PSI - Issue 77

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 77 (2026) 475–483

© 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers Abstract This work aims to compare the performance of multi-damage identification on a laminated plate, using the non-destructive inspection methods: digital shearography and thermography. Low-energy impacts created two internal damages on a carbon-fibre reinforced polymer (CFRP) plate, producing barely visible impact damage (BVID). A harmonic and transient thermal load was applied according to the method used to reveal internal damage. The phase maps were acquired by using the digital shearography system during the cooling stage of the plate after applying a pulsed thermal load. Afterwards, these maps were post-processed to enhance the phase variations indicative of internal damage, thereby making their identification clearer. The lock-in and pulsed thermography methods involve the acquisition of several thermograms over time. In lock-in thermography, thermograms are acquired during harmonic thermal loading, whereas in pulsed thermography, they are acquired during the cooling stage after applying a thermal load. Damage identification was performed based on the analysis of the phase, processed using Fast Fourier Transform (FFT) algorithm, on the analysis of the filtered thermograms, processed through Principal Components Analysis (PCA) method. The results from the digital shearography reveal the locations of the two impacts and the extension of internal damage. However, PCA images from thermography only show the extent of higher-energy impact damage, while lower-energy impact damage is barely visible. The findings in this work indicate that digital shearography is a more suitable method than thermography for identifying internal damage in thin laminated plates, due to its higher sensitivity, easier setup, and faster measurement time. International Conference on Structural Integrity Inspection of Damage on Laminated Plates: Thermography vs Shearography João Queirósª, Hernâni Lopes b , Luís Mourão c , Viriato dos Santos d, * ª FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal b DEM-ISEP, Instituto Politécnico do Porto, Rua Dr. António Benardino de Almeida 431, Porto 4249-015, Portugal c CIETI/NBIN-ISEP, Instituto Politécnico do Porto, Rua Dr. António Benardino de Almeida 431, Porto 4249-015, Portugal d IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1,Lisboa 1049-001, Portugal

* Corresponding author. Tel.: +0-351-21-841-841-9463 fax: +0-351-21-841-7915. E-mail address: viriato@tecnico.ulisboa.pt

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers 10.1016/j.prostr.2026.01.060