4. Delamination Growth in Composite Plates Under Fatigue Loading Conditions

Composite materials are usually characterized by very extraordinary specific strength and stiffness properties which can be strongly affected by intra-laminar and inter-laminar damages. In particular, delaminations can be strongly influenced by the fatigue induced material degradation which can initiate delamination growth phenomena at a relatively low number of cycles gradually leading to the increase of the damaged area and to the reduction of the overall structural stiffness. In the present chapter an algorithm is proposed which, by means of non-linear analyses, can correlate the increase of delaminated area to fatigue cycles. The proposed algorithm adopts Paris Law formulation based propagation criterion which can take into account the local damage accumulation along the delamination front.