Research on the service performance of buckled joints in glass fiber-reinforced thermoplastic composite pipes

Joints are important connections for realizing long-distance transportation via composite pipes and have been widely used in oil and gas transportation. A joint is also a weak link influencing the safe operation of pipelines. In this work, a three-dimensional assembly model of glass fiber-reinforced plastic composite pipes and metal buckling joints was constructed and analyzed using the finite element method (FEM) to investigate the influence of the buckling amount and structural parameters of joints on the sealing performance of joints. The results showed that the sealing performance of the joint gradually improved with increasing buckling. When a larger amount of buckling occurs, the RTP will undergo excessive plastic deformation, and the sealing performance of the joint decreases. The optimized structural parameters of the metal joint are a buckling amount of 5 mm, several serrations of 13, a tooth height of 3 mm, and two serration angles of 55° and 25°. When using optimized parameters and extreme working conditions (the internal pressure is 19.2 MPa), the maximum stress of the innermost fiber exceeds the tensile strength with a higher risk of failure. However, the optimized design of the joint can meet the requirement of safe operation at a standard pressure of 6.4 MPa.