Research On Nondestructive Testing Technology Of Composite Materials Based On Resonance Behavior

The microstructure of composite materials is a complex multiphase system,where materials and structures are formed simultaneously.Various process parameters are difficult to achieve precise control during the material processing.Structural defects such as pores,delamination,cracks,and matrix debonding are prone to occur.These defects/damages can significantly reduce the bearing capacity and service life of the material,which may affect the safe operation ability of equipment such as aerospace vehicles.Then,it will seriously restrict the promotion and application of composite materials.In order to improve the service life of composite materials and avoid safety accidents,it is necessary to carry out rapid,accurate,and efficient non-destructive testing work on composite materials.Non destructive testing of composite materials using local defect resonance behavior and optical interferometry measurement technology is based on traditional structural vibration detection technology.By identifying the characteristic frequencies of local defect areas,damage localization and imaging are achieved.The method has the advantages of non-contact,low frequency dependence,and high detection efficiency.Therefore,this thesis conducts research on the non-destructive testing technology of composite materials based on local defect resonance behavior and optical interferometry measurement technology.The research content specifically includes the following aspects.Firstly,the basic concepts of structural vibration and the foundation of acoustic vibration detection are introduced.The physical properties and anisotropic elastic mechanical properties of CFRP(Carbon Fiber Reinforced Plastics,CFRP)laminated plates are analyzed.On this basis,the physical mechanism of local defect resonance is analyzed in detail.The characteristic frequency expression corresponding to FBH(Flat Bottom Hole,FBH)defects is obtained.Secondly,ABAQUS finite element software is used to simulate the vibration process of the tested sample under the excitation of piezoelectric transducers,as well as the detection process of FBH defects and lamination defects.The characteristic frequency correspounding to local defect resonance is determined through two solving methods: implicit dynamics and natural frequency identification.Then,the frequency domain analysis method of structural mechanics is used to conduct in-depth research on CFRP laminates with different distribution characteristics of FBH defects and delamination defects in COMSOL Multiphysics software.The full link model of laser defect detection is established.In the optical interferometry process,the influence of different defect distribution characteristics on the laser phase is deeply analyzed.The internal relationship between the characteristic frequency correspounding to local defect resonance and defect size is determined.Finally,taking an aluminum plate model with FBH defects as an example,the relationship between the sample size and the characteristic frequency correspounding to local defect resonance is analyzed in detail.The parameter setting of spatial step under scanning detection mode is analyzed.The threshold setting of spatial step(5mm,5mm)can simultaneously consider detection speed,detection accuracy,and imaging effect.To study the resonance behavior of local defects,starts with theoretical research and numerical simulations.The detection ability of non-destructive testing based on local defect resonance behavior and the feasibility of using laser phase change to detect defect distribution characteristics are effectively verified.It provides a theoretical basis for subsequent experimental research on non-destructive testing of composite materials.