Study On The Parameter Identification Methods Of Fiber-reinforced Composite Matarial Under Room Temperature And Thermal Environment

Among composite materials,the fiber-reinforced composites are widely recognized and applied in various fields.Compared with traditional materials,fiber-reinforced composites have high specific strength and specific stiffness,high temperature resistance,fatigue resistance and good thermal stability,and have been widely applied in the fields of ships,buildings,vehicles and aerospace.Nowadays,there are a large number of fiber-reinforced composite structures made of this type of materials in practical engineering.As their service environments become more and more diverse,the vibration and fatigue failure problems caused by them become more and more complex and severe,especially in the thermal environment.In order to further study and curb the problems of structure fatigue and damage caused by vibration,the priority is to accurately obtain this type of composite material parameters,such as the elastic moduli,loss factors and Poisson’s ratios in the longitudinal,transverse and shear directions of the fiber.The parameters have important engineering and academic significance for response prediction,fatigue life prediction,dynamic performance optimization and other links.In addition,as for the research on material parameters identification of fiber-reinforced composites under different environments,it provides a new solution and method for the material parameters.Therefore,it is necessary to study the material parameters identification methods of fiber-reinforced composites under room temperature and thermal environment.The specific research contents are as follows:(1)A fiber-reinforced composite parameter tester based on laser scanning under room temperature environment is developed and applied.Firstly,the hardware structures are established,and the functions as well as control and measurement advantages of the software and the corresponding modules based on LabVIEW are also described.Then,the theoretical model of composite parameter tester is built.Then,an appropriate step size is chosen to construct the iterative vector of the material parameters,and the theoretical principle about the identification of material parameters is explained in details.Finally,by using this instrument,the material parameters of two TC500 carbon fiber/resin composite beam specimens in different fiber directions are identified,which are also compared with the material parameters provided by the manufacturer.The results show that the reliability of the developed composite material tester and the effectiveness of the related algorithm have been verified.(2)The method for parameter identification of fiber-reinforced composites based on planar acoustic wave excitation is studied under room temperature.Firstly,the theoretical model of fiber-reinforced composite thin plate under planar acoustic wave excitation is established,and theoretical solution to the time-domain vibration response is also obtained through the formula derivation.Then,using the particle swarm optimization algorithm,the parameters identification method for fiber-reinforced composites is constructed and its principle is explained.Next,based on the test system,the natural frequencies and vibration responses of composite thin plate are obtained through VMD method.Finally,according to the theory and the measured data,and based on the iterative identification calculation of particle swarm,the parameters of CF140 carbon fiber/epoxy resin material can be successfully identified,and the identified parameters are verified and analyzed.(3)The material parameters identification method of fiber-reinforced composites with temperature and amplitude dependence under the thermal environment is studied.Firstly,to demonstrate the temperature and amplitude dependent phenomena,a series of nonlinear dynamic characterization experiments of two different types of PRD-YG-03 carbon fiber/epoxy composite thin plates in thermal environment are undertaken.Then,from the perspective of material nonlinearity,the expressions of complex elastic moduli of such composite materials are assumed by introducing the temperature and amplitude dependent fitting coefficients.Subsequently,the iterative identification principle of nonlinear elastic moduli and loss factors of FRPC is illustrated,and the identified results obtained by this method are indirectly validated by comparing the calculated natural frequencies and damping data with the experimental ones of another composite thin plate.Besides,the influences of the scale of population,mutation operator,crossover operator are discussed for better utilizing the differential evolution algorithm with high accuracy and efficiency.