A Comparative Study on the Post-Buckling Behavior of Reinforced Thermoplastic Pipes (RTPs) Under External Pressure Considering Progressive Failure

The collapse pressure is a key parameter when RTPs are applied in harsh deep-water environments. To investigate the collapse of RTPs, numerical simulations and hydrostatic pressure tests are conducted. For the numerical simulations, the eigenvalue analysis and Riks analysis are combined, in which the Hashin failure criterion and fracture energy stiffness degradation model are used to simulate the progressive failure of composites, and the “infinite” boundary conditions are applied to eliminate the boundary effects. As for the hydrostatic pressure tests, RTP specimens were placed in a hydrostatic chamber after filled with water. It has been observed that the cross-section of the middle part collapses when it reaches the maximum pressure. The collapse pressure obtained from the numerical simulations agrees well with that in the experiment. Meanwhile, the applicability of NASA SP-8007 formula on the collapse pressure prediction was also discussed. It has a relatively greater difference because of the ignorance of the progressive failure of composites. For the parametric study, it is found that RTPs have much higher first-ply-failure pressure when the winding angles are between 50° and 70°. Besides, the effect of debonding and initial ovality, and the contribution of the liner and coating are also discussed.