Safety evaluation of 70 MPa-capacity type III hydrogen pressure vessel considering material degradation of composites due to temperature rise

This study aims to estimate the mechanical behavior of 70 MPa-capacity type III hydrogen pressure vessels composed of very thick carbon/epoxy composite layers around 40 mm and an aluminum liner, while also considering material degradation of composites. Each composite layer is modeled independently using the ply-based modeling technique, and the variations in the winding angle and the composite thickness of the dome sections are considered. In addition, the temperature distribution of composite layers during the pressurization process is calculated using heat transfer analysis, and temperature-dependent material properties are implemented for each finite element to estimate the stress distribution of the pressure vessel. The analysis results reveal that when material degradation due to temperature rises is considered, the existing winding pattern and the candidate autofrettage pressures satisfy all conditions of the design regulation for type III pressure vessels.