Structural health monitoring of type 4 composite fuel tank based on correlation between ultrasonic attenuation and crack density.

As the number of FCEV vehicles increases, the importance of safe hydrogen fuel storage becomes larger. Hydrogen energy needs a high-pressure composite pressure vessel called a type 4 fuel tank. The type 4 fuel tank consists of a plastic liner and filament winding of composite fibers. During use, the hydrogen fuel tank is repeatedly charged and discharged, which causes damage to the composite region of the fuel tank. Therefore, to ensure the safe use of hydrogen fuel, it is necessary to monitor the condition of the hydrogen fuel tank. This article proposes a new, practical structural health monitoring (SHM) method based on the correlation between ultrasonic attenuation and crack density. The propagating ultrasonic wave attenuates by interaction with the damages in the composite materials of the fuel tank. Hydraulic cycle tests were performed to reproduce repeated damages in the fuel tanks. The micro-CT imaging method was used to verify the actual crack density of the fuel tank. The attenuation of the ultrasonic wave propagation and the crack density of fuel tanks were combined in one equation using the hydraulic test cycle as a parameter. With this practical SHM method, real-time structural health monitoring of type 4 fuel tanks can be done by measuring ultrasonic wave propagation on the fuel tank with the PZT active sensor network, offering hope for improved safety in the automotive and aerospace industries. [ABSTRACT FROM AUTHOR]