Research On Infrared Thermal Wave Nondestructive Testing Technology Of Carbon Fiber Materials

Carbon fiber composite material is an advanced composite material with low density,high strength,high temperature resistance,corrosion resistance,etc.It has been widely used in aerospace,military,automotive and other fields in recent years.Due to the complex structure of composite material components,various defects such as delamination,debonding and cracks are easily generated inside under cyclic stress and external impact,and it is difficult to directly detect from the surface,which seriously affect the reliability and safety of the components.Therefore,it is necessary to research and develop non-destructive testing technology which can detect the internal molding defects of materials.Among various non-destructive testing methods,infrared radiation imaging testing has become an effective means to solve the problem of non-destructive testing of carbon fiber composite materials due to its fast,intuitive,non-contact,and large detection area at a time.This article first introduced the active infrared nondestructive testing technology from the basic principles,development history,research status,etc.and the feasibility of pulse excitation infrared thermal wave nondestructive testing technology in detecting internal defects of carbon fiber materials was analyzed.Then the thermal conduction of the carbon fiber plate under pulse excitation and the influence of internal defects on the surface temperature field distribution were theoretically analyzed.A pulse-excited infrared thermal wave nondestructive inspection system was built,and the influence of size,depth and other factors on defect detection was analyzed.Next,several infrared image defect extraction methods and infrared thermal image sequence processing methods such as frame difference method,polynomial fitting method,principal component analysis method were analyzed,and the advantages and disadvantages of the processing results were compared.Among them,the pulse phase algorithm and its influencing factors were analyzed emphatically,and the sampling time was optimized,which can effectively improve the algorithm's defect detection effect,and can realize the accurate detection of defects with an area of 73.9 ~2or more.In order to solve the problem that the defect extraction results are difficult to mark on the test piece in time,a pulse excitation infrared non-destructive testing and projection marking system was established,and a camera-assisted projection transformation method was proposed.Through the auxiliary camera to shoot the test piece and the projected image at the same time,the accurate position of the defect extraction result in the image coordinate system of the projector was obtained,which solved the problem of image registration caused by factors such as the viewing angle difference between the projector and the thermal imager,and improved the marking accuracy of defects effectively.In this paper,the artificial defect carbon fiber board with blind holes made on the back was selected as the test object,the flash was used for pulse excitation and the infrared image sequence is recorded by the thermal imager.The image sequence was processed by the pulse phase algorithm optimized for the sampling time,and the defect contour was extracted.After that the extraction result was processed by the camera-assisted projection transformation method,and projected by the projector to the surface of the test piece to realize the accurate marking of internal defects in materials.