Aluminum-carbon fiber composite pile leg of offshore wind power installation platform and forming method

Abstract

The application discloses an aluminum-carbon fiber composite pile leg of an offshore wind power installation platform and a forming method, and belongs to the technical field of ocean engineering equipment, and comprises a pile leg body, characterized in that: the material of the pile leg body is a three-dimensional orthogonal fabric reinforced aluminum matrix composite material, carbon fibers and aluminum alloys form a three-dimensional interpenetrating network structure instead of a laminated structure; the three-dimensional orthogonal fabric is formed by orthogonal weaving of three groups of carbon fiber bundles in the warp direction, the weft direction and the normal direction, constitutes a space grid framework, and aluminum alloys infiltrate and fill the grid gaps and coat the carbon fibers. The application adopts the three-dimensional orthogonal fabric reinforced aluminum matrix composite material, carbon fibers and aluminum alloys form a three-dimensional interpenetrating network structure, the interlaminar shear strength is greater than or equal to 120 MPa, reaches the level of the matrix metal, fundamentally eliminates the delamination failure defect, and the damage tolerance is increased by 3-5 times. The pile leg fully embodies the characteristics of light weight and good corrosion resistance, and the 30-year full life cycle cost is reduced by 40%.

Description

Technical Field

[0001] This invention relates to the field of marine engineering equipment technology, specifically to an aluminum-carbon fiber composite pile leg for an offshore wind power installation platform and its forming method. Background Technology

[0002] The legs of offshore wind turbine installation platforms are the key load-bearing structures supporting the platform's ascent above the sea surface, requiring them to simultaneously meet stringent requirements such as high strength, high rigidity, lightweight, resistance to seawater corrosion, and long service life. Existing technologies mainly use low-alloy high-strength steel (such as Q690) for manufacturing, which has significant drawbacks including heavy weight (density 7.85 g / cm³), severe corrosion (seawater corrosion rate 0.1-0.3 mm / year), and high maintenance costs.

[0003] Carbon fiber reinforced polymer (CFRP) composites possess superior properties, with specific strength and specific stiffness far exceeding those of metals. Their density is only 1.6 g / cm³, axial tensile strength can reach 3.5-7.0 GPa, and elastic modulus can reach 230-800 GPa. Existing fiber metal laminate (FML) technologies, such as CARALL (carbon fiber reinforced aluminum alloy laminate), are mainly used in the aerospace field (e.g., aircraft wings and fuselages). They employ a two-dimensional layered lamination structure, manufactured through autoclave lamination processes, and their thickness is typically less than 10 mm.

[0004] However, the use of aluminum-carbon fiber composite materials in the legs of large offshore wind power installation platforms faces the following technical bottlenecks: (i) Structural limitations: The existing FML is a two-dimensional layered structure (0° / 90° layup), with low interlayer shear strength (<50MPa). Under alternating marine loads, it is very easy to delaminate and expand, which cannot meet the fatigue resistance requirements of the pile leg.

[0005] (ii) Size limitations: The autoclave lamination process is limited by equipment size and cannot manufacture large marine structures with a diameter of 2-4 meters and a length of 60-120 meters.

[0006] (iii) Manufacturing defects: The interlayer adhesive interface is prone to electrochemical corrosion and interface debonding in seawater environment, and the autoclave process has high energy consumption, long cycle and high cost.

[0007] Therefore, there is an urgent need to develop a new type of pile leg material system and manufacturing technology that combines the toughness of metals, the high stiffness of composite materials, three-dimensional anti-delamination ability, and can be manufactured in a large-scale and low-cost manner. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide an aluminum-carbon fiber composite pile leg for an offshore wind power installation platform. This pile leg fundamentally solves the interlayer failure problem by constructing a three-dimensional interpenetrating network structure and spatial gradient material distribution, thereby achieving the optimal match between material performance and functional requirements.

[0009] Another objective of this invention is to provide an in-situ winding-induction melting integrated manufacturing method for aluminum-carbon fiber composite pile legs of offshore wind power installation platforms. This method breaks through the size limitations of autoclaves and realizes direct net forming manufacturing of large pile legs.

[0010] The objective of this invention is achieved through the following technical solution: A type of aluminum-carbon fiber composite leg for an offshore wind power installation platform, comprising a leg body, characterized in that: the leg body is made of a three-dimensional orthogonal fabric reinforced aluminum matrix composite material, wherein the carbon fiber and aluminum alloy form a three-dimensional interpenetrating network structure, rather than a layered composite structure; the three-dimensional orthogonal fabric is formed by three sets of carbon fiber bundles interwoven in the warp, weft and normal directions to form a spatial grid skeleton, and the aluminum alloy is melt-infiltrated to fill the grid gaps and cover the carbon fiber.

[0011] Furthermore, the normal carbon fiber bundles penetrate the thickness direction of the pile leg wall, with a density of 4-8 bundles / 10cm², and are implanted by mechanical needle punching or high-pressure gas injection to form a spatial positive interlocking structure with the warp and weft fibers, so that the interlaminar shear strength is ≥120MPa.

[0012] Furthermore, the carbon fiber surface has a chemical vapor deposition nano-silicon carbide transition layer with a thickness of 50-200 nm. The nano-silicon carbide transition layer is used to prevent the aluminum-carbon interface reaction from generating a brittle Al4C3 phase, improve the wettability of aluminum melt, and provide a modulus gradient transition from carbon fiber to aluminum alloy.

[0013] Furthermore, the material composition of the aluminum alloy, by mass percentage, is: Si 7.0-9.0%, Mg 0.3-0.7%, Cu 0.05-0.15%, Ti 0.1-0.3%, RE 0.05-0.15%, with the balance being Al.

[0014] Furthermore, the material composition of the aluminum alloy, by mass percentage, is: Si 8.0%, Mg 0.5%, Cu 0.10%, Ti 0.2%, RE 0.10%, with the balance being Al.

[0015] Furthermore, after the aluminum alloy is melt-infiltrated, it forms an Al-Si-C metallurgical bond with the carbon fiber. Before melting-infiltration, the aluminum alloy is a filamentous material.

[0016] Furthermore, the pile leg body is a rotating cylindrical structure with an outer diameter of 2.0-4.5m and a wall thickness of 40-120mm.

[0017] An in-situ winding-induction melting integrated manufacturing method for aluminum-carbon fiber composite pile legs of offshore wind power installation platforms includes the following steps: Step 1: Core mold preparation: Clean the surface of the rotating core mold and apply a release agent, and pre-lay the first layer of meridional carbon fiber bundles as a positioning layer; Step 2: In-situ three-dimensional orthogonal weaving: Using a multi-axis winding head, carbon fibers are laid in the warp direction, wound in the circumferential direction, and implanted in the normal direction to form a three-dimensional orthogonal fabric with a thickness of 0.5-1.2 mm per layer; Step 3: In-situ induction melting and infiltration: The induction coil moves with the winding head, maintaining a lag distance of 200-500 mm, and heats the aluminum alloy wire to a melting and infiltration temperature of 600-680℃, causing the aluminum alloy to melt and form droplets. The droplets infiltrate into the three-dimensional orthogonal fabric under capillary action. The aluminum alloy wire feed speed is 0.5-3.0 m / min, and the induction power is 500-2000kW. Step 4: In-situ cooling and solidification: A combination of follow-up air cooling and water mist cooling is used, with a cooling rate of 80-150℃ / min, to control the refinement of the solidified structure; Step 5: Cyclic weaving-melting infiltration: Repeat steps 2 to 4, layer by layer, to the designed wall thickness, and form an interface-free integral structure between layers through in-situ metallurgical bonding; Step Six: Post-processing: After the cyclic weaving and melt infiltration are completed, the material is demolded and then subjected to heat treatment.

[0018] Furthermore, in step three, in-situ induction melting is carried out in a local argon protective atmosphere, with the oxygen content controlled below 500 ppm to prevent oxidation of the aluminum melt.

[0019] Furthermore, in step three, the rotational speed of the rotating mandrel is 0.5-5 rpm, which matches the moving speed of the winding head and the melting rate to ensure manufacturing continuity.

[0020] The beneficial effects of this invention are: This application employs a three-dimensional orthogonal fabric-reinforced aluminum matrix composite material. The carbon fiber and aluminum alloy form a three-dimensional interpenetrating network structure, creating a three-dimensional interlocking structure. The interlaminar shear strength is ≥120MPa, reaching the level of the matrix metal, fundamentally eliminating delamination failure defects and increasing damage tolerance by 3-5 times. The pile leg of this application combines the toughness of metal, the high stiffness of composite materials, and three-dimensional anti-delamination capability, while also enabling large-scale and low-cost manufacturing. Detailed Implementation

[0021] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand the advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0022] Example 1: Legs of a 1200-ton offshore wind power installation platform Design parameters: Platform operating capacity: 1200 tons Operating water depth: 50m Number of pile legs: 4 Single pile leg dimensions: outer diameter 3.2 m, wall thickness 80 mm, total length 90 m (3 sections × 30 m). A type of aluminum-carbon fiber composite leg for an offshore wind power installation platform includes a leg body. The leg body is made of a three-dimensional orthogonal fabric reinforced aluminum matrix composite material. The carbon fiber and aluminum alloy form a three-dimensional interpenetrating network structure, rather than a layered composite structure. The three-dimensional orthogonal fabric is formed by three sets of interwoven carbon fiber bundles in the warp, weft, and normal directions, constituting a spatial grid skeleton. The aluminum alloy is melt-infiltrated to fill the gaps in the grid and covers the fibers. The leg body is a rotating cylindrical structure with an outer diameter of 2.0-4.5m and a wall thickness of 40-120mm. The normal carbon fiber bundles penetrate the wall thickness direction of the leg, with a density of 4-8 bundles / 10cm², and are implanted by mechanical needle punching or high-pressure gas injection, forming a spatially interlocking structure with the warp and weft fibers, resulting in an interlayer shear strength ≥120MPa.

[0023] Material system: Carbon fiber: T700S-12K, single filament diameter 7μm, tensile strength 4.9 GPa, tensile modulus 230 GPa, density 1.80g / cm³; The aluminum alloy has a filamentous structure. The material composition of the aluminum alloy, by mass percentage, is: Si 8.0%, Mg 0.5%, Cu 0.10%, Ti 0.2%, RE 0.10%, with the balance being Al, and a density of 2.68 g / cm³.

[0024] An in-situ winding-induction melting integrated manufacturing method for aluminum-carbon fiber composite pile legs of offshore wind power installation platforms includes the following steps: Step 1: Core mold preparation: Clean the surface of the rotating core mold and apply a release agent. Pre-lay the first layer of warp carbon fiber bundles as a positioning layer; pre-lay the first layer of 0° axial fiber bundles as a positioning layer, with tension controlled at 80-100 N to ensure straightness and no wrinkles.

[0025] Step 2: In-situ three-dimensional orthogonal weaving: Using a multi-axis winding head, carbon fibers are laid in the warp direction, wound in the circumferential direction, and implanted in the normal direction to form a three-dimensional orthogonal fabric with a thickness of 0.5-1.2mm per layer; Specifically, start the multi-axis winding head and perform spatial weaving in the following sequence: Warp laying: The winding head moves along the mandrel axis to lay 0° fiber bundles, forming a longitudinal skeleton; Circular winding: The winding head rotates around the mandrel, laying 90° fiber bundles that interweave with the warp fibers; Z-direction implantation: Key innovation - Short fiber bundles are vertically implanted into the pre-laid layers through a mechanical needle-punching mechanism or high-pressure gas jet, penetrating the thickness direction to form a three-dimensional interlocking network; After each layer of three-dimensional fabric (thickness 0.5-1.2 mm), it is lightly compacted using a rubber roller (pressure 0.5-1.0 MPa) to remove air and increase density.

[0026] Step 3: In-situ Induction Melting: The induction coil moves with the winding head, maintaining a lag distance of 200-500 mm, and heats the aluminum alloy wire to 600-680℃ to melt it. In this embodiment, the optimal melting temperature for in-situ induction melting is controlled at 610-650℃. The molten droplets penetrate into the three-dimensional orthogonal fabric under capillary action. The aluminum alloy wire feed speed is 0.5-3.0 m / min, and the induction power is 500-2000 kW. In this embodiment, in-situ induction melting is carried out in a local argon protective atmosphere, with the oxygen content controlled below 500 ppm to prevent oxidation of the aluminum melt.

[0027] Key technical parameters: The induction coil follows the movement of the winding head, maintaining a lag distance of 200-500 mm (ensuring the fabric is stable before melting and infiltration). The aluminum alloy wire is heated to melt within 2-3 seconds in the induction coil, and the molten droplets penetrate the three-dimensional fabric under capillary action and slight pressure. The melting and infiltration temperature is strictly controlled at 600-680℃: above the Al-Si eutectic point (577℃) to ensure fluidity, and below 700℃ to prevent the large-scale formation of the Al4C3 brittle phase; By adjusting the induction power (800-1500 kW) and the aluminum wire feeding speed (1.0-2.5 m / min), the melting and penetration depth is controlled to match the fabric thickness, ensuring complete and pore-free impregnation.

[0028] The rotational speed of the mandrel is 0.5-5 rpm, which is matched with the moving speed of the winding head and the melting rate to ensure manufacturing continuity.

[0029] Step 4: In-situ cooling and solidification: A combination of follow-up air cooling and water mist cooling is used, with a cooling rate of 80-150℃ / min, to control the refinement of the solidified structure; The specific steps are as follows: After melting and infiltration are completed, immediately start the follow-up cooling system: first air cooling (compressed air, 30-60 seconds) to below 400℃, then water mist cooling (20-40 seconds) to below 150℃; The cooling rate is controlled at 80-150℃ / min to obtain a fine α-Al dendrite (grain size 30-50μm) + lamellar eutectic Si structure, ensuring high strength and good toughness.

[0030] Step 5: Cyclic weaving-melting infiltration: Repeat steps 2 to 4, layer by layer, to the designed wall thickness, and form an interface-free integral structure between layers through in-situ metallurgical bonding; Interlayer bonding mechanism: The upper layer of molten aluminum undergoes local remelting and diffusion with the lower layer of solidified metal, forming an in-situ metallurgical bond without a true interface, and the interlayer bonding strength reaches the level of the matrix.

[0031] Step Six: Post-processing: After the cyclic weaving and melt infiltration are completed, the material is demolded and then subjected to heat treatment.

[0032] The specific steps are as follows: First, the rotating core mold shrinks (radial shrinkage 5-10 mm), and the whole thing is demolded; Secondly, T6 heat treatment is performed: solution treatment at 530℃ for 6 hours (water quenching) + artificial aging at 155℃ for 8 hours to spheroidize Si particles and improve elongation. Then, CNC machining of the connection interface: locally remove carbon fiber in the flange area (using laser or water jet cutting) to expose the metal substrate, and machine bolt holes or threads; Finally, surface protection treatment: micro-arc oxidation or spraying polyurethane coating can be selected to improve surface hardness and corrosion resistance.

[0033] The manufacturing equipment used in the above-mentioned in-situ winding-induction melting integrated manufacturing method for pile legs—the large-scale in-situ winding-induction system—has the following technical parameters for each component: Rotary core mold: Diameter 2.0-4.5m, length 15-30m (segmented), speed adjustable from 0.5-5rpm; Function: Bearing The fabric is loaded and provides winding tension, and the mandrel is designed as an expandable / contractable structure for easy demolding.

[0034] Multi-axis winding head: A 6-DOF robotic arm with a working radius of 5-8m and a repeatability accuracy of ±0.5mm; its function is to realize the three-dimensional orthogonal interlacing of complex spatial trajectories.

[0035] Fiber feeding mechanism: Three independent servo controls, tension adjustable from 50-200 N, response frequency >50 Hz; function: feeds carbon fiber bundles in the warp, weft, and Z directions respectively.

[0036] Induction melting unit: Medium-frequency induction heating, frequency 10-50kHz, power adjustable from 500-2000kW; function: in-situ melting of aluminum wire and melting of fabric, heating depth 5-15mm.

[0037] Aluminum alloy wire feeding mechanism: φ2-5mm aluminum wire, feeding speed 0.5-3.0m / min, tension control accuracy ±2%; function: precisely control the amount of melted metal, matching the fiber volume fraction.

[0038] Temperature control system: Infrared temperature measurement (range 300-1000℃) + PID closed-loop control, accuracy ±10℃; Function: Control the melting and infiltration temperature within the optimal range of 600-680℃.

[0039] Protective atmosphere chamber: Local argon gas protection shield, argon gas flow rate 50-200 L / min, O2 < 500 ppm; function: to prevent oxidation of high-temperature aluminum melt.

[0040] Follow-up cooling system: air cooling (compressed air) + water cooling (atomization) combination, cooling rate 50-200℃ / min; controls the refinement of solidification structure.

[0041] Example 2 An aluminum-carbon fiber composite pile leg for an offshore wind power installation platform, the difference between this embodiment 2 and embodiment 1 is that: the material composition of the aluminum alloy, by mass percentage, is: Si 9.0%, Mg 0.7%, Cu 0.15%, Ti 0.3%, RE 0.15%, with the balance being Al.

[0042] Example 3 An aluminum-carbon fiber composite pile leg for an offshore wind power installation platform, the difference between this embodiment 3 and embodiments 1 and 2 is that the material composition of the aluminum alloy, by mass percentage, is: Si 7.0%, Mg 0.3%, Cu 0.05%, Ti 0.1%, RE 0.05%, with the balance being Al.

[0043] In the above three embodiments, the aluminum alloy material comprises: The mechanism of Si is to form an Al-Si eutectic (melting point 577℃), reduce the melting and infiltration temperature, and improve the fluidity of the melt. The mechanism of Mg is as follows: solid solution reinforcement, and reaction with the SiC coating on the carbon fiber surface to generate Mg2Si reinforcing phase; The mechanism of Cu is: micro-strengthening, controlling the potential difference with carbon fiber, and reducing galvanic corrosion; The mechanism of Ti is to refine grains and improve melt filling ability; The mechanism of action of RE (Ce+La) is to improve the wettability of the melt to carbon fibers and reduce the contact angle; The mechanism of aluminum's function is that, as a basic or primary material, it can greatly reduce the weight of the pile legs.

[0044] Experiments were conducted using the aluminum-carbon fiber composite pile legs of the offshore wind power installation platform produced in Example 1, and the following relevant data were obtained, as shown in Table 1: Table 1

[0045] As shown in Table 1, the aluminum-carbon fiber composite pile legs of the offshore wind power installation platform in Embodiment 1 of this application fully meet the requirements in terms of stiffness and strength, while reducing the weight by 58% compared with the steel piles of the prior art. Furthermore, the seawater corrosion resistance rate is increased to 0.018 mm / year, demonstrating strong corrosion resistance.

[0046] In the three embodiments described above, the surface of the carbon fiber used was modified: this is crucial to ensuring a good aluminum-carbon bond, and specifically includes the following steps: (1) Remove the sizing agent from the carbon fiber surface: ablate in air at 400-450℃ for 30-60 minutes to remove the epoxy sizing agent; (2) Gas phase oxidation: ozone or oxygen plasma treatment is used to introduce active oxygen-containing groups such as -COOH and -OH on the fiber surface, increasing the surface oxygen content to 15-25%; (3) Deposition of nano-transition layer: A nano-silicon carbide transition layer with a thickness of 50-200 nm is prepared on the fiber surface by chemical vapor deposition (CVD). The nano-silicon carbide transition layer is referred to as: CVD-SiC nano-transition layer.

[0047] The nano-silicon carbide transition layer has the following three functions: First, a chemical barrier: preventing Al from reacting with C at high temperatures to form the brittle Al4C3 phase; Secondly, wetting is improved: the contact angle between SiC and Al melt is about 60°, which is much smaller than the 120° of the C / Al system, thus promoting melt penetration; Thirdly, the modulus gradient is: CFRP (230GPa) → SiC (450GPa) → Al (70GPa), which alleviates the stress concentration at the interface.

[0048] Compared with existing technologies, the cost analysis of the aluminum-carbon fiber composite pile legs of the offshore wind power installation platform produced in Example 1 is shown in Table 2: Table 2

[0049] As shown in Table 1, although the initial manufacturing cost of the aluminum-carbon fiber composite pile leg of the offshore wind power installation platform in Embodiment 1 of this application is 30-40% higher than that of the steel pile leg, the 58% weight reduction leads to a reduction in installation cost and maintenance-free characteristics, resulting in a 40% reduction in the total life cycle cost over 30 years, which has significant commercial competitiveness.

[0050] The aluminum-carbon fiber composite pile legs of the offshore wind power installation platform in this application have the following technical features: (I) Structural Creativity – Three-Dimensional Interpenetrating Networks Completely Solve Interlayer Failure Traditional fiber-reinforced metal laminates such as CARALL have a two-dimensional layered structure with an interlaminar shear strength of <50 MPa, making them prone to delamination under marine fatigue loads. The Z-axis fiber-through structure of this invention forms a three-dimensional interlocking structure with an interlaminar shear strength ≥120 MPa, reaching the level of the matrix metal. This fundamentally eliminates the delamination failure mode and increases damage tolerance by 3-5 times.

[0051] (II) Material Creativity – Gradient Hybridization for Performance Space Optimization Instead of a simple uniform mixture, the material is designed with a dual-gradient distribution in both the radial and axial directions, based on the corrosion field of the marine environment and the stress field of the pile legs. The inner surface layer is enriched with corrosion-resistant metal, the core is enriched with high-strength and high-rigidity fibers, and the outer surface layer is machinable, achieving a multi-functional integration of "one material, multiple uses," which improves the weight reduction efficiency by 15-20% compared to uniform materials.

[0052] (III) Interface Creativity – Achieving Metallurgical-Grade Bonding with Nanoscale Transition Layers The CVD-SiC nanotransition layer (50-200 nm) not only prevents the formation of harmful Al4C3 phase, but also provides a modulus gradient transition from carbon fiber (230 GPa) to aluminum alloy (70 GPa), with an interfacial shear strength ≥80 MPa, far exceeding that of traditional adhesive bonding (<20 MPa) and mechanical bonding.

[0053] (iv) Manufacturing Creativity – In-situ Integrated Molding Breaks Through Size Limitations For the first time, the "weaving" of textile engineering and the "melting and infiltration" of metallurgical engineering are integrated into a single device, directly manufacturing finished pile legs with a diameter of 4 meters and a length of 30 meters from fiber bundles and aluminum wires. This eliminates the need for ultra-large autoclaves, reduces equipment investment by 60% compared to traditional solutions, and achieves a material utilization rate of >95%.

[0054] (v) Economic Creativity – Significantly Reduced Life Cycle Costs Although the initial manufacturing cost is 30-40% higher than that of steel pile legs, the 58% weight reduction leads to lower installation costs and maintenance-free characteristics, resulting in a 40% reduction in the total life cycle cost over 30 years. This gives it significant commercial competitiveness and fully demonstrates its lightweight and corrosion-resistant properties.

[0055] The above description is merely illustrative of the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made without creative effort within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aluminum-carbon fiber composite leg for an offshore wind power installation platform, comprising a leg body, characterized in that: The material of the pile leg body is a three-dimensional orthogonal fabric reinforced aluminum matrix composite material. The carbon fiber and aluminum alloy form a three-dimensional interpenetrating network structure, rather than a layered composite structure. The three-dimensional orthogonal fabric is formed by three sets of carbon fiber bundles interwoven in the warp, weft and normal directions to form a spatial grid skeleton. The aluminum alloy melts and infiltrates to fill the gaps in the grid and covers the carbon fiber.

2. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 1, characterized in that: The normal carbon fiber bundles penetrate the thickness direction of the pile leg wall, with a density of 4-8 bundles / 10cm². They are implanted by mechanical needle punching or high-pressure gas injection, forming a spatial positive interlocking structure with the warp and weft fibers, so that the interlayer shear strength is ≥120MPa.

3. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 1, characterized in that: The carbon fiber surface has a chemical vapor deposition nano-silicon carbide transition layer with a thickness of 50-200 nm. The nano-silicon carbide transition layer is used to prevent the aluminum-carbon interface reaction from generating a brittle Al4C3 phase, improve the wettability of aluminum melt, and provide a modulus gradient transition from carbon fiber to aluminum alloy.

4. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 1, characterized in that: The material composition of the aluminum alloy, by mass percentage, is: Si 7.0-9.0%, Mg 0.3-0.7%, Cu 0.05-0.15%, Ti 0.1-0.3%, RE 0.05-0.15%, with the balance being Al.

5. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 4, characterized in that: The material composition of the aluminum alloy, by mass percentage, is: Si 8.0%, Mg 0.5%, Cu 0.10%, Ti 0.2%, RE 0.10%, with the balance being Al.

6. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 1, characterized in that: After the aluminum alloy is melt-infiltrated, it forms an Al-Si-C metallurgical bond with the carbon fiber. Before melting-infiltration, the aluminum alloy is a filamentous material.

7. The aluminum-carbon fiber composite pile leg of the offshore wind power installation platform as described in claim 1, characterized in that: The pile leg body is a rotating cylindrical structure with an outer diameter of 2.0-4.5m and a wall thickness of 40-120mm.

8. A method for in-situ winding-induction melting integrated manufacturing of aluminum-carbon fiber composite pile legs for offshore wind power installation platforms according to any one of claims 1-7, characterized in that: Step 1: Core mold preparation: Clean the surface of the rotating core mold and apply a release agent, and pre-lay the first layer of meridional carbon fiber bundles as a positioning layer; Step 2: In-situ three-dimensional orthogonal weaving: Using a multi-axis winding head, carbon fibers are laid in the warp direction, wound in the circumferential direction, and implanted in the normal direction to form a three-dimensional orthogonal fabric with a thickness of 0.5-1.2 mm per layer; Step 3: In-situ induction melting and infiltration: The induction coil moves with the winding head, maintaining a lag distance of 200-500 mm, and heats the aluminum alloy wire to the melting and infiltration temperature of 600-680℃, causing the aluminum alloy to melt and form droplets. The droplets infiltrate into the three-dimensional orthogonal fabric under capillary action. The aluminum alloy wire feed speed is 0.5-3.0 m / min, and the induction power is 500-2000kW. Step 4: In-situ cooling and solidification: A combination of follow-up air cooling and water mist cooling is used, with a cooling rate of 80-150℃ / min, to control the refinement of the solidified structure; Step 5: Cyclic weaving-melting infiltration: Repeat steps 2 to 4, layer by layer, to the designed wall thickness, and form an interface-free integral structure between layers through in-situ metallurgical bonding; Step Six: Post-processing: After the cyclic weaving and melt infiltration are completed, the material is demolded and then subjected to heat treatment.

9. The in-situ winding-induction melting integrated manufacturing method for aluminum-carbon fiber composite pile legs of offshore wind power installation platforms as described in claim 8, characterized in that: In step three, in-situ induction melting is carried out in a local argon protective atmosphere, with the oxygen content controlled below 500 ppm to prevent oxidation of the aluminum melt.

10. The in-situ winding-induction melting integrated manufacturing method for aluminum-carbon fiber composite pile legs of offshore wind power installation platforms as described in claim 8, characterized in that: In step three, the rotational speed of the rotating mandrel is 0.5-5 rpm, which matches the moving speed of the winding head and the melting rate to ensure manufacturing continuity.

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