Carbon fiber reinforced composites (CFRP) are widely used in the aviation industry and other fields. During service, the surface of CFRP is vulnerable to impact and damage defects, which poses a threat to the safety of CFRP quality. The halogen lamp is used as the active heat source of the sample. Based on the built optical pulse thermography (OPT) test system, The sample with impact damage under long pulse excitation is studied. The thermal response of impact damage samples was collected by infrared camera A655sc. The original infrared image sequence is processed by pulse phase method (PPT), thermal signal reconstruction (TSR), and total harmonic distortion (THD). The results show that the signal-to-noise ratio (SNR) of Original images processed by PPT, TSR, and THD is improved, while the SNR of THD is significantly improved. More impact damage defects recognition effect is obtained by optical pulse thermography.
Honeycomb structures are widely used in aerospace and other fields, which are prone to debonding defects during service. Therefore, it is necessary to detect the defects of honeycomb structures in time. In this paper, the square-wave thermography detection principle was studied. The thermal conduction of CFRP / Al honeycomb panel with debonding defects was simulated by the finite element analysis. Pulse phase thermography (PPT), principal component analysis (PCA), thermal signal reconstruction (TSR), and total harmonic distortion (THD) ware studied for the original infrared image sequence. The signal-to-noise ratio (SNR) was calculated and the processing results ware compared. PCA-PC1 had the maximum SNR, which could reduce the background noise interference in square-wave thermography. Square-wave thermography can accurately detect and identify the debonding defects of the honeycomb structure.
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