海洋纤维增强热塑性立管极限承载拉力预测方法

海洋新型纤维增强热塑性立管因其可盘卷、耐腐蚀、耐疲劳和轻质化等优点，在深水油气开发中应用前景十分广阔。热塑性立管具有复合材料的各向异性、受力耦合效应及复杂的本构关系，且承受浮体运动和复杂海洋环境载荷，其失效模式尚未明确。针对轴对称载荷作用下纤维增强热塑性立管极限承载力问题，进行热塑性管稳态热传导和热应力的理论推导，求解了稳态温度和应力分布，首次给出了在任意温度载荷作用下管体径向位移的解析解，并直接求解其径向、轴向、环向和剪切应力。采用各向同性层Von Mises和各向异性层最大应力（Max Stress）准则或Tsai-Hill准则判定热塑性管的失效，基于应力分布、失效准则和二分法计算了热塑性管的极限载荷。温度载荷、纤维铺设角度和径厚比对管道的应力分布影响显著。不同温度载荷会改变失效指数沿径向的变化趋势，增大轴向拉力将增大热塑性管的失效指数，选用不同的失效准则在管体失效判定上存在一定的差异。热塑性管温度越低、纤维铺设角越小及径厚比越大，管道对轴向拉伸载荷的承载能力越强。

Prediction method for ultimate tensile strength of marine fiber-reinforced thermoplastic riser

Marine thermoplastic riser reinforced with novel fibers have broad prospects in deepwater oil and gas development due to their advantages such as coilability, corrosion resistance, fatigue resistance, and lightweight. Thermoplastic riser exhibit the anisotropy of composite materials, stress coupling effects, complex constitutive relationships, and withstand floating body motion and complex marine environmental loads, with failure modes yet to be clarified. Focusing on the ultimate bearing capacity of fiber-reinforced thermoplastic riser under axisymmetric loading, theoretical derivations of steady-state heat conduction and thermal stress in thermoplastic pipes are conducted. Solutions for steady-state temperature and stress distributions are obtained. Analytical solutions for radial displacement of the pipe body under any temperature load are provided for the first time. Radial, axial, circumferential, and shear stresses are directly solved. Failure of thermoplastic pipes is determined using the isotropic layer Von Mises and anisotropic layer maximum stress (Max Stress) criteria or the Tsai-Hill criterion. Based on stress distribution, failure criteria, and bisection method, the ultimate load of thermoplastic pipes is calculated. Temperature load, fiber layup angle, and thickness-to-diameter ratio significantly affect stress distribution in the pipeline. Different temperature loads change the trend of failure index along the radial direction. Increasing axial tension increases the failure index of thermoplastic pipes. Different failure criteria result in differences in pipe body failure determination. Lower temperatures, smaller fiber layup angles, and larger thickness-to-diameter ratios result in higher bearing capacity of the pipeline under axial tensile loads.