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Thickness determination in active thermography for one and multilayer semitransparent materials

  • Flash thermography is a well-known non-destructive testing technique and has proven to be a valuable tool to examine material defects and to determine thermal material parameters and the thickness of test specimens. However, its application to semitransparent materials is quite new and challenging, especially for semitransparent multilayer materials like glass fiber reinforced polymer (GFRP). Here, in order to deduce the thickness of coated and uncoated semitransparent specimens as well as the depth of defects in such specimens by means of flash thermography, we apply an analytical model based on the quadrupole method by Maillet et al. to calculate the temperature development during the flash thermography experiment. The model considers semitransparency of the sample and thermal losses at its surface. It supports the use of an arbitrary temporal shape of the heating pulse to properly describe the measurement conditions for different heat sources. By fitting the results of theFlash thermography is a well-known non-destructive testing technique and has proven to be a valuable tool to examine material defects and to determine thermal material parameters and the thickness of test specimens. However, its application to semitransparent materials is quite new and challenging, especially for semitransparent multilayer materials like glass fiber reinforced polymer (GFRP). Here, in order to deduce the thickness of coated and uncoated semitransparent specimens as well as the depth of defects in such specimens by means of flash thermography, we apply an analytical model based on the quadrupole method by Maillet et al. to calculate the temperature development during the flash thermography experiment. The model considers semitransparency of the sample and thermal losses at its surface. It supports the use of an arbitrary temporal shape of the heating pulse to properly describe the measurement conditions for different heat sources. By fitting the results of the analytical model to experimental data it is possible to determine the thickness of the specimen, provided the thermal material parameters are known, e.g., by calibration experiments with samples of the same material with known thickness. We will show that thickness determination of semitransparent test specimens is possible both for transmission and reflection configuration, with and without a blackened sample surface at either front or back side of the sample. As an example, Figure 1 shows the experimentally obtained temperature differences of the surface of a blackened GFRP sample in transmission configuration with the coating facing the flash lamp (usual configuration, (a)) or the infrared camera (unusual configuration, (b)). Using the proposed method, the thickness of the sample can be determined for both configurations.zeige mehrzeige weniger

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Metadaten
Autor*innen:Raphael Bernegger
Koautor*innen:Simon Altenburg, Mathias Röllig, Christiane Maierhofer
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2017
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Absorption coefficient; Analytical model; GFRP; Heterogeneous; Pulse thermography; Semitransparent
Veranstaltung:19th International Conference on Photoacoustic and Photothermal Phenomena
Veranstaltungsort:Bilbao, Spain
Beginndatum der Veranstaltung:16.07.2017
Enddatum der Veranstaltung:20.07.2017
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:13.12.2017
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
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