Detection of defects in composite plates by Cooling Down Thermography (CDT)
Przemysław D. Pastuszak, Konrad Nering, Aleksander Muc
Quarterly No. 2, 2014 pages 111-115
DOI:
keywords: Cooling Down Thermography (CDT), fibrous composites, subsurface defects
abstract In this work, a novel approach of thermal non-destructive testing of composite structures is presented. Among the widely-known pros and cons of Active Infrared Thermography (AIRT), there is still space for its cognition and development. In general, AIRT is based on heat transfer which is changed by the presence of subsurface flaws, variation of thicknesses, corrosion etc. Internal defects disturb normal heat diffusion within the material due to different thermophysical properties, and the result is variation of the amplitude and phase of the response signal on the surface of investigated objects. Typically, external excitation is performed by different heat sources (i.e. halogen lamps). Application of a thermoelectric module as a heat flux activation source presents clear disadvantages in terms of versatility, but it creates new possibilities of testing components which cannot be heated e.g., due to thermal expansion or space limitation for the excitation source. In addition, this approach provides quick measurement. The investigated samples are previously cooled down by the thermoelectric module, and then they are exposed to a higher ambient temperature. An infrared camera monitors the surface temperature variation both during the cooling and heating stage in order to reveal subsurface flaws. The main aim of this work is to examine the effectiveness of Cooling Down Thermography (CDT) to detect artificial delaminations in composite plates.