The fatigue behavior of (±55°)_3 filament wound GRP pipes with a surface crack under internal pressure

摘要

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-cycje (A-N) curves.