Abstract: Actual thickness of the liners of hoop-wrapped composite cylinders may have a deviation of 0 ~ +30% affected by the thickness variation of seamless steel tubes for cylinders. The variation of the actual thickness of the liner has an influence on the autofrettage effect of the composite cylinders, and may affect the anti-fatigue performance of the cylinders. Finite element method was used to analyze the stress of glass fiber hoop-wrapped composite cylinders with steel liners with different thickness. Numerical results show that hoop pre-stress on liners decreases under the same autofrettage pressure, and the mean hoop stress on liners increases during working process, which weakens the fatigue resistance of the composite cylinders; but the alternating stress amplitude decreases during working process, which improves the anti-fatigue performance of the cylinders. Therefore, both Goodman and SWT equations taking the effect of mean stress into account were utilized to calculate equivalent alternating stress amplitude. The equivalent alternating stress amplitude on the liners from the two methods both decreases slightly as the thickness of the liners increases, which indicates that the combined action of the two can improve the anti-fatigue performance of the composite cylinders slightly. So the positive thickness variation of the liners does not decrease the fatigue resistance of hoop-wrapped composite cylinders.

Key words: composite cylinders, hoop-wrapped, fatigue performance, finite element analysis, thickness variation