Cryogenic mechanical and hydrogen-barrier properties of carbon fiber composites for type V cryo-compressed hydrogen storage vessels

Carbon fiber composites for type V cryo-compressed hydrogen (CcH2) storage vessels should have both pressure-bearing and hydrogen-barrier properties. However, hydrogen leakage and delamination defects are prone to occur under cryogenic temperatures (CT) and high pressures. In the current work, polyethylene (PE) films were added to the interlayers of carbon fibers for blocking hydrogen permeation. After hot-pressing treatment, the films melted and wrapped the fibers to form a cross-linked network structure. Then, the resin impregnation and curing were conducted to obtain integrated composites with significant cryogenic mechanical and hydrogen-barrier properties. The results demonstrated that the cross-linked network structure resulted in a 22.7% increase in the cryogenic adhesion force. Under the toughening effects of PE, the longitudinal and transverse tensile strength increased by 23.2% and 21.2%, respectively, while maintaining high cryo-toughness. When 3 layers of PE films were added, the hydrogen permeability coefficients at room and cryogenic temperature were 1.0 × 10−15 mol/(m·s·Pa) and 0.6 × 10−15 mol/(m·s·Pa), respectively, which are lower than the international standard values. Numerous dense PE spherulites with irregular distribution were formed under the action of hot-pressing treatment, which generated tortuous paths within the composites to inhibit hydrogen permeation. The prepared composites may be useful in the manufacture of linerless type V CcH2 storage vessels.