Effect of Trailing Edge Damage on Full-Scale Wind Turbine Blade Failure

Modern wind turbine rotor blades are normally assembled from large parts bonded together by adhesive joints. The structural parts of wind turbine blades are usually made of composite materials, where sandwich core materials as well as fibre composites are used. For most of the modern wind turbine blades the aerodynamically formed outer shell structure is manufactured as an upper and a lower part in separate moulds in order to simplify the production process. The aerodynamic shell structures are then bonded to internal load bearing structures during the production process. Adhesive joints exist where the load bearing structure is connected to the shells and at the joints of the upper and lower shells, usually at the leading and trailing edges. Maintenance inspections of wind turbines show that cracks in the vicinity of the trailing edge are typically occurring forms of damage. The cause of trailing edge failure is very complex and can arise from manufacturing flaws, damages during transportation and erection as well as under general and extreme operational conditions.
The focus in this study is put on the geometrical nonlinear buckling effect of the trailing edge under combined loading and how it affects the ultimate strength of a holistic blade. For this reason a 34m long blade was studied experimentally and numerically under ultimate load until blade collapse. The interaction between trailing edge buckling on damage onset and sandwich panel failure was studied in detail. Numerically applied fracture mechanics approaches showed good agreement with the experimental results and helped to understand the relations between trailing edge buckling and blade collapse.