FATIGUE BEHAVIOR OF COMPOSITE PRESSURE VESSELS WITH ALUMINUM ALLOY LINERS

The composite pressure vessel with an aluminum liner is widely used for high pressure gas storage these days. In the manufacturing process of composite cylinders with a metal liner, the autofrettage treatment, which induces a compressive residual stress on the liner of a composite pressure vessel, is one of the important methods for increasing the fatigue life of the pressure vessel. In this study, the fracture location and fatigue life of the composite pressure vessel with an aluminum liner were analyzed with the finite element method and verified through a fatigue test of the liner material and a pressure cycling test of composite cylinders. The nonlinear finite element analysis shows that the autofrettage pressure increases the fatigue life of the liner. The leak position was changed from the cylinder to the dome knuckle part, and from the dome knuckle part to the boss neck part. The change of the leak position can be explained with the change of maximum strain. This FEM analysis results, also, agree with the results of cyclic pressurizing test. The method applied in this study will be a good example for finding out the optimum condition of the autofrettage pressure for a composite pressure vessel and can be applied to the different vessels with larger sizes.