A study of the effectiveness of traditional water coupled and non-contact ultrasonic C-Scan systems for wet damaged Glass Fiber Reinforced Polymer (GFRP) composites has been performed. Long term immersion for up to 24 months, of impact damaged GFRP plates in hot water at 65°C and 93°C causes serious matrix degradation. Water diffusion is followed by water uptake measurements. The use of water coupled pulse-echo ultrasonics proved ineffective after long-term water immersion as damaged areas become ultrasound-invisible. The use of air-coupled through thickness ultrasonics is examined for damage detection and evaluation. The contrast between impact damaged areas and water diffused areas is restored. Calibrating the system to a dry condition specimen, a good qualitative and quantitative indication of the degraded state of specimens can be obtained. This monitoring system for the degradation process proves to be very promising.
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