Blade materials, testing methods and structural design - Wind Power Generation and Wind Turbine Design - page 458

Imperfection Amplitudes and Flapwise Test Results
Normalized Rotor Radius
Geometric Imperfection Sensitivity
Normalized Imperfection Pattern
Figure 28: Response of imperfection amplitude compared with test results [ 81 ].
but the local strain at the maximum geometric imperfection amplitude is linearly
depending on the imperfection amplitude. The epic centre of the buckling shape
mode is at the core and fl ange material transition, but the structural collapse of the
structure is at the geometric imperfection amplitude.
The advantages of applying a sandwich construction, as opposed to traditional
a single skin laminate, in the fl anges of a load-carrying box girder, was studied by
Berggreen et al . [83] for a future, very large, 180 m wind turbine rotor. The study
showed that buckling by far is the governing criterion for the single skin design.
A signifi cant weight reduction by more than 20% and an increased buckling
capacity was obtained with the sandwich construction in comparison with the