Experimental study on fatigue resistance of composite joints with protruding-head bolts

Composite bolted joints made from carbon fibre/epoxy material with quasi-isotropic and 0degrees-dominated lay-ups were fatigue tested to investigate their fatigue resistance. The fatigue tests were carried out under cyclic loading with stress ratio R = -1. Strain gauge measurements were done to analyze strain distribution and load transfer between bolt rows. Extensometers were used to measure relative displacement between the composite plates. Fatigue fracture of bolts was the dominant failure mode of the specimens. Load transfer calculations have shown that the different bolt rows transfer slightly different amounts of the applied load. Extensometer measurements show that the relative displacement between the composite plates is strongly affected by fatigue damage accumulation in the joint system. The obtained results on the fatigue life of the joints suggest a linear dependence between the joint resistance to fatigue and the number of bolts. This makes it possible to predict the fatigue life of composite joints with different configuration. (C) 2001 Elsevier Science Ltd. All rights reserved.