Preparation method of axially-reinforced flexible composite pipe
By constructing an independent axial reinforcement layer on the outside of the traditional flexible composite pipe, the problem of insufficient axial load-bearing capacity of traditional flexible reinforced thermoplastic pipes under actual working conditions is solved, achieving a balance between improved axial performance and flexibility, and adapting to harsh working conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional flexible reinforced thermoplastic pipes have insufficient axial load-bearing capacity, tensile and crush resistance under actual working conditions, and existing improvement solutions are either costly or lack flexibility.
An independent axial reinforcement layer composed of tightly arranged continuous fibers is constructed outside the traditional ±54.7° spiral winding reinforcement layer, and a special device and process are used to make it form a strong mechanical interlock with the spiral reinforcement layer.
It significantly improves the axial mechanical properties of the pipeline, increases the axial tensile modulus and crush resistance, while maintaining flexibility and production efficiency, and adapts to harsh working conditions.
Smart Images
Figure CN121848631A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flexible composite pipe technology, and specifically relates to a method for preparing an axially reinforced flexible composite pipe. Background Technology
[0002] In the field of traditional flexible reinforced thermoplastic pipes (RTP), the ±54.7° (also known as the "golden angle") spiral winding reinforcement layer is a widely adopted technology. This angle is based on the "grid theory" to achieve the optimal solution of equal strength in a thin-walled cylinder subjected only to internal pressure. However, under actual complex working conditions, this technology has significant and unresolved inherent defects: insufficient axial load-bearing capacity and shortcomings in tensile and crush resistance. That is, under the ideal state of only internal pressure load, the ±54.7° winding can evenly distribute the circumferential and axial stresses, but in actual laying and operation, the pipe is subjected to a large number of axial loads not dominated by internal pressure, such as: the drag force during laying, axial bending and tension caused by uneven terrain settlement, momentum load caused by changes in the velocity of the internal transported medium, and the risk of axial crush (buckling) caused by external hydrostatic pressure in deep-sea applications. Under the above working conditions, the axial strength of the traditional structure mainly relies on the shear transmission of the resin matrix and fiber-resin interface, which is inefficient and prone to overall failure.
[0003] In response to the above problems, existing technical improvement solutions and their limitations include: (1) increasing the number of spiral winding layers or the amount of fiber: this method has limited improvement on axial strength and significantly increases cost and tube stiffness, sacrificing flexibility; (2) using 0° (axial) unidirectional tape or fabric: this method is usually used as part of the inner lining or outer protective layer (such as placing axial fabric in a multi-layer structure), its reinforcing fibers are wrapped by a large amount of matrix resin, failing to form an independent, continuous, and directly stressed reinforcing skeleton, and the interface with the spiral layer is poor and easy to peel off. Summary of the Invention
[0004] To address the problems existing in the above-mentioned background technology, the present invention provides a method for preparing an axially reinforced flexible composite tube based on an innovative secondary composite structure of a spiral wound main body reinforcement + an independent axial layer. After completing the traditional ±54.7° spiral fiber winding reinforcement layer and curing / forming it, an independent axial reinforcement layer composed of tightly arranged continuous fibers is constructed on its exterior. Through a special device and process, it forms a strong mechanical fit with the spiral reinforcement layer.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing an axially reinforced flexible composite tube includes the following steps: (1) Inner lining preparation: HDPE pipe special raw materials and color masterbatch are melt-extruded using a single screw extruder to form a flexible composite pipe inner lining; The key process parameters are controlled as follows: the barrel temperature of the single screw extruder is 180~220°C, the die temperature is 190~210°C, and the cooling water temperature is 15~25°C, to ensure that the inner wall of the inner liner meets the quality requirements of being smooth and defect-free. (2) Helical fiber winding reinforcement layer forming: The glass fiber prepreg tape is spirally wound at ±54.7° on the outer surface of the inner liner obtained in step (1) using a fiber winding machine to form a helical fiber winding reinforcement layer on the outside of the inner liner, thereby obtaining a helical reinforced tube blank; (3) Construction of independent axial fiber reinforcement layer: The spiral reinforced tube blank is preheated, axial fiber bundles are laid and arranged and hot-pressed in sequence through a special axial fiber synchronous laying and hot-pressing composite system to form an independent axial fiber reinforcement layer on the outer surface of the spiral reinforced tube blank, which is then hot-pressed and composited with the spiral fiber winding reinforcement layer. The whole process is continuous and completed in one go. The axial fiber synchronous laying and hot-pressing composite system includes a preheating and guiding module, a multi-axis fiber yarn feeding frame and a fiber flattening and laying head module. The preheating and guiding module preheats and guides the spiral reinforced tube blank sequentially. The multi-axis fiber yarn feeding frame is used to simultaneously draw out multiple axial fiber bundles. The fiber flattening and laying head module is used for laying and arranging the axial fiber bundles and hot-pressing composite. Specifically, the spiral reinforced tube blank rotates at a constant speed and passes through the preheating and guiding module under the drive provided in the preheating and guiding module. The module is used to preheat the outer surface of the spiral reinforced tube blank with infrared technology to the HDPE matrix temperature of 120~135°C. Then, a multi-axis fiber yarn feeding frame is used to draw out multiple axial fiber bundles. Under tension control, all the drawn axial fiber bundles are precisely spread and laid flat through the fiber flattening and laying head module, and arranged closely at a set interval on the outer surface of the preheated spiral reinforced tube blank, almost 100% covering the circumference of the spiral reinforced tube blank, forming an unconsolidated axial fiber reinforcement layer. Finally, under tension control and the temperature of the outer surface of the spiral reinforced tube blank, the axial fiber bundles and the spiral fiber winding reinforcement layer are hot-pressed together. Each axial fiber bundle is equipped with an independent tension sensor and controller, and the axial fiber bundle consists of 16 to 64 strands. The tension control is achieved through the tension sensor and controller, and is set to a relatively high and uniform tension, such as 80 to 100 N / bundle, to establish axial preload within the pipe. The set spacing is 1.1 to 1.3 times the bundle width, which is the center distance of the axial fiber bundles. The axial fiber bundle is a high-strength, high-modulus continuous fiber bundle, and the axial fiber is specifically selected from T700 grade carbon fiber, S-2 glass fiber or para-aramid. (4) Co-extrusion coating and post-processing of outer protective layer: After hot pressing and composite in step (3), the tube body is immediately put into a crosshead die extruder to co-extrude a layer of molten weather-resistant and wear-resistant outer protective layer on the outside of the tube body; the molten protective layer material can further penetrate the axial fiber layer to strengthen the overall composite; finally, after cooling, testing, fixed-length cutting, coiling and packaging, the axially reinforced flexible composite tube of the present invention is obtained. The outer protective layer is made of HDPE; The extruder has an extrusion temperature of 210~230°C and a die head pressure controlled at 15~35 MPa.
[0006] The present invention also provides an axially reinforced flexible composite pipe prepared by the above method.
[0007] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention achieves a revolutionary improvement in the axial mechanical properties of pipes by adding an independent axial reinforcing layer outside the traditional spiral fiber winding layer; it uses a special device system to lay continuous fibers with high tension to build an efficient axial load-bearing "skeleton" in the pipe, which improves the axial tensile modulus and crush resistance by more than 50% compared with the traditional ±54.7° winding pipe; the axial layer directly bears the main axial load, breaking through the bottleneck of traditional structure relying on spiral fiber shear transmission.
[0008] (2) The innovative flexible composite pipe structure obtained by the present invention significantly enhances the axial performance while perfectly maintaining the core functional advantages of the pipe. Its internal ±54.7° spiral layer completely retains the optimal circumferential pressure bearing capacity, and the external axial layer has minimal impact on the pipe's flexibility because the fiber direction is consistent with the bending, thus ensuring excellent laying adaptability.
[0009] (3) The preparation process of this invention is efficient and controllable. The integrated device enables online, continuous, and one-time molding of the axial reinforcement layer, which can be seamlessly connected with traditional production lines, greatly improving production efficiency and product consistency. The improved axial strength enables high-quality and stable manufacturing of high-performance flexible composite pipes, providing a reliable solution for harsh working conditions. Attached Figure Description
[0010] Figure 1 This is a schematic diagram of the construction system for the independent axial fiber reinforcement layer in the flexible composite tube described in this invention.
[0011] Figure 1 The components are labeled as follows: 1. Spiral reinforced tube blank, 2. Preheating and guiding module, 3. Preheated spiral reinforced tube blank, 4. Multi-axis fiber yarn laying frame, 5. Fiber flattening and laying head module. Detailed Implementation
[0012] The present invention will be further described below with reference to specific embodiments and accompanying drawings.
[0013] A method for preparing an axially reinforced flexible composite tube includes the following steps: (1) Inner lining preparation: HDPE pipe special raw materials and color masterbatch are melt-extruded using a single screw extruder to form a flexible composite pipe inner lining; The key process parameters are controlled as follows: the barrel temperature of the single screw extruder is 180~220°C, the die temperature is 190~210°C, and the cooling water temperature is 15~25°C, to ensure that the inner wall of the inner liner meets the quality requirements of being smooth and defect-free. (2) Helical fiber winding reinforcement layer forming: The glass fiber prepreg tape is spirally wound at ±54.7° on the outer surface of the inner liner obtained in step (1) using a fiber winding machine to form a helical fiber winding reinforcement layer on the outside of the inner liner, thereby obtaining a helical reinforced tube blank; (3) Construction of independent axial fiber reinforcement layer: The spiral reinforced tube blank is preheated, axial fiber bundles are laid and arranged and hot-pressed in sequence through a special axial fiber synchronous laying and hot-pressing composite system to form an independent axial fiber reinforcement layer on the outer surface of the spiral reinforced tube blank, which is then hot-pressed and composited with the spiral fiber winding reinforcement layer. The whole process is continuous and completed in one go. The axial fiber synchronous laying and hot-pressing composite system includes a preheating and guiding module, a multi-axis fiber yarn feeding frame and a fiber flattening and laying head module. The preheating and guiding module preheats and guides the spiral reinforced tube blank sequentially. The multi-axis fiber yarn feeding frame is used to draw out the axial fiber bundles. The fiber flattening and laying head module is used for laying and arranging the axial fiber bundles and hot-pressing composite. Specifically, the spiral reinforced tube blank rotates at a constant speed and passes through the preheating and guiding module under the drive provided in the preheating and guiding module. The module is used to preheat the outer surface of the spiral reinforced tube blank with infrared technology to the HDPE matrix temperature of 120~135°C. Then, a multi-axis fiber yarn feeding frame is used to draw out multiple axial fiber bundles. Under tension control, all the drawn axial fiber bundles are precisely spread and laid flat through the fiber flattening and laying head module, and arranged closely at a set interval on the outer surface of the preheated spiral reinforced tube blank, almost 100% covering the circumference of the spiral reinforced tube blank, forming an unconsolidated axial fiber reinforcement layer. Finally, under tension control and the temperature of the outer surface of the spiral reinforced tube blank, the axial fiber bundles and the spiral fiber winding reinforcement layer are hot-pressed together. Each axial fiber bundle is equipped with an independent tension sensor and controller, and the axial fiber bundle consists of 16 to 64 strands. The tension control is achieved through the tension sensor and controller, and is set to a relatively high and uniform tension, such as 80 to 100 N / bundle, to establish axial preload within the pipe. The set spacing is 1.1 to 1.3 times the bundle width, which is the center distance of the axial fiber bundles. The axial fiber bundle is a high-strength, high-modulus continuous fiber bundle, and the axial fiber is specifically selected from T700 grade carbon fiber, S-2 glass fiber or para-aramid. (4) Co-extrusion coating and post-processing of outer protective layer: After hot pressing and composite in step (3), the tube body is immediately put into a crosshead die extruder to co-extrude a layer of molten weather-resistant and wear-resistant outer protective layer on the outside of the tube body; the molten protective layer material can further penetrate the axial fiber layer to strengthen the overall composite; finally, after cooling, testing and fixed-length cutting, the axially reinforced flexible composite tube of the present invention is obtained. The outer protective layer is made of HDPE; The extruder has an extrusion temperature of 210~230°C and a die head pressure controlled at 15~35 MPa.
[0014] Example The specifications and materials of the flexible composite pipe prepared in this embodiment are as follows: Pipe body: A composite pipe with an inner diameter of 150mm and an outer diameter of 182.4mm; Inner lining: Made of extruded HDPE layer with a thickness of 5mm; Spiral reinforcement layer material: PE aramid tape; Axial reinforcement layer material: para-aramid fiber bundles; Outer coating: High-density polyethylene (HDPE) with a thickness of 3mm; The specific preparation steps are as follows: (1) Preparation of inner lining layer The HDPE inner liner is formed on the mandrel using a conventional extrusion process; The key process parameters are controlled as follows: the barrel temperature of the single screw extruder is 200°C, the die temperature is 200°C, and the cooling water temperature is 20°C, to ensure that the inner wall of the inner liner meets the quality requirements of being smooth and defect-free. (2) Spiral reinforcement layer winding Completed on a multi-axis CNC winding machine; Path and program settings: In the CNC system, the winding angle of the reinforcing material is set to 54.7° (corresponding to the optimal circumferential strength), and the pitch is set to 15mm; Tension parameter setting and implementation: Based on the structural design, the winding tension of the reinforcing material is set to Tr = 220 N (approximately 22 kgf). Then the winding process is started, and the reinforcing material is wound by the main yarn feeder along the set path to obtain a spiral reinforced tube blank; (3) Construction of axial reinforcement layer Completed on a dedicated axial fiber synchronous laying and hot-pressing composite system; The outer surface of the spiral reinforced tube blank is preheated with infrared radiation to the HDPE matrix temperature of 130°C using a preheating and guiding module. A multi-axis fiber feeding frame is used to draw out 16 axially aligned aramid fiber bundles with a tension of 80N / bundle. All the drawn axial fiber bundles are precisely spread and laid flat through the fiber flattening and laying head module. The spacing is set to be 1.1 times the bundle width between the center of the axial fiber bundles, forming an unconsolidated axial fiber reinforcement layer. Finally, under tension control and at the outer surface temperature of the spiral reinforced tube blank, the axial fiber bundles and the spiral fiber winding reinforcement layer are hot-pressed together. (4) Co-extruded outer coating The above-mentioned pipe body is placed in a co-extrusion production line, and an HDPE outer coating is co-extruded at an extrusion temperature of 220°C and a die head pressure of 20MPa. The outer coating thickness is 3mm; (5) Post-processing: The tube obtained in step (4) is cooled, cut to a fixed length, coiled and packaged to obtain the axially reinforced flexible composite tube of the present invention.
[0015] This embodiment successfully prepared an axially reinforced flexible composite tube, the key effect of which is: The axially reinforced flexible composite pipe achieves core indicators such as overall pipe tensile strength ≥300 kN and operating radius ≤1.5 m, and has been successfully demonstrated in engineering applications.
Claims
1. A method for preparing an axially reinforced flexible composite pipe, characterized in that, Includes the following steps: (1) Inner lining preparation: HDPE pipe special raw materials and color masterbatch are melt-extruded using a single screw extruder to form a flexible composite pipe inner lining; (2) Helical fiber winding reinforcement layer forming: The glass fiber prepreg tape is spirally wound at ±54.7° on the outer surface of the inner liner obtained in step (1) using a fiber winding machine to form a helical fiber winding reinforcement layer on the outside of the inner liner, thereby obtaining a helical reinforced tube blank; (3) Construction of independent axial fiber reinforcement layer: The spiral reinforced tube blank is preheated, axial fiber bundles are laid and arranged and hot-pressed in sequence through a special axial fiber synchronous laying and hot-pressing composite system to form an independent axial fiber reinforcement layer on the outer surface of the spiral reinforced tube blank, which is then hot-pressed and composited with the spiral fiber winding reinforcement layer. The whole process is continuous and completed in one go. The axial fiber synchronous laying and hot-pressing composite system includes a preheating and guiding module, a multi-axis fiber yarn feeding frame and a fiber flattening and laying head module. The preheating and guiding module preheats and guides the spiral reinforced tube blank sequentially. The multi-axis fiber yarn feeding frame is used to simultaneously draw out multiple axial fiber bundles. The fiber flattening and laying head module is used for laying and arranging the axial fiber bundles and hot-pressing composite. Each axial fiber bundle is equipped with an independent tension sensor and controller, and the axial fiber bundle consists of 16 to 64 strands; the tension control is achieved through the tension sensor and controller, with a tension of 80 to 100 N / bundle. The axial fiber bundle is a high-strength, high-modulus continuous fiber bundle; (4) Co-extrusion coating and post-processing of outer protective layer: After hot pressing and composite in step (3), the tube body is immediately put into a crosshead die extruder, and a layer of molten weather-resistant and wear-resistant outer protective layer is co-extruded and coated on the outside of the tube body; finally, after cooling, testing, fixed-length cutting, coiling and packaging, the axially reinforced flexible composite tube is obtained.
2. The preparation method according to claim 1, characterized in that, The key process parameters for step (1) are controlled as follows: the barrel temperature of the single screw extruder is 180~220°C, the die temperature is 190~210°C, and the cooling water temperature is 15~25°C.
3. The preparation method according to claim 1, characterized in that, Step (3) includes the following specific operations: the spiral reinforced tube blank rotates at a constant speed and passes through the preheating and guiding module under the drive set in the preheating and guiding module. The module is used to preheat the outer surface of the spiral reinforced tube blank with infrared to the HDPE matrix temperature of 120~135°C. Then, a multi-axis fiber yarn release frame is used to draw out multiple axial fiber bundles. After tension control, all the drawn axial fiber bundles are accurately unfolded and laid flat through the fiber flattening and laying head module. They are arranged closely on the outer surface of the preheated spiral reinforced tube blank at a set interval, almost 100% covering the circumference of the spiral reinforced tube blank, forming an unconsolidated axial fiber reinforcement layer. Finally, under tension control and the temperature of the outer surface of the spiral reinforced tube blank, the axial fiber bundles and the spiral fiber winding reinforcement layer are hot-pressed together. The set spacing is 1.1 to 1.3 times the bundle width, which is the center distance of the axial fiber bundles. The axial fibers are specifically selected from T700 grade carbon fiber, S-2 glass fiber, or para-aramid.
4. The preparation method according to claim 1, characterized in that, The outer protective layer in step (4) is made of HDPE; The extruder has an extrusion temperature of 210~230°C and a die head pressure controlled at 15~35 MPa.
5. An axially reinforced flexible composite pipe prepared by any one of claims 1 to 4.