Carbon fiber composite anchorage device and preparation method thereof

Abstract

The invention relates to the technical field of marine mooring anchor cable protection, in particular to a carbon fiber composite anchorage device and a preparation method thereof. The carbon fiber composite anchorage device comprises a bearing body and a carbon fiber composite winding layer arranged on the periphery of the bearing body. The carbon fiber composite winding layer sequentially comprises an inner-layer functional area, a middle-layer transition area and an outer-layer bearing area from inside to outside in the radial direction; the carbon fiber winding angle of the inner-layer functional area is in a first angle range, and the fiber orientation in the first angle range is mainly circumferential winding and is used for resisting circumferential expansion stress; the fiber winding angle of the middle-layer transition area is in a second angle range, and the fiber orientation in the second angle range is gradually decreased in a stepped mode from inside to outside and used for forming stress transition; the fiber winding angle of the outer-layer bearing area is in a third angle range, and the fiber orientation in the third angle range is mainly axial winding and is used for bearing axial tension. The carbon fiber composite anchorage device effectively solves the problem that an anchorage device is poor in fatigue resistance and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of marine mooring anchor protection technology, and in particular to a carbon fiber composite anchor and its preparation method. Background Technology

[0002] Existing bonded anchors for carbon fiber composite cables typically place the cable body into a steel or alloy sleeve, utilizing the mechanical interlocking and adhesive friction generated by the epoxy aggregate mixture to transfer the load. However, this type of anchor is prone to significant stress concentration at the leading edge of the bonded section, leading to interface slippage or splitting failure. If friction extrusion reinforcement is used, excessive radial pressure can easily damage the surface layer of the carbon fiber composite, reducing the strength utilization rate.

[0003] When the aforementioned anchorages are applied to marine mooring, the following technical challenges arise: Corrosion and maintenance risks: Steel sleeves are highly susceptible to external wall corrosion and interface crevice corrosion in marine environments characterized by high salt spray, humidity, and seawater immersion, leading to strength degradation and making it difficult to meet the long-term maintenance-free requirements of offshore facilities. Dynamic fatigue failure: The unique wave cyclic loads and bending-torsional coupling effects of the marine environment significantly exacerbate the cumulative damage of the shear peak at the anchorage leading edge, resulting in a substantial reduction in fatigue life. High verification difficulty and cost: Traditional material systems are difficult to match the stringent safety margin requirements of marine engineering equipment. Long-term reliability verification under multi-field coupling environments is complex, significantly increasing the total life-cycle cost.

[0004] Therefore, there is an urgent need to develop a carbon fiber composite cable anchoring technology that is corrosion-resistant, fatigue-resistant, and suitable for marine environments. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a carbon fiber composite anchor and its preparation method, aiming to solve the problems of poor fatigue resistance and corrosion resistance of existing carbon fiber composite anchors in marine environments.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: In a first aspect, a carbon fiber composite anchor includes: The load-bearing body includes a load transfer medium through which a carbon fiber composite cable is inserted; and a carbon fiber composite winding layer disposed on the outer periphery of the load-bearing body. The carbon fiber composite winding layer includes an inner functional area, a middle transition area, and an outer load-bearing area in a radial direction from the inside to the outside; wherein, the fiber winding angle of the inner functional area is within a first angle range, and the fiber orientation within the first angle range is mainly circumferential winding to resist circumferential expansion stress. The fiber winding angle of the middle layer transition zone is within the second angle range. The fiber orientation within the second angle range decreases in a stepwise manner from the inside to the outside, which is used to form stress transition. The fiber winding angle of the outer bearing area is within the third angle range, and the fiber orientation within the third angle range is mainly axial winding, which is used to bear axial tensile force.

[0007] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0008] As a preferred technical solution, the carbon fiber composite anchor further includes a sleeve with a tapered inner hole; the load transfer medium is filled between the tapered inner hole and the carbon fiber composite cable.

[0009] As a preferred technical solution, in the carbon fiber composite anchor, the taper angle of the conical inner hole of the sleeve is 2° to 6°.

[0010] As a preferred technical solution, the carbon fiber composite anchor has the following characteristics: the first angle range is ±75° to ±90°; the second angle range is ±75° to ±45°; and the third angle range is 0° to ±20°.

[0011] As a preferred technical solution, in the carbon fiber composite anchor, the winding angle variation step of the inner functional area, the middle transition area and the outer load-bearing area of ​​the adjacent layers is no more than 10°.

[0012] As a preferred technical solution, in the carbon fiber composite anchor, the residual tension deviation of each layer after curing in the inner functional area, the middle transition area and the outer load-bearing area is less than 5%.

[0013] As a preferred technical solution, the carbon fiber composite anchorage wherein the load transfer medium is a modified epoxy resin or a particulate epoxy resin, and its modulus is distributed in a gradient along the axial or radial direction.

[0014] Secondly, a method for preparing any of the above-mentioned carbon fiber composite anchors, comprising: S1: Prepare to support the main body; S2: Fibers are wound around the outer surface of the supporting body to form an inner functional area; S3: Fibers are wound around the outer surface of the inner functional area to form a middle transition area; S4: Fibers are wound around the outer surface of the middle transition zone to form an outer bearing zone; During the winding process in steps S2 to S4, phased tension control is applied to the fiber: In step S2, a constant first tension is applied; In step S3, a second tension is applied, which decreases linearly with the increase of the number of winding layers; In step S4, a third tension is applied, which decreases non-linearly with the increase of the number of winding layers, and the final value of the third tension is lower than the final value of the second tension.

[0015] As a preferred technical solution, in the method for preparing the carbon fiber composite anchor, in step S2, a winding angle of ±85° is used; in step S3, the winding angle gradually decreases from ±75° to ±45°; and in step S4, a winding angle of ±15° or 0° is used.

[0016] Beneficial Effects: The carbon fiber composite anchorage provided by this invention completely replaces traditional metal anchorages with layered, circumferentially reinforced carbon fiber composite sleeve anchorage technology. Using a carbon fiber or hybrid fiber composite sleeve as the main load-bearing structure, combined with parametrically controlled multi-stage tension-controlled circumferential winding layup and a high-performance interfacial bonding medium, it achieves efficient load transfer and interfacial safety protection for cable anchorage through integral sleeve molding. This effectively solves the problems of poor fatigue resistance and corrosion resistance of carbon fiber composite anchorages in marine environments. Attached Figure Description

[0017] Figure 1 This is a perspective view of the carbon fiber composite anchor provided by the present invention; Figure 2 This is a front cross-sectional view of the carbon fiber composite anchor provided by the present invention; Figure 3 This is a side cross-sectional view of the carbon fiber composite anchor provided by the present invention. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. For techniques and methods known to those skilled in the art, The methods and devices may not be discussed in detail, but where appropriate, the techniques, methods, and devices described should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] like Figures 1 to 3 As shown, this invention provides a carbon fiber composite anchor, mainly comprising a load-bearing body 10 and a composite material winding layer 20 disposed around the outer periphery of the load-bearing body 10. The load-bearing body 10 is the core load-bearing component of the anchor, comprising a carbon fiber composite cable 100 inserted internally and a load transfer medium 110. In this embodiment, the load-bearing body 10 further includes a sleeve 120 having a tapered inner hole. The load transfer medium 110 fills the space between the tapered inner hole of the sleeve 120 and the carbon fiber composite cable. To avoid stress singularities (extreme stress concentration points) at right-angled edges, the tapered inner hole of the sleeve is designed with a specific taper angle, preferably ranging from 2° to 6° (e.g., 4°). This taper design effectively converts axial tensile force into controllable normal compressive stress and tangential shear stress. The load transfer medium is preferably a modified epoxy resin or particulate epoxy resin, whose modulus can be designed to have a gradient distribution along the axial or radial direction to better match the stiffness of the fiber layer.

[0023] The composite material winding layer on the outside of the sleeve is not a uniform layer at a single angle, but rather employs a graded winding structure with stress path matching. A protective layer 160 is then placed outside the composite material winding layer, such as... Figure 3 As shown, the winding layer is divided into three functional regions radially from the inside out: For example, the inner functional area (layers 1-8) 130: This area is in close contact with the load-bearing body, and its fiber winding angle is within a first angle range (e.g., ±75° to ±90°, preferably ±85°). This winding method, which is close to perpendicular to the axis (circumferentially dominant), is mainly used to bear the circumferential expansion pressure transmitted by the medium, and its principal stress direction matching rate can reach more than 90%, thus establishing a stable pre-compression stress field.

[0024] Intermediate Transition Zone (Layers 9-14) 140: This region is located in the middle, with its fiber winding angle within the second angle range (e.g., ±75° to ±45°). Within this region, the fiber orientation decreases stepwise from the inside out (e.g., gradually changing from ±75° to ±45°), with each layer's angle change step not exceeding 10°. This technical solution creates a smooth stress transition zone, specifically designed to resist interfacial shear stress concentration caused by the conical inner wall, achieving continuous stiffness and avoiding abrupt changes in interlayer stress.

[0025] Outer load-bearing area (15-20 layers) 150: This area is located on the outermost side, and its fiber winding angle is in the third angle range (e.g., 0° to ±20°, preferably ±15° / 0°). This axially dominant winding method makes the fiber direction almost parallel to the axis, which can directly and efficiently bear the axial tensile force component transmitted from the cable.

[0026] Through the above structure, this invention is the first to explicitly map stress tensor decomposition to fiber layup angle, realizing the specialized division of labor and synergy of functions in each layer.

[0027] Based on the same inventive concept, this invention also provides a method for preparing a carbon fiber composite anchor, specifically comprising: preparing a load-bearing body; inserting a carbon fiber composite cable into a sleeve and injecting or filling the gap with a load-transfer medium; winding fibers on the outer surface of the load-bearing body (specifically the sleeve) to form an inner functional zone; applying a constant first tension (high tension) to ensure close contact between the fiber layer and the load medium during this stage; for example, for the first to eighth inner layers, a winding angle of ±85° is used, and a constant tension of 180N is maintained; this step establishes a basic pre-stress field; continuing winding on the outer surface of the inner functional zone to form a middle transition zone; during this stage, the winding angle begins to change (e.g., from ±75° to ±45°), while the diameter of the sleeve and the wound layers gradually increases (e.g., from 45mm to 75mm); to compensate for the geometric increase in winding stress due to the increase in diameter, the applied second tension decreases linearly with the increase in the number of winding layers; for example, the tension decreases linearly from 167N to 105N. Continue winding on the outer surface of the intermediate transition zone to form the outer load-bearing zone. At this stage, use a small winding angle (e.g., ±15° or 0°). To compensate for shrinkage differences during subsequent curing, the applied third tension decreases non-linearly with the number of winding layers (e.g., decreases according to a specific function), and its final value (e.g., 45-50N) is significantly lower than the final value of the second tension.

[0028] In this embodiment, a three-stage tension control method is adopted: first maintaining high tension, then linearly decreasing it, and finally non-linearly decaying it, constructing a coupled control model of "winding tension - geometric curvature - curing shrinkage". Through this reverse-designed tension path, the residual tension deviation of each layer of material after curing is controlled within 5%, effectively overcoming the "loose inside and tight outside" problem commonly found in traditional equal-tension winding. As a result, in actual use, each layer of fiber can work together to bear the force, avoiding premature relaxation due to insufficient inner layer tension, and significantly increasing the service life of the component under cyclic loads from the conventional 200,000 cycles to over 500,000 cycles.

[0029] The carbon fiber composite anchorage provided by this invention is suitable for both parallel cables and stranded cables. By adjusting the formulation of the medium and the taper angle of the conical inner wall, it can adapt to the anchoring requirements of cables with different diameters and strength grades. Applications include, but are not limited to, the following scenarios: Mooring of deep-sea aquaculture platforms: Deep-sea aquaculture platforms typically employ 3-5 carbon fiber composite cables for multi-point mooring. Corrosion failure of traditional cylindrical steel anchors in saltwater environments is a major risk. The conical composite anchors of this invention completely avoid steel corrosion and improve fatigue life through stress-balanced design. Floating offshore wind turbine foundations: Floating wind turbine platforms need to withstand multi-directional cyclic loads from wind, waves, and currents, making the fatigue conditions of mooring cables more complex than those on aquaculture platforms. The conical sleeve of this invention can efficiently bear both internal pressure and shear stress simultaneously. Multi-layered progressive winding better adapts to complex multiaxial stress states, and the equivalent stress matches the fiber direction more closely, significantly improving the reliability of the entire system.

[0030] Ocean energy harvesting devices: Wave energy and tidal energy devices operate in the most severe environments, needing to withstand high-frequency wave impacts, tidal current impacts, and floating object collisions. The design of this invention is particularly suitable for these conditions: the conical inner wall has strong stress dispersion capabilities, which can "absorb" most of the impact energy; the combination of multi-layered gradient and variable stiffness design provides higher damage tolerance, so that even if local damage occurs, it will not lead to overall failure.

[0031] The technical solutions provided by the present invention will be further explained and illustrated below through specific embodiments.

[0032] The deep-water aquaculture platform mooring system employs a parallel cable bonded anchorage consisting of seven carbon fiber composite rods. The rods are directly connected by φ7.5mm parallel carbon fiber composite cables, each with a breaking strength of 110 kN and a strength rating of 2500 MPa, totaling a breaking strength of 773 kN for all seven. The design working tensile force is 773 kN (equal to 1 breaking strength, meeting the requirements of deep-water aquaculture operations).

[0033] The composite material anchor has a taper of 4°, an outer diameter of φ75 mm, an inner diameter (loading end) of φ45 mm, an inner diameter (fixed end) of φ52 mm, a total sleeve wall thickness of 14-22 mm, and a total length of 180 mm.

[0034] This platform uses a tapered sleeve with an inner wall inclination angle of 4°. When the medium is under the combined action of axial tension and circumferential expansion, the force exerted by the medium on the inner wall is decomposed into two components: normal stress (radial internal pressure). p Perpendicular to the inner wall and pointing outward, tangential stress (shear component) τ (along the direction of inclination of the inner wall) According to the design internal pressure p = 35 MPa and circumferential stress formula σ = p·D / (2 t To ensure that the circumferential stress of the inner fiber does not exceed the design allowable 1400 MPa (considering dynamic strength reduction and safety factor), the following is required:t ≥ 35×75 / (2×1400) ≈ 0.94 mm. However, considering the stiffness requirements of multi-layer designs and the reliability of actual engineering projects, the total thickness is selected. t It is approximately 21.6 mm thick and consists of 20 layers, with each layer averaging 1.08 mm.

[0035] 1. The anchorage adopts a three-layer functional design:

[0036] 2. During the fabrication of composite anchors, the tension control in the three stages is as follows: Layers 1-8 (inner layers): winding angle ±85°, axial feed speed of each layer v_axial = 2.5 mm / s (constant), winding tension T = 180 N (constant), total thickness approximately 8.6 mm.

[0037] Layer 9: Winding angle ±75°, v_axial = 2.8 mm / s, winding tension T = 167 N.

[0038] Layer 10: Winding angle ±65°, v_axial = 3.8 mm / s, winding tension T = 151 N.

[0039] Layer 11: Winding angle ±55°, v_axial = 5.0 mm / s, winding tension T = 135 N.

[0040] Layer 12: Winding angle ±45°, v_axial = 8.5 mm / s, winding tension T = 120 N.

[0041] Layers 13-14 (lower middle layer): Winding angle ±45°, v_axial = 8.5-10 mm / s, winding tension T = 120-105 N, total thickness approximately 6.5 mm.

[0042] Layer 15: Winding angle ±45°, v_axial = 10 mm / s, winding tension T = 105 N.

[0043] Layer 16: Winding angle ±30°, v_axial = 14 mm / s, winding tension T = 80 N.

[0044] Layer 17: Winding angle ±20°, v_axial = 18.5 mm / s, winding tension T = 65 N.

[0045] Layers 18-20: winding angle ±15° / 0°, v_axial = 22 mm / s, winding tension T = 45-50 N, total thickness approximately 6.5 mm.

[0046] 3. The manufacturing process is as follows: Step 1 (Winding): Install the inner lining mold on the winding machine and begin CNC winding. Set the sleeve speed and wind layers 1-20 sequentially according to the three-stage tension control parameter table. Pause for 1-2 minutes after each layer to observe whether the fiber arrangement is uniform. Only proceed to the next layer after confirming that there is no misalignment.

[0047] Step 2 (Curing): After the winding is completed, the entire anchor is placed in a constant temperature curing chamber and cured according to the process requirements of the resin system.

[0048] Step 3 (Demolding and Inspection): After curing, demold from the core mold and perform visual inspection (for defects such as cracks, delamination, and bulges), dimensional inspection (diameter, length, and wall thickness), and shear strength test.

[0049] Step 4 (Surface Treatment): Grind the surface of the 7 carbon fiber composite cable bundles to remove the protective film, and align them to the axial center of the sleeve using the positioning plate.

[0050] Step 5 (Medium Injection): After preparing the media of different moduli, pour them into the loading end of the sleeve after vacuum defoaming. Use vibration to vent for 5-10 minutes to ensure that the media fills all gaps and is free of air bubbles. Let it stand at room temperature until the media solidifies.

[0051] In summary, this invention discloses a carbon fiber composite anchor and its preparation method, comprising: a load-bearing body, the load-bearing body including a load transfer medium through which carbon fiber composite cables are inserted; and a composite material winding layer disposed on the outer periphery of the load-bearing body; the composite material winding layer includes, from the inside to the outside, an inner functional zone, a middle transition zone, and an outer load-bearing zone in a radial direction; wherein, the fiber winding angle of the inner functional zone is within a first angle range, and the fiber orientation within the first angle range is mainly circumferential winding to resist circumferential expansion stress; the fiber winding angle of the middle transition zone is within a second angle range, and the fiber orientation within the second angle range decreases stepwise from the inside to the outside to form stress transition; the fiber winding angle of the outer load-bearing zone is within a third angle range, and the fiber orientation within the third angle range is mainly axial winding to bear axial tensile force. This invention, through a functionalized layered progressive winding angle design, achieves a high degree of alignment between the fiber direction and the principal stress component (alignment > 85%), improving strength utilization by 25-30% compared to traditional homogeneous winding structures. By implementing staged tension control during the fabrication process, a uniform distribution of residual tension after curing of each layer (deviation <5%) was achieved, homogenizing the stress amplitude of each layer and significantly improving the fatigue life of the anchor under cyclic loads. The layered, progressively varying design creates redundant force transmission paths, preventing overall failure due to localized interlayer delamination and improving the safety factor. The use of an all-composite material structure completely eliminates electrochemical corrosion sources, resulting in a long maintenance-free period in marine environments and significantly reduced total lifespan costs. The three-stage tension control method effectively solves the "loose inside, tight outside" problem caused by traditional constant-tension winding, improving the finished product yield.

[0052] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A carbon fiber composite anchor, characterized in that, include: The load-bearing body includes a load transfer medium through which a carbon fiber composite cable is inserted; and a carbon fiber composite winding layer disposed on the outer periphery of the load-bearing body. The carbon fiber composite winding layer includes, from the inside to the outside, an inner functional area, a middle transition area, and an outer load-bearing area in a radial direction. The fiber winding angle of the inner functional area is a first angle range, and the fiber orientation within the first angle range is mainly circumferential winding to resist circumferential expansion stress. The fiber winding angle of the middle layer transition zone is within the second angle range. The fiber orientation within the second angle range decreases in a stepwise manner from the inside to the outside, which is used to form stress transition. The fiber winding angle of the outer bearing area is within the third angle range, and the fiber orientation within the third angle range is mainly axial winding, which is used to bear axial tensile force.

2. The carbon fiber composite anchorage according to claim 1, characterized in that, The load-bearing body also includes a sleeve having a tapered inner hole; the load transfer medium is filled between the tapered inner hole and the carbon fiber composite cable.

3. The carbon fiber composite anchorage according to claim 2, characterized in that, The taper angle of the tapered inner hole of the sleeve is 2° to 6°.

4. The carbon fiber composite anchorage according to claim 1, characterized in that, The first angle range is ±75° to ±90°; the second angle range is ±75° to ±45°; and the third angle range is 0° to ±20°.

5. The carbon fiber composite anchorage according to claim 1, characterized in that, In the inner functional area, the middle transition area, and the outer bearing area, the step size of the winding angle change between adjacent layers is no greater than 10°.

6. The carbon fiber composite anchorage according to claim 1, characterized in that, The residual tension deviation of each layer after curing in the inner functional area, middle transition area and outer load-bearing area is less than 5%.

7. The carbon fiber composite anchorage according to claim 2, characterized in that, The load transfer medium is a modified epoxy resin or a particle-modified epoxy resin, and its modulus is distributed in a gradient along the axial or radial direction.

8. A method for preparing a carbon fiber composite anchor according to any one of claims 1 to 7, characterized in that, include: S1: Prepare to support the main body; S2: Fibers are wound around the outer surface of the supporting body to form an inner functional area; S3: Fibers are wound around the outer surface of the inner functional area to form a middle transition area; S4: Fibers are wound around the outer surface of the middle transition zone to form an outer bearing zone; During the winding process in steps S2 to S4, phased tension control is applied to the fiber: In step S2, a constant first tension is applied; In step S3, a second tension is applied, which decreases linearly with the increase of the number of winding layers; In step S4, a third tension is applied, which decreases non-linearly with the increase of the number of winding layers, and the final value of the third tension is lower than the final value of the second tension.

9. The method for preparing the carbon fiber composite anchor according to claim 8, characterized in that, In step S2, a winding angle of ±85° is used; in step S3, the winding angle gradually decreases from ±75° to ±45°; in step S4, a winding angle of ±15° or 0° is used.

Images