Composite Blades of Wind Turbine: Design, Stress Analysis, Aeroelasticity, and Fatigue

In this chapter, four main topics in composite blades of wind turbines including design, stress analysis, aeroelasticity, and fatigue are studied. For static analysis, finite element method (FEM) is applied and the critical zone is extracted. Moreover, geometry, layup, and loading of the turbine blades made of laminated composites are calculated and evaluated. Then, according to the stress analysis, critical layer is specified and safety factor is studied based on Tsai-Wu failure criterion. Aeroelasticity is the main source of instability in structures that are subjected to aerodynamic forces. One of the major reasons of instability is the coupling of bending and torsional vibration of flexible bodies, which is known as flutter and considered in this study. Numerical and analytical methods are applied for considering the flutter phenomenon of the blades. For numerical method, the FEM and Joint Aviation Requirements (JAR-23) standard and for analytical method, two-degree freedom flutter and Lagrange’s equations are utilized. Also, lifetime prediction of a horizontal axis wind turbine composite blade is investigated. Accumulated fatigue damage modeling is employed as a damage estimation rule based on generalized material property degradation

The effect of uniformly distributed carbon nanotubes and rotation on the frequencies of fiber metal laminated cylindrical shells

In this manuscript, the effects of carbon nanotubes and rotation on the free vibration of fiber metal laminated circular cylindrical shell based on Love’s first approximation theory have been studied. The representative volume element is consisting of four phases: fiber, carbon nanotubes (CNTs), polymer matrix and metal. Initially, the CNTs have been added to the matrix and then the fiber phase has been reinforced by them. Finally, the adhesive fiber prepreg has been combined with the thin metal layers. The generated cylindrical shell can be named CNT/fiber/polymer/metal laminates (CNTFPMLs) cylindrical shell. The effects of different parameters such as lay-ups, volume fractions of metal and composite sections, mass fraction of CNTs on the frequencies of CNTFPMLs cylindrical shell with respect to rotational speed have been considered. The results demonstrated that the frequency changes of CNTFPMLs cylindrical shell are different with growing for various volume fraction of fiber. The difference between backward and forward modes for different mass fractions increase with growing th

Agglomeration effects on the vibrations of CNTs/fiber/polymer/metal hybrid laminates cylindrical shell

This work studies the agglomeration effect of continuously graded single-walled carbon nanotubes (SWCNTs) on the vibration of SWCNTs/fiber/polymer/metal laminates cylindrical shell. The strain-displacement relations are applied according to the Kirchhoff Love’s first approximation shell theory, whereas the dimensionless frequencies of the structure are obtained by means of the beam modal function model. Fiber, carbon nanotubes (CNTs), polymer matrix and metal are four phases constituting the agglomerated CNTs/fiber/polymer/metal laminate (CNTFPML) cylindrical shell. In the first step, we introduce the CNTs randomly within the matrix, such that the volume fraction can be assumed to be continuously graded in the thickness direction. We determine the effect of the CNTs agglomeration on the elastic properties of CNT-reinforced composites, by means of the Eshelby-Mori-Tanaka approach here applied on an equivalent fiber. In the second step, the fiber is introduced as reinforcement phase in the CNT-reinforced composite. Finally, the adhesive fiber prepreg is combined with the thin metal layers. Thus, we study the sensitivity of the vibration behavior of the cylindrical shell to the following input parameters, namely: the CNTs agglomeration and distribution, the mass and volume fractions of the fiber, the boundary condition and lay-ups