Research On Fatiague Performance Of Composite Wind Turbine Blade Spar

As a device that receives wind energy,wind turbine blade is the cornerstone of the entire wind power system.The operating conditions of the blade not only require the blade to have excellent static mechanical performance,but also require the great dynamic mechanical performance of the blade,that is,the fatigue performance.The fatigue performance depends not only on the reasonable design of the blade,but also on the fatigue performance of the main load-bearing part of the blade,that is,the spar.This paper studies the pultrusion process of the glass fiber reinforced epoxy composites pultruded spar,the static mechanical performance and fatigue performance of the pultruded composites,and combines the experimental analysis and finite element analysis to study the fatigue mechanism of unidirectional glass fiber reinforced composites.1.Composites with different fiber volume content and different resin types were prepared by the pultrusion process.The results show that the static mechanical performance of epoxy composites are positively correlated with fiber volume content.The effect of fiber volume content on the fatigue performance of pultruded epoxy composites is not consistent between low-cycle fatigue and high-cycle fatigue,the higher the fiber volume content,the better the low-cycle fatigue performance of the composites,while the opposite is true for high-cycle fatigue.The fatigue performance of polyurethane composites is better than that of epoxy composites.2.The effects of micro-sized talcum powder content on epoxy resin viscosity,pultrusion process stability,the dynamic and static performance of composites were studied.The results show that talcum powder can improve the static mechanical performance and fatigue performance of composites.At lowcycle fatigue,the fatigue performance of the composites with 3 wt%talcum powder is better;at the time of high-cycle fatigue,the fatigue performance of the composites with 6 wt%talcum powder is better.This is the result of the competition of crack propagation in the matrix and talcum powder hindering crack propagation under low-cycle fatigue and high-cycle fatigue.3.Two kind of composite spars were prepared by pultrusion and vacuum infusion processes respectively,and the static mechanical performance and fatigue performance of the spars prepared by the two processes were studied and compared.Due to the limitation of the forming process,the tensile and compressive performance of the two kind of composite spars are quite different.The fatigue performance of the pultruded composite spar and the vacuum infusion composite spar is not much different.In low-cycle fatigue,the fatigue performance of the pultruded composite spar is better.With the increase in the number of fatigue cycles,the fatigue performance of the two kind of composite spars become closer and closer.4.Through the method of finite element analysis,the influence of factors such as fiber modulus and volume content,resin toughness and modulus on the fatigue performance of unidirectional composites is analyzed.The results of finite element analysis show that the fatigue performance of unidirectional composites increases with the increase of fiber volume content and modulus,and increases with the increase of resin modulus and toughness.Since the initial mechanism of fatigue failure considered in this paper is the occurrence of cracks in the matrix,it does not agree well with the experimental results.