Bolt fatigue in CFRP joints

Bending of titanium bolts in in-plane loaded composite joints is potentially fatigue critical. We propose an analytical model for calculation of bending stress in protruding and countersunk-head bolts in composite joints. The model allows for presence of liquid shim and considers the load transfer by friction. We perform experiments on six types of joints, including variants with and without liquid shim or frictionless tape between the plates, and with different levels of bolt pretension. Using the bending stress, we fit an S–N equation to the test results and compare predictions of variable-amplitude fatigue life to experimental results from the literature.