Tensor integrated total variation regularization for thermography NDT of composites

•Optical Pulse Thermography for the NDT of debond defects in CFRP.•The Tensor Integrated Total Variation Regularization algorithm is proposed with low-rank and sparse modeling in an iterative manner.•The irregular shape CFRP are having varying defect diameters and depths are evaluated. The carbon fiber reinforced polymer (CFRP) is being used frequently in the manufacturing of aerospace, rail, and other mechanical structures, where the optical pulse thermography (OPT)-based non-destructive testing (NDT) is generally used for the quality inspection, However, the output thermal sequences in OPT-based inspection suffer from uneven illumination and high-frequency thermal noise. Consequently, the inspection of defects (debonds) becomes difficult. To remedy it, post-image processing algorithms are generally carried out. The usefulness of such algorithms, however, is limited by the shape-complexity of the CFRP specimen. In this paper, we propose a tensor nuclear norm (TNN)-based low-rank and sparse total variation regularization (TVR) for CFRP debond defect detection. The integrated low-rank and sparse components are jointly and iteratively optimized. The proposed algorithm removes noise and segments/extracts the defects information from the thermal video sequences with improved resolution and contrast. Compared to the general image processing algorithm used for OPT-based NDT testing, the proposed algorithm is faster and in terms of F-score is more accurate.