Bending Properties of Unbonded Flexible Risers with Composite Materials

doi:10.16183/j.cnki.jsjtu.2021.144

Abstract

Abstract:

Unbonded flexible risers are widely applied to transport oil and gas resources from seabed to platform, and composite cylindrical layers are sometimes contained due to design requirements. Based on an 8-layer unbonded flexible riser model, the bending properties of the unbonded flexible risers with composite cylindrical layers are studied. A theoretical method of combining axisymmetric and bending loads acting on unbonded flexible risers is proposed, and a numerical method with detailed geometric characteristics taken into account is established for verification. The influence of two typical composite materials as well as the fibre volume fraction on the bending properties of the unbonded flexible risers is analyzed. The theoretical and the numerical results are in good agreement, which shows that the bending properties of the unbonded flexible risers are greatly affected by the axial Young’s modulus of the composite cylindrical layers, and composite material with larger axial Young’s modulus would greatly enhance the bending stiffness of the unbonded flexible risers, expecially in the full-slipping stage. In addition, the axial tensile stiffness and bending stiffness of full-slipping stage are proportional to the fibre volume fraction of the composite cylindrical layers.

Key words: unbonded flexible risers, composite materials, cylindrical layers, bending stiffness, fibre volume fraction

CLC Number:

P751

LIU Qingsheng, XUE Hongxiang, YUAN Yuchao, TANG Wenyong. Bending Properties of Unbonded Flexible Risers with Composite Materials[J]. Journal of Shanghai Jiao Tong University, 2022, 56(9): 1247-1255.

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层数	名称	条带数	内径/mm	铺设角/(°)	材料
1	骨架层	1	31.60	-87.5	AISI304
2	内部护套层	-	35.10	-	尼龙12
3	抗压铠装层	2	40.05	-85.5	FI-15
4	加强层	-	46.25	-	复合材料
5	抗拉铠装层	40	47.75	-35.0	FI-41
6	加强层	-	50.75	-	复合材料
7	抗拉铠装层	44	52.25	35.0	FI-41
8	外部护套层	-	55.25	-	-

方法	力学性能
方法	E_a/MN	E_i/(kN·m²)
理论	105.88	1.19, 1.42
数值	99.19	1.41
试验	91.19	1.19, 1.04

材料	弹性模量/GPa			μ₁₂	μ₁₃	μ₂₃	G₁₂/GPa
材料	E₁	E₂	E₃	μ₁₂	μ₁₃	μ₂₃	G₁₂/GPa
1	9.40	4.02	4.01	0.36	0.36	0.49	4.08
2	16.0	1.07	3.86	0.44	0.44	0.45	0.56

复合材料	E_i/(kN·m²)
复合材料	理论方法不考虑外压	理论方法考虑外压	数值方法
玻纤/环氧树脂	11.51	11.74	11.52
钢丝/高密度聚乙烯	18.92	19.15	18.57

层结构及轴对称载荷影响	E_i/(kN·m²)
层结构及轴对称载荷影响	含防摩擦层尼龙-11模型	含复合材料玻纤/环氧树脂模型	含复合材料钢丝/高密度聚乙烯模型
第1, 2, 3, 5, 7, 8层结构的综合作用	0.85	—	—
第4层	0.15	4.61	7.81
第6层	0.19	6.05	10.26
轴对称载荷作用	0.23 (0.2 MPa外压载荷作用)	—	—
总计	1.42	11.74	19.15