Speaker
Description
Liquid hydrogen, characterized by its low mass density and high volumetric energy, is actively promoted as an ideal spacecraft fuel. However, due to its cryogenic storage temperature and the risk of leakage, it imposes extremely high demands on the tank structure and material property. Currently, most liquid hydrogen storage tanks are made of metal materials such as aluminum alloys and titanium alloys, which are heavy and difficult to process. In addition, reducing the weight of the tank is beneficial for improving the spacecraft's range and response capability, while also allocating more weight to the payload. Under the same strength requirements, all-carbon fiber composite tanks (type V tanks) reduce the weight by approximately 40% compared to aluminum alloy tanks, making them a transformative technology that overturns traditional cryogenic hydrogen storage equipment.
In the current study, by adding multiple layers of polyethylene films between carbon fiber layers, the leakage mode of liquid hydrogen was shifted from microcrack leakage to diffusion, resulting in an exponential decrease in fuel permeation. Moreover, the impact of film crystal structure on the diffusion of hydrogen molecules was studied. By inducing the formation of spherulites within the polyethylene film, the hydrogen-barrier properties of the film could be enhanced. Furthermore, a multilayered progressive barrier structure was constructed to enable the permeation of liquid hydrogen through the composite to be controlled. Ultimately, the issue of poor hydrogen-barrier property in carbon fiber composite was addressed.
During the experiment, the carbon fiber composites were subjected to 10,000 cycles of cyclic loading under cryogenic conditions (77 K), followed by testing the gas permeation coefficient of the samples using the pressure difference method. The research results indicate that when the crystal structure transforms from lamella structure to spherulite structure, the gas permeation coefficient of polyethylene film decreases from 17.0×10^(-15) mol/(m·s·Pa) to 7.3×10^(-15) mol/(m·s·Pa), representing a decrease of 57.3%. This reduction is attributed to the relatively open structure of lamella structure, which possess larger crystal voids and defects, resulting in a relatively higher gas permeation rate. Conversely, the surface and internal structure of spherulites are relatively dense. The spherulites create tortuous pathways for the permeation of hydrogen, thereby increasing the diffusion resistance of hydrogen molecules and enhancing the hydrogen-barrier property of the film. The gas permeation coefficient of the composite decreases with an increase in the number of film layers. When three layers of polyethylene film are added, the gas permeation coefficients of the carbon fiber composites at room temperature and cryogenic temperature are 1.0×10^(-15) mol/(m·s·Pa) and 0.6×10^(-15) mol/(m·s·Pa), respectively, both meeting the usage requirements. Therefore, the composites with cryogenic hydrogen-barrier properties can be used to fabricate Type V hydrogen storage tanks, promoting the application of liquid hydrogen propulsion technology in the aerospace field.
Acknowledge:
This work was supported by the National Key R&D Program of China (2023YFC3010301), Project of Emission Peak and Carbon Neutrality of Jiangsu Province, China (grant number BE2022001-2).
| Submitters Country | China |
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