Thermally stimulated luminescence for defect characterization in composites

Onderzoeksgroepen: Lumilab en Mechanics of Materials and Structures

Promotoren: Prof. Mathias Kersemans en Prof. Philippe Smet

Begeleiding: Saeid Hedayatrasa en Florian Cougnon

Inlichtingen: tel. 09/264.43.42 of contacteer rechtstreeks een betrokken persoon (de contactgegevens opvragen door op de naam te klikken)

Thermally stimulated luminescence for defect

Over the past 30 years, composite materials have taken a strong position in aerospace, automotive industry or wind energy, as they exhibit some unique properties such as a high specific stiffness and strength, good fatigue durability, and high resistance against corrosion. A counter side of composite materials is that these materials are prone to defects. Therefore, reliable inspection techniques are essential in order to evaluate the structural health of large composite structures.

Figure 1: Schematic representation of the setup for defect inspection by means of thermally stimulated luminescence at the composite surface.
Figure 1: Schematic representation of the setup for defect inspection by means of thermally stimulated luminescence at the composite surface.

The UGent-MMS group has acquired a leading status in the field of non-destructive testing of composites by means of infrared thermographic defect inspection. The working principle of infrared thermography is based on the anomalous heat wave transport through a composite when defects are present. Heat is mostly externally delivered to the composite structure by means of radiation of high-power flash lamps. Inspection and analysis of the surface temperature by means of a thermographic camera allows to visualize and characterize the size and location of the defects. Although this inspection technique is very promising, necessity of a sensitive thermographic camera requires large investment costs. One way to omit this large cost, is by the application of a (thermo)-luminescent layer on top of the composite. The luminescent layer consists of BaSiON particles suspended in an epoxy matrix which allows to convert heat into luminescent light emission. Internal defects deteriorate the heat wave propagation through the composite. Therefore, on a local scale,  the light activation within the luminescent layer is also affected by the presence of the defects. This difference in emitted light intensity can be easily observed by means of a conventional low-cost camera in the visual spectrum, and consequently allows for defect visualization.


In this thesis, the feasibility of this approach is evaluated for the first time. At first instance, it is up to the student to grasp the benefits, drawbacks and limitations of this technique. In a later stage, the student will focus on the analysis of the time-dependency of the luminescent behaviour in order to retrieve spatial information on the defect distributions within the sample. This is done by comparison of the obtained results with conventional defect inspections by means of  infrared thermography.


In conclusion, this research concerns a topic which has a major relevance with regard to today’s challenges in industry and is the result from an interplay between the fields of material science, and solid-state physics. For this challenging project, we are looking for a student with a dedicated enthusiasm for experimental physics and a natural interest to theoretical concepts.


  • Dit thesisonderwerp kan ook opgenomen worden in het kader van de Educatieve Master Fysica en Sterrenkunde.
  • Aan dit onderwerp is geen mobiliteitsaspect verbonden. Er kan met de promotoren wel overlegd worden over gerelateerde stage-activiteiten en/of vakken aan andere universiteiten.