Leakage Investigation of Epoxy-Based Composite Laminates for Reusable Cryogenic Propellant Tanks

Abstract

Experimental studies on the gas leakage behaviour of carbon composite laminates are taking place at the German Aerospace Center to further promote the potential use of carbon fibre composites as propellant tank material for reusable launch vehicles. The leak rates of IM7/5320-1 prepreg unidirectional and cross-ply samples are measured using helium mass spectrometry. The leakage behaviour of the samples shows a significant deterioration after being cryogenically cycled with liquid nitrogen. Samples featuring thin plies with approximately 20% of the standard ply thickness are also tested to assess their impact on leakage resistance. The latest results indicate an enhanced gas-tightness of cross-ply laminates with thin plies at helium gauge pressures of 2 bar, but no significant advantage at 4 bar compared to the UD samples. The helium leakage test bed and the test routine are presented along with the latest results and future plans of this ongoing work.