Failure analysis of 2D C/SiC composite z-pinned/bonded hybrid single-lap joints

Z-pinned/bonded hybrid joints are widely used in the 2D C/SiC composite structures, whose mechanical behavior and failure mechanisms are directly related with the structure integrity. The hybrid joints for 2D C/SiC composite structures are formed by depositing SiC into the gap of z-pinned joints. To evaluate the SiC bonding effect, the tensile experiments for two kinds of z-pinned joints with and without bonded layer were conducted. It was proved that the failure modes of the pin were the tensile and shear failure, and the bonded layer was the interlaminar shear failure of the substrate plate instead of the shear failure of SiC bonded layer due to the smaller interlaminar shear strength. The bonded zone states of specimens were also examined, which were reproduced in the shell-fastener numerical model with surface-based cohesive behavior. Combining with shear strength theory, a numerical model is developed to study the failure processes of the hybrid joints. The SiC bonded zone areas can also greatly influence the failure response of the hybrid joints. The large SiC bonded layer zone can improve the shear strength of the joints. The failure of the joints is determined by the SiC bonded layer when the SiC bonded zone is large enough. This study can be helpful to evaluate and design the SiC bonded zone states of the hybrid joints in the engineering application.