Detailed characteristics of shear stiffness for coated biaxial warp-knitted fabrics subjected to coupled shear-tension loads

Abstract

In order to reveal shear deformation mechanisms of architectural non-crimp fabric (NCF) composites, detailed shear stiffness-nonlinearities for a typical coated warp-knitted NCF composite under shear-tension coupling loading were studied from experimental investigation and FEA models. Shear-tension coupling effects on shear stiffness of the NCF composite were investigated for different stress states. Its shear stiffness shows significant nonlinear characteristics which are highly tensile stress level (TSL) related, and therefore a critical TSL value was obtained for the studied material. Moreover, a new method for determination of shear stiffness was proposed, and its feasibility was verified by FEA simulation using UMAT. In addition, differences in shear stiffness and micro-deformation mechanisms between NCF and plain-woven fabric (PWF) composites were analyzed specifically. Apparently, the yarn-to-yarn compression on the yarns could contribute to the different stiffness variations between these two composites.