The fatigue damage evolution in the load-carrying composite laminates of wind turbine blades

A critical material design criterion for the composite material used in the load-carrying laminates of a wind turbine blade is the fatigue resistance. From a few characteristic parameters defining the wind turbine, the governing equations for the stresses working in the load-carrying laminates will be presented. Stresses, which experimentally will be related to fatigue resistance of conventional composite material systems, are used in the laminates. The corresponding fatigue damage is studied in composite materials primarily based on the 3D X-ray computed tomography scanning technique. During this, it is possible to show that the fatigue damage during tension/tension and tension/compression loading is influenced by the bundle architecture of the off-axis oriented backing layers present in the non-crimp fabrics used in the load-carrying laminates while the compression/compression fatigue damage is different.