Fatigue strength validation for CFRP composites

Fibre-reinforced Polymer Composites (FRPCs) are used today instead of isotropic and conventional materials as a result of their high specific stiffness and strength. As a result, they are often selected for weight-critical structural applications such as aircraft, launch vehicles, or space satellites. In addition, FRPCs possess superior formability properties that ease the development of tailored designs and are increasingly used in applications such as wind turbines rotor blades. Concerning fatigue, FRPCs are considered sometimes as fatigue insensitive, but this is only valid if design strain levels are kept low (4000 u.s is for instance the typical level used for carbon reinforced composites in the aircraft industry). Actually, fatigue in FRPCs is quite a complex phenomenon caused by the different types of damage that can occur (fibre fracture,matrix cracking, fibre buckling, fibre-matrix interface failure, delamination, interactions between several damage types), and the inherent heterogeneity and large number of configurations (multitude of fibres, matrices, manufacturing methods, stacking sequences, etc.) of these materials