Tightening torque characteristics of C/C composite threaded fasteners at room temperature

The tightening characteristic of threaded fasteners made of C/C composite under the conditions of no locking adhesive (non-glue coating) and plastering the locking adhesive (glue coating) were investigated. The experiments were done to investigate the correspondence between tightening torques and clamping force of C/C composite threaded fasteners under two conditions, meanwhile, both friction coefficients of thread and bearing-surfaces were analyzed. The results indicate that the clamping force of the glue coating state will be increased by 20%-82% more than that of non-adhesive state under the same tightening torque. Under the glue coating state, the curve of clamping force with tightening torque shows a good linear relationship. And for the non glue coating and glue coating states, the average friction coefficients of thread and bearing-surfaces for the non glue coating bolts are 0.41, 0.35 and 0.59, 0.41, respectively. There is a slight difference between two conditions about the allocation ratio of torque components.