Mechanical behavior of non⁃metallic intelligent coiled tubing under internal pressure based on finite element simulation

doi:10.19491/j.issn.1001-9278.2025.08.010

Abstract

Abstract:

In this study， the mechanical behavior of DN50/PN1.6 MPa non⁃metallic intelligent coiled tubing under internal pressure were investigated using finite element simulation. The effects of key manufacturing parameters， including fiber volume fraction in the reinforcement layer， thickness of the armored fiber optic layer， and the number of reinforcement layers， were analyzed in terms of stress distribution across structural layers and internal cables. Results showed that under an internal pressure of 2.5 MPa （1.5 times the nominal pressure）， the cables remained in an elastic deformation state， ensuring functional integrity. The tubing’s ultimate internal pressure capacity reached approximately 10 MPa， at which point functional failure occurred. Stress analysis revealed a spiral distribution in structural layers and alternating high⁃low stress patterns in the cables. Increasing the fiber volume fraction and the number of reinforcement layers significantly reduced stress on the stainless steel armor layer and cables， enhancing pressure resistance. In contrast， increasing the armor layer thickness had a marginal effect. A higher fiber volume fraction improved the reinforcement layer’s load⁃bearing capacity while reducing stress in adjacent layers. Additionally， increasing both armor thickness and reinforcement layers lowered stress across all layers， with reinforcement layers exhibiting a more pronounced influence. For optimal performance and cost efficiency， the recommended manufacturing parameters include a fiber volume fraction of 70%， 4~6 reinforcement layers， and a stainless steel armor thickness of 0.25 mm.

Key words: internal pressure, non?metallic intelligent coiled tubing, finite element simulation, functional damage

CLC Number:

TQ320.6

ZHANG Xuemin, ZHANG Xueru, LI Houbu, CHEN Yanhua, SUN Qiyao. Mechanical behavior of non⁃metallic intelligent coiled tubing under internal pressure based on finite element simulation[J]. China Plastics, 2025, 39(8): 62-68.

Figures/Tables 17

Fig.1. Schematic diagram of the non⁃metallic intelligent coiled tubing structure

参数

内径/

外径/

加热缆集成层厚度/

光纤集成层厚度/

单层纤维增强层厚度/

增强层层数

外保护层厚度/

纤维缠绕角度/

（°）

数值

2.1

3.3

Tab.1. Specific parameters of the structural layer of non⁃metallic intelligent coiled tubing

Fig.2. Geometric model of the non⁃metallic intelligent coiled tubing

材料	弹性模量/ MPa	泊松比	屈服强度/ MPa	拉伸强度/ MPa
PE⁃RT	650	0.40	16.2	—
PE	1 100	0.40	20.5	—
纯铜	108 000	0.32	220.0	263
316L不锈钢	103 627	0.30	600.0	830

Tab.2. Isotropic material parameters

参数

线密度/

dtex

断裂强力/

断裂强度/

cN•dtex^-1

断裂伸长率/

Tab.3. Polyester fiber material parameters

Fig.3. Coupling of reference point RP⁃2 with the end of the tubing

Fig.4. Stress distribution of inner lining of the non⁃metallic intelligent coiled tubing

Fig.5. Stress distribution diagram of each structural layer of the non⁃metallic intelligent coiled tubing

Fig.6. Stress distribution diagram of the cable and stainless steel armor layer in 2.5 MPa internal pressure

内衬层

加热缆

集成层

光纤集成层

（增强层PLY⁃1）

聚酯纤维增强层

（PLY⁃2）

Tab.4. Maximum stress of each structural layer of the non⁃metallic intelligent coiled tubing under 10 MPa internal pressure

Fig.7. Diagram of stress distribution of the cables and stainless steel armor layer under 10 MPa internal pressure

Fig.8. Effect of fiber volume fraction on the maximum stress of reinforcing layer and cable in the tubing

Fig.9. Effect of fiber volume fraction on stress of each structural layer of the tubing

Fig.10. Effect of thickness of the stainless steel armor layer on the maximum stress of reinforcing layer and cable in the tubing

Fig.11. Effect of stainless steel armor layer thickness on stress of various structural layers of the tubing

Fig.12. Effect of number of fiber reinforcement layers on the maximum stress of reinforcing layer and cable in the tubing

Fig.13. Effect of number of fiber⁃reinforced layers on stress of each structural layer of the tubing

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