Research On The Technology Of CFRP Laminate Defect Detection Using Binary Phase Coded Infrared Thermal Wave Imaging

Carbon fiber reinforced polymer(CFRP)has advantages of high temperature resistance,corrosion resistance,high specific strength and high specific modulus,which lead to the great application of CFRP in the fields of aviation,aerospace,new energy and automobile.Many defects are usually exhibited during the application and fabrication of CFRP laminate.It's important to detect those defects in order to prevent the occurrence of serious security incidents and economic losses which the CFRP laminates with subsurface defects caused.The traditional detection methods with low detection efficiency,high cost and Not suitable in-service Detecting,cannot meet the requirements of detecting,it is necessary to find a relative effective,simple,and reliable non-destructive testing and evaluation(NDT&E)technique which meets the requirements for the CFRP laminates with subsurface defect detection.Binary phase coded infrared thermal wave imaging(BPC-TWI)is a new kind of infrared thermography,which has merits of noncontact,high efficiency and strong anti-interference ability,it can meet the requirements of CFRP laminates with subsurface defects detection.Therefore,Binary phase coded infrared thermal wave imaging thermography was deeply investigated.Firstly,the origin of improving the detection resolution and anti-interference ability of BPC-TWI was theoretically analyzed from binary phase coded signal.According to the theory of heat conduction,the 3D heat conduction model were developed under the heat flux of binary phase coded.The computer simulations of the response characteristics of binary phase coded thermal wave signal were carried out to analyze the effects of different modulation parameters(coded length,Excitation frequency,sampling frequency power density),which provides theoretical guidance for the subsequent study of experiment.Secondly,binary phase coded infrared thermal wave imaging testing system was developed,and the detecting software system based on Labview was developed.On this basis,Different modulation parameters under sine and square carrier signal experiments were carried out.Then the effects of different modulation parameters under two carrier signal on binary phase coded thermal wave signal response features were investigated through experiments.Experiments under sine carrier that were used to verify the validation of numerical analysis.Finally,the effects on binary phase coded thermal wave signal response features were investigated through experiments of different modulation parameters under Chirp and Chirp square carrier signals.Furthermore,the reasonable range of testing parameters for defects of CFRP laminate sample was investigated by these experiments.The contrast experiments under different carrier signals were carried out.Under the same conditions,the square carrier and Chirp carrier has better defect detection capability and antiinterference capability of the BPC-TWI.The contrast experiments between binary phase coded infrared thermal wave imaging,infrared lock-in imaging and infrared thermal wave radar imaging for detecting of defects of CFRP laminate were carried out,and results showed that infrared thermal wave imaging thermography has better depth resolution and anti-interference capability.