INFLUENCE OF INTERFACE OF COMPOSITE BLADES FAILURE IN TWIST

A fiber composite airfoil, typical for high-tip speed compressor applications, is subjected to load conditions anticipated to be encountered in such applications, and its structural response is theoretically investigated. The analysis method used consists of composite mechanics embedded in pre- and post-processors and coupled with NASTRAN. The load conditions examined include thermal due to aerodynamic heating, pressure due to aerodynamic forces, centrifugal, and combinations of these. The various responses investigated include root reactions due to various load conditions, average composite and ply stresses, ply delaminations, and the fundamental modes and the corresponding reactions. The results show that the thermal and pressure stresses are negligible compared to those caused by the centrifugal forces. Also, the core-shell concept for composite blades is an inefficient design (core plies not highly stressed) and appears to be sensitive to interply delaminations. The results are presented in graphical and tabular forms to illustrate the types and amount of data required for such an analysis, and to provide quantitative data of the various responses which can be helpful in designing such composite blades.

Download Full-text

Modal analysis of an iced offshore composite wind turbine blade

Wind Engineering ◽

10.1177/0309524x211011685 ◽

2021 ◽

pp. 0309524X2110116

Author(s):

Oumnia Lagdani ◽

Mostapha Tarfaoui ◽

Mourad Nachtane ◽

Mourad Trihi ◽

Houda Laaouidi

Keyword(s):

Wind Turbine ◽

Modal Analysis ◽

Turbine Blade ◽

Natural Frequencies ◽

Wind Turbine Blade ◽

Resonance Phenomenon ◽

Mode Shapes ◽

The Finite Element Method ◽

Numerical Work ◽

Composite Blades

In the far north, low temperatures and atmospheric icing are a major danger for the safe operation of wind turbines. It can cause several problems in fatigue loads, the balance of the rotor and aerodynamics. With the aim of improving the rigidity of the wind turbine blade, composite materials are currently being used. A numerical work aims to evaluate the effect of ice on composite blades and to determine the most adequate material under icing conditions. Different ice thicknesses are considered in the lower part of the blade. In this paper, modal analysis is performed to obtain the natural frequencies and corresponding mode shapes of the structure. This analysis is elaborated using the finite element method (FEM) computer program through ABAQUS software. The results have laid that the natural frequencies of the blade varied according to the material and thickness of ice and that there is no resonance phenomenon.

Download Full-text

Aeroelastic Behavior of Low Aspect Ratio Metal and Composite Blades

Volume 1: Turbomachinery ◽

10.1115/86-gt-243 ◽

1986 ◽

Cited By ~ 1

Author(s):

James F. White ◽

Oddvar O. Bendiksen

Keyword(s):

Aspect Ratio ◽

Opposite Effect ◽

Design Parameters ◽

Aeroelastic Stability ◽

Low Aspect Ratio ◽

Supersonic Flutter ◽

Type Mode ◽

The Stability ◽

Composite Blades ◽

Plate Type

The aeroelastic stability of titanium and composite blades of low aspect ratio is examined over a range of design parameters, using a Rayleigh-Ritz formulation. The blade modes include a plate-type mode to account for chordwise bending. Chordwise flexibility is found to have a significant effect on the unstalled supersonic flutter of low aspect ratio blades, and also on the stability of tip sections of shrouded fan blades. For blades with a thickness of less than approximately four percent of chord, the chordwise, second bending, and first torsion branches are all unstable at moderately high supersonic Mach numbers. For composite blades, the important structural coupling between bending and torsion cannot be modeled properly unless chordwise bending is accounted for. Typically, aft fiber sweep produces beneficial bending-torsion coupling that is stabilizing, whereas forward fiber sweep has the opposite effect. By using crossed-ply laminate configurations, critical aeroelastic modes can be stabilized.

Download Full-text

Mechanical Behavior of Anti-Symmetrically Laminated Composite Blades

Volume 4: Turbo Expo 2005 ◽

10.1115/gt2005-68667 ◽

2005 ◽

Author(s):

Masahiro Hojo ◽

Ryosaku Hashimoto ◽

Akinori Ogawa ◽

Yasushi Sofue ◽

Yukio Matsuda

Keyword(s):

Finite Element ◽

Mechanical Behavior ◽

Rotational Speed ◽

Laminated Composites ◽

Laminated Composite ◽

Aircraft Engines ◽

Finite Element Analyses ◽

Coupling Effects ◽

Angle Change ◽

Composite Blades

Anti-symmetrically laminated composites have coupling effects between tensile stress and twisting deformation, and are very attractive as fan blade materials of aircraft engines. Blades fabricated by anti-symmetrically laminated composites can automatically adjust the stagger angle to better aerodynamic conditions with change of axial force or rotational speed owing to the coupling effects. Thus, the anti-symmetrically laminated composite blades are expected to improve aerodynamic efficiency and the stability of aircraft engines. In this paper, the mechanical behavior of anti-symmetrically laminated composite blades is evaluated by spin tests and finite element analyses. Three kinds of blades fabricated by carbon/epoxy laminated composites in different anti-symmetrical stacking sequences were tested. A non-contact measurement technique using a multi-channel optical fiber sensor was used for measurements of blade deformations at high-speed rotating conditions, up to 10,000 rpm. The twisted angle change at the blade tip could be successfully measured. The twisted angle change increased in proportion to the second power of rotational speed, and the maximum angle change was about 4 degree at 10,000 rpm. The finite element analysis results agreed well with the spin test results. Furthermore, the three-dimensional deformation of the test blades was evaluated based on finite element analyses.

Download Full-text