Competing residual compression and overwrap damage in autofrettaged thin-walled Type III composite pressure vessels

Autofrettage is commonly applied to metal-lined composite pressure vessels to improve fatigue resistance by introducing compressive residual stress into the liner. However, in thin-walled Type III vessels with filament-wound carbon-fiber/epoxy overwraps, excessive autofrettage may cause irreversible matrix-dominated damage and weaken the constraint imposed by the composite overwrap. This study investigates the burst and fatigue responses of a 56 L thin-walled Type III composite pressure vessel under different autofrettage pressures using a sequential finite element framework coupled with a three-dimensional progressive damage model. Acoustic emission monitoring, hydrostatic burst tests, pressure-cycling fatigue tests, and post-fatigue microscopic observations were used to validate and interpret the predictions. Increasing autofrettage pressure intensified retained matrix tensile damage in the overwrap and promoted earlier fiber tensile damage during repressurization. Experimentally, the burst pressure decreased from 90 to 81 MPa as autofrettage pressure increased from 44 to 60 MPa, while fatigue life decreased from 740 to 575 cycles. The model captured these degradation trends with mean absolute percentage errors of 3.2 and 2.3% for burst pressure and fatigue life, respectively. The results indicate that autofrettage design should be damage-limited rather than pressure-maximized.