Load mitigation of wind turbine blade by aeroelastic tailoring via unbalanced laminates composites

The parametric study of unbalanced tri-axial non-crimp fabrics laminates, typically used in the blade skin layup, showed that the highest bend-twist coupling up to 0.56 was achieved when all three kinds of unbalances (i.e. ply-angle, ply-material and ply-thickness unbalances) were simultaneously present in the laminates. Based on aeroelastic tailoring via unbalanced laminates, the bend-twist coupling towards feather of various degrees was implanted to the skin layup of a variable-speed collective-pitch controlled 5 MW wind turbine rotor blades and fully-coupled aero-servo-elastic analyses were performed. The results showed that when the ply-thickness unbalance is added in the skin layup, in addition to already existing ply-angle and ply-material unbalances, an average increase in the coupling magnitude by approximately 51% along the blade length and a reduction in fatigue load and collective-pitch demand by approximately 1.6–2.9% and 5.5–19.9% across the range of applied stochastic winds ranging from 7 m/s to 23 m/s.