GRP Composite Pipe Elbows Subject to an Internal Pressure and In-Plane Bending: An Experimental Study

The use of polymer composite materials in the piping industry is increasingly gaining popularity. However, the design rules of these novel materials are relatively more complex and high safety factors are applied, requiring costly experimental validation. Experimental tests on e-glass reinforced polymer (GRP) pipe elbows is limited and in view of these challenges, this study presents a set of experimental results obtained from a series of pressurization and in-plane bending tests of polyester pipe elbows reinforced with e-glass chopped strand and woven roving mats. Details of the specimen manufacturing procedure, testing fixture and loading setup, are also given. A data acquisition system was setup to control, monitor and record the applied loads, the resulting meridional and hoop strains around the mid-plane of the elbows. A total of 3 specimens were tested where the first specimen was subject to an increasing positive pressure until global failure and was used to serve as a benchmark for the other two specimens. The latter were similarly subject to a positive pressure limited to the first-ply-failure load region established from the initial test. Both specimens were unpressurized and then subjected to a two cycle opening and unloading in-plane bending moment. Results show that the GRP pipe elbows were capable of sustaining loads beyond the identified failure initiation and successive bending cycles produced pipe elbow stiffening effect.