Pressurizing test of CFRP model tank in cryogenic temperature

The authors present in this study an approach demonstrating the performance of a toughened epoxy CFRP concept tank under internal pressure at a cryogenic temperature. Three tanks were prepared with eight-ply unidirectional (UD) quasi-isotropic lay-ups of two different patterns and cloth lay-up. Each tank was cylindrical with a diameter of 600mm and length of 1200mm, covered with an aluminum flange at one end and a 600mm hemispherical CFRP dome at the other. The gauge length used was the central 300mm of the cylindrical section with a wall thickness of 1.1mm and made from IM600/#133 toughened epoxy CFRP. Each of the tanks was installed into a metallic chamber with the outside being under vacuum in order to preserve the cryogenic condition. The inside of the tank was pressurized with liquid nitrogen (LN₂) together with gaseous helium (GHe) with the aim of detecting the onset of damage from the GHe leakage. The experiments were performed as follows. Firstly, helium gas leakage was measured and indicated no damage resulting from a water pressure of 1 MPa at room temperature (R.T.). Secondly, LN₂ storage was performed without pressurization in order to evaluate any damage onsets due to the cryogenic condition. Following LN₂ storage, no damage was detected within the gauge section of the tank. Thirdly, the tank was pressurized with LN₂ and GHe to 0.98 MPa at gauge pressure (MPaG) and indicated the gauge section to has kept intact. Therefore, it was concluded that the materials and concept CFRP tank structure were successfully demonstrated under pressurization in cryogenic conditions. Although technical steps remain regarding engineering structures, CFRP appears to be a promising candidate for the realization of lightweight pressure vessels such as launch vehicle cryogenic tanks.