Study of load distribution in the threads of composite fasteners

Three dimensional finite element model of composite fastener was established based on Abaqus to predict the thread load distribution of composite fasteners. In order to simulate the real situation, the nut was placed on an elastic foundation and the tension-compression modulus asymmetry of C or SiC matrix composites was considered by Abaqus users' subroutine USDFLD. Furthermore, Yamamoto's method for the metal threaded connections was empirically extended to the connections by C or SiC matrix composites with special consideration of the anisotropy and tension-compression modulus asymmetry. The effectiveness of the extended Yamamoto's method (EYM) was validated by finite element method (FEM) for different materials and different geometry parameters. The results show that the load distribution of composite fasteners is usually more uniform than that of the metal fasteners. In addition, the nonuniformity of load distribution increases with the pitch-to-diameter ratio, but the relative rotation of bolt and nut almost have no effect on the load distribution.