A STUDY OF THE MECHANICAL-PROPERTIES OF WOVEN SILK FABRICS .2. ANALYSIS OF THE SHEARING PROPERTIES OF WOVEN SILK FABRICS

The gap between the wrap and weft threads at their crossover points in woven silk fabrics is responsible for the very low values of shear stiffness and hysteresis of shear force in these fabrics. The existence of this gap is proved by using shear-deformation theory and making experiments on silk fabric. A quantitative determination of the gap is obtained by using strip-biaxial-extension experiments and measuring the retardation strain. The gap observed for woven silk fabrics is 6-7 μm. Since microscopical observation of the cross-section of silk fabrics does not show the gap, the gap measured by mechanical methods is called an 'effective gap'. The gap has a strong effect on the mechanical properties of silk fabrics, especially their shear properties.