An effective stress parameter for long-term fatigue strength of fiber-reinforced plastic pipes

The currently used American Society for Testing and Materials (ASTM) procedure and a modified American Petroleum Institute (API) method for cyclic pressure strength of fibre reinforced plastic (FRP) pipes are critically discussed together with the test results generated by Battelle. In addition, two new damage parameters, recently proposed by the authors, are examined using the Battelle tests as a database. An equivalent stress range damage parameter, Δσ¯, is recommended which combined the loading condition, hoop stress range and normalized mean stress, and FRP pipe material properties. The proposed damage parameter, Δσ¯, can be used in the engineering evaluation of fatigue performance of pressured fiberglass pipes. The Δσ¯ provides substantial improvement over the ASTM recommended parameter, hoop stress range. Using the Δσ¯, the fatigue data for different mean pressures are consolidated into a narrow scatter band.