{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T23:24:57Z","timestamp":1775863497210,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2025,8,1]],"date-time":"2025-08-01T00:00:00Z","timestamp":1754006400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia (FCT)"},{"name":"LAETA Base Funding"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Compos. Sci."],"abstract":"<jats:p>This study comprehensively compares the performance of two non-destructive testing (NDT) techniques\u2014active thermography (AT) and digital shearography (DS)\u2014for identifying various damage types in composite structures. Three distinct composite specimens were inspected: a carbon-fiber-reinforced polymer (CFRP) plate with flat-bottom holes, an aluminum honeycomb core sandwich plate with a circular skin-core disbond, and a CFRP plate with two low-energy impacts damage. The research highlights the significant role of post-processing methods in enhancing damage detectability. For AT, algorithms such as fast Fourier transform (FFT) for temperature phase extraction and principal component thermography (PCT) for identifying significant temperature components were employed, generally making anomalies brighter and easier to locate and size. For DS, a novel band-pass filtering approach applied to phase maps, followed by summing the filtered maps, remarkably improved the visualization and precision of damage-induced anomalies by suppressing background noise. Qualitative image-based comparisons revealed that DS consistently demonstrated superior performance. The sum of DS filtered phase maps provided more detailed and precise information regarding damage location and size compared to both pulsed thermography (PT) and lock-in thermography (LT) temperature phase and amplitude. Notably, DS effectively identified shallow flat-bottom holes and subtle imperfections that AT struggled to clearly resolve, and it provided a more comprehensive representation of the impacts damage location and extent. This enhanced capability of DS is attributed to the novel phase map filtering approach, which significantly improves damage identification compared to the thermogram post-processing methods used for AT.<\/jats:p>","DOI":"10.3390\/jcs9080398","type":"journal-article","created":{"date-parts":[[2025,8,4]],"date-time":"2025-08-04T15:30:06Z","timestamp":1754321406000},"page":"398","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Inspection of Damaged Composite Structures with Active Thermography and Digital Shearography"],"prefix":"10.3390","volume":"9","author":[{"given":"Jo\u00e3o","family":"Queir\u00f3s","sequence":"first","affiliation":[{"name":"INEGI, Institute of Science and Innovation in Mechanical and Industrial Engineering, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9344-8503","authenticated-orcid":false,"given":"Hern\u00e2ni","family":"Lopes","sequence":"additional","affiliation":[{"name":"DEM-ISEP, Instituto Polit\u00e9cnico do Porto, 4249-015 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7635-2219","authenticated-orcid":false,"given":"Lu\u00eds","family":"Mour\u00e3o","sequence":"additional","affiliation":[{"name":"CIETI\/NBIN-ISEP, Instituto Polit\u00e9cnico do Porto, 4249-015 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3662-6166","authenticated-orcid":false,"given":"Viriato","family":"dos Santos","sequence":"additional","affiliation":[{"name":"IDMEC, Instituto Superior T\u00e9cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,8,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Heslehurst, R.B. 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