Research On The Dynamic Characteristics Of The Connection Structure Of Composite Materials

Due to the excellent characteristics of low density,high specific strength and high temperature resistance,the application range of composite materials is getting wider and wider and the proportion is getting larger and larger.The current research focus on the mechanical connection structure of composite materials is focused on strength,failure and fatigue.In composite mechanically connected structures,the contact stiffness of the bonding surface has an important influence on the dynamic characteristics of the structure,but there is currently little research on the dynamic characteristics of the overall system.This article has carried out dynamic research on the connection structure of composite materials,mainly including:(1)The stress-strain relationship of the single-layer material was used to derive the stress-strain relationship of the laminated plate structure,and the anisotropic symmetric laminate composite pavement model was established.Based on the three-dimensional equivalent elastic constant theory,the anisotropic material laminate structure was calculated by Matlab software self-programming.The three-dimensional equivalent elastic constant was compared with the experimental results in literature.On this basis,the material properties of the T700 / 7901 composite laminate were calculated,and the third-direction elastic constant of the material was calculated and deduced,which provides a basic theoretical support for subsequent finite element modeling and simulation.(2)Based on the rough surface contact model,the normal and tangential contact mechanical models of the rough surface were analyzed,and the mechanical model of the contact interface was derived based on this model.Finally,the dynamic differential equation of the connection structure including the Iwan model was established,which provides the basis for the subsequent nonlinear modeling of the bolt connection structure and the parameter identification of the bolt joint.(3)The finite element model of the layered laminate composite bolted structure was established,and the dynamic and static simulations were compared with the equivalent material parameter finite element model.(4)The modal characteristic simulation was carried out for the composite plate and the connection structure,the first four natural frequencies of the structure are calculated,and on this basis,the main elastic modulus ratio and the order of the plywood layering on thecomposite connection structure Natural frequency influence.The dynamic response simulation analysis of the composite connection structure was carried out,and the steady state forced vibration response and transient vibration response of the connection structure were discussed.(5)A composite material plate and a bolt-connected cantilever beam structure test stand were built,dynamic experiments were carried out,the experimental and finite element simulation results were compared and analyzed,and the errors of the layered model and the equivalent material parameter model were analyzed.The natural frequency of the connection structure under different bolt pre-tightening torques was tested.At the same time,the natural frequency of the structure was identified using the harmonic response test method,and the stiffness and equivalent damping parameters of the composite bolted structure were identified in conjunction with the nonlinear model of the joint surface.(6)The research results provide a method for the dynamic modeling of composite plate structures and connection structures,and the identification of bonding surface parameters.