الفهرس | Only 14 pages are availabe for public view |
Abstract The main objectives of this research were the aero-structural, and fatigue analyses of a small-scale H-rotor vertical axis wind turbine blades (VAWT) made from composite materials. These objectives were studied with the focus of fracture behavior of joints manufactured from composite materials. The H-rotor VAWT blades failure due to adhesive delamination in addition to adhesive joint failure between skins were studied. Classical fatigue analysis using “Goodman method” accompanied by the fracture mechanics theory using “Paris’ Law” was performed in this study in order to estimate the blade life. The small-scale VAWT is designed to be self-start and operate on a residential roof located at Port Said-Egypt. The VAWT blades are made from S-2 fiberglass/ Epoxy composite. Detailed stress analysis of the H-rotor VAWT blade with different wall thicknesses is discussed and presented. The rotor blade design is based on the maximum values of deflection and bending stresses at extreme loading conditions. Rotor blades made from Carbon fiber/ Epoxy composite were also investigated in this study and the stress analysis results were compared with that of the S-2 fiberglass/ Epoxy composite blades. The results showed that the wind turbine performance was improved by 8 % when using the NACA 0021 airfoil instead of the NACA 0015 airfoil. In addition, by designing the wind turbine using 3 blades, the performance was improved by 24.4 % in preference to 4 blades and by 62 % in preference to 5 blades. The structural analysis revealed that the S-2 fiberglass/ Epoxy composite material is promising for manufacturing the VAWT blades counter to the Carbon fiber composites. Blades made from Carbon fiber/ Epoxy composite subjected to higher values of maximum bending stress and more deflection was caused to the blades than the S-2 fiberglass/ Epoxy composite blades at different values of the tip speed ratio by a percentage ranging from 20 % to 85 % according to the operating conditions and the blade thickness. The adhesive delamination and adhesive joint failure between skins, the blade wall thickness and the type of blade fixation can significantly shorten the VAWT blade life . According to the modified Goodman method, The VAWT S-2 fiberglass/Epoxy composite blade will live up to 3 x 1011 cycles, which satisfies the design criteria for the 20-30 years lifespan of the composite wind turbine blades under fatigue loading. While in the case of blade damage due to adhesive delamination the blade will live up to 3 x 105 cycles (almost 1 day) and 3 x 106 cycles (almost 11 days) if it is subjected to adhesive joint failure between skins. |