Strength Research And Design Optimiazation For Ply Stucture Of Wind Turbine Blade

The importance of Wind turbine blades as components for catching the wind power is self-evident. And it obviously has the significance of the engineering practice and scientific value to solve the problem, how to minimize the blade's cost on the basis of structural integrity and high aerodynamic efficiency, while it is necessary for figure out this problem to have better knowledge and understanding of strength properties of the blade composite ply structure. Present research situation of home and abroad mainly treat the strength of ply structure as the measure of the structural integrity of a blade and there is no further study about the stress distribution between internal ply of the blade and the influence by the stress components on the strength of the ply structure, the influence by ply angle on the different structural regions. Moreover, the current preliminary design method of the ply structure based on Bernoulli-Euler beam theory proposed by some scholars does not meet the actual strength requirements. Consequently, this paper analyzes the structural strength of composite ply properties, the influence on the strength of ply structure by ply angles and finally the ply structure is optimized based on the method of experimental design, so as to provide research-based optimization method for lay structure. The main contents of this paper and conclusions are as follows:(1) As the contents of this study is expanded by the basis of composite strength of law and the Tsai-Wu failure criteria, thus, we firstly give the method of the geometric modeling for the blade and how to define ply structure and Tsai-Wu failure criterion of strength.(2) In order to study the influence on the strength for three regions with different structural characteristics of the blade by the ply angle, the blade of finite element model is established, a variety of ply angle is designed, the Tsai-Wu strength index values of the nodes, under different ply schedules, along the ply thickness at several sections is extracted. The result shows that ply angle of the blades has specific affect on each region of blade, optimization of ply angle need to consider the existence of different structural features of the whole blade.(3) In order to research and analyze, for the blade root, the strength properties and the reason of the fact, that the preliminary design method of the ply structure based on Bernoulli-Euler beam theory proposed by some scholars does not meet the actual strength requirements, the blade of finite element model is modeled, static structural response of the blade is simulated at various wind speed, the stress and displacement components of the nodes along the ply thickness at several sections of the root is extracted. The result, with the use of Tsai-Wu failure criterion, shows that the sections of the root do not meet the plane hypothesis, in-plane stress components (In-plane transverse normal stress and shear stress) are the main factor affecting the root strength, and that the method of ply structure design should consider the in-plane stress components.(4) Through Design of Experiment with the design objective to minimize the amount of the plies, Various ply schedules is made and many finite element models of the blades is simulated, finally, the ply structure, designed by the ply preliminary design method based on Bernoulli-Euler beam theory, of the blade with the strength not meeting the acquirement at the root is optimized. Moreover, the influence by 0°plies and±45°plies on the blade structural strength is discussed, the result shows the coupling is existed between the influence by 0°plies and±45°plies on the strength, and that±45°ply is the main factor affecting the blade structural strength.