Measuring the Twisting Rigidity of Woven Fabrics

An apparatus has been developed to determine twisting rigidities of woven fabrics by subjecting fabric samples to monotonically increasing twist. In order to avoid slack in the test specimen and permit a reliable measurement, tensioning weights are applied. The twisting moment acting on the fabric is measured, along with the in-plane load that is simultaneously developed by the coupling effect between the in-plane and out- of-plane deformation modes. The twisting deformation of the fabric is described to correlate the complex deformation with properties that can be measured, based on an elastic plate model. A plot of measured twisting rigidities versus preload yields a straight line that does not pass through the origin, and a small twisting rigidity at zero preload is graphically determined. The in-plane load caused by the twisting process is connected with the in-plane shear strain that relates twisting moment through one of the coupling rigidities.