AE MONITORING OF CRYOGENIC PROPELLANT TANK

In order to study the cryogenic properties of CFRP tank, we conducted pressurization test of a small filament-wound (FW) tank at cryogenic temperatures. We first investigated the orientation dependence of acoustic emission (AE) signals at both room temperature and LN2 temperature by using artificial source. Lamb-mode dispersive AE signals were monitored in the CFRP tank. In tests at room temperature, we used A0-mode Lamb waves for source location. However A0-mode Lamb waves at several angles were hardly observed at LN2 temperature. In this study S0-mode were used for source location. 60% of tank wall was damaged before this test, and many AE signals are generated from this damaged zone. We developed a new method to separate AE signals generated at damaged zone utilizing signal duration. When the AEs from monitoring (or non-damaged) zone are evaluated, detail source location is possible using arrival time differences of AEs. Next we conducted pressurization test of the CFRP tank at LN2 temperature. About 660 AE events were visually extracted from detected 2800 AE hits. We then investigated the duration of AE events and 100 AE events are evaluated as AE generated at non-damaged zone. Source locations of 7 AE events are obtained from the area where leakage was identified by snoop test conducted after the pressurization test.