On innovative concepts of wind turbine blade design

Recent work at Risø DTU on wind turbine blades has shown that more failure mechanisms need to be taken into account, than the classical ones such as buckling, material failure, etc. One of the failure modes, which were demonstrated in fullscale tests and are not part of a commercial certification test, is transverse shear distortion of the cross section. Another failure mechanism is the non-linear out-ofplane deformation of the load carrying cap laminate, which could be the reason for some failure of today’s wind turbine blades. These two potential failure mechanisms are taken into account in the design of a new innovative 40m load carrying box girder presented in this paper. Also buckling and inplane material failure in the longitudinal direction is considered in the design. The box girder has been designed by Risø DTU and manufactured be SSP Technology A/S and makes use of 3 patented reinforcements in order to prevent interlaminar failure in the caps and transverse shear distortion. The material savings in the cap is up to 40% compared to the traditional SSP Technology design. This suggests that substantial weight savings can be obtained, at least when the failure criteria mentioned above are considered alone. Furthermore, subcomponent testing has been performed to support the numerical analysis and the coming full-scale test.The current work seems to confirm that significant improvement in the structural components of wind turbine blade can be obtained by utilization of the invented structural solutions.