Fatigue initiation

Abstract

This chapter explains how fatigue initiation in FMLs can be evaluated and predicted, assuming that the phenomenon primarily affects the fatigue property of the metal constituents. It is illustrated how definition of initiation in the theory enables the utilization of Wöhler failure life curves obtained for the monolithic metal, in combination with stress concentration factors and laminated plate theory. The accuracy of prediction is discussed in relation to the match between the conditions for the adopted Wöhler curves and the predicted conditions. In the end, the theory is related to the application of mechanically fastened joints, where a combination of tension and bending impose different fatigue initiation lives in each individual metal layer.