Effects of parameters of stitching on pull-off carrying capacity of composite T-joint

Two-dimensional plane strain models were used to analyze the failure of stitched specimens. The interface failure condition was simulated with cohesive zone model, and the reinforcement effect of stitching was simulated with nonlinear spring elements inserted into the upper and lower interface of layer. The mechanical properties of the nonlinear spring elements (bridging law) were obtained based on micromechanical approach. The finite element analysis results agree well with test data. Based on the verified finite element model, the parametric analysis of stitching reinforcement in the flange area was done and parameters include the material, diameter of the stitch and density of stitching. The effects of parameters on pull-off carrying capacity of T-joint were studied. Results show that stitching can effectively improve the pull-off load capacity of T-joints and make the load capacity remain high under a large loading displacement. The pull-off load capacity of the T-joint increases as the diameter of stitch and density of stitching increase, and the influences of diameter and density are significant. The tensile strength of stitch is the main factor that affects the property of stitch and the pull-off strength of T-joint increases as the tensile strength of stitch increases, while the pull-off strength of T-joint increases as the tensile modulus of stitch decreases, but the influence of tensile modulus is not that significant of tensile strength.