Study On Identification Of Stratified Defects Of Carbon Fiber Composites Based On Ultrasonic Lamb Wave

The comprehensive performance of carbon fiber composites is superior.So it is widely used in various fields.Because the defects of the material itself or some of the carbon fiber composite materials made of components and equipment will bring about potential safety hazard when we use it,even cause huge losses.Therefore,the detection of material defects is particularly important.Ultrasonic nondestructive testing technology is currently a more advanced non-destructive testing technology,and computer tomography technology has been more mature and widely used in the medical field.The main content of this paper is to combine ultrasonic non-destructive testing technology with computer tomography to detect and identify the layered defects of carbon fiber composites.And the constant are given as follows:By reviewing the domestic and foreign literatures,we understand the propagation characteristics of ultrasonic waves in homogeneous and anisotropic materials,and give the dispersion equations and dispersion curves of ultrasonic Lamb in these two different materials,which provides a theoretical basis for the extraction of ultrasonic Lamb wave excitation signals and get the time of fly in the finite element simulation and experiment.The theoretical basis of computer tomography is introduced in detail,and the mathematical formulas of parallel scanning filter back projection algorithm and fan scan filter back projection algorithm based on central slice theorem are deduced.Finally,the details of step of these two algorithms are given respectively.By contrast,the fan-shaped scan filter back-projection algorithm is selected finally for the image reconstruction algorithm used in this paper simulation and experiment.Selecting the carbon fiber composite multi-purpose plate T300 / 5028 as the object of this paper,the ABAQUS finite element software was used to establish the thin plate model with the layered defects in different positions.The five-cycle Henning window sinusoidal signal is used to simulate the propagation of ultrasonic lamb waves in the thin plate.We should extract the data of TOF.Through the MATLAB program to write fan scan filter back projection algorithm program,the extracted travel time data into the algorithm to reconstruct the thin film model,the defect information is clearly visible.Finally,the experimental platform was built to carry out experiments,and the experimental results were obtained.Due to the limitations of the experimental conditions,the imaging quality of the experiment is not as good as that of the simulation.However,the imaging effect is very impressive.At the same,I analyzed the reason of the phenomenon.The combination of simulation and experiment shows that the technology can be applied to engineering practice,which lays the foundation for the follow-up research.