Research On The Failure Process Of Wind Turbine Blade Based On Multiscale Analysis

As one of the core components of the wind turbine,wind turbine blades are usually made of composite materials to meet the strength requirements.During the time that the wind turbine in serves,the blades are damaged and destroyed in various forms.In-depth understanding of the failure process of composite material blades will help the optimization of design and fault diagnosis of composite material blades,and has engineering reference value and practical significance for extending the service life of the blade design.The mechanical properties of component materials in composite materials and microstructure features are very relevant to the evolution of macrostructure damage.For this reason,this paper conducts multi-scale analysis research on the failure process of wind turbine blades.The main work content is as follows:The structural damage of composite blades includes intra-layer damage and inter-layer damage.The macro-microscopic analysis method is proposed for composite material intra-layer damage.The smallest microstructure-unit cell is extracted from the macrostructure,and divide the unit cell into several subcells,and deduce the unit cell stress through the stress of the subcells.On the basis of the universal unit cell model,the subcell strain is replaced by the subcell stress to derive an improved unit cell model algorithm,which realizes the correlation between the microscale and the macroscale.The macro-mesoscopic analysis method is proposed for composite material inter-layer damage,and the process of combining the blade laminated plate model at the mesoscopic level and the local displacement load of the macroscopic blade is explained.A 5MW blade is selected as the research object,and the blade layering strategy,material properties and blade load calculation method are described.On this basis,the blade macroscopic finite element analysis model is established,and the blade micromechanical model is established according to the unit cell model algorithm and embedded in the macroscopic finite element analysis model to complete the blade macro-micro coupled finite element analysis model.According to the macro-microscopic analysis method,the failure criterion and stiffness degradation model of the composite material are selected,the macro-micro multi-scale damage analysis process is established,and the wind turbine blades are analyzed in the macro-micro multi-scale,and obtain the failure area and the damage evolution process of the fibers and the matrix in different angle layer,and the relationship between the failure unit stress and the wind speed.The results show that the damage mainly occurs in the transition zone of the trailing edge and the root zone of the trailing edge.According to the macro-mesoscopic analysis method,the delamination damage simulation of the blade area prone to delamination damage is carried out.The bilinear constitutive model is introduced and the interface element damage criterion and damage extension criterion are selected to simulate the evolution process of the inter-layer damage and interface element failure of the blade laminate.The results show that comparing the two interface layers arranged symmetrically,the interface layer distributed on the outside of the blade is more severely damaged than the interface layer distributed on the inside of the blade,and the damage spreads faster.Comparing each interface layer,the more closer to the sandwich layer,the interface layer is more severe the damage and the faster the damage expansion.Through the research in this paper,the multi-scale damage analysis method of composite material blades is mastered.The damage failure evolution process of different angle layers of composite material blades and the inter-layer damage failure evolution process of composite material blades have been obtained.The feasibility of the composite material blades multi-scale analysis method is proved,and provide support for blade design optimization.