Fatigue Life of Single-lap Composite Samples over Tightening Torque of Bolted Joints

The effects of clamping torque on the fatigue life behavior of single-lap composite bolted joints were examined using experimental and numerical techniques. Fatigue tests were performed on composite samples while torques applied on the bolted joints were 1.5, 3, and 8 N.m. Experimental results demonstrated an increase in fatigue life as high as 4 times with an increase in applied torques. Fatigue life data were drastically improved at high cycle regime particularly in 8 N.m as compared with other applied torques. Higher values of applied torques provoked delamination mode around the holes in composite samples. Fatigue damage progress and failure was analyzed through use of 3-D finite element (FE) method on the basis of the Hashin model. The numerical fatigue life results closely agreed with the experimental life data. FE results further enabled to evaluate damage direction and modes of failure in composite samples.

Keywords:

Bolted joints , fatigue life , tightening torque