Structural Anisotropy, Failure Criterion, and Shear Strength of Woven Fabrics

For structural and load-carrying applications, more detailed information about woven fabrics, which are increasingly used as reinforcements for composites, is desirable for design purposes. This paper investigates the issues related to woven fabric strength. First, the direction dependence or anisotropy of tensile strength as well as the breaking strain 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 analytically. Moreover, the Tsai-Wu failure cri terion is used, assuming it is valid for woven fabrics, at least at the first quadrant where failure stresses are all tensile. Unknown coefficients in the failure criterion are deter mined based on the experimental results. Fabric shear strength is then predicted based on the measured uniaxial tensile strengths of the fabric at the principal and off-axial directions. Influences of various directions of the off-axial tensile test on predictions of fabric shear strength are also studied.