The fatigue behavior of (±55°)3 filament wound GRP pipes with a surface crack under internal pressure

In this study, the fatigue behavior of (±55°)3 filament wound composite pipes with a surface crack under alternating internal pressure has been investigated. Glass reinforced plastic (GRP) pipes were made of E-glass/epoxy and tested in an open-ended condition. For this study, a PLC controlled hydraulic test stand has been established. Test specimens have antisymmetric six layers which have ±55° winding angles. Fatigue tests of the pipes with a surface crack which have notch aspect ratio a/c = 0.2 and notch-to-thickness ratios a/t = 0.25, 0.38 and 0.50 in the axial direction have been carried out in accordance with ASTM D-2992. This standard allows a frequency of 25 cycles per minute and an R = 0.05 stress ratio. Tests have been performed at three different maximum stress levels, which were 50%, 40% and 30% of the ultimate hoop stress. Final failure of the GRP pipes has been examined and fatigue test results are presented by means of (S–N) curves and delamination damage zone area–cycle (A–N) curves.