Photothermal porosity estimation in carbon fiber reinforced plastics based on the virtual wave concept

Holger Plasser, Günther Mayr, Gregor Thummerer, Günther Hendorfer, Peter Burgholzer

Research output: Chapter in Book/Report/Conference proceedingsConference contributionpeer-review

1 Citation (Scopus)


High strength and light weight, justify the frequent use of carbon fibre reinforced plastics for aeronautical applications. The manufacturing process of such material systems is a multi-stage process and susceptible to the formation of air-filled voids. This porosity weakens the epoxy matrix and causes noticeable degradation of mechanical properties. Active thermography with optical-excitation is an advantageous photothermal method because due to the infrared camera it is a non-contacting, fast testing method for the estimation of material properties or for defect detection. We use the Virtual Wave Concept, which allows ultrasonic testing methods for photothermal measurement data. Based on this ability, we apply the through-transmission method to determine the Time-of-Flight of virtual waves, which is directly related to the porosity dependent diffusion time. A signalto-noise ratio dependent approach is used for the temporal truncation of measurement data to get the optimum evaluation time. This ensures to evaluate only time-ranges which contain information of the heat diffusion inside the sample. In addition, undesired effects of heat losses due to convection and radiation are reduced. After the evaluation procedure is shown for simulated data, we demonstrate the experimental pixel-wise estimation of the porosity affected thermal diffusion times on a real aerospace part in transmission configuration. The results are validated by X-ray computed tomography reference measurements, where a good match can be achieved with active thermography results.

Original languageEnglish
Title of host publicationThermosense
Subtitle of host publicationThermal Infrared Applications XLII
EditorsBeate Oswald-Tranta, Joseph N. Zalameda
Number of pages11
ISBN (Electronic)9781510635951
ISBN (Print)9781510635951
Publication statusPublished - 2020
EventThermosense 2020: Thermal Infrared Applications XLII - Virtual, Online, United States
Duration: 27 Apr 20208 May 2020

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceThermosense 2020: Thermal Infrared Applications XLII
Country/TerritoryUnited States
CityVirtual, Online


  • Active thermography
  • Aerospace application
  • CFRP
  • Photothermal testing
  • Porosity
  • Virtual Wave Concept


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