Infrared Thermography to DetectDelamination and Porosity in Carbon/Epoxy

Infrared thermography (IRT) has already proved its capability to deal with several types of defects buried in different types of composite materials and now is amongst the aeronautical standards. However, the real use of infrared thermography is still somehow limited, needing additional tests and validation. The aim of this work is to contribute to the assessment of infrared thermography as a technique to be used to both estimate the porosity amount and distribution in a carbon/epoxy material as well as to detect a thin delamination in presence of porosity. The detection of a defect with infrared thermography is based on the thermal contrast induced by such a defect, or k l u b d n u o s e h t o t t c e p s e r h t i w t c e f e d e h t f o s e i t r e p o r p l a m r e h t t n e r e f f i d e h t y b r e t t e bm aterial. The presence of porosity means a relatively high percentage of gases entrapped within the material. Besides, a delamination practically means a volume of gases (generally a thin layer) at the interface fiber/fiber, or fiber/matrix. Therefore, the resultant differences in thermal characteristics between the defect and the bulk material are very small which reduces the possibility of the defect to be distinguished. Then, this work wants to investigate whether infrared thermography can be used to detect delamination in such uneasy circumstances. Two different procedures are pursued: flash thermography through local variation of the thermal diffusivity, and lockin thermography through local variation of the phase angle.