Fatigue of bolted composite joints
J. Schön, Swedish Defence Research Agency, Sweden
The initial coefficient of friction might be as low as 0.1. During fatigue loading it increases before stabilizing at a lower value than peak value. Should the reduction in clamping pressure due to wear and other processes cause the fasteners to become lose, load transfer during fatigue loading from friction forces will initially increase and then decrease to maybe zero. The two main failure modes are hole wear and bolt failure. During hole wear, the hole is elongated and how fast wear particles are transported out of the hole is crucial. Bolt failure is a metal fatigue failure and often occurs during low amplitude loading.