Abstract
This study presented a failure analysis of a 52.3 m composite wind turbine blade under static loading. Complex failure characteristics exhibited at the transition region of the blade were thoroughly examined and typical failure modes were indentified. In order to predict multiple failure modes observed in the tests and gain more insights into the failure mechanisms of the blade, a Finite Element (FE) simulation was performed using a global-local modeling approach and Progressive Failure Analysis (PFA) techniques which took into account material failure and property degradation. Failure process and failure characteristics of the transition region were satisfactorily reproduced in the simulation, and it was found that accumulated delamination in spar cap and shear web failure at the transition region were the main reasons for the blade to collapse. Local buckling played an important role in the failure process by increasing local out-of-plane deformation, while the Brazier effect was found not to be responsible for the blade failure.
Highlights
With the expansion of wind energy in recent years, the sizes of wind turbine blades have become increasingly large in order to capture more power from wind and further reduce the cost of energy [1,2].When blades are small tip deflection is a major driver in structural design and blade failure is of less concern
In order to predict the complex failure characteristics of the blade, this study proposes a Finite Element (FE) modeling method based on a commercial FE program and further investigated the mechanisms leading to the blade failure
Two FE models used in the global-local modeling approach were assessed by comparing predicted results with experimental measurements available in the 2.5 MW loading set, and failure process and the final failure characteristics of the transition region were predicted
Summary
With the expansion of wind energy in recent years, the sizes of wind turbine blades have become increasingly large in order to capture more power from wind and further reduce the cost of energy [1,2].When blades are small tip deflection is a major driver in structural design and blade failure is of less concern. In order to investigate the failure behavior of large blades installed on multi-megawatt (MW) wind turbines, some researchers have carried out failure tests on full-scale blades. Jensen et al [5,6,7] tested a 34 m blade and its load-carrying box girder under flap-wise bending and found that the Brazier effect induced a large deformation in the spar cap and the further delamination buckling were the cause leading to structural collapse. Overgarrd et al [8,9] tested a 25 m blade to failure under flap-wise bending and concluded that the ultimate strength of the blade was governed by instability phenomena in the form of delamination and buckling instead of the Brazier effect. It can be seen that failure causes varied among blades and little consensus has been reached
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