Investigation on the Ratio of Bending Rigidity of Fabric to Yarn for Low Twist Filament Yarn

The ratio of bending rigidity of fabric to yarn in the case of low twist filament weft yarn was studied. Samples of fabrics with different weft densities were prepared; their other parameters were identical. After steam setting treatment, the bending rigidity of the fabrics was measured. The results showed that the rigidity of the fabric per thread in the weft direction decreases as the weft density increases. However; the theoretical equations suggest an inverse trend. To explain the difference, the thickness of the fabric was considered. It was shown that the reduction in fabric bending rigidity was due to the decrease in fabric thickness. The fixed end beam theory for the deflection of weft yarns as well as the flattening effect of low twist filament weft yarns were used to explain the reduction in fabric thickness when the weft densities increase. It was concluded that in the case of low twist filament weft yarn, Leaf's theoretical equations could not he used to predict the ratio of the bending rigidity of fabric to yarn.