Assessment of the Effect of Hybrid GFRP CFRP Usage in Wind Turbine Blades on the Reduction of Fatigue Damage Equivalent Loads in the Wind Turbine System

2015-01-05
Gözcü, Ozan
Farsadi, Touraj
Şener, Özgün
Kayran, Altan
The use of hybrid GFRP-CFRP material in wind turbine blades is investigated for its effectiveness in reducing fatigue damage equivalent loads in the whole wind turbine system, and comparisons are made against the baseline full GFRP blade in terms of strength, deformation, dynamic characteristics, weight and cost of the blade. To achieve load alleviation in the whole wind turbine system, bending-twisting coupling in composite blades is exploited through the use of off-axis plies in the spar caps of the blades. Fatigue damage equivalent load is used as the metric to assess the effect of off-axis ply placement in the main spar caps of the turbine blade on the load alleviation in the whole wind turbine system. Study is conducted utilizing both linear and non-linear blade models in the multi-body models of the wind turbine system. For the purposes of the study, 5 MW multi-body wind turbine models are set up in two separate wind turbine multi-body dynamic codes SWT and PHATAS that use superelement and non-linear beam blade definitions, respectively. Multi-body dynamic simulations of the wind turbine system are performed for the power production load case using the normal turbulence model as the external wind loading. Time history results of simulations are used to calculate fatigue damage equivalent loads at the selected monitor points in the wind turbine system. Results show that in the overall, with the introduction of off-axis CFRP spar cap plies in the blades, higher reductions in the damage equivalent loads can be achieved in the wind turbines system compared to the use of full GFRP in the main spar caps of the blade. Preliminary study on the effect of off-axis spar cap plies on the strength, deformation, dynamic characteristics, weight and cost of the bend-twist coupled blades also show that bend-twist coupled blades do not have any disadvantages when compared to the baseline blade. © 2015, American Institute of Aeronautics and Astronautics Inc. All rights reserved.