Marine riser and preparation method thereof

Abstract

The invention belongs to the technical field of ocean engineering, and discloses a marine riser and a preparation method thereof, the marine riser comprises a lining layer, a structure enhancement layer and an external protection layer which are coaxially and tightly bonded in sequence from inside to outside; the structure reinforcing layer is formed by repeatedly overlapping and curing a plurality of basic paving layer units along the wall thickness direction of the pipe body; the spiral winding single-layer strips of the basic laying layer units are sequentially a single-layer positive spiral strip, a double-layer negative spiral strip, a single-layer positive spiral strip, a single-layer negative spiral strip, a double-layer positive spiral strip and a single-layer negative spiral strip from inside to outside. The spiral winding angles of the spiral winding single-layer strips are consistent, and the spiral winding angles of the positive spiral strips and the negative spiral strips are opposite in direction. The in-plane coupling term sum in the in-plane stiffness matrix [A] of the basic laying layer unit, the bending-torsion coupling term sum in the bending stiffness matrix [D] and the coupling stiffness matrix [B] are 0, and complete decoupling of structural mechanical response is achieved.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, specifically relating to a marine riser and its preparation method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Offshore risers are critical equipment connecting floating production facilities to deep-sea wellheads. In seawater, they not only suffer from long-term corrosion and erosion but also must withstand complex loads such as internal pressure, axial tension, bending, and external water pressure. Traditionally, offshore risers are made of steel. However, as offshore oil and gas resource development moves towards deeper and ultra-deeper seas, the length and wall thickness of steel risers have increased, resulting in excessive weight. This not only increases the load on surface platforms, limiting their operational capabilities, but also risks the risers breaking under their own weight. Furthermore, traditional steel risers are prone to corrosion. Under long-term exposure to seawater, localized corrosion can occur, reducing structural reliability and service safety.

[0004] To solve the above-mentioned technical problems, the prior art discloses a non-metallic, non-bonded flexible mixed transport pipe for deep-sea mining. The mixed transport pipe includes, from the inside out, an inner lining layer, an internal pressure-resistant reinforcing layer, a first wear-resistant layer, a first compensation reinforcing layer, a second wear-resistant layer, a second compensation reinforcing layer, a third wear-resistant layer, a skeleton layer, an isolation layer, a first tensile reinforcing layer, a fourth wear-resistant layer, a second tensile reinforcing layer, and an outer covering layer. The first compensation reinforcing layer, the second compensation reinforcing layer, the skeleton layer, the first tensile reinforcing layer, and the second tensile reinforcing layer are all formed by winding continuous long fiber reinforcing strips.

[0005] The above solution has the following drawbacks: The reinforcing layer in the above scheme is made of fiber and resin composite FRP (i.e., glass fiber reinforced plastic, hereinafter referred to as FRP) and then wound. Since FRP material has anisotropy, if the winding layup design is not proper, non-zero coupling terms will appear in the in-plane stiffness matrix [A], coupling stiffness matrix [B] and bending stiffness matrix [D] of the reinforcing layer, which will produce a variety of unfavorable coupling deformations under complex service loads, such as bending during tension or additional torsion during bending. The coupling deformation in the marine riser will weaken its load-bearing capacity, shorten its fatigue life, cause premature structural failure and endanger long-term reliability. In other fields, the winding method of plying is mostly the traditional staggered plying. For example, a carbon fiber flexible lightweight composite pipe disclosed in the prior art is disclosed as having a carbon fiber layer, a polyester braided layer, a polyester winding layer, a flame-retardant adhesive layer, and a glass fiber braided layer from the inside out. Adjacent polyester winding layers are spirally interwoven on the outside of the polyester braided layer, and the winding angles of adjacent polyester winding layers are opposite. The coupling term in the in-plane stiffness matrix [A] of traditional staggered plying is 0, which can avoid tension-shear and compression-shear coupling. However, the coupling stiffness matrix [B] of staggered plying is not 0, and tension-bending and compression-bending coupling exist. Figure 1 As shown, traditional staggered plies exhibit out-of-plane deformation under in-plane loads; some plies employ traditional symmetrical plies, but the coupling terms in the bending stiffness matrix [D] of traditional symmetrical plies are not zero, such as... Figure 2 As shown, traditional symmetrical plywood undergoes in-plane deformation under bending loads, making it impossible to avoid bending-torsion coupling. It is evident that existing plywood methods cannot simultaneously eliminate all coupling effects such as tension-shear, compression-shear, tension-bending, compression-bending, and bending-torsion in the same plywood structure. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a marine riser and its manufacturing method, which can solve the technical problem that the use of traditional interlaced plying in the reinforcement layer in the prior art will cause coupling deformation and weaken the load-bearing capacity of the reinforcement layer.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In one aspect, a marine riser is provided, comprising an inner liner, a structural reinforcement layer, and an outer protective layer that are coaxially and tightly bonded from the inside out. The structural reinforcement layer is formed by repeatedly stacking and curing several basic layup units along the pipe wall thickness direction; The basic layup unit consists of eight continuous spirally wound single-layer strips. The spirally wound single-layer strips of the basic layup unit, from the inside to the outside, are: single-layer positive spiral strip, double-layer negative spiral strip, single-layer positive spiral strip, single-layer negative spiral strip, double-layer positive spiral strip, and single-layer negative spiral strip. Helical winding angle of a single-layer spiral-wound strip Consistent spiral winding angles of positive and negative spiral strips The directions are opposite.

[0008] Preferably, a damping layer is added between the structural reinforcement layer and the outer protective layer.

[0009] Preferably, a carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer is coated between the structural reinforcement layer and the damping layer, and between the damping layer and the outer protective layer.

[0010] Preferably, the damping layer uses a modified nitrile rubber or polyurethane elastomer matrix.

[0011] Preferably, the fiber volume content in the structural reinforcement layer is 20% to 80%; the fiber is selected from one or more combinations of carbon fiber, basalt fiber, glass fiber, and aramid fiber; the matrix material is a polymer matrix, which is a thermosetting polymer or a thermoplastic polymer.

[0012] Preferably, the spiral winding angle of the spirally wound single-layer strip is... The range of values ​​is .

[0013] Secondly, a method for preparing the aforementioned marine riser is provided, the specific steps of which include: Preparation of inner lining: The tubular inner lining is prepared by extrusion molding process to ensure that the surface of the inner lining is smooth and the wall thickness is uniform; The outer wall of the inner lining layer is formed by a winding process, in which eight consecutive spiral single-layer strips are wound in sequence to form a basic layup unit. Several basic layup units are repeatedly stacked and solidified along the pipe wall thickness direction to form a structural reinforcement layer. A carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer is coated on the outside of the structural reinforcement layer, and then a damping layer is prepared on the outside of the carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer. A toughened epoxy gradient layer of end-carboxyl liquid nitrile rubber is coated on the outside of the damping layer, and finally the outer protective layer is prepared.

[0014] Preferably, the spiral wound single-layer strips of the basic layup unit, from the inside out, are: single-layer positive spiral strip, double-layer negative spiral strip, single-layer positive spiral strip, single-layer negative spiral strip, double-layer positive spiral strip, and single-layer negative spiral strip.

[0015] Preferably, the spiral winding angle of the spirally wound single-layer strip is... Consistent spiral winding angles of positive and negative spiral strips The directions are opposite.

[0016] Preferably, the spiral winding angle of the spirally wound single-layer strip is... The range of values ​​is .

[0017] Compared with the prior art, the advantages and positive effects of this invention are: The structural reinforcement layer of this invention is formed by stacking and curing several basic layup units. The spirally wound single-layer strips of the basic layup units, from the inside out, are: a single-layer positive spiral strip, a double-layer negative spiral strip, a single-layer positive spiral strip, a single-layer negative spiral strip, a double-layer positive spiral strip, and a single-layer negative spiral strip; the spiral winding angle of the spirally wound single-layer strips is... Consistent spiral winding angles of positive and negative spiral strips The directions are opposite, and the positive and negative helical strips are of equal thickness. The layup design of this invention makes the in-plane coupling terms in the in-plane stiffness matrix [A] of the basic layup unit... and Bending-torsional coupling terms in the bending stiffness matrix [D] and With the coupling stiffness matrix [B] set to 0, the tension-shear, compression-shear, tension-bending, compression-bending, and bending-torsion coupling effects are simultaneously eliminated, achieving complete decoupling of the structural mechanical response. This ensures high structural stability of the marine riser during long-term service, improves its load-bearing capacity and fatigue life, and thus guarantees the continuity and safety of deep-sea oil and gas production. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a diagram showing the out-of-plane deformation distribution of interleaved layers under in-plane loads in existing technologies. Figure 2 This is a diagram showing the in-plane deformation distribution of symmetrical plywood under bending load in the prior art. Figure 3 This is a schematic diagram of the composition of the marine riser in Embodiment 1 or Embodiment 2 of the present invention; Figure 4 This is a cross-sectional view of the marine riser of Embodiment 1 or Embodiment 2 of the present invention; Figure 5 This is a cross-sectional view of the basic layup unit of Embodiment 1 or Embodiment 2 of the present invention; Figure 6 This is an in-plane deformation distribution diagram of the structural reinforcement layer of Embodiment 1 or Embodiment 2 of the present invention under bending load; In the picture: 1. Inner lining layer; 2. Structural reinforcement layer; 21. Positive spiral strip; 22. Negative spiral strip; 3. Outer protective layer. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] Example 1 This embodiment discloses a marine riser, such as Figure 3 , Figure 4 As shown, the structure includes an inner liner 1, a structural reinforcement layer 2, and an outer protective layer 3, which are coaxially and tightly bonded from the inside out. It should be noted that the inner liner 1 is located at the innermost part of the marine riser, and its main function is to provide fluid sealing, prevent leakage of the internal transported medium, and protect the structural reinforcement layer from erosion by the internal fluid. The structural reinforcement layer 2 is the main load-bearing structure of the marine riser, and its main function is to withstand various mechanical loads faced by the marine riser during service, ensuring the structural integrity and safety of the marine riser. The outer protective layer 3 is located at the outermost part of the marine riser, and its main function is to protect the internal structure from erosion and mechanical damage from the external environment, such as seawater corrosion, abrasion, and external impact.

[0023] In this embodiment, the structural reinforcement layer 2 is formed by repeatedly stacking and curing several basic ply units along the pipe wall thickness direction. It can be understood that a basic ply unit refers to a repetitive structural unit that constitutes the structural reinforcement layer 2. Through the stacking and curing of multiple basic ply units, a load-bearing structural reinforcement layer 2 is formed.

[0024] In this embodiment, as Figure 5 As shown, the basic layup unit comprises eight consecutive helically wound single-layer strips. From the inside out, the helically wound single-layer strips of the basic layup unit are: single-layer positive helical strip 21, double-layer negative helical strip 22, single-layer positive helical strip 21, single-layer negative helical strip 22, double-layer positive helical strip 21, and single-layer negative helical strip 22; the helical winding angle of the helically wound single-layer strips is... Consistent spiral winding angles of positive spiral strip 21 and negative spiral strip 22 The directions are opposite, and the positive spiral strip 21 and the negative spiral strip 22 have the same thickness.

[0025] It is understandable that positive spiral strip 21 refers to a single-layer strip with a positive spiral winding direction, and negative spiral strip 22 refers to a single-layer strip with a negative spiral winding direction. Whether it is positive spiral strip 21 or negative spiral strip 22, its spiral winding angle... Consistency, that is, the spiral winding angle of the positive spiral strip 21 and the negative spiral strip 22. The absolute values ​​are the same, but the spiral winding angles of the positive spiral strip 21 and the negative spiral strip 22 are different. The directions are opposite.

[0026] By using this plying method, the in-plane coupling terms in the in-plane stiffness matrix [A] of the basic ply element can be reduced. and Bending-torsional coupling terms in the bending stiffness matrix [D] and With the coupling stiffness matrix [B] set to 0, the tension-shear, compression-shear, tension-bending, compression-bending, and bending-torsion coupling effects are simultaneously eliminated, achieving complete decoupling of the structural mechanical response.

[0027] In this embodiment, a single-layer positive spiral strip 21, a double-layer negative spiral strip 22, and a single-layer positive spiral strip 21 constitute the first symmetrical sublayer, and a single-layer negative spiral strip 22, a double-layer positive spiral strip 21, and a single-layer negative spiral strip 22 constitute the second symmetrical sublayer. The two symmetrical sublayers are anti-symmetrically distributed on opposite layup surfaces. In addition, this layup method can reduce the reversing frequency of the guide head during fiber winding and improve the local buckling resistance of the riser.

[0028] In this embodiment, the stiffness matrix of the basic ply unit is calculated based on the classical laminate theory of composite materials. The specific calculation process involves a recursive derivation from material properties to single-layer stiffness, and then to the overall stiffness of the laminate. The specific steps are as follows: Step 1: Determine the engineering elastic constants of a single-layer slab; The material properties of the reinforcing fiber and resin matrix were obtained, and the four fundamental engineering elastic constants of the monolayer strip in the principal direction of the material were determined by micromechanical models (such as the Halpin-Tsai equation) or experimental measurements: : Elastic modulus in the fiber direction (longitudinal modulus); : Elastic modulus perpendicular to the fiber direction (transverse modulus); Poisson's ratio; In-plane shear modulus; Step 2: Calculate the reduced stiffness matrix of the single-layer plate under the principal axes of the material. ; Using the engineering elastic constants obtained in step one, calculate the reduced stiffness matrix of the single-layer plate in the principal material direction coordinate system. The components: ; ; ; ; in, To satisfy the reciprocal relationship.

[0029] Step 3: Calculate the off-axis stiffness matrix of a single-layer slab in the ply direction. ; For the ply angle is For any layup, the stiffness needs to be transformed from the material principal axis (1-2) coordinate system (direction 1 is along the fiber direction, direction 2 is perpendicular to the fiber direction) to the laminate (xy) coordinate system to obtain the off-axis stiffness matrix. Its transformation formula is: ; ; ; ; ; ; Step 4: Solve for the overall stiffness matrix of the laminated plate by integration [A], [B], [D]; After obtaining the off-axis stiffness matrix of all plies Then, along the thickness direction of the laminate... By integrating, we can obtain the overall tensile stiffness matrix [A], coupled stiffness matrix [B], and bending stiffness matrix [D].

[0030] For a laminated plate composed of n layers, the formula for calculating its stiffness matrix components is: ; ; ; in, ; Number the layers, starting from the bottom layer. To the top floor .

[0031] From the geometric mid-surface of the laminate to the first The distance between the upper surfaces of the layer.

[0032] That is, the first Layer thickness .

[0033] In this embodiment, there are single-layer positive spiral strips 21, double-layer negative spiral strips 22, single-layer positive spiral strips 21, single-layer negative spiral strips 22, double-layer positive spiral strips 21, and single-layer negative spiral strips 22; the spiral winding angle of the single-layer strips is described. Consistent spiral winding angles of positive spiral strip 21 and negative spiral strip 22 The directions are opposite. It should be noted that... and It's about angles It is an odd function, therefore it exists. and When the number of positive and negative angles in the layup sequence is equal, and the thickness of each layer is the same, all and During the summation process, positive and negative values ​​cancel each other out, thus reducing the in-plane coupling terms. and It equals 0.

[0034] The bending-torsional coupling term in this embodiment and It also equals 0 because the entire layer is antisymmetric. and It's about angles The odd function is so that all positions are symmetrical about the plane in the ply geometry, i.e., the first ply. Layer and First Layers and , and They are opposites. Furthermore, due to the geometric symmetry of the symmetrical positions about the mid-plane, their thickness coordinates have equal cube differences, i.e. Therefore, during summation, the contributions of each pair of symmetrical plies are canceled out, ultimately... and It equals 0.

[0035] More importantly, under the premise of satisfying the above-mentioned balance and antisymmetry, this embodiment makes the coupling stiffness matrix [B] that is necessarily present in antisymmetric plies zero at the same time through a specific ply arrangement. This design breaks through the conventional understanding in traditional laminate theory that antisymmetric plies are necessarily accompanied by non-zero matrices.

[0036] To verify that the basic ply unit proposed in this embodiment can achieve a coupling stiffness matrix [B] of 0 and a bending-torsional coupling term in the bending stiffness matrix [D] and The in-plane coupling term in the in-plane stiffness matrix [A] is 0. and To set it to 0, here is a specific example: Set the spiral winding angle The angle is 55°, and it is compared with traditional staggered ply and traditional symmetrical ply, that is, the basic ply unit is [+55° / -55° / -55° / +55° / -55° / +55° / +55° / -55°], the staggered ply unit is [+55° / -55° / +55° / -55° / +55° / -55° / +55° / -55°], and the symmetrical ply unit is [+55° / -55° / +55° / -55° / -55° / +55° / -55° / +55°].

[0037] In this embodiment, the material parameters are selected based on a typical carbon fiber / epoxy resin composite system: E1=131GPa, E2=9GPa, G 12 =5.4GPa,v 12 =0.3, and the single-layer ply thickness is 0.125mm. Based on this set of typical parameters, the calculation results of the basic ply unit are shown in Table 1, the calculation results of the staggered ply unit are shown in Table 2, and the calculation results of the symmetrical ply unit are shown in Table 3.

[0038] Table 1 Calculation results of basic ply unit

[0039] Table 2 Calculation results of staggered ply units

[0040] Table 3 Calculation results of symmetrical plywood elements

[0041] By comparing the calculation results of the three different plywood elements above, it can be seen that the coupling stiffness matrix [B] of the staggered plywood element is not 0, so there is an in-plane-out-plane coupling effect, namely tension-bending coupling and compression-bending coupling; the bending stiffness matrix [D] of the symmetric plywood element contains bending-torsional coupling terms. and Since the value is not 0, there is bending-torsional coupling deformation; however, the coupling stiffness matrix [B] of the basic ply element is 0, so there is no tension-bending or compression-bending coupling deformation, and the bending-torsional coupling term in the bending stiffness matrix [D] is not 0. and Since the value is 0, there is no bending-torsional coupling deformation, and the in-plane coupling term in the in-plane stiffness matrix [A] is zero. and Since the coefficient of thermal equilibrium is 0, there are no tension-shear or compression-shear coupling effects. This characteristic of uncoupled deformation ensures high structural stability of the marine riser during long-term service, improves its load-bearing capacity and fatigue life, and thus guarantees the continuity and safety of deep-sea oil and gas production.

[0042] like Figure 2As shown, the deformation distribution of symmetrically ply units under bending loads exhibits significant asymmetry, indicating that torsional coupling deformation occurs in addition to curvature changes. And as... Figure 6 As shown, the deformation distribution of the basic ply unit is symmetrical when subjected to bending load, which indicates that bending only causes curvature change and does not cause torsional deformation.

[0043] In this embodiment, a damping layer (not shown in the figure) is added between the structural reinforcement layer 2 and the outer protective layer 3. It should be noted that the main function of the damping layer is to convert mechanical vibration energy into thermal energy or other forms of energy to attenuate the vibration. In actual marine environments, marine risers are subjected to complex dynamic loads and vibrations, such as ocean currents, waves, and vortex-induced vibrations. These vibrations can lead to structural fatigue and trigger severe vibrations in the higher-order modes of the marine riser, which is one of the main causes of fatigue damage, joint loosening, and even structural fracture, reducing the service life of the marine riser. By designing a damping layer, the vibration response of the riser can be reduced, structural fatigue can be decreased, and the service life can be extended.

[0044] It should also be noted that in this embodiment, because the marine riser adopts a fully decoupled ply structural reinforcement layer 2, the combination of the fully decoupled ply structure and the externally constrained damping layer produces a synergistic effect that goes beyond simple superposition. Since the fully decoupled ply structural reinforcement layer 2 completely eliminates bending-torsional coupling, it ensures that the marine riser will not experience static torsional deformation under enormous deep-water external or internal pressure. This fundamentally eliminates pressure-induced interfacial torsional shear, avoids the risk of pre-stripping of the damping layer due to hydrostatic pressure, and ensures reliable adhesion between the damping layer and the pipe body throughout its entire lifespan. Under vortex-induced vibration loads, the fully decoupled ply design removes unnecessary torsional shear loads from the damping layer, allowing the damping layer to only perform the vibration reduction function required by the design. Under the same sea conditions, it can delay the fatigue aging and interfacial failure of the damping layer, giving the marine riser higher reliability and maintenance-free potential in deep-sea environments.

[0045] In this embodiment, a carboxyl-terminated liquid nitrile butadiene rubber (hereinafter referred to as CTBN) toughened epoxy gradient layer (not shown in the figure) is coated between the structural reinforcement layer 2 and the damping layer, and between the damping layer and the outer protective layer 3. The CTBN toughened epoxy gradient layer can penetrate into the fiber pores in the structural reinforcement layer 2 to form a mechanical interlock, and can also chemically crosslink with the damping layer to prevent interlayer slippage of the damping layer under high pressure shear.

[0046] It should be noted that the main function of the CTBN-toughened epoxy gradient layer is to provide a smooth transition in mechanical properties from one material to another. The CTBN-toughened epoxy gradient layer combines the excellent adhesion and rigidity of epoxy resin with the flexibility and toughness of rubber and emulsion. Epoxy resin, as the matrix, provides good adhesion, ensuring a tight bond with adjacent layers; CTBN imparts elasticity to the layer, enabling it to absorb and disperse stress.

[0047] This is because the structural reinforcement layer 2, as the main load-bearing structure, needs to possess good rigidity; while the damping layer, to achieve vibration reduction, needs to possess good flexibility and viscoelasticity; and the outer protective layer needs to provide corrosion resistance and wear resistance. The significant differences in mechanical properties between these layers can easily lead to shear stress or delamination stress concentration at the interface when the marine riser is subjected to dynamic loads. The CTBN-toughened epoxy gradient layer, as an intermediate buffer layer, can both penetrate into the fiber pores of the structural reinforcement layer 2 to form a mechanical interlock and chemically cross-link with the damping layer, preventing interlaminar slippage of the damping layer under high-pressure shear; and provide a smooth transition of mechanical properties from the structural reinforcement layer 2 to the damping layer, reducing interface stress concentration.

[0048] In this embodiment, the damping layer uses a modified nitrile rubber or a polyurethane elastomer matrix. It should be noted that modified nitrile rubber is a material whose performance is optimized through chemical or physical methods; nitrile rubber itself possesses excellent oil resistance, heat resistance, and abrasion resistance. The polyurethane elastomer matrix is ​​a polymer material with excellent elastic and viscoelastic properties, exhibiting good flexibility, abrasion resistance, oil resistance, chemical corrosion resistance, and controllable mechanical properties.

[0049] It is understandable that both modified nitrile rubber and polyurethane elastomer matrices have excellent viscoelasticity. The damping layer, through the viscoelastic properties of the material, converts the mechanical energy generated during vibration into heat energy for dissipation, thereby effectively reducing the vibration response of the marine riser under external excitation, reducing structural fatigue, and extending its service life.

[0050] In this embodiment, the fiber volume content in the structural reinforcement layer 2 is 20% to 80%; the fibers are selected from one or more combinations of carbon fiber, basalt fiber, glass fiber, and aramid fiber; the matrix material is a polymer matrix, which is either a thermosetting polymer or a thermoplastic polymer. It should be noted that the fiber volume content in the structural reinforcement layer 2 refers to the volume percentage of fibers in the composite material. This parameter directly affects the mechanical properties of the composite material, such as strength, stiffness, and density. The fiber volume content in the structural reinforcement layer 2 is 20% to 80%, which ensures that the structural reinforcement layer, while meeting specific mechanical properties, has sufficient strength and stiffness to resist various loads in the marine environment and optimizes material utilization.

[0051] Understandably, fibers, as the reinforcing phase in composite materials, provide the primary strength and stiffness. Different types of fibers possess different mechanical properties, densities, corrosion resistance, and other characteristics. For example, carbon fiber has high strength, high modulus, low density, and good corrosion resistance, making it suitable for applications requiring extremely high strength and stiffness. Basalt fiber offers good high-temperature resistance, corrosion resistance, and fatigue resistance, and its relatively low cost makes it a viable alternative or supplement to carbon fiber. Glass fiber is inexpensive and possesses good insulation and corrosion resistance, but its strength and modulus are lower than those of carbon fiber and aramid fiber. Aramid fiber boasts high strength, high modulus, low density, and excellent impact resistance and fatigue resistance, but its compressive strength is relatively poor. By selecting appropriate fiber types, the structural reinforcement layer 2 can be provided with the necessary mechanical properties and environmental adaptability to meet the challenges of marine risers under complex loads and corrosive environments.

[0052] It is also understandable that the matrix material is the continuous phase in a composite material, used to bond fibers, transfer loads, and protect fibers from environmental erosion. The properties of the matrix material, such as toughness, temperature resistance, and chemical resistance, are crucial to the overall performance of the composite material. The polymer matrix can be a thermosetting polymer or a thermoplastic polymer. Thermosetting polymers, such as epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, bismaleimide resins, and cyanate ester resins, form a three-dimensional network structure after curing, exhibiting excellent heat resistance, chemical resistance, and dimensional stability. Thermoplastic polymers, such as polyaryletherketones, polyarylether sulfides, polysulfones, high-performance polyimides, polyamides, fluoropolymers, and polyolefins, can be softened by heating and hardened by cooling, exhibiting good toughness, impact resistance, and recyclability.

[0053] It should be noted that the spiral winding angle of a single-layer spiral-wound strip... The range of values ​​is Spiral winding angle The anisotropic mechanical properties of the helically wound single-layer strip, such as axial stiffness, torsional stiffness, and bending stiffness, are determined. In this embodiment, the helical winding angle... The optimal angle is 55°, as this angle is widely used in current research as the best layup angle for tubular structures to satisfy the force equilibrium conditions of thin-walled cylindrical shells under internal pressure in mesh theory. .

[0054] Example 2 This embodiment discloses a method for preparing a marine riser as disclosed in Embodiment 1, the specific steps of which include: Preparation of the inner lining: High-density polyethylene (HDPE) material is selected, and a tubular inner lining is prepared by extrusion molding process to ensure that the surface of the inner lining is smooth and the wall thickness is uniform. The outer wall of the inner lining layer is formed by a winding process, in which eight consecutive spiral single-layer strips are wound in sequence to form a basic layup unit. Several basic layup units are repeatedly stacked and solidified along the pipe wall thickness direction to form a structural reinforcement layer. When the structural reinforcement layer is wound and the resin is in a semi-cured state, a CTBN-modified CTBN toughened epoxy gradient layer is coated on the outside of the structural reinforcement layer. Through a layered coating process, a continuous gradient distribution transitioning from high resin content to high rubber content is formed in the radial thickness direction, thereby playing a dual role of stress buffering and chemical bridging.

[0055] Subsequently, a damping layer is prepared on the outside of the CTBN toughened epoxy gradient layer and tightly bonded to the tube surface through spiral winding or hot pressing coating process to ensure that the damping layer has a uniform thickness and is free of air bubbles.

[0056] A CTBN-toughened epoxy gradient layer is coated on the outside of the damping layer, and finally a high-density polyethylene (HDPE) outer protective layer is prepared by hot extrusion coating or hot melt winding process.

[0057] It is understandable that when the basic layup unit is spirally wound with single-layer strips, the sequence from the inside to the outside is: single-layer positive spiral strip, double-layer negative spiral strip, single-layer positive spiral strip, single-layer negative spiral strip, double-layer positive spiral strip, and single-layer negative spiral strip.

[0058] It is also understandable that the spiral winding angle of a single-layer spirally wound strip is... Consistent spiral winding angles of positive and negative spiral strips The directions are opposite. The spiral winding angle of a single-layer spiral-wound strip. The range of values ​​is .

[0059] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A marine riser, characterized in that, It includes an inner lining layer, a structural reinforcement layer, and an outer protective layer that are coaxially and tightly bonded from the inside out; The structural reinforcement layer is formed by repeatedly stacking and solidifying several basic layup units along the pipe wall thickness direction; The basic layup unit comprises eight consecutive spirally wound single-layer strips, and the spirally wound single-layer strips of the basic layup unit, from the inside to the outside, are as follows: single-layer positive spiral strip, double-layer negative spiral strip, single-layer positive spiral strip, single-layer negative spiral strip, double-layer positive spiral strip, and single-layer negative spiral strip. The spiral winding angle of the spirally wound single-layer strip Consistent spiral winding angles of positive and negative spiral strips The directions are opposite.

2. A marine riser as described in claim 1, characterized in that, A damping layer is added between the structural reinforcement layer and the outer protective layer.

3. A marine riser as described in claim 2, characterized in that, A carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer is coated between the structural reinforcement layer and the damping layer, and between the damping layer and the outer protective layer.

4. A marine riser as described in claim 2, characterized in that, The damping layer uses a modified nitrile rubber or polyurethane elastomer matrix.

5. A marine riser as described in claim 1, characterized in that, The fiber volume content in the structural reinforcement layer is 20% to 80%; the fiber is selected from one or more combinations of carbon fiber, basalt fiber, glass fiber, and aramid fiber; the matrix material is a polymer matrix, which is a thermosetting polymer or a thermoplastic polymer.

6. A marine riser as described in claim 1, characterized in that, The spiral winding angle of the spirally wound single-layer strip The range of values ​​is .

7. A method for preparing a marine riser as described in any one of claims 1-6, characterized in that, The specific steps include: Preparation of the inner liner: The tubular inner liner is prepared by extrusion molding process to ensure that the surface of the inner liner is smooth and the wall thickness is uniform; The outer wall of the inner lining layer is formed by a winding molding process, in which eight consecutive spiral wound single-layer strips are wound in sequence to form a basic layup unit. Several basic layup units are repeatedly stacked and solidified along the pipe wall thickness direction to form a structural reinforcement layer. The carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer is coated on the outside of the structural reinforcement layer, and then a damping layer is prepared on the outside of the carboxyl-terminated liquid nitrile rubber toughened epoxy gradient layer. An epoxy gradient layer toughened with end-carboxyl liquid nitrile rubber is coated on the outside of the damping layer, and finally an outer protective layer is prepared.

8. The method for preparing a marine riser as described in claim 7, characterized in that, The basic layup unit consists of a single-layer spiral strip wound from the inside out, which is as follows: a single-layer positive spiral strip, a double-layer negative spiral strip, a single-layer positive spiral strip, a single-layer negative spiral strip, a double-layer positive spiral strip, and a single-layer negative spiral strip.

9. The method for preparing a marine riser as described in claim 7, characterized in that, The spiral winding angle of the spirally wound single-layer strip Consistent spiral winding angles of positive and negative spiral strips The directions are opposite.

10. The method for preparing a marine riser as described in claim 7, characterized in that, The spiral winding angle of the spirally wound single-layer strip The range of values ​​is .

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