Pulsed and Vibro Thermographic results
The CFRP
specimens were manufactured and purposely damaged via impact, in the Cranfield
composite centre. Sample A4 was manufactured via manual woven, and the other two
samples were unidirectional. The composites consist of laying up pre-preg
piles to form a laminate stack, the material is then autoclave processed at 180oC
and 7 bars for a few hours suitable for the thermoset resin cure, this is
according to the supplier’s specification (Hexcel). There were three specimens,
one that was undamaged, and two that had been impacted with a force of 15 and
20 J of energy. The infrared camera used in this experiment was a FLIR Phoenix,
with inSb sensor material, 3-5 mm, 640x512 pixels and allows data acquisition
at 50Hz.
The
surface of the specimens were positioned parallel to the camera lens. The data was acquired for 40 seconds with a 1.5
millisecond integration time, that includes 10 frames before the flashes, plus
1990 frames during cooling a total of 2000 frames where recorded. The software
used to acquire the data was RDac from FLIR. For signal processing MATLAB and
Ir_view from Visiooimage inc were employed. Two advanced processing techniques
were used; PCT (principal component thermography) and PPT (pulsed phase
thermography).
