Abstract: As key components of natural gas vehicles, high-pressure gas cylinders are widely used. In order to improve the mileage of the natural gas vehicles, the storage pressure of natural gas should be increased to improve the energy density. Therefore, a 30 MPa fully-wrapped compressed natural gas cylinder for vehicles has been designed and developed to improve the market competitiveness of the natural gas vehicles. The fully-wrapped composite cylinder adopts mixed fiber winding mode: low-angle helical winding, high-angle helical winding and hoop winding. Effects of different auto-frettage pressures on the fatigue properties of the fully-wrapped cylinders were investigated based on the ANSYS composite PrepPost component under ANSYS Workbench platform. The alternating stress amplitude was modified using the SWT mean stress equation. The results show that the auto-frettage treatment of the cylinder does not change the alternating stress amplitude of the liner, but it can reduce the mean stress, and the optimum auto-frettage pressure of the cylinder is 52 MPa under the premise of satisfying the fiber stress ratio, and the number of fatigue cycles is about 15000 times.

Key words: composite gas cylinders, fiber winding methods, auto-frettage pressure, fatigue analysis, fiber stress ratio