Influence Of Low Cycle Fatigue On Natural Frequency And Damping Of Composites

Compared with traditional metal materials,composite materials have the characteristics of light weight,high specific strength,high specific stiffness and high damping performance,which have been widely used in various load-bearing system components in the field of aerospace.In the field of Aeronautics and Astronautics,when the power system and load-bearing components bear the dynamic load,they are often accompanied by the generation of vibration,which is generally harmful to the system and components,so the research on the vibration characteristics of the components in the aeronautics and Astronautics system has been paid more attention.At the same time,the complex load-bearing environment and the increasing requirements of continuous working performance make the fatigue problem of composite materials get more and more attention.Therefore,it is of great significance to study the influence of fatigue on the vibration modal parameters of composite materials.The main contents and conclusions of this paper are as follows:(1)The fatigue vibration modal tests of unidirectional composite materials are carried out.For the specimens with 0 °,± 45 ° and 90 ° fiber orientation,the fatigue vibration modal tests under three different fatigue stress levels are carried out respectively,and the natural frequency and loss factor data in the fatigue process are obtained.Based on the exponential model and even polynomial model,the test data are fitted,and the model which can accurately describe the change of natural frequency attenuation rate and loss factor with the fatigue cycle ratio is obtained.(2)The fatigue vibration modal test of 2.5D woven composite was carried out.For the 2.5D weft composite,the fatigue vibration modal tests were carried out at 80% and 85% stress levels respectively.Based on the natural frequency attenuation rate model and the loss factor model of unidirectional composite materials,the test data are fitted.On this basis,for the loss factor of 2.5D composite materials,an index like model with better fitting effect is proposed to fit and compare it.(3)Based on the theory of natural frequency finite element and the damage model of composite materials,a method of natural frequency analysis of composite materials considering fatigue damage is established for unidirectional composite materials and laminated composite materials.Based on the established method,the corresponding program is developed in the ANSYS finite element analysis platform,and the natural frequency variation of 0 °,± 45 ° unidirectional plate and I-beam laminated plate considering fatigue damage is simulated.Compared with the test data,which proves the validity of the analysis method.(4)Based on the 2.5-D composite double cosine rectangular geometric cell model and the natural frequency analysis method of composite considering fatigue damage,a 2.5-D composite natural frequency analysis method considering fatigue damage is established,and the corresponding program is developed on the ANSYS finite element analysis platform.which proves that The effectiveness of 2.5D composite natural frequency analysis method considering fatigue damage.