Effect of Z-pin parameters on pull-off carrying capacity of composite T-joints

Two-dimensional plane strain models were used to analyze the failure of Z-pin reinforced T-joint specimens. The cohesive zone model was used to simulate the interface failure, and the reinforcement effect of Z-pin was simulated by the inserting of nonlinear springs into the upper and lower interfaces of delamination. The mechanical properties (bridging law) of nonlinear spring were obtained by micromechanical approach. The numerical results agree well with the testing values. Based on the verified finite element method, the effects of the diameter, density and inserting angle et al of Z-pin on the pull-off carrying capacity of T-joints were studied. Results show that Z-pin reinforcement can effectively improve the pull-off carrying capacity of T-joints and delay the decrease of the load after peak loading significantly compared to the T-joints before Z-pin reinforcement. The pull-off carrying capacity of T-joint increases as the diameter and density of Z-pin increase and decreases as the inserting angle of Z-pin increases. In the angle range investigated, the pull-off carrying capacity of T-joints reaches the best when the inserting angle is 60°. The effect of diameter and density of Z-pin on pull-off carrying capacity is much more significant than that of inserting angle.