Fatigue Crack Growth Behavior of Filament Wound Composite Pipes in Corrosive Environment

Abstract

The stress corrosion crack growth behavior of ±45°, ±55°, and ±75° filament wound composite pipes with surface crack subjected to 0.6 M HCl acid under alternating internal pressure was investigated. E-glass/epoxy pipes consist of six layers with stacking sequences of (+45/-45) 3, (+55/-55)3, and (+75/-75)3. Dilute (0.6M) HCl acid was applied to the surface crack region by a corrosion cell mounted on the outer surface of the pipe. The specimens were tested at room temperature and exposed to open-ended fatigue tests in which the pipes can deform freely in the axial direction. The tests were performed in accordance with the ASTM D-2992 standard. The surface notches with different a/t and a/c forms were cut on the outer surface of the pipe parallel to the pipe axis. The internal pressure was generated by conventional hydraulic oil for fatigue loading. The low cycle tests were applied with 0.42 Hz frequency and R = 0.05 stress ratio. After the corrosion fatigue test, the fracture surfaces were examined and observed damage mechanisms discussed.