Study On The Dynamic Degradation Characteristics Of Fiber-reinforced Composite Thin Plates Under Thermal Environment

Fiber-reinforced composite plates have the advantages of anti-fatigue,vibration reduction and high temperature resistance,which are widely used in high-temperature environments.After long-term work,the structural function will be degraded,which will cause catastrophic accidents to the entire working systems.Therefore,it is of great engineering and academic significance to study the performance degradation of such structures and scientific evaluation methods.In this paper,the dynamic performance of composite plates under different temperatures and time is tested through experiments,and a dynamic performance degradation model is established.The correctness of the model is verified by experiments,and the dynamic performance degradation law of composite plates is analyzed in depth.The main content of the paper is listed as follows:(1)A dynamic performance test system for composite plates is established.The effects of degradation time and heating temperature are considered to test the dynamic performance of fiber-reinforced composite plates under different thermal environments.A dynamic stiffness method is proposed to analyze the dynamic degradation law of composite plates.The study found that during the constant temperature heating process,the natural frequency of the composite plate gradually decreased,and the higher the temperature,the more serious the degradation phenomenon;and under the change of the thermal environment,The natural frequency of the composite plate gradually decreases during the heating and keeping temperature stages.After the cooling stage,the natural frequency gradually increases,but the change trend of the damping ratio is opposite to that of the natural frequency.(2)For the problem of dynamic degradation of composite plates under constant temperature environment,a function of dynamic elastic moduli of composite plate with respect to heating temperature and degradation time is proposed,a theoretical model of dynamic performance degradation under thermal environment is established,and the particle swarm optimization is introduced in detail.The algorithm finds the optimal value of the dynamic elastic moduli under the corresponding heating temperature and degradation time.The CFtool in Matlab is utilized to solve the process of the undetermined coefficients in the function model,and the theoretical model is verified by experiments.The results show that the proposed degradation model takes into account the degradation of material parameters,the calculation accuracy of the dynamic characteristics of the composite plate is improved,and the purpose of analyzing and predicting the dynamic performance degradation law of composite plates under a constant temperature environment are achieved.(3)For the problem of the dynamic performance degradation of composite plates under the change of thermal environment,in order to improve the accuracy of the degradation model to solve the dynamic characteristics,the elastic moduli,loss factor and thermal expansion coefficients of composite plates are taken into account.In three stages,their functions about temperature and time were established,the undetermined coefficients were determined by the quantum particle swarm optimization algorithm and Matlab software,and the dynamic performance degradation model of composite plates under thermal environment changes was obtained.Variations of natural frequency,vibration response and damping ratio of the thin plate are analyzed under the heating,constant temperature and cooling stages.The research in this paper further reveals the dynamic performance degradation law of composite plates under complex high temperature environments,which has an important predictive effect on the performance degradation behavior of composite plates subjected to dynamic loads for a long time in the thermal environment.And it provides important suggestions and selection basis for the evaluation and prediction of the dynamic performance of composite plates in engineering practice.