| dc.description.abstract | Glass Fibre Reinforced Epoxy (GRE) composite tubes have wider application in oil and gas industry due to their durability and strength. An extensive qualification program is required to determine the performance of the pipes concerning pressure, temperature, chemical resistance, fire performance, electrostatic performance, impact, and compression. ISO 14692 qualifies GRE pipes based on regression analysis from a long term test. This conventional test procedure requires 14 months to estimate the remaining properties at the end of expected life (20-50 years). The composite pipe manufacturers certainly require a more efficient yet reliable short-term test. A new portable automated
pressure test rig is developed to achieve the five multiaxial stress ratios: pure axial 0H:1A, hoop to axial 1H:1A, pure hydrostatic 2H:1A, quad hoop to axial 4H:1A, and pure hoop 1H: 0A loading. The test rig serves as an alternative to the existing short-term test procedure, specified in ASTM D2992. A test method is developed based on the ultimate elastic wall stress (UEWS) concept. UEWS test internally pressurises the pipes, holds and releases the pressure based on the set value one cycle. Ten such cycles form one cycle group at a constant pressure level. The procedure is continued at increased pressure levels until the pipe shows weepage. A LabVIEW program is developed to accomplish the UEWS test and runs on the Touch Panel Computer. NI compactRIO and NI modules read the pressure values, measure strain gauge readings and control the opening and closing of the solenoid valves. Hoop and axial strain measurements are acquired during the test. First ply failure points are estimated from the captured strain values. The failure envelope is constructed based on the first ply failure points. The effects of winding angles are studied by subjecting pipes with winding angles [±45°]4, [±55°]4, and [±63°]4. The results of the UEWS tests indicate that each winding angle dominate a certain optimum stress ratio namely, [±45°]4 for axial dominated loadings (1H:1A and 0H:1A); [±55°]4 excel at pure hydrostatic loading (2H:1A), while [±63°]4 show domination along the quad hoop to axial 4H:1A and 1H:0A stress ratios. To study the effects of ageing, the pipes are hydrothermally aged and are subjected to UEWS tests. The results show for the aged pipes show a considerable degradation of strength compared to the results of the virgin pipes due to moisture absorption. Several failure modes namely transverse matrix cracking, white striations, weepage, fibre breakage, ring formation were observed during the UEWS tests | en_US |
