FATIGUE LIFE PREDICTION OF NOTCHED COMPOSITE COMPONENTS

The local stress/strain approach has been used to predict the fatigue lives of notched composite components. The method was based on a micro stress analysis and the application of a multiaxial fatigue parameter incorporating the alternating strain components on the critical plane. This parameter was able to correlate the fatigue lives obtained under a variety of multiaxial loading and geometrical configurations, enabl ing a generalized fatigue life curve to be determined on the basis of limited experimental data. The ability of the multiaxial fatigue param eter to relate the fatigue behaviour of composites was illustrated by predicting the locations of crack initiation sites in a unidirectional silicon carbide fibre reinforced titanium plate containing a circular hole tested under constant amplitude cyclic loading. The same approac h was also successfully employed to predict the fatigue lives of graph ite reinforced epoxy composite tubes with circular holes tested under several combinations of cyclic tension and torsion.