Tensile properties of marine fiber reinforced composite flexible pipes

Key words:  tensile properties  thermoplastic material  winding angle  Poisson 's ratio

Abstract:

Replacement of composite flexible pipes made of fiber-reinforced composites instead of traditional carbon steel pipes is the trend of offshore oil and gas selection. A study on the tensile properties of reinforced thermoplastic pipes (RTPs) was presented. A mechanical model of RTPs with an arbitrary number of reinforced layers in tension was constructed by combining the constitutive relationship of elastoplastic materials with the stress continuity condition. On this basis, the effects of various parameters such as the winding angle, the fiber content of structurally reinforced layers, and the Poisson 's ratio on the tensile properties of the RTPs were analyzed, and then a tensile test was carried out for validation. The results show that the winding angle of the structurally reinforced layers is the main factor affecting an RTP 's tensile performance, where the decrease of the winding angle significantly improves the longitudinal strength. The winding angle which is less than ±45° results in a higher strength in the longitudinal direction. In addition, the increase of the fiber content of structurally reinforced layers cannot effectively improve the overall tensile strength of RTPs within the effective strain range. The Poisson 's ratio has little effect on the overall tensile properties of the RTPs. The experimental results are in good agreement with the numerical simulation results.