Development of an Experimental Apparatus and Method for Characterizing the Leakage of Helium Gas through Composites Due to Cryogenic Operation

Carbon fiber composite cryogenic fuel tanks are very attractive to the aerospace industry. More information is needed on micro-cracking and how different composite formulations perform at cryogenic temperatures. In this study a cryogenic bulge test fixture was developed to rapidly screen small scale composite samples that are easily formulated in the laboratory. The design goal was to develop a simple fixture that induced thermal and mechanical strains in the same fixture. The pressure decay rate of helium gas through the composite sample after cryogenic operation gives a measure of the amount of micro-cracking induced. Uncertainty analysis techniques were employed to determine the resolution of the pressure decay determined from the bulge test