The critical plane damage parameter used in multiaxial fatigue has been applied to predict fatigue lives of smooth and notched fibre composite specimens. The method was based on microstress analysis and the application of a multiaxial fatigue parameter, which incorporated the alternating strains and stresses on the critical plane. This parameter was able to correlate the fatigue lives obtained under a variety of constant amplitude single and multiaxial loading conditions. A generalized strain-life curve has been developed based on a combination of the alternating shear and maximum normal strains on a plane parallel to the fracture plane. This parameter needs only to be related to the experimental data of composite laminae loaded in one direction in order to determine stress-life curves for any other loading and direction. The predicted curves were in very good agreement with both smooth and notched specimen fatigue data.
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