The influence of ply-drop position in thickness direction under fatigue loading (R = -1) has been studied for a highly oriented composite laminate dropping from 20 to 12 plies. Compressive and tensile strengths have been determined for several configurations of ply-drop locations. Fatigue tests at a load ratio of R=-1 have been performed up to rupture. The first damages clearly identified are delaminations close to the drop-offs. Their initial locations and propagations kinetics before final failure were observed. Finite element simulations were performed to find out initiation spots of delamination. An interlaminar stress criterion has been proposed to predict initiation of delaminations. Effects of ply-drops configuration on fatigue are discussed.
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