Shear Properties of Warp-Knitted Outerwear Fabrics

In this paper an experimental study is reported of the low-stress deformations in shear for a wide range of warp-knitted fabrics, including commercially-finished synthetic apparel outerwear fabrics, laboratory-produced wool/polyester samples, and a series of laid-in warp-knitted constructions. Features of fabric shear deformation and recovery curves such as their shape, asymmetry, linearity, and degree of hysteresis are discussed by analyzing the results in terms of elastic and frictional resistance to shear deformation. The effect of tension on fabric shear parameters is investigated. The shear behavior of warp-knitted fabrics is compared with corresponding properties of woven and double-knitted fabrics; it is shown that the laid-in warp-knitted structures exhibit much lower values of frictional shear stress and in most cases lower values of shear rigidity than do the ordinary warp-knitted structures. The effect of warp-knit construction on fabric shear behavior is examined for a series of laboratory-produced fabrics, and the effects of fabric relaxation are studied. Fabric shear properties are shown to depend largely on the inherent nature of the warp-knit construction ( viz. the combination of loop and underlap) and show very little systematic telationship with such structural variables as fahric thickness and weight per unit area of fabric. The effect of relaxation is found to be much less for shear deformation than the corresponding effect on bending behavior for warp-knitted fabrics.