Fatigue failure analysis of surface-cracked (±45°)3 filament-wound GRP pipes under internal pressure

In this study, the fatigue behavior of (+/- 45 degrees)(3) filament-wound composite pipes with a surface crack under alternating internal pressure was investigated. Glass-reinforced plastic (GRP) pipes were made of E-glass/epoxy and tested in the open-ended condition. The pipes had a surface crack with a notch-aspect ratio of a/t = 0.2 and notch-to-thickness ratios of a/t = 0.25, 0.38, or 0.50 in the axial direction. Tests were carried out in accordance with ASTM D2992. This standard offers 25 cycles/min and a load ratio of R = 0.05. Tests were performed at three different load levels: 50%, 40%, and 30% of ultimate hoop stress. Whitening, leakage, and final failure of GRP pipes were observed, and fatigue test results were presented by means of S-N curves.