Determination of In-plane Shear Rigidity Modulus of Warp Knitted Non-Crimp Fabrics based on Bias Extension Experiment

Fabrics as reinforcement in composites due to its high performance and weight saving property, are progressively replacing metals in aerospace, automotive and other applications. During the composite forming process, many deformation mechanisms occur which affects the composites property, so it is necessary to understand their mechanical behavior for better simulation of the forming process during manufacturing as well as for other applications. In this paper, the in-plane shear rigidity modulus of glass warp knitted Non-Crimp Fabrics (NCFs) was experimentally investigated by using uniaxial bias extension (UBE) test. The force-displacement curves were recorded from a universal testing machine at low speed (static condition). The relation between normalized shear force and the shear angle was approximated to a polynomial function by a fifth degree, then the shear stress function was calculated. By analyzing deformation behavior and shear rigidity, the in-plane modulus of shear rigidity as a function to shear angle was delivered by the derivation of stress equations. The influence of the fabric structure and stitching pattern on the rigidity was also analyzed.