Research On The Inherent Characteristics Of Ceramic Based Carbon Nanotube Reinforced Composite Turbine Blades

Twisted blade is a blade model used in aerospace and turbomachinery.On the one hand,the complexity of blade structure,such as twist,curvature,cross-section non-uniformity and thickness variation,makes the research of blade difficult.The advanced ceramic matrix composite is also an ideal material for the engine blade.The advanced ceramic matrix composite is also an ideal material for the engine blade.Ceramic matrix composites integrate carbon fiber and ceramic matrix,retain the characteristics of high temperature resistance of ceramics,and have high mechanical strength and thermal cracking resistance.In order to meet the weight and strength requirements of blade structure,non-uniform structure such as taper is often used to model the blade.The vibration of the blade,especially the resonance of the blade,will produce large stress,which will lead to fatigue failure.Therefore,the vibration analysis of turbine blades has been concerned for decades.In this paper,carbon nanotubes(CNT)reinforced ceramic matrix composite pre-twisted blades with elastic boundary conditions are studied.In this paper,carbon nanotube reinforced ceramic matrix composite pre-twisted blades with elastic boundary conditions are studied.The dynamic model of pre twisted blade is established and its vibration characteristics are analyzed.The main research contents include the following aspects:(1)The orthogonal polynomial is used as the admissible displacement functions,a set of the spring group are used to simulate different boundary conditions,and the Lagrange equation is used to establish the differential equation of the rotating pre-twisted blade.The accuracy of the model is verified by comparing the frequencies.Then,the influence of varying-thickness,rotation speed,twisted angle and boundary conditions on the natural frequency and modal shape of pre twisted blade is studied.(2)The carbon nanotube reinforced ceramic matrix composite is applied to the blade modeling,and the vibration differential equation of the composite pre-twisted blade is derived.The numerical method is used to solve the vibration differential equation to obtain the natural characteristics of the pre-twisted blade.The influence of material parameters on the vibration characteristics of pre twisted blades are mainly studied.(3)Considering the chord-wise curvature of the blade and the thermal environment,the dynamic model of the blade with circular section in the thermal environment is established.After verifying the correctness of the model.The effects of temperature and blade geometry parameters on the vibration of CNT reinforced ceramic matrix composite blades are analyzed.(4)The functional gradient of carbon nanotube reinforced composite matrix is considered.The dynamic model of carbon nanotube reinforced dual-functionally gradient composite blade with circular arc section in thermal environment was established.The influence of material parameters and the change of functional gradient of matrix material on the vibration of CNT reinforced functional gradient composite blades under thermal environment was mainly studied.