościowe i zachowanie się przy użytkowaniu. Przy testach zużycia stosowano cykle obciążenia o amplitudach 2, 4, 6, 8, 10 i 12 mm. Jako parametry strukturalne determinujące parametry mechaniczne dzianiny uwzględniono istniejące przestrzenie dla ruchu włókna oraz długość rzutu grzebieni igielnicowych za igłami. Na podstawie wykonanych badań opisano szczegółowo zależności pomiędzy poszczególnymi parametrami.