PSI - Issue 77

ScienceDirect Structural Integrity Procedia 00 (2026) 000 – 000 Structural Integrity Procedia 00 (2026) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 77 (2026) 673–680

© 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 paper presents a novel method for identifying multiple internal damages in laminated composite plates using filtered phase maps acquired by digital shearography (DS). The technique analyzes interference phases acquired at fixed intervals during the cooling phase after a pulsed thermal load. By correlating consecutive interference phases, a phase map is generated for each step. These maps are then processed: first, a band-pass filter isolates the small phase deviations caused by internal damage; second, the filtered maps are coherently summed to enhance the damage-induced signal against background noise significantly. The effectiveness of the method is demonstrated on a carbon-fiber-reinforced polymer (CFRP) plate containing two internal damages from low-energy impacts. Results show that the filtered phase maps enable superior identification of both the location and size of the damage compared to standard post-processing techniques. Furthermore, generating phase maps between small time intervals minimizes speckle decorrelation, and the subsequent summation step effectively mitigates random distortions from air convection and external vibrations, yielding filtered maps with a significantly better signal-to-noise ratio (SNR). The influence of the shearing direction on damage detectability is also investigated. Overall, this approach provides a robust and enhanced evaluation of damage in composite structures. © 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 Keywords: Multiple damage identification; CFRP plate; Digital shearography; Band-pass filter Abstract This paper presents a novel method for identifying multiple internal damages in laminated composite plates using filtered phase maps acquired by digital shearography (DS). The technique analyzes interference phases acquired at fixed intervals during the cooling phase after a pulsed thermal load. By correlating consecutive interference phases, a phase map is generated for each step. These maps are then processed: first, a band-pass filter isolates the small phase deviations caused by internal damage; second, the filtered maps are coherently summed to enhance the damage-induced signal against background noise significantly. The effectiveness of the method is demonstrated on a carbon-fiber-reinforced polymer (CFRP) plate containing two internal damages from low-energy impacts. Results show that the filtered phase maps enable superior identification of both the location and size of the damage compared to standard post-processing techniques. Furthermore, generating phase maps between small time intervals minimizes speckle decorrelation, and the subsequent summation step effectively mitigates random distortions from air convection and external vibrations, yielding filtered maps with a significantly better signal-to-noise ratio (SNR). The influence of the shearing direction on damage detectability is also investigated. Overall, this approach provides a robust and enhanced evaluation of damage in composite structures. © 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 Keywords: Multiple damage identification; CFRP plate; Digital shearography; Band-pass filter International Conference on Structural Integrity Improving Damage Identification by Shearography Phase Map Analysis H. Lopes a, *, J. V. Araújo dos Santos b , M.A.P. Vaz c a DEM-ISEP, Instituto Politécnico do Porto, Rua Dr. António Benardino de Almeida 431, Porto 4249-015, Portugal b IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1,Lisboa 1049-001, Portugalª c FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal International Conference on Structural Integrity Improving Damage Identification by Shearography Phase Map Analysis H. Lopes a, *, J. V. Araújo dos Santos b , M.A.P. Vaz c a DEM-ISEP, Instituto Politécnico do Porto, Rua Dr. António Benardino de Almeida 431, Porto 4249-015, Portugal b IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1,Lisboa 1049-001, Portugalª c FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: hml@isep.ipp.pt * Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: hml@isep.ipp.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 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

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.2026.01.083 Information classification: Internal Information classification: Internal