• Shi, Zhengwei
• Howie, Tucker
• Georgeson, Gary
• Flinn, Brian
• Jang, Sei-Hum

Abstract

Incipient thermal damage of CFRP composites is a serious problem as it can significantly reduce mechanical properties of a composite and it is not detectable by common inspection methods such as ultrasound. To detect this incipient thermal damage, DGEBA-DETA epoxy coatings doped with a thermally responsive fluorescent probe were applied to CFRP composite panels and subjected to localized heating at 204 °C and 232 °C. At short exposure times (5 min) a yelloworange fluorescence from the probe is observed, but for longer exposure times the fluorescence changes to a blue-green color. This shift in fluorescence wavelength was attributed to the superposition of the probe fluorescence and the matrix fluorescence, which was also found to grow with thermal exposure. After 30 minute exposures at 232 °C, the fluorescence begins to decrease due to oxidation of the matrix; however, the areas surrounding the quenched region are still fluorescent enabling optical detection of the damage even with the quenching of the fluorescence. Removing the thermally oxidized surface layer by sanding was found to restore the fluorescence. Copyright 2013 by Aurora Flight Sciences.

Topics

• impedance spectroscopy
• surface
• composite
• quenching