Nondestructive testing of bonding defects in multilayered ceramic matrix composites using THz time domain spectroscopy and imaging

摘要

The accurate detection and imaging of small debonded regions in a 3-layer ceramic matrix composite (CMC) with two bonded layers is a challenge within terahertz (THz) nondestructive detection. To solve this problem, an improved imaging method for detecting bonding defects is proposed based on the statistical characteristics of variance and kurtosis to detect defects in the upper/lower adhesive layers in a multilayered CMC. The proposed method can ultimately realize a detection accuracy of 50 and 250 mu m for bonding defects in the upper and lower adhesive layers, respectively, and achieve a better imaging result compared with power imaging method. Moreover, there is a corresponding relationship between the statistical characteristic value and the bonding defect size-the larger the statistical characteristic value, the larger the bonding defect size-which can be used as a reference to quantify the defect size.