Gradient sleeve for improving shear resistance of carbon fiber composite cable

Abstract

The invention relates to the technical field of marine mooring anchor cable protection, in particular to a gradient sleeve for improving the shear resistance of a carbon fiber composite cable. The sheath comprises a carbon fiber composite sleeve which comprises a body and a protective layer arranged on the outer wall of the body; the modified polyurethane foam material gradient filling layer is arranged on the inner wall of the body; the foam material gradient filling layer is divided into a strong bonding area, a transition area and a port protection area; the strong bonding area is located at the end, close to the anchoring sleeve, of the carbon fiber composite sleeve. By adopting the sleeve made of a carbon fiber material, the cable can resist the aging effect of wind wave flow transverse force and marine environment for a long time, and the defect that a traditional polymer sheath is easy to crack and deform is avoided; the foam filled inside is tightly bonded through gradient design, interface gaps between a traditional filling material and a cable and between the traditional filling material and a sheath are eliminated, seawater permeation is blocked, and stress concentration at an anchoring connector can be dispersed through elastic deformation of the foam.

Description

Technical Field

[0001] This invention relates to the field of marine mooring anchor cable protection technology, and in particular to a gradient sleeve for improving the shear resistance of carbon fiber composite cables. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) mooring cables have shown great promise in marine engineering due to their high specific strength, high specific modulus, and excellent corrosion resistance. However, their anchoring interface with anchorages, especially bonded anchorages, is prone to stress concentration and shear damage under complex marine environmental loads, becoming a key weakness restricting their reliability and durability. Therefore, external sheaths are commonly used in this field to protect the cables and anchoring interfaces.

[0003] Currently, protection solutions for CFRP mooring cables and anchoring joints mainly rely on the following traditional sheath designs: 1. Heat-shrinkable polymer sheathing method: This method typically uses heat-shrinkable polymer materials such as polyethylene (PE) and polyvinyl chloride (PVC) to create a tubular sheath, which is then wrapped around the surface of the CFRP cable and the anchoring interface area. Heating causes it to shrink, thus tightly adhering to the component surface and forming a physical barrier layer to prevent the intrusion of corrosive media such as seawater and chloride ions, and to some extent buffering external lateral impacts. However, these materials have high hardness and poor elastic recovery. Under the long-term action of alternating wind, wave, and current lateral forces, they are prone to brittle cracking due to fatigue or debonding from the substrate. Their buffering effectiveness is limited, and for large components, it is difficult to ensure uniform heating during installation.

[0004] 2. Rubber Buffer Sleeve Nesting Method: This method uses elastic materials such as nitrile rubber and neoprene rubber, processed into buffer sleeves of specific shapes, and nested at the contact points or easily impacted sections between the cable and the anchor. It relies on the high elastic deformation of the rubber material to absorb impact energy and dampen vibrations. However, under long-term exposure to marine ultraviolet radiation, ozone, and temperature variations, rubber materials are prone to hardening, cracking, and permanent compression deformation, leading to a sharp decline in protective performance. Furthermore, its fit with complex anchoring interfaces (such as conical surfaces and corners) is often insufficient, frequently resulting in blind spots in protection, and maintenance and replacement costs are high.

[0005] 3. Composite Coating Sheathing Method: This method forms a multi-layer composite coating on the substrate surface through a coating process. For example, an epoxy resin underlayer is first coated to enhance adhesion, followed by a high-performance top layer such as polyvinyl fluoride or polyetheretherketone to provide corrosion and wear resistance. Although this method can achieve good interfacial adhesion and uniform coverage, the overall thickness of the coating system is limited, and the stiffness is insufficient, making it difficult to effectively restrain the macroscopic displacement of the cable at the anchorage port. It has little effect on suppressing the cutting effect caused by excessive displacement.

[0006] Existing sheathing solutions are mostly applicable to clamping anchors, and generally suffer from the following common defects: Limited performance and insufficient synergy: The aforementioned solutions either focus on sealing and corrosion protection or on buffering and energy absorption, making it difficult to simultaneously meet the dual requirements of rigid protection and flexible coordination in the complex and ever-changing marine dynamic environment. Their material properties and structural forms cannot achieve effective synergy between protective performance and displacement control capabilities.

[0007] Poor long-term durability: The inherent defects of traditional polymer and rubber materials in terms of fatigue resistance and aging resistance lead to the performance degradation of the sheath system after long-term service. The protection life is often lower than the design life of the mooring cable itself, forming a bottleneck effect.

[0008] Poor compatibility with bonded anchors: In particular, existing sheath designs struggle to effectively address the shear damage problem at the anchorage interface between CFRP cables and bonded anchors. They fail to create a balanced rigid-flexible mechanical environment to disperse stress concentration at the anchor barrel end, thus failing to fundamentally alleviate the shearing effect and becoming a technical bottleneck restricting the safe application of CFRP mooring cables.

[0009] Therefore, there is an urgent need in the field for a new sheath solution that can balance long-term protection and active stress management, and is particularly suitable for CFRP cable-bonded anchor systems. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a gradient sleeve for improving the shear resistance of carbon fiber composite cables, aiming to solve the problem that existing protective sleeves for CFRP mooring cables and anchoring interfaces cannot simultaneously provide protection and displacement control.

[0011] The above-mentioned objective of this invention is achieved through the following technical solution: A gradient sleeve for improving the shear resistance of carbon fiber composite cables, used for fitting at the connection between the cable and the anchoring system, comprising: A carbon fiber composite sleeve includes a body and a protective layer disposed on the outer wall of the body; A gradient filling layer of foam material is disposed on the inner wall of the body; the gradient filling layer of foam material is divided into a strong bonding area, a transition area and a port protection area; wherein, the strong bonding area is located at the end of the carbon fiber composite sleeve near the anchoring sleeve.

[0012] 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.

[0013] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables, wherein the body adopts a symmetrical ply design with alternating 90° and 0° plies, wherein the proportion of 90° plies is not less than 60%.

[0014] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables with foam material further includes: a strain transition layer, wherein the strain transition layer is disposed between the gradient filling layer and the inner wall of the body.

[0015] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables, wherein the material used in the strong bonding area is modified polyurethane foam, and the compression deformation rate of the strong bonding area is greater than 60%.

[0016] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables, wherein the modified polyurethane foam contains chopped fibers and / or micro-elastomer particles.

[0017] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables, wherein the material of the transition zone is hydrophobic polyurethane foam containing nano-silica.

[0018] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables is provided with a connecting flange at one end of the carbon fiber composite sleeve near the anchoring sleeve, and the carbon fiber composite sleeve is connected to the anchoring sleeve by the flange.

[0019] As a preferred technical solution, the gradient sleeve for improving the shear resistance of carbon fiber composite cables, wherein the strain transition layer is made of flexible carbon fiber composite material or aramid fiber composite material.

[0020] Secondly, a method for installing a gradient sleeve to improve the shear resistance of carbon fiber composite cables as described in the first aspect, comprising: The carbon fiber sheath is fitted over the connection between the cable and the anchoring system; Foam raw materials for forming the gradient filling layer of the foam material are sequentially injected into the inner cavity of the carbon fiber shell; after vacuum degassing, the gradient filling layer is obtained. The carbon fiber shell is connected to the anchor sleeve using bolts.

[0021] Beneficial Effects: The gradient sleeve for improving the shear resistance of carbon fiber composite cables provided by this invention, by using a carbon fiber sleeve, can withstand the lateral forces of wind, waves, and currents, as well as the aging effects of the marine environment, over a long period, avoiding the defects of traditional polymer sheaths that are prone to cracking and deformation. The modified polyurethane foam filling inside, through gradient design and tight bonding, eliminates the interface gaps between traditional filling materials and cables / sheaths, preventing seawater infiltration. The synergistic effect of the rigidity of the carbon fiber composite sheath and the flexibility of the foam filling layer can also effectively limit the displacement of the mooring cable at the anchor port, avoiding a sudden increase in local stress caused by excessive displacement of the cable, thereby alleviating the cut effect and solving the problem that traditional structures cannot simultaneously achieve protection and displacement control. Attached Figure Description

[0022] Figure 1 This is a perspective view of the gradient sleeve for improving the shear resistance of carbon fiber composite cables provided by the present invention; Figure 2 is a cross-sectional view of the gradient sleeve for improving the shear resistance of carbon fiber composite cables provided by the present invention; Figure 3 This is a cross-sectional view of the gradient sleeve for improving the shear resistance of carbon fiber composite cables provided by the present invention during use; Figure 4 This is a diagram showing the changes in rotation angle and displacement of the CFRP cable system after it is subjected to force. Detailed Implementation

[0023] 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.

[0024] 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... This is merely illustrative and is in no way intended to limit the invention or its application or use. All other embodiments derived by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0025] 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, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "package" are used in this specification… When "includes", it indicates the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] 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.

[0027] like Figures 1 to 3 As shown, the present invention provides a gradient sleeve for improving the shear resistance of carbon fiber composite cables, comprising: a carbon fiber composite sleeve 10, including a body 100 and a protective layer 110 disposed on the outer wall of the body 100; a gradient foam material filling layer 20 disposed on the inner wall of the body 100; the gradient foam material filling layer 20 is divided into a strong bonding area 200, a transition area 210 and a port protection area 220; wherein, the strong bonding area 200 is located at one end of the carbon fiber composite sleeve near the anchoring sleeve 40.

[0028] In this embodiment, the use of a carbon fiber composite sleeve can withstand the lateral forces of wind, waves, and currents, as well as the aging effects of the marine environment, over a long period, avoiding the defects of traditional polymer sheaths that are prone to cracking and deformation. The modified polyurethane foam filling inside is tightly bonded through a gradient design (designed as a strong bonding zone, transition zone, and port protection zone according to functional positioning). This not only eliminates the interface gap between the traditional filling material and the cable / sheath, preventing seawater infiltration, but also disperses stress concentration at the anchoring interface through its own elastic deformation. The synergistic effect of the rigidity of the carbon fiber composite sheath and the flexibility of the foam filling layer can effectively limit the displacement of the mooring cable at the anchor port, preventing a sudden increase in local stress caused by excessive displacement of the cable, thereby alleviating the cut effect and solving the problem that traditional structures cannot simultaneously achieve protection and displacement control.

[0029] In this embodiment, the strong bonding area is a region formed by filling with low-density, high-elasticity, and high-damping modified polyurethane foam, with a density range of 150-300 kg / m³. 3The compression set must be >60%. Premixing short-cut carbon fibers or micro-elastomer particles into the foam in this region forms a micro-spring network, which can significantly improve its energy absorption efficiency and creep resistance. The transition zone is a region filled with medium-density, closed-cell >95% hydrophobic polyurethane foam. By adding fillers such as nano-silica, the foam acquires superhydrophobic properties, forming a reliable liquid sealing valve. The port protection zone is a region filled with high-density, high-strength modified polyurethane foam or epoxy foam. Its density can reach 500-700 kg / m³. 3 It possesses a certain degree of rigidity and can form a strong mechanical interlock with the carbon fiber sheath end, together constituting a rigid reinforcing ring, structurally reinforcing the weakest end area.

[0030] In one implementation of this invention, a symmetrical ply design alternating between 90° and 0° plies is employed. The 90° plies comprise at least 60% of the cable and are primarily responsible for bearing torsional loads and shear stresses caused by wind, waves, and currents, providing fatigue resistance. The 0° plies, along the cable axis, are mainly used to provide circumferential stiffness and limit lateral displacement. The protective layer is a functional coating, such as a fluorosilane-based antifouling coating or a graphene-reinforced wear-resistant coating.

[0031] In one implementation of the present invention, a strain transition layer 120 is provided between the gradient filling layer of the foam material and the inner wall of the body, that is, a thin layer of flexible carbon fiber composite material or aramid fiber composite material is added. This layer has a relatively low modulus and better toughness. Its core function is to act as a "strain transition layer" between the outer rigid sheath and the inner flexible foam, absorbing and dispersing the interfacial shear stress caused by the difference in stiffness between the two, and preventing the foam from being "shorn" by the rigid sheath.

[0032] In one embodiment of the present invention, a connecting flange 30 is provided at one end of the carbon fiber composite sleeve near the anchoring sleeve, and the carbon fiber composite sleeve is connected to the anchoring sleeve by the flange. The carbon fiber composite sleeve can be firmly fixed to the anchoring sleeve by the flange and bolts.

[0033] Based on the same inventive concept, this invention also provides an installation method for a gradient sleeve to improve the shear resistance of carbon fiber composite cables, comprising: fitting a carbon fiber shell onto the connection between the cable and the anchoring system; sequentially injecting foam material for forming a gradient filling layer into the inner cavity of the carbon fiber shell; obtaining the gradient filling layer through vacuum degassing; and connecting the carbon fiber shell to the anchoring sleeve with bolts. It should be noted that an injection hole is provided on the carbon fiber shell, through which the foam material can be injected, or it can be injected directly through the other end of the carbon fiber shell.

[0034] The technical solution of the present invention will be further explained and illustrated below through specific embodiments.

[0035] Example 1 The structure of this invention is adopted for the CFRP mooring cable of a certain 5MW floating wind power platform: Carbon fiber composite sheath body (adopting a symmetrical layup design with alternating 90° and 0° layups, of which 90° layups account for 80%): inner diameter 40mm, outer carbon fiber layer (T700 woven fabric + modified epoxy resin) thickness 5mm, connecting flange thickness 10mm, flange diameter 35mm, and 8 embedded stainless steel inserts (bolt hole diameter 22mm). Polyurethane foam filling layer: main body density 25kg / m³, density gradually changes to 30kg / m³ within 120mm of anchor end, butyl rubber bonding layer thickness 0.8mm, and internal cavity gap ≤0.2mm after filling; Bolted connection assembly: 8 M18 stainless steel bolts, preload torque 30N m, fluororubber sealing ring thickness 4mm, water-swellable rubber strip cross section 2mm×2mm. Installation steps: Pretreatment: Clean the surface of the CFRP cable anchor cylinder (wipe with isopropyl alcohol) and the inner wall of the sheath body, and apply a butyl rubber adhesive layer to the inner layer of the sheath and the surface of the cable; Foam filling: Modified polyurethane foam raw material mixed with short-cut fibers (components A and B are mixed in a 1:1 ratio), hydrophobic polyurethane foam, and epoxy foam are injected into the inner cavity through the pre-reserved injection holes in the sheath. After vacuum degassing (vacuum degree -0.095MPa), the foam is cured for 24 hours (25℃) to ensure a filling rate of ≥98%. Connection and fixing: Embed the fluororubber sealing ring into the sealing groove of the sheath connecting flange, align it with the anchor flange, insert the stainless steel bolts and tighten the double nuts, controlling the preload torque to 30N using a torque wrench. m; Sealing test: Apply soapy water to the outside of the connecting flange, and introduce 0.2MPa compressed air into the inside. If no bubbles are generated within 30 minutes, it is considered qualified. Based on the CFRP cable length L=2000mm, diameter d=30mm, concentrated force 500N, modulus 160GPa, load... P For a value of 500N, the formula for the moment of inertia is:

[0036] The formula for the deflection of a free end subjected to a concentrated force is:

[0037] The formula for the angle of rotation of a free end subjected to a concentrated force is:

[0038] After applying the sheath, the CFRP cable has a length L = 2000 mm and a diameter d = 30 mm, while the sheath has a length of 1500 mm and a diameter of 45 mm. The free end is subjected to a concentrated force of 200 N. The calculation results are as follows: Figure 4 As shown, under the same load, the free end displacement of the CFRP cable without a sheath is 84 mm, and the rotation angle (the angle between the dashed lines) is 4°. After adding the sheath, the free end displacement is 17 mm, and the rotation angle is 0.7°, which provides stronger restraint on the lateral displacement of the CFRP cable compared to the case without a sheath.

[0039] Extended analysis based on Example 1 is shown in Table 1, which illustrates the displacement / rotation angles of CFRP cables of different diameters before and after applying the sheath. After applying the sheath, the displacement and rotation angles of the CFRP cables are significantly reduced, with the effect being particularly pronounced in smaller tonnage (size) CFRP cables.

[0040] Table 1. Analysis of displacement and rotation angle of CFRP cables / sheaths of different sizes

[0041] In summary, this invention discloses a carbon fiber composite mooring cable sheath and connection structure. This structure is suitable for CFRP mooring systems of offshore floating structures (such as floating wind power platforms and deep-sea aquaculture vessels). It not only tightly wraps around the CFRP mooring cable to form all-round protection, but also achieves firm anchoring with the anchor tube through bolted connection components. At the same time, it utilizes the internal filling structure and body characteristics to achieve multiple core functions: it can resist the impact of wind, wave, and current loads and seawater corrosion, effectively disperse stress concentration at the anchoring interface, reduce the displacement of the mooring cable at the anchor tube end, and alleviate the cutting effect; it can also prevent seawater infiltration through closed-cell filling and sealing design, avoiding failure of the cable and anchoring components due to corrosion, and ultimately ensuring the long-term reliable operation of the mooring system in the marine environment, providing an integrated solution for the protection and anchoring of CFRP mooring cables.

[0042] 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 gradient sleeve for improving the shear resistance of carbon fiber composite cables, used for fitting at the connection between the cable and the anchoring system, characterized in that, include: A carbon fiber composite sleeve includes a body and a protective layer disposed on the outer wall of the body; A gradient filling layer of foam material is disposed on the inner wall of the body; the gradient filling layer of foam material is divided into a strong bonding area, a transition area and a port protection area; wherein, the strong bonding area is located at the end of the carbon fiber composite sleeve near the anchoring sleeve.

2. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 1, characterized in that, The body adopts a symmetrical ply design with alternating 90° and 0° ply layers.

3. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 1, characterized in that, It also includes a strain transition layer, which is disposed between the foam material gradient filling layer and the inner wall of the body.

4. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 1, characterized in that, The material used in the strong bonding area is modified polyurethane foam, and the compression deformation rate of the strong bonding area is greater than 60%.

5. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 4, characterized in that, The modified polyurethane foam contains chopped fibers and / or micro-elastomer particles.

6. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 1, characterized in that, The transition zone is made of hydrophobic polyurethane foam containing nano-silica.

7. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 1, characterized in that, A connecting flange is provided at one end of the carbon fiber composite sleeve near the anchoring sleeve, and the carbon fiber composite sleeve is connected to the anchoring sleeve by the flange.

8. The gradient sleeve for improving the shear resistance of carbon fiber composite cables according to claim 3, characterized in that, The strain transition layer is made of flexible carbon fiber composite material or aramid fiber composite material.

9. A method for installing a gradient sleeve to improve the shear resistance of carbon fiber composite cables as described in claim 1, characterized in that, include: The carbon fiber sheath is fitted over the connection between the cable and the anchoring system; The foam raw material used to form the gradient filling layer of the foam material is sequentially injected into the inner cavity of the carbon fiber shell; A gradient filling layer is obtained after vacuum degassing. The carbon fiber shell is connected to the anchor sleeve using bolts.

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