Microcrack Investigation and Mitigation for Cryogenic Systems

WCT prior experience has shown that microcracks can be generated as a liquid hydrogen composite tank wall cools from room temperature conditions down to liquid hydrogen temperature. Cycling between these temperature levels causes these cracks to grow andpotentially form delaminations between the plies resulting in leak paths. This Phase II program will define microcracks as they are generated and grow and will evaluate a series of concepts for mitigation of these microcracks. Rockwell Science Center isa principal subcontractor on this program. They will develop the optimal strategy for deflecting and blunting cracks and preventing crack coalescence and leak paths from forming. At least three resin systems will be evaluated under this program. Owingto safety requirements liquid helium will be used as the cryogenic fluid for specimen exposure and cycling. Vacuum pumping equipment and tooling will be provided to enable use of an existing Air Force vacuum chamber for testing with liquid helium. Whileflat panel laminates will be used to verify the success of mitigation concepts, two methods proposed are not feasible for verification by panel testing and two 18