Study on the single shear performance and failure mechanism of GFRP fasteners based on progressive damage model

Due to their lightweight and high-strength characteristics, composite fasteners have become one of the focal points in the field of composite material connections. This paper establishes progressive damage models for specimens with different connection methods. Through the implementation of the VUMAT subroutine based on the Hashin failure criteria, the single shear performance and damage processes of GFRP fasteners in bolt, screw, and stud connections are analyzed. The results indicate that bolts exhibit the highest single shear strength, followed by screws, with studs being the weakest, which is related to the structure of the specimens. The relative errors between the ultimate loads predicted by the finite element model and those obtained from experiments are 3.28%, 3.34%, and 5.49%, respectively. Bolts tend to approximate planar fracture characteristics, screw fracture surfaces show a pointed apex shape, while studs display stepped cracks. These findings align well with experimental results, verifying the reliability of the model.