Mechanical charaterization of S-glass and E-glass reinforced epoxy composite elbow pipe joints submerged in sea water

In many engineering applications composite pipes are generally used because of their high strength and stiffness, excellent fatigue and corrosion resistance. More than 70 percent of the world’s oil and gas transport pipelines are beyond 40 years old and there is a need to change them due to their gradual degradation in their operating environment. This research experimentally investigated the implication of sea water immersion on the impact behaviour of glass/epoxy composite elbow pipe joints. Glass-epoxy elbow pipe joints with E-glass and S-glass were fabricated using hand lay-up method. The pipe joints were immersed under sea water for 3 and 6-month periods, after which they were impacted according to ASTM D2444 at three different energy levels of 10 J, 12.5 J and 15 J at room temperature. Then they underwent monotonic burst pressure tests (ASTM D1599) and axial compression tests (ASTM D695–15). Finally the split disk tests (ASTM D2290) were performed on the untreated E-glass and S-glass pipe rings. The results showed that the contact force was higher in E-glass pipe joints with a mean value of 1.8 kN compare to 0.98 kN in S-glass pipe joints. S-glass pipe joints also showed maximum final displacement of 8 mm whereas it was only 6.5 mm for the elbow joints fabricated with E-glass. It was observed that the axial compressive strength was 957.50 MPa in the S-glass elbow pipe joints and was only 339.87 MPa in the elbow joints fabricated with E-glass fiber. Eruption and weepage failures were detected from the burst pressure tests in accordance to the applied impact energies and exposure time to sea water. At the pressure of 17.23 MPa, the E-glass elbow pipe joints damage was discovered to rupture but samples made of S-glass fiber have achieved whiteness first and then after reaching the pressure of 18.1 MPa the samples ruptured. The split disk tests concluded that the performance of tubular specimens under internal pressure developed high hoop stresses of 17.11 MPa and 22.24 MPa respectively for the E-glass and S-glass tubular rings. It can be concluded that after impact, internal pressure, axial compressive strength and hoop tensile strength, S-glass elbow joints showed more elastic nature, strain efficiency and strength when compared with the E-glass elbow pipe joints under both dry and submerged in the sea water.

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