A Comparative Study of Static and Fatigue Behaviors for Various Composite Orthotropic Properties for a Wind Turbine Using a Coupled FEM-BEM Method

Master's Thesis from the year 2013 in the subject Engineering - Mechanical Engineering, grade: 4.06/4.5 GPa, , language: English, abstract: In the wind industry, the current trend is towards building larger and larger

turbines. This presents additional structural challenges and requires blade materials that

are both lighter and stiffer than the ones presently used. This work is aimed to aid the

work of designing new wind turbine blades by providing a comparative study of different

composite materials.

A coupled Finite-Element-Method (FEM) - Blade Element Momentum (BEM) code was

used to simulate the aerodynamic forces subjected on the blade. The developed BEM

code was written using LabView allowing an iterative numerical approach solver taking

into the consideration the unsteady aerodynamic effects and off ¿design performance

issues such as Tip Loss, Hub Loss and Turbulent Wake State therefore developing a more

rational aerodynamic model. For this thesis, the finite element study was conducted on

the Static Structural Workbench of ANSYS, as for the geometry of the blade it was

imported from a previous study prepared by Cornell University. Confirmation of the

performance analysis of the chosen wind turbine blade are presented and discussed blade

including the generated power, tip deflection, thrust and tangential force for a steady flow

of 8m/s.

The elastic and ultimate strength properties were provided by Hallal et al. The Tsai-

Hill and Hoffman failure criterions were both conducted to the resulting stresses and

shears for each blade composite material structure to determine the presence of static

rupture. A progressive fatigue damage model was conducted to simulate the fatigue

behavior of laminated composite materials, an algorithm developed by Shokrieh.

It is concluded that with respect to a material blade design cycle, the coupling between a

finite element package and blade element and momentum code under steady and static

conditions can be useful. Especially when an integration between this coupled approach

and a dynamic simulation tool could be established, a more advanced flexible blade

design can be then analyzed for a novel generation of more flexible wind turbine blades.