Acoustic emission monitoring of CFRP tank at ambient and cryogenic temperatures

Four-channel Acoustic Emission (AE) monitoring was conducted for both the ambient and cryogenic tests of an unlined filament-wound (FW) CFRP tank. We first evaluated the soundness of the tank by using traditional AE parameter analysis. The Kaiser effect was observed in an ambient test. The felicity ratio calculated from the AE-onset stress and the maximum previous stress indicated that the pressure was close to a critical pressure that could cause damage. Sudden energy increase points that probably indicate large damage occurrence were also observed several times in the ambient test. Snoop testing conducted after the ambient test revealed several leaks in the repaired area. We conducted a cryogenic test after the ambient test. In the fill-process, boiling and droplet-impacting of LN₂ made it difficult to monitor fracture-induced AE signals. Serious leakage from the repaired area occurred at 2.0MPa in the pressurization process. High-energy AE signals were observed three times before the pressure reached 2.0MPa. Several new leaks were found in the repaired area and dome parts. Only one leak was found near the monitoring area on a wrinkle. A waveform-based detailed source location analysis was performed near the leak after the test. Sources of seven AE events were located in the area where the leakage was found.