Influence of Stress Ratio on the Reliability of Al/Carbon-Fiber Composite Hydrogen Tanks

Hydrogen has been proposed as an important energy source for fuel cell vehicles (FCV), and the hydrogen storage tank is considered to be indispensable key equipment for hydrogen application. Currently, Al/carbon-fiber composite hydrogen tanks have become a study focus due to their outstanding properties such as high stiffness-density and strength-density ratio. In standards of this type hydrogen tanks, stress ratio is a primary parameter to be determined. Raising the stress ratio, the reliability will be increased; however, the hydrogen storage density will be decreased accordingly. In this paper, a study on the relationship between the stress ratio and reliability is carried out based on the static strength reliability analysis. The stress-strength interference model is used for the calculation of reliability. For fiber reinforced hydrogen tanks, the stress variance is mainly influenced by two classes of random variables, and the quantity of random variables is affected by the number of composite layers which depends on the stress ratio. So by analysis of stress distribution, the influence of stress ratio on the reliability is revealed, and a theoretical method is developed that can be used for selecting rational stress ratio in the standard.