Study Of Strength And Stiffness For Composite Wind Turbine Blade Considering Effects Of Progressive Failure And Environment Load

The progressive failure process and stiffness degradation of the 3-D complicated configuration composite blade has been studied by introducing a failure criterion. The failure criterion applied in this paper considers three kinds of different damages, namely matrix tensile/compressive failure, fiber-matrix shear failure and fiber failure. By Using FEA software ABAQUS combine with user-subroutines USDFLD, the authors analyzed the stiffness and failure behavior of the blade structure, and the results considering different temperature and humidity are also presented. Some improvements for the analysis model of blade have been done based on the above analysis.In this paper, the finite element method has been adopted to analysis the blade structure strength, stiffness and progressive failure considering the temperature and humidity loads. The improved model has been put forward and some optimized results have been provided. The conclusions are listed as follow:1. Matrix damage is the main failure model for the material of composite blade. The damage zone appeared likely at the part with severely change of curvature, where the most severe stresses concentration exist. the progressive accumulation and development of damage of Blade material will lead to blade damage, which decrease the overall stiffness of blade and increases blade deformation. These are the important factors inducing early failure of blade. It is beneficially to the strengthening and toughening of the blade design by using of reasonable size fan in the transition.2. In considering the cumulative damage behavior of materials, there are some shocks on the stiffness attenuation curve in displacement map. It indicates that after the destruction of blade structure, the stiffness degradation makes its stability worse; it also shows that local instability exists in the blade structure.3. Temperature and humidity can not be ignored on the stiffness and strength of blade. When considering temperature only, the stiffness of blade drop with temperature decreasing, as well as the strength of blade. While considering the effect of temperature and humidity both, the composite stiffness and strength will reduce due to moisture absorption, and damage become more seriously as well. Besides, this effect is more serious with the increase of temperature at the same humidity. 4. It is effective to reduce blade mass and increases the strength, rigidity and stability of blade structure by progressively reducing the thickness of skin, increasing beam thickness but only increase the thickness of the web root. On this basis, by reducing the±45°ply in the skin and the web layer and adjusting the stacking sequence of the method can also further improve the strength, stiffness and stability of the blade structure.In addition, by reducing the skin and web 90°layer and increasing the 0°layer method can achieve better results.5. On the ground of ply angle optimization, we have obtained more reasonable results through genetic algorithm to further optimize the thickness of blade.The Project is sponsored by "Liaoning BaiQianWan Talents Program".