Research On Scanning Infrared Thermal Imaging Non-destructive Detection Technology For Defects Of CFRP Laminates

Carbon fiber reinforced composite is widely used in aerospace,petrochemical industry,wind power generation,automobile,ship and military industry due to its excellent performance,but it is easy to produce many defects and damages in the process of preparation and application,which will greatly affect the performance and service life of carbon fiber composite.Scanning infrared thermal wave imaging nondestructive testing technology has the advantages of large single scanning area and fast speed,which provides a new way for the rapid detection of defects in CFRP laminates.In this paper,the principle analysis and simulation technology of scanning infrared thermal wave imaging nondestructive testing,the development of scanning infrared thermal wave imaging nondestructive testing system,and the algorithm of scanning infrared image sequence processing are systematically studied.Firstly,the heat transfer process and temperature field distribution of CFRP laminates excited by Gauss type linear heat flow are studied.The heat conduction model of CFRP laminate under the Gauss Heat flow excitation is established,and the finite element method is used to solve the model.The influences of laser power,scanning speed and geometrical characteristics of defects on the surface temperature signal are analyzed.The applicability of scanning infrared thermal wave detection technology to the detection of defects in CFRP laminates is discussed.Secondly,a scanning array laser excited infrared thermal wave imaging nondestructive testing system is built,and the relevant experimental research is carried out.Specifically,it includes hardware system construction and software system design.The infrared image processing software can reconstruct the acquired image sequence in quasi-static state,or use infrared image sequence processing algorithm to process the reconstructed image sequence;design and prepare the simulation sample of CFRP laminate defects,improve the quasi-static reconstruction algorithm,and improve the quasi-static reconstruction algorithm Operation speed of.Through the experimental study,the influence of the geometric characteristics of the defect on the surface temperature signal of the test sample is analyzed,and the correctness of the model is verified.Finally,the infrared image sequence processing algorithms(phase pulse thermography,PPT,principal component analysis,PCA,partial least square regression,PLSR)in the scanning and detection environment are studied,and the above algorithms are used to process the infrared image sequence and extract the temperature signal characteristics.Compared with the reconstructed image,the signal-to-noise ratio of the feature image extracted by PLSR and PPT is higher than that of other methods.The method of likeness optical flow is proposed to suppress the transverse thermal diffusion of heat flow.The image sequence enhanced by likeness optical flow method significantly improves the transverse thermal diffusion effect of heat flow,improves the signal-to-noise ratio of image,and improves the defect detection ability.