Acoustic emission monitoring of CFRP tank at ambient and cryogenic temperature

Four channels Acoustic Emission (AE) monitoring was conducted for both the ambient and cryogenic tests of unlined filament-wound (FW) CFRP tank. We first evaluated soundness of the tank by using traditional AE parameter analysis. Kaiser effect was obtained at an ambient test. Felicity ratio calculated from AE-onset stress and the maximum previous stress indicated that the pressure was close to a critical pressure to cause damage. Sudden energy increases points which probably indicate large damage occurrence were also observed several times at the ambient test. Several leak points were found in repaired area by snoop test conducted after the ambient test. After the ambient test, we conducted cryogenic test. In the fill-process, boiling and droplet-impacting of LN ₂ made difficult to monitor fracture induced AE signals. In the pressurization process, serious leakage from the repaired area occurred at 2.0MPa. High energy AE signals were observed three times before pressure reached 2.0MPa. Several new leak points were found in the repaired area and doom parts. Only one leak point was found near the monitoring area on a wrinkle. Waveform based detailed source location near the leak point was conducted after the test. Source locations of 7 AE events are obtained from the area where leakage was found.