Nondestructive Inspection Of Carbon Fiber Reinforced Plastic(CFRP)Laminates Using Ultrasonic Guided Wave

Carbon fiber reinforced plastic(CFRP)laminates are widely utilized in modern aircraft and ship industries due to their excellent physical properties.They have the advantages of low density,high strength rate,high modulus rate,corrosion resistance,low coefficient of thermal expansion.Therefore,they are often used to manufacture the fuselage,wing and nacelle of an airplane.Note that the defects caused by fracture and interfacial debonding may occur during the manufacture of laminates or they are in service.The defects may lead to serious results if they could not been detected in time.The traditional methods for CFRP laminates include visual testing,C-scan testing,nonlinear ultrasonic testing,grating testing,X-ray imaging,and so on.In recent years,the technique of ultrasonic guide waves for CFRP laminates has received a lot of interests.This technique has the advantages of high efficiency and low cost.It can inspect a large area of a laminate simultaneously.However,compared with the propagation of guided waves in a homogeneous plate.that of guided waves in a CFRP laminate is far more complex because of the strong anisotropy of the laminate.In this study,the dispersion equation of guided waves in the CFRP laminate is derived by using the technique of partial waves.Then the equation is numerically evaluated.Moreover,the dispersion characteristics of guided waves in the laminates with different plies and ply-orientations are investigated.The interaction between the guided wave and different defects in the laminate are simulated by the finite element method(FEM).The influence of kinds of factors on the guided waves is studied based on the simulation and the mode used in the section is determined.The contents of this dissertation are arranged as the following.Chapter Ⅰ is the introduction of the background of this dissertation.The progress about the nondestructive inspection of CFRP laminates is introduced.Chapter Ⅱ introduces the theory on the propagation of guided waves in CFRP laminates.The dispersion equation of guided waves in CFRP laminates is derived.In addition,the dispersion curves of the guided wave in CFRP laminates are obtained by calculating the dispersion equation.In chapter Ⅲ,the excitation and propagation of guided waves in CFRP laminates are simulated by the finite element method(FEM).The interaction between guided waves and the defects in CFRP laminates is investigated.The influence of the factors such as the ply number,the defect types and defect sizes on the scattering of the guided waves is studied.Chapter IV is conclusions and prospects.The contents and achievements of this dissertation are summarized.The plans of our future work are presented.