Estimation of Defect Depth in Carbon Fibre Reinforced Polymer Using Frequency Modulated Thermal Wave Imaging: An Analytical Study

Abstract

Frequency modulated thermal wave imaging (FMTWI) is an efficient and affective thermal nondestructive testing and evaluation (NDT&E) technique for qualitative and quantitative analysis for defects in test materials. FMTWI utilizes low peak power heat sources modulated within a frequency sweep to excite the material under test. The paper demonstrates a novel analytical approach for heat diffusion in isotropic material using FMTWI technique to distinguish defects located at different depths inside the test sample. The frequency modulated thermal excitation has been illuminated over carbon fibre reinforced polymer (CFRP) material to compute thermal response over the object under test. The mapped temperature response is analysed further for defect detectability in terms of correlation coefficient and time delay. Further, the presented analytical approach for defects located at different depths are comparted with the simulation model of CFRP test material. Lastly, different frequency and time domain data analysis schemes have been applied to detect defects in terms of thermal contrast. Results demonstrates the detection capability of FMTWI technique using correlation based matched filter method to provide better test resolution and sensitivity.