Progressive Damage Model For Wind Turbine Blade Adhesive Structure

Blade is one of the core components of wind energy conversion in wind turbine.Due to the limitation of existing blade manufacturing technology,most blades are assembled in the form of adhesive.The blade suction,the joint of the front and back edges of the pressure side shell,and the bonding structure formed between the web and the beam cap play a role in the transfer of load,and have a significant effect on the mechanical properties of the blade.However,the fatigue load of the adhesive structure under normal working conditions is very complex,which leads to the fatigue failure of the adhesive structure easily in the blade operation,making the adhesive structure the weakest link of the blade.Therefore,it is of great engineering significance to carry out the research on the fatigue failure of the adhesive structure.However,most of the existing researches focus on the fatigue failure of the middle layer of the adhesive structure or the adhesive layer,ignoring the gradual decline of the overall stiffness and the sudden decline of the local stiffness during the fatigue failure process of the adhesive structure.In view of this,this thesis takes the adhesive structure of wind turbine blades as the research object,takes the stiffness of the structure as the entry point,establishes the progressive damage model of the adhesive structure,and conducts an in-depth study on the gradual decline of stiffness of the adhesive structure without local failure and the influence of local stiffness drop caused by local failure on the fatigue failure process of the adhesive structure.The main research work of this thesis is as follows:(1)The stiffness degradation model of adhesive structure was established.Based on the fatigue characteristics of laminated plates and adhesive layers,stiffness degradation models of laminated plates and adhesive layers were established respectively.The stiffness degradation model of adhesive structure was established by combining the stiffness distribution coefficient of laminated plate and adhesive layer.Example analysis showed that compared with the existing models,the stiffness degradation model of the adhesive structure established in this thesis has higher accuracy.The model can effectively describe the stiffness degradation process of the adhesive structure under the action of fatigue load,and reasonably characterizing the gradual stiffness decline in the progressive damage model of the adhesive structure.The model can also provide a theoretical basis for the subsequent establishment of the progressive damage model of the adhesive structure.(2)The progressive damage model of wind turbine blade adhesive structure was established.In order to accurately simulate the fatigue failure process of the adhesive structure,the stiffness degradation model of the adhesive structure was used to describe the gradual decline of the stiffness of the adhesive structure without local failure.Based on the fatigue failure mechanism of adhesive structures,the failure modes at the local failure points of adhesive structures were determined by the improved 3D Hashin criterion,the improved Yehstratton criterion and the quadratic nominal strain criterion.The stiffness coefficient reduction method and cohesion model were used to characterize the local stiffness drops at the local failure points of adhesive structures.The fatigue failure process of the structure was compiled into a program in FORTRAN language and inserted into ABAQUS software to establish the progressive damage model of the adhesive structure.The progressive damage model of the adhesive structure is used to analyze the fatigue failure process of the adhesive structure of the I-beam of wind turbine blades.The results show that the progressive damage model of the adhesive structure established in this thesis can effectively simulate the fatigue failure process of the adhesive structure of the I-beam.