A study of protector for high-pressure hydrogen tank used for drones flying by fuel cells (A study of shock absorbing carbon fiber protector for high-pressure hydrogen tank)

From the previous time, unmanned aircrafts (drones) are being used in fields such as agriculture, logistics, and disaster response. Therefore, it is expected as a machine that creates new technologies and services in the 4th Industrial Revolution. In recent years, there has been a demand for the practical application of drones equipped with a fuel cell as a power source, which enables longer-distance flight. However, in order to operate a fuel cell drone, it is necessary to develop a protector that protects the high-pressure hydrogen tank from the impact of a crash. Therefore, the authors focused on carbon fiber as a protector for hydrogen tanks. Then, in this research, protectors for hydrogen tanks with 6 different layers and weaves were manufactured. And collision tests of these protectors were performed. Based on results obtained in collision tests, energy absorption qualities of protectors were compared and evaluated. As a result, it was clarified that the quality of energy absorption varies depending on the specifications, such as the direction of fibers and the presence or absence of plain weave sheets, even in protectors made from carbon fiber. In particular, the authors clarified the following. In the case of the Carbon Fiber Uni Direction (CFUD) sheet, in which the directional angle of the fibers is the same as the directional angle of the wedge-shaped projections or an angle with a small difference (90 degrees or 72 degrees)., the energy absorption of the protector made of this sheet alone is not good. In addition, a composite sheet that combines a CFUD sheet and a plain weave sheet has better energy absorption than a plain weave sheet alone. After clarifying the foregoing, the authors evaluated protectors with a three-stage evaluation test based on the guideline of the Ministry of Economy, Trade and Industry. Then, it was confirmed that the "Safety requirements for high-pressure hydrogen gas storage containers (tanks) to be mounted on drones" were satisfied by equipped carbon fiber protectors.