STRUCTURAL ANISOTROPY, FAILURE CRITERION, AND SHEAR-STRENGTH OF WOVENFABRICS

For structural and load-carrying applications, more detailed informati on about woven fabrics, which are increasingly used as reinforcements for composites, is desirable for design purposes. This paper investiga tes the issues related to woven fabric strength. First, the direction dependence or anisotropy of tensile strength as well as the breaking s train and initial modulus of the fabrics are examined experimentally. A harmonic expression is then adopted to approximate the experimental results so that this tensile strength anisotropy can be expressed anal ytically. Moreover, the Tsai-Wu failure criterion is used, assuming it is valid for woven fabrics, at least at the first quadrant where fail ure stresses are all tensile. Unknown coefficients in the failure crit erion are determined based on the experimental results. Fabric shear s trength is then predicted based on the measured uniaxial tensile stren gths of the fabric at the principal and off-axial directions. Influenc es of various directions of the off-axial tensile test on predictions of fabric shear strength are also studied.