Predicting failure pressure of reinforced thermoplastic pipes based on theoretical analysis and experiment

Because they transport high-temperature and high-pressure oil and gas, the pressure-carrying capacity of reinforced thermoplastic pipes (RTPs) needs to be high. This study develops two analytical models to estimate deformation and stresses in RTPs with any number of layers under internal pressure based on their nonlinear mechanical behaviors. The Hashin-Yeh failure criterion and the damage evolution model of composite materials are combined, and changes due to deformation are introduced to the winding angle to analyze the progressive failure of RTPs. The modeling covered stress analysis, failure evaluation, and material degradation. By comparing their results with those of the finite element model (FEM) and experiments, the advantages and disadvantages of the two theoretical models are determined. The stress distribution and failure pressure calculated by them were in good agreement with those obtained by the FEM and the experiments. However, the accuracy of calculation of the proposed model (model-I) was clearly better than that of homogenization model (model-Il), and its results of failure pressure and the failure sequence were more accurate. Model-I was thus used to obtain the optimal range for the winding angle of the fiber's, and to discuss the influence of diameter-to-thickness (D/t) ratios on the first-ply failure (FPF) pressure and burst pressure.