Bendable composite coated steel bar and its special winding equipment, manufacturing and bending forming method

Abstract

The application discloses a bendable composite-wrapped steel bar, a special winding device and a manufacturing and bending forming method thereof, and belongs to the technical field of building materials and structural engineering. The wrapped steel bar comprises a steel bar body and a continuous fiber reinforced composite material wrapping layer (referred to as a composite material wrapping layer), and the composite material wrapping layer is divided into at least one composite material wrapping layer straight section and at least one composite material wrapping layer bending section for subsequent bending operation along the axial direction of the steel bar. The composite material wrapping layer straight section is formed by impregnating continuous fibers with high stiffness resin (i.e., rigid resin) to ensure the bonding and anchoring force of the wrapped steel bar and concrete; the composite material wrapping layer bending section is formed by impregnating continuous fibers with high deformation capacity resin (i.e., ductile resin), and is suitable for on-site bending forming in the dual scenes of delivery inspection and engineering construction. The application realizes the online alternating glue application process of the two sections of the steel bar through the special winding device, realizes the partition control of stiffness and ductility in single continuous winding, and realizes the visual identification of the preset bending section through the resin color difference. The technology not only solves the industry problem that the existing composite-wrapped steel bar cannot be directly bent, but also avoids the defect that the bonding performance of the wrapped steel bar with only ductile composite material and concrete is insufficient, and the whole process does not need secondary coating and secondary curing, and the production efficiency is high, the construction is convenient, and the technology is suitable for large-scale industrial production, and is especially suitable for the scenes of coastal engineering, cross-sea bridges and other corrosion environments such as ocean, deicing salt and the like which have double requirements of corrosion resistance and bending forming of the steel bar.

Description

Technical Field

[0001] This invention relates to the field of building materials and structural engineering technology, specifically to a bendable composite-coated steel bar, its dedicated winding equipment, and its manufacturing and bending method. It is particularly suitable for engineering scenarios with dual requirements for corrosion resistance and bending performance of steel bars in corrosive environments such as marine and de-icing salt environments, such as coastal engineering, marine artificial islands, cross-sea bridges, port terminals, and coastal buildings. Background Technology

[0002] Steel reinforcement corrosion is one of the core causes of performance degradation and premature failure in reinforced concrete structures. In harsh service environments rich in chloride ions, such as marine environments and de-icing salt fields, steel reinforcement corrosion is particularly prominent. To address this issue, the engineering community has developed four mainstream corrosion-resistant reinforcement technologies: epoxy-coated steel bars, galvanized steel bars, stainless steel bars, and composite material bars. However, all of these technologies have significant drawbacks: the epoxy coating on epoxy-coated steel bars is easily damaged during transportation and construction, leading to a loss of its anti-corrosion effect; galvanized steel bars have poor corrosion resistance in chloride ion environments and a short protection period; stainless steel bars are expensive, costing approximately five times that of ordinary ribbed steel bars, significantly increasing project costs; and composite material bars have significantly different mechanical properties from steel bars, and their supporting design specifications are not yet complete, limiting their application to specific engineering scenarios, and requiring engineers to master the corresponding design methods and specifications.

[0003] To overcome the aforementioned technical deficiencies, patent CN115653203A discloses a composite-coated steel bar. This steel bar uses ribbed steel bars as the core and is covered with a thin layer of fiber-reinforced composite material. Compared with the prior art, it has multiple advantages: First, the impact resistance and peel resistance of the composite coating are far superior to traditional coatings; second, its corrosion resistance is comparable to that of stainless steel bars, and its protective effect is significant; third, it can still maintain good bonding performance with concrete after being coated with the composite material; fourth, it has a significant cost advantage compared to stainless steel bars; and fifth, it basically retains the original mechanical properties of the steel bar, so designers do not need to adjust existing design methods or update their existing knowledge system.

[0004] In existing composite-coated steel reinforcement technologies, the resin matrix for the composite coating is typically made of thermosetting resins with high stiffness and strength, such as epoxy resin and vinyl ester resin (also referred to as rigid resins in this article). These rigid resins provide sufficient hardness and strength to the composite coating, resisting impacts and friction damage during construction. Furthermore, during structural service, they efficiently transfer the compressive and shear stresses applied by the concrete to the steel reinforcement ribs. However, rigid resins generally have low tensile elongation at break, typically less than 5% (typically, the Huipah AM-8910A / B system reaches a maximum of 4.5%, and the West System 105 / 205 system averages 3.4%, data source: publicly available product manuals from both manufacturers).

[0005] According to current product standards for corrosion-resistant reinforcing bars [such as "Corrosion-Resistant Reinforcing Bars for Reinforced Concrete" (GB / T33953-2025) or "Zinc-Aluminum Alloy Coated Reinforcing Bars for Reinforced Concrete" (GB / T32968-2016)], corrosion-resistant reinforcing bars must also meet the bending performance requirements of ordinary reinforcing bars during delivery inspection [see "Steel for Reinforced Concrete Part 1: Hot-Rolled Plain Round Steel Bars" (GB1499.1-2024) and "Steel for Reinforced Concrete Part 2: Hot-Rolled Ribbed Steel Bars" (GB 1499.2-2024)]. In the bending test, the reinforcing bar must be bent to 180° around a bending head of a specified diameter, and no cracks should appear on the surface of the bent portion of the reinforcing bar after bending. Based on the stress during the bending process, when the composite-coated reinforcing bar is bent around the bending head, tensile strain will occur on its outer surface. The solution to this tensile strain simplifies to a pure bending problem of a two-dimensional plane beam. It is assumed that the length of the central axis of the reinforcing bar remains constant during bending (i.e., the plane section assumption is satisfied), and that the thickness of the composite coating is uniformly distributed along the reinforcing bar. A simplified diagram is shown below. Figure 1 As shown in the figure. d The diameter of the reinforcing bar; D The diameter of the bending head of the bending machine; t The thickness of the composite coating is taken as the maximum thickness of the existing process (1.2 mm, the worst case). R 0 represents the radius of the neutral axis of the curved segment relative to the center of the curve; R Ext Let the radius of the outer edge of the cladding layer relative to the center of the bend be:

[0006] According to the test parameters and steel bar specifications specified in GB 1499.1-2024 and GB 1499.2-2024, the maximum bending strain on the outer side of the wrapped steel bar is calculated using Equation 1-3 and summarized in Table 1.

[0007] Table 1. Maximum bending strain on the outer side of the reinforcing bar calculated according to Equations 1-3 and national standard parameters.

[0008] As shown in Table 1, under certain unfavorable combinations, the theoretical maximum tensile strain on the outer surface of the composite-coated steel bar can reach 58.3%, which far exceeds the elongation at break of rigid resin. This inevitably leads to cracking of the composite coating. Therefore, the existing composite-coated steel bar technology cannot meet the factory inspection and delivery acceptance requirements of conventional corrosion-resistant steel bars.

[0009] Furthermore, in practical engineering applications, reinforcing bars often need to be bent and shaped according to structural design requirements, such as forming stirrups, hooks, or other shapes, to meet functional requirements such as anchorage and erection. However, existing composite-coated reinforcing bar technology, which forms a rigid resin composite coating on the surface of the reinforcing bars, also cannot meet the manufacturing requirements of curved reinforcing bars.

[0010] Therefore, the lack of bending performance in existing composite-coated steel reinforcement technology in both factory acceptance and on-site construction has become a key bottleneck restricting the large-scale promotion and application of this new technology.

[0011] Currently disclosed technologies related to composite steel bars made of composite materials and steel bars, such as the steel-continuous fiber composite bar disclosed in patent CN1936206A, the composite FRP bar disclosed in patent CN105401695A, and the FRP steel bar composite bar disclosed in patent CN206070879U, all suffer from the same bending processing difficulties. FRP is an abbreviation for Fiber-Reinforced Polymer. Existing solutions to this problem mainly fall into two categories: one is proposed in CN115653203A, which involves bending after curing, then re-coating the cracked area with composite material and curing it again. This solution is prone to interface defects, making it difficult to guarantee the quality of the bent section. The other is proposed in CN110821047A, which involves peeling off the composite material from the bent section after curing, then re-coating the exposed area with composite material after bending. This solution also suffers from the drawback of secondary processing. Both of the above solutions are based on the design concept of "destroy first, then repair," which fails to achieve integrated molding. This not only leads to complicated production processes, extended processing cycles, and low automation, but more importantly, the interface of the secondary coating is prone to becoming a weak link in structural stress and corrosion protection, making it impossible to guarantee the long-term reliability of the bending area.

[0012] Besides the two publicly available solutions mentioned above, a perhaps more direct approach is to use ductile resin to create a composite coating for the entire reinforcing bar. However, the inventors' experimental research shows that although the tensile elongation of ductile resins (such as polyurethane) can meet bending requirements (typically, Sika TCC-6060 A / B averages 200%, data source: publicly available product manuals from manufacturers), their strength and stiffness are relatively low (e.g., Sika TCC-6060 A / B has a tensile strength of 28 MPa and a tensile modulus of elasticity of 159 MPa, compared to Huibai epoxy resin AM-8910A / B with a tensile strength of 79 MPa and a tensile modulus of elasticity of 2900 MPa, data source: publicly available product manuals from both manufacturers). This results in a significant reduction in the bond strength between the composite-coated reinforcing bar and the concrete. Figure 2This displays the results of pull-out tests conducted by the inventors and test results of composite-coated steel bars made using both epoxy (rigid) and polyurethane (flexible) resins. Figure 2 As shown in (d)-(f), the maximum bond strength between epoxy resin-coated steel bars and concrete is 66.4 kN, while that of polyurethane-coated steel bars is 8.43 kN. The latter is about 87% lower than the former, which is difficult to meet the requirements for bonding performance with concrete.

[0013] In summary, existing technologies present an irreconcilable technical contradiction: while rigid resins can meet the requirements for bonding, corrosion resistance, and mechanical properties in composite coatings, they cannot meet bending requirements; conversely, while ductile resins can meet bending requirements, they suffer from insufficient bonding performance. Therefore, there is an urgent need in this field to develop a technical solution that can simultaneously satisfy the mechanical and corrosion resistance properties of composite coatings, the adaptability to steel bending, and the efficiency of large-scale production. Summary of the Invention

[0014] To address the inherent contradiction between the rigid mechanical performance requirements of the composite-coated steel reinforcement and the bending ductility requirements in existing composite-coated steel reinforcement technologies, as well as the technical defects of existing bending solutions such as cumbersome processes and unstable forming quality, this invention proposes a bendable composite-coated steel reinforcement, its dedicated winding equipment, and its manufacturing and bending forming method. While ensuring the corrosion resistance and bonding performance with concrete of the steel reinforcement, it enables direct bending forming of the continuous fiber-reinforced composite material coating after overall curing. Simultaneously, it meets the bending requirements of both delivery inspection and engineering construction scenarios, effectively avoiding cracking and peeling of the composite coating during bending.

[0015] The purpose of this invention is: firstly, to provide a bendable composite-coated steel bar that takes into account both the high stiffness and high bonding performance requirements of the straight section and the high ductility requirements of the bent section, while retaining the original corrosion resistance and mechanical properties of the steel bar, and adapting to the engineering bending and forming requirements. Secondly, a special winding device adapted to the steel bar is provided to achieve precise and automatic switching of resin and single winding of continuous fibers, ensuring product molding quality and production efficiency. Thirdly, a differentiated adhesive application method and bending forming method for the steel bar are provided to achieve integrated manufacturing and precise, non-destructive bending of the steel bar, while meeting the efficiency requirements of large-scale production and the ease of operation in on-site construction.

[0016] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a bendable composite-coated steel bar, comprising a steel bar body and a continuous fiber-reinforced composite material coating (hereinafter referred to as the composite coating) covering the outer surface of the steel bar body. The composite material coating is divided along the axial direction of the steel bar into at least one straight segment of the composite material coating and at least one bent segment of the composite material coating for subsequent bending operations; the bent segment of the composite material coating corresponds to the position of the subsequent bending processing of the composite material coated steel bar, including bending test for delivery inspection and bending processing for engineering construction. The straight sections of the composite coating are formed by impregnating continuous fibers with high-stiffness resin (i.e., rigid resin), and the bent sections of the composite coating are formed by impregnating continuous fibers with high-deformation-capacity resin (i.e., ductile resin). The rigid resin exhibits a significantly smaller tensile fracture strain than the ductile resin, with the rigid resin exhibiting a tensile fracture strain of <5% and the ductile resin exhibiting a tensile fracture strain of ≥60%. This ensures that after the composite coating is fully cured, the reinforcing bar meets the delivery inspection bending performance requirements specified in "Steel for Reinforced Concrete - Part 1: Hot-rolled Plain Round Steel Bars" (GB 1499.1-2024) and "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB 1499.2-2024) without the composite coating cracking or peeling. Furthermore, it adapts to the diverse bending and forming needs in engineering construction.

[0017] The composite coating described in this invention has been fully cured before bending, and there is no need to remove or repair the composite coating during the bending process.

[0018] Optionally, the straight section of the composite coating and the bent section of the composite coating are seamlessly integrated in the axial direction, and the two are formed by the same bundle of continuous fibers in a single continuous winding process, without any interface formed by secondary coating, peeling or re-curing in between.

[0019] Optionally, the rigid resin and the ductile resin have different colors to facilitate visual identification of the location and start and end range of the bending section of the composite coating.

[0020] Optionally, the rigid resin is at least one selected from epoxy resin, epoxy acrylate, vinyl resin, phenolic resin, cyanate ester resin, and bismaleimide resin.

[0021] Optionally, the ductile resin is at least one of polyurethane, silicone rubber, nitrile rubber, and carboxyl-terminated nitrile rubber toughened epoxy resin.

[0022] Optionally, the continuous fiber is at least one of glass fiber, carbon fiber, basalt fiber, silicon carbide fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, polyester fiber, polypropylene fiber, flax fiber, and bamboo fiber.

[0023] Optionally, the thickness of the composite coating is 0.1-1.2 mm (e.g., 0.1 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, etc.), and it is uniformly distributed along the axial direction of the steel bar body, with a thickness error ≤ ±0.05 mm.

[0024] In a second aspect, the present invention provides a special winding device for producing the above-mentioned bendable composite-coated steel bars, comprising a continuous fiber winding host, a first resin dispensing module, a second resin dispensing module, a Y-shaped impregnation tube, a position sensing unit, and a controller. The continuous fiber winding host is used to clamp and drive the steel bar body to rotate, while guiding the continuous fibers to move along the axial direction of the steel bar body for winding. The first resin dispensing module and the second resin dispensing module are both modules that integrate resin storage, metering, transportation and mixing (two-component resin) functions, and are used to store and supply rigid resin and ductile resin respectively; The Y-shaped impregnation tube has two input ends and one output end. The two input ends are respectively connected to the first resin dispensing module and the second resin dispensing module. The output end is used to guide the continuous fiber through so that the continuous fiber is impregnated with resin during its journey. The position sensing unit uses a laser displacement sensor or a grating ruler sensor to obtain the winding position of the continuous fiber in the axial direction of the steel bar body in real time. The controller is communicatively connected to the continuous fiber winding host, the first resin dispensing module, the second resin dispensing module, and the position sensing unit, respectively. The controller is configured to: acquire preset axial segmentation position information of the reinforcing bar body; monitor the axial winding position of the continuous fiber on the reinforcing bar body in real time (position monitoring accuracy ≤ ±0.5 mm); and automatically control the first and second resin distribution modules to supply corresponding resin to the Y-shaped impregnation tube according to the segmentation position information and the monitoring position, so that the continuous fiber is impregnated with different resins according to the different axial positions of the reinforcing bar body during a single continuous winding process.

[0025] In this invention, the controller is communicatively connected to a position sensing unit, which can be a laser displacement sensor or a grating ruler sensor. This unit is used to acquire the real-time winding position of the continuous fiber along the axial direction of the rebar body and transmit the position signal to the controller. The controller automatically triggers the start / stop switching of the first resin distribution module and the second resin distribution module based on preset segmented position information and the monitored position. The response time for the start / stop switching is ≤0.1 s. When the current winding position is detected to be in a straight segment, the first resin distribution module is controlled to supply rigid resin to the Y-shaped impregnation tube. When the current winding position is detected to be in a bent segment, the second resin distribution module is controlled to supply ductile resin to the Y-shaped impregnation tube. This allows the continuous fiber to be impregnated with different resins according to the different axial positions of the rebar during a single continuous winding process.

[0026] Optionally, the two forked input ends of the Y-shaped impregnation tube are respectively connected to the first resin dispensing module and the second resin dispensing module, the length of the vertical leg section is 50-100 mm, and the Y-shaped impregnation tube is a disposable injection-molded part of polypropylene or polyethylene.

[0027] A third aspect of the present invention provides a method for manufacturing the above-mentioned bendable composite-coated steel bars, comprising the following steps: (1) The surface of the steel bar body is pretreated. The pretreatment may include straightening, rust removal and degreasing. After rust removal, the surface roughness of the steel bar Ra=1.6-6.3 μm and after degreasing, the surface is free of oil and water stains. (2) Fix the pretreated steel bar body in the above-mentioned winding equipment, start the winding equipment, and make the continuous fibers move along the axial direction of the steel bar body for winding; (3) According to the preset segment position information, when the continuous fiber is wound to the straight segment position of the steel bar body, the controller controls the first resin distribution module to supply rigid resin to the Y-shaped impregnation tube so that the continuous fiber is impregnated with rigid resin in the straight segment; when the continuous fiber is wound to the bent segment position of the steel bar body, the controller controls the second resin distribution module to supply ductile resin to the Y-shaped impregnation tube so that the continuous fiber is impregnated with ductile resin in the bent segment; the continuous fiber is impregnated with rigid resin in the straight segment and with ductile resin in the bent segment to form a composite coating that is continuous along the axial direction of the steel bar body and has performance partitioning. (4) After completing the winding and impregnation, the composite-coated steel bar body to be cured is cured to obtain a straight-shaped bendable composite-coated steel bar.

[0028] Optionally, the application of rigid resin and ductile resin in step (3) is completed by the controller mentioned above, which automatically starts, stops and switches the resin according to the real-time monitoring data of the axial position of the steel bar body.

[0029] A fourth aspect of the present invention provides a method for bending and forming the above-mentioned bendable composite-coated steel bar, comprising the following steps: (1) Provides a straight-shaped bendable composite-coated steel bar prepared by the above-described manufacturing method; (2) Use a steel bar bending machine to bend the continuous fiber reinforced composite material coating section, with a bending angle of 0°-180°: a. If used for delivery inspection, the bending angle and the diameter of the bending head shall comply with the requirements of "Steel for Reinforced Concrete - Part 1: Hot-rolled Plain Round Steel Bars" (GB 1499.1-2024) and "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB1499.2-2024); b. If used for engineering construction, the bending angle and the inner diameter of the bend shall comply with the requirements of the "Code for Construction of Concrete Structures" (GB50666-2011).

[0030] Optionally, after step (1) and before step (2), the following step is also included: by identifying the color difference between rigid resin and ductile resin, the position and start and end range of the continuous fiber-reinforced composite material coating bending segment on the bendable composite material coating steel bar are determined.

[0031] Beneficial effects: 1. This invention, through a performance-zoning design of the composite coating, fundamentally solves the technical problems of traditional rigid composite coatings for steel bars being unable to be bent and insufficient bonding in fully ductile composite coatings. While ensuring high stiffness, high bonding anchorage force, and corrosion resistance in straight sections, it imparts sufficient ductility to bent sections, enabling direct bending of the steel bar after the composite coating has been cured as a whole. This not only meets the delivery inspection bending performance test requirements specified in "Steel for Reinforced Concrete" (GB 1499.1-2024 / GB 1499.2-2024), but also adapts to the on-site construction bending processing requirements of "Code for Construction of Concrete Structures" (GB 50666-2011). It breaks through the dual bottlenecks of composite-coated steel bars in factory acceptance and engineering application, expands its engineering application scope, and improves on-site construction convenience.

[0032] 2. The special winding equipment designed in this invention achieves automatic and precise resin switching (position monitoring accuracy ≤ ±0.5 mm, response time ≤ 0.1 s) through the linkage of dual resin distribution modules, a position sensing unit with high-precision position sensing function and controller. Combined with disposable Y-type impregnation tubes, it not only ensures uniform impregnation of continuous fibers, but also reduces equipment maintenance costs, providing special equipment support for integrated manufacturing.

[0033] 3. This invention employs a differentiated adhesive application process involving the single continuous winding of the same bundle of fibers. This process completes the performance-specific shaping of the composite coating during integrated manufacturing. There is no interface formed between straight and bent sections due to secondary wrapping, peeling, or re-curing, eliminating the need for subsequent repair processes such as secondary wrapping and curing. This fundamentally differs from the existing "destruct first, then repair" approach. This process significantly simplifies the production process, shortens the manufacturing cycle, and improves production efficiency, laying a solid foundation for the fully automated and large-scale industrial production of composite-coated steel bars.

[0034] 4. This invention achieves visual identification of the bending section of the composite coating through the color differentiation design of rigid resin and ductile resin, enabling construction personnel to quickly and accurately locate the bendable area, effectively avoiding cracking of the composite coating due to misoperation, and significantly improving the efficiency of on-site bending processing and product yield.

[0035] 5. The bendable composite-coated steel bars of this invention basically retain the original mechanical properties of ordinary steel bars. The thickness of the composite coating is limited to 0.1-1.2 mm, and the thickness error is ≤±0.05 mm. Designers do not need to adjust the existing design methods and specifications of concrete structures, adapt to the existing application system of engineering projects, reduce the cost of technology promotion and application, and at the same time, the entire bending process does not require destructive removal or repair of the composite coating. While meeting the bending requirements of dual scenarios, it extends the service life of the structure. Attached Figure Description

[0036] Figure 1 A schematic diagram for calculating the maximum tensile strain borne by the outer layer of the bent section of composite-coated steel reinforcement; Figure 2 Pull-out tests and results of composite-coated steel bars made of epoxy resin (rigid) and polyurethane (flexible) resins are presented. (a) shows the two types of composite-coated steel bars; (b) shows the specimen composition; (c) shows the pull-out test apparatus; (d) shows the bond force-slip curve of epoxy resin composite-coated steel bars; (e) shows the bond force-slip curve of polyurethane composite-coated steel bars; and (f) compares the maximum bond force of the two types of composite-coated steel bars. Figure 3 This is a schematic diagram of the structure of the bendable composite-coated steel bar provided in an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a special winding device for bendable composite-coated steel bars provided in an embodiment of the present invention; Figure 5 A schematic diagram illustrating the manufacturing process of a bendable composite-coated steel bar according to an embodiment of the present invention; Figure 6 A schematic diagram of the bending and forming method of bendable composite-coated steel bars provided in an embodiment of the present invention; Figure 7This is a schematic diagram of the structure of a bendable composite-coated steel bar with both ends bent at 90° according to Embodiment 1 of the present invention, wherein (a) is a schematic diagram of the overall shape of the steel bar after bending, and (b) is a schematic diagram of the axial segmentation and coordinate calibration of the steel bar before bending. Figure 8 This is a schematic diagram illustrating the fabrication and bending process of the bendable composite-coated steel bar with both ends bent at 90°, as provided in Embodiment 1 of the present invention. Figure 9 This is a schematic diagram of the structure of the composite-coated irregular stirrup provided in Embodiment 2 of the present invention, wherein (a) is a schematic diagram of the overall shape of the irregular stirrup after bending, and (b) is a schematic diagram of the axial segmentation and coordinate calibration of the stirrup before bending. Figure 10 This is a schematic diagram illustrating the fabrication and bending process of the composite-coated irregular stirrup provided in Embodiment 2 of the present invention.

[0037] The following are explanations of the reference numerals in the attached figures: 1-Reinforcing bar body; 2-Straight section of composite material coating; 3-Bent section of composite material coating; 4- Bending indenter; 5- Neutral shaft; 6- Composite coating; 11-Continuous fiber winding main unit; 12-Y-type impregnation tube; 13-First resin dispensing module; 14-Second resin dispensing module; 15-Controller; 16-Position sensing unit; 17-Fiber yarn roll. Detailed Implementation

[0038] This invention provides a bendable composite-coated steel bar, its dedicated winding equipment, and a method for manufacturing and bending it. To make the objectives, technical solutions, and implementation effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0039] This invention provides a bendable composite-coated steel bar, comprising a steel bar body and a composite coating covering the outer surface of the steel bar body. The composite coating has at least one straight segment and at least one bent segment arranged axially along the steel bar body. Each bent segment is axially and continuously connected to an adjacent straight segment, and both are formed from the same bundle of continuous fibers in a single continuous winding process, without any secondary coating, peeling, or re-curing interfaces in between.

[0040] The straight section of the composite coating is formed by impregnating rigid resin with continuous fibers. The bent section of the composite coating is formed by impregnating ductile resin with the same bundle of continuous fibers. The tensile breaking strain of the ductile resin in the bent section of the composite coating is ≥60%, so that the area can withstand the corresponding tensile deformation without cracking or peeling during the bending of the reinforcing bar. According to the requirements of "Steel for Reinforced Concrete - Part 1: Hot-rolled Plain Round Steel Bars" (GB 1499.1-2024) and "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB 1499.2-2024), the theoretical tensile strain at the outermost edge of the bent section of commonly used steel bars is between 11.6% and 58.3% when performing the necessary bending test for delivery inspection. This invention limits the tensile breaking strain of the ductile resin to ≥60%, which provides sufficient safety margin for the 180° ultimate bending performance test during delivery inspection, and can fully adapt to the conventional bending requirements of engineering construction, ensuring that the composite coating does not crack or peel during the bending process.

[0041] In this embodiment, the composite coating adopts a resin partition design with different rigidity and ductility, which can accurately meet the functional requirements of different sections of the reinforcing bar: (1) For the straight sections of the composite coating, in addition to being able to withstand the roller pressure of the bending machine's bending shaft without being crushed during bending, it also needs to meet the mechanical performance requirements such as corrosion resistance, wear resistance, impact resistance, and high adhesion to concrete. Rigid resins such as epoxy resin and vinyl ester resin can give the composite coating high compressive strength, hardness, and stiffness, which perfectly match the above performance requirements. The inventors conducted concrete pull-out tests on composite coated steel bars made of rigid and ductile resins. The results showed that when using ribbed steel bars of the same specification, the maximum adhesion force between the epoxy resin-based composite coated steel bars and concrete was 66.4 kN; while the polyurethane-based composite coated steel bars were only 8.43 kN, which was only 13% of the former. Figure 2 As shown in the figure. The test results confirm that the use of a rigid resin design is necessary and effective for straight sections where high bonding performance is required.

[0042] (2) For the bent section of the composite coating, its contribution to the overall anchorage force of the steel bar mainly comes from the mechanical anchorage effect (pin effect) of the hook, and has a low dependence on the bonding performance of the coating surface. Therefore, using ductile resin in this area can meet the requirements of 180° limit bending test during delivery inspection and diversified angle bending during engineering construction without significantly sacrificing the overall anchorage performance of the steel bar, and ensure that the coating does not crack or peel during the bending process.

[0043] In summary, this invention, through a partitioned design of rigid resin in straight sections and ductile resin in bent sections, ensures both the corrosion resistance of the reinforcing steel and its bonding performance with concrete while meeting the requirements for bending and forming in engineering projects. It allows for direct bending after the composite coating has been fully cured, while overcoming the shortcomings of existing technologies such as long construction cycles for intermediate coating breaks, unstable quality of secondary reinforcement after bending, and poor bonding performance of the fully ductile resin coating.

[0044] In this embodiment, the number of straight and bent segments of the composite coating can be flexibly set according to the actual engineering application scenario, without specific quantity limitations. This design significantly enhances the applicability and flexibility of the bendable composite-coated steel reinforcement, better meeting the diverse requirements of different concrete structures for the shape and performance of the reinforcement. Figure 3 For example, Figure 3 This is a schematic diagram of the structure of the bendable composite-coated steel bar of the present invention, where 1 is the steel bar body, 2 is the straight section of the composite coating, and 3 is the bent section of the composite coating. The straight section of the composite coating uniformly covers the straight section of the steel bar body, providing the steel bar with high rigidity, high bonding strength, and reliable corrosion protection; the bent section of the composite coating uniformly covers the bending part of the steel bar body, and its ductile resin component can withstand the tensile deformation caused by bending without cracking, effectively avoiding the coating damage problem of traditional composite-coated steel bars when bent, and achieving a dual balance between corrosion protection and bending workability.

[0045] In some embodiments, the rigid resin is selected from at least one of epoxy resin, epoxy acrylate, vinyl resin, phenolic resin, cyanate ester resin, and bismaleimide resin; the ductile resin is selected from at least one of polyurethane, silicone rubber, nitrile rubber, and carboxyl-terminated nitrile rubber toughened epoxy resin, and the rigid resin and ductile resin are designed with different colors to facilitate visual identification by construction personnel of the location and start and end range of the bending section of the composite coating.

[0046] In some embodiments, the continuous fiber is selected from at least one of glass fiber, carbon fiber, basalt fiber, silicon carbide fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, polyester fiber, polypropylene fiber, flax fiber, and bamboo fiber, and can be flexibly selected according to engineering anti-corrosion requirements, mechanical requirements and cost budget.

[0047] In some embodiments, the thickness of the composite coating is 0.1-1.2 mm and is uniformly distributed along the axial direction of the steel bar body, with a thickness error of ≤±0.05 mm. This thickness design can ensure the anti-corrosion protection effect and structural rigidity of the composite coating without excessively increasing the overall cost of the steel bar, while also adapting to the bending and processing requirements of the steel bar.

[0048] In some embodiments, the number of straight segments of the composite coating is three, and the number of bent segments of the composite coating is two, forming a bendable composite-coated steel bar with 90° bends at both ends (e.g., Figure 7 As shown in the figure, it is applicable to longitudinal reinforcing bars in reinforced concrete beam structures.

[0049] In other embodiments, the number of straight segments of the composite coating is three, and the number of bent segments of the composite coating is two, forming a composite-coated steel bar (composite-coated irregular stirrup) consisting of a 90° bend and a 135° bend (e.g. Figure 9 As shown in the figure, it is applicable to concrete structures such as wave walls, breakwaters, and crash barriers.

[0050] This invention provides a specialized winding device for producing the aforementioned bendable composite-coated steel bars. This device is modified from an existing continuous fiber winding machine. By adding a dual resin distribution module, a controller, a position sensing unit, and a Y-shaped impregnation tube, it achieves differentiated resin impregnation and single-pass continuous winding of the continuous fibers. The overall structure of the device is as follows: Figure 4 As shown.

[0051] The specialized winding equipment specifically includes: a continuous fiber winding host 11, a Y-shaped impregnation tube 12, a first resin dispensing module 13, a second resin dispensing module 14, a controller 15, and a position sensing unit 16. The first resin dispensing module 13 and the second resin dispensing module 14 are two independent automatic resin dispensing modules, used for storing and supplying rigid resin and ductile resin respectively. Both are modules that integrate resin storage, metering, conveying, and two-component resin mixing functions, and can precisely control the resin injection rate and supply amount.

[0052] The continuous fiber winding host 11 is used to clamp and drive the steel bar body 1 to rotate, while guiding the continuous fiber to move along the axial direction of the steel bar body 1, thereby realizing the winding and forming of the continuous fiber on the surface of the steel bar body 1. The controller 15 is communicatively connected to the continuous fiber winding host 11, the first resin dispensing module 13, the second resin dispensing module 14, and the position sensing unit 16. The position sensing unit 16 is a laser displacement sensor or a grating ruler sensor, independently installed at the end of the longitudinal guide rail of the continuous fiber winding host 11, with a position monitoring accuracy of ≤±0.5 mm. It can acquire the winding position of the continuous fiber in the axial direction of the steel bar body 1 in real time and transmit the position signal to the controller 15. The controller 15 automatically triggers the start and stop switching of the two resin dispensing modules according to the preset segment information, and the response time of the start and stop switching is ≤0.1 s.

[0053] The Y-shaped impregnation tube 12 is a disposable injection-molded component made of polypropylene or polyethylene. Its two bifurcated input ends are connected to the outlets of the first resin distribution module 13 and the second resin distribution module 14, respectively. The output end corresponds to the continuous fiber travel path of the continuous fiber winding host 11, enabling differentiated resin impregnation of the continuous fiber during its travel. The vertical leg section of the Y-shaped impregnation tube 12 is 50-100 mm long. This length is designed based on the fastest continuous fiber travel speed determined by the continuous fiber winding host, the minimum resin injection rate determined by the controller, and the selected resin and fiber types, ensuring that the continuous fiber is completely impregnated with resin when it travels this length. The length of the slanted leg is flexibly designed according to the equipment installation space and is not strictly limited, as long as the resin flows smoothly into the vertical leg section. The disposable Y-shaped impregnation tube design requires no cleaning, allows for quick replacement, and reduces environmental treatment costs and equipment maintenance procedures.

[0054] In this embodiment, the controller 15 identifies the distance between the current winding position and the starting end of the steel bar body 1 through the position sensing unit 16, and then compares it with the input axial segmentation information of the steel bar body to accurately determine the start and stop times of the first and second resin distribution modules, so as to realize the automatic and accurate switching of resin and ensure the accurate forming of the straight and bent sections of the composite coating.

[0055] This invention provides a method for producing bendable composite-coated steel bars using the aforementioned specialized winding equipment, such as... Figure 5 As shown, the specific steps include: (S1) Pretreatment of the steel bar body: The steel bar body is straightened, rust removed and degreased. After rust removal, the surface roughness of the steel bar body Ra=1.6-6.3 μm, and after degreasing, there is no oil or water stains on the surface. The pretreated steel bar body can effectively remove rust, stains, grease and other attachments on the surface, ensuring good bonding between the composite coating and the steel bar body.

[0056] (S2) Equipment clamping and parameter setting: Fix the pretreated steel bar body on the clamp of the continuous fiber winding host 11 of the above-mentioned special winding equipment, pass the continuous fiber through the Y-shaped impregnation tube 12 and fix it on the surface of the steel bar body; at the same time, input the steel bar body diameter, axial segment position information and injection rate of the two resins into the controller 15 to complete the equipment parameter preset.

[0057] (S3) Differentiated Glue Application and Continuous Winding: Start the continuous fiber winding host 11, drive the steel bar body 1 to rotate, and guide the continuous fiber to move along the axial direction of the steel bar body for continuous winding; the controller 15 monitors the winding position in real time according to the preset section position information. When the winding reaches the straight section of the steel bar body, the controller controls the first resin distribution module 13 to supply rigid resin to the Y-shaped impregnation tube 12, so that the continuous fiber is impregnated with rigid resin and then wound on the surface of the steel bar body; when the winding reaches the bending section of the steel bar body, the controller 15 automatically closes the first resin distribution module 13 and triggers the second resin distribution module 14 to supply ductile resin to the Y-shaped impregnation tube 12, so that the continuous fiber is impregnated with ductile resin and the winding of this section is completed; during the winding process, the equipment maintains a stable rotation speed and travel rate to ensure that the continuous fiber is tightly and uniformly wound, forming a composite coating that is continuous along the axial direction of the steel bar body 1 and has performance zones.

[0058] (S4) Curing treatment: After the winding is completed, the composite-coated steel bar to be cured is cured to obtain a straight-shaped bendable composite-coated steel bar. The straight-shaped steel bar can be bent according to the bending and forming method of the present invention according to the engineering requirements.

[0059] In this embodiment, the continuous fiber can be made of at least one of glass fiber, carbon fiber, basalt fiber, etc. During the winding process, the axial angle between the continuous fiber and the rebar body can be flexibly adjusted by controlling the rotation speed of the rebar body and the axial travel speed of the continuous fiber yarn head. This manufacturing method achieves differentiated resin application for the straight and bent sections of the rebar body through an innovative variable resin impregnation process. After curing, it can be directly bent to avoid cracking of the composite coating. At the same time, it overcomes the defects of existing technologies such as intermediate wrapping and secondary reinforcement. It can be used to manufacture various curved composite coated rebars such as stirrups and bent-up bars, solving the technical bottleneck of the promotion and application of new corrosion-resistant rebars and enriching its engineering application scenarios.

[0060] In the differentiated adhesive application and winding step, the controller 15 can precisely control the injection rate of the resin distribution module according to preset parameters to ensure sufficient impregnation of continuous fibers. After curing, the straight sections of the reinforcing bar body 1 form a composite coating with high rigidity and hardness, while the bent sections form a composite coating with good ductility and easy bending. During subsequent bending processing, the straight sections of the composite coating can withstand the roller pressure of the bending machine without being crushed, and the bent sections of the composite coating can withstand tensile deformation without cracking, realizing non-destructive bending and forming of the reinforcing bar.

[0061] The bending and forming method for bendable composite-coated steel bars provided in this invention is based on the straight-shaped bendable composite-coated steel bars produced by the above-mentioned manufacturing method. By identifying the position of the bending segment of the composite coating, a steel bar bending machine is used for precise bending, simultaneously adapting to the bending requirements of both delivery inspection and engineering construction scenarios. The process of this bending and forming method is as follows: Figure 6 As shown, the specific steps include: (S11) Preparation of straight-shaped bendable composite-coated steel bars: Provide straight-shaped bendable composite-coated steel bars prepared by the above-mentioned manufacturing method, ensuring that the composite coating is completely cured and that there are no defects such as damage or cracks on the surface.

[0062] (S12) Bending area identification: By identifying the color difference between rigid and ductile resins, the location and start and end range of the bending section of the composite coating on the steel bar body can be quickly and accurately determined to avoid misoperation.

[0063] (S13) Precision bending process: Fix the steel bar body on the steel bar bending machine, and bend the composite-coated bending section. The bending angle is 0°-180°. The specific requirements are as follows: a. If used for delivery inspection, the bending angle and bending head diameter shall strictly comply with the provisions of "Steel for Reinforced Concrete - Part 1: Hot-rolled Plain Round Steel Bars" (GB 1499.1-2024) and "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB1499.2-2024) to ensure that the steel bars pass the factory inspection and delivery acceptance. b. If used for construction bending, the bending angle and the inner diameter of the bend shall meet the requirements of the "Code for Construction of Concrete Structures" (GB 50666-2011) and be made into composite-coated steel bars of the required shape.

[0064] During the bending process, there is no need to destructively remove or repair the composite coating. The ductile resin in the bent section of the composite coating can withstand the tensile deformation caused by bending, ensuring that the coating is free from cracking and peeling, effectively preserving the anti-corrosion protection performance of the steel bar. At the same time, the bent steel bar can still maintain good bonding performance with the concrete, which not only meets the bending performance requirements for delivery inspection, but also adapts to the stress and usage requirements of the engineering structure.

[0065] The present invention will be further described in detail below through specific embodiments. It should be noted that the process procedures not described in particular below are all conventional operations that can be implemented or understood by those skilled in the art by referring to the prior art; the reagents and instruments used, unless otherwise specified, are all conventional products that can be purchased through commercial channels.

[0066] Example 1: Composite reinforced steel bars with both ends bent at 90° This embodiment aims to produce a bendable composite-coated steel bar with 90° bends at both ends, as shown in Figure 7(a). This type of steel bar is widely used as longitudinal reinforcing bar in reinforced concrete beam structures. Its 90° bend design at both ends can achieve effective anchorage with concrete.

[0067] (1) Construction of dedicated winding equipment The existing continuous fiber winding machine is modified by adding two automatic resin dispensing modules, one for supplying epoxy resin (Huipa AM-8910A / B, tensile strength 79 MPa, elastic modulus 2900 MPa) and the other for supplying thermosetting polyurethane (Sika TCC-6060 A / B, tensile strength 28 MPa, elongation at break 200%). A disposable Y-shaped impregnation tube made of polypropylene (vertical leg length 80 mm) is also provided. The two automatic resin dispensing modules, a laser displacement sensor-type position sensing unit (position monitoring accuracy ≤ ±0.5 mm), and the controller are connected communicatively. Simultaneously, their dispensing ports are connected to the two bifurcated input ends of the Y-shaped impregnation tube, thus constructing the flexible composite-coated rebar winding equipment described in this invention.

[0068] (2) Raw material preparation and pretreatment HRB400 steel bars with a nominal diameter of 16 mm and a length of 2.45 m were prepared and sequentially passed through a steel bar straightening machine, a rust removal machine, and a CO2 surface cleaning machine for straightening, rust removal, and degreasing pretreatment. This ensured the surface roughness of the steel bars reached Ra = 1.6-6.3 μm, and that the surface was free of oil and water stains. The pretreated steel bars were then fixed at both ends to the continuous fiber winding main unit clamp of a specialized winding equipment. Simultaneously, glass fibers with a linear density of 2400 Tex were prepared, passed through the disposable Y-type impregnation tube of the equipment, and fixed to the surface of the steel bars.

[0069] (3) Equipment parameter preset In the controller's software interface, input the diameter of the reinforcing bar and the axial segmentation parameters, specifically: reinforcing bar diameter 16 mm, segment 1 length 800 mm, segment 2 length 850 mm, segment 3 length 800 mm, segment 1-2 bending angle 90°, segment 2-3 bending angle 90°. The controller's backend automatically calibrates the axial segment coordinates based on these parameters, using the winding start point as coordinate (0,0), defining straight segment 1 from (0,0) to (750,0), bent segment 1 from (750,0) to (850,0), straight segment 2 from (850,0) to (1600,0), bent segment 2 from (1600,0) to (1700,0), and straight segment 3 from (1700,0) to (2450,0). The axial segmentation and coordinate calibration of the reinforcing bar are as follows: Figure 7 As shown in (b).

[0070] (4) Differentiated sizing and continuous winding Start the dedicated winding equipment, set the rotation speed of the rebar body to 20 rpm, and the horizontal movement speed of the guide wire head to 10 mm / min, so that the axial angle between the glass fiber and the rebar body is +86.5°. At the start of winding, the controller triggers the first resin distribution module corresponding to the epoxy resin, setting the resin injection rate to 5 mL / min to supply rigid resin to the straight section of the rebar body. When the guide wire head moves horizontally to coordinate (750,0), the controller automatically shuts off the first resin distribution module and triggers the second resin distribution module corresponding to the thermosetting polyurethane, switching the resin injection rate to 6 mL / min to supply ductile resin to the bent section 1. When the guide wire head moves to coordinate (850,0), the controller automatically switches back to the first resin distribution module, restoring the epoxy resin supply and the 5 mL / min injection rate. When the guide wire head moves to coordinate (1600,0), it switches back to the second resin distribution module to supply ductile resin. When the guide wire head moves to coordinate (1700,0), it switches back to the first resin distribution module to supply rigid resin. When the guide wire head moves horizontally to coordinate (2450,0), the controller simultaneously shuts down the two resin dispensing modules and stops all other operating actions of the equipment. Through the above-mentioned differentiated sizing and continuous winding, a single layer of glass fiber is formed on the surface of the rebar body, with an angle of +86.5° to the axial direction of the rebar and an average thickness of about 0.5 mm. The composite coating is evenly distributed along the axial direction, with a thickness error of ≤±0.05 mm.

[0071] (5) Composite coating curing treatment Uncured composite-coated steel bars are removed from the continuous fiber winding machine and transferred to an environmental chamber at 25°C and 50% relative humidity. The uncured composite-coated steel bars are kept rotating around the axis at a speed of 20 rpm to prevent uneven resin flow. After 24 hours of constant temperature and humidity curing, the composite coating is fully cured, resulting in a straight, bendable composite-coated steel bar with 90° bends at both ends.

[0072] (6) Bending and forming process A steel bar bending machine was used to perform dual-scenario bending verification on two cured composite material wrapping sections. a. Delivery inspection scenario: In accordance with the requirements of "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB 1499.2-2024), a 180° bending test was conducted with a bending indenter diameter of 4 × 16 mm = 64 mm. After bending, the coating showed no cracking or peeling, meeting the factory acceptance standards. b. Construction Scenario: In accordance with the requirements of the "Code for Construction of Concrete Structures" (GB 50666-2011), a 90° bend is performed with an inner diameter of 6 × 16 mm = 96 mm. The bending process and the finished product are shown below. Figure 8 As shown.

[0073] In both scenarios, the bent sections of the composite-coated steel bars remain intact without cracking or peeling, while the straight sections of the composite-coated steel bars show no crushing or damage, thus meeting both delivery inspection requirements and engineering usage needs.

[0074] Example 2: Composite-coated steel reinforcement (also known as composite-coated irregular stirrups) This embodiment aims to fabricate a composite-wrapped irregular-shaped stirrup, such as... Figure 9 As shown in (a), this type of stirrup is widely used in concrete structures such as wave walls, breakwaters, and crash barriers. Its shape consists of a 90° bend and a 135° bend, which can meet the seismic resistance, impact resistance and anchoring requirements of special structures.

[0075] (1) Construction of dedicated winding equipment The same equipment modification scheme as in Example 1 was adopted: the existing continuous fiber winding host was modified by adding two sets of automatic resin dispensing modules, which are used to supply epoxy resin (Huipa AM-8910A / B, tensile strength 79 MPa, elastic modulus 2900 MPa) and thermosetting polyurethane (Sika TCC-6060 A / B, tensile strength 28 MPa, elongation at break 200%), respectively, and equipped with disposable Y-type impregnation tubes made of polypropylene (vertical leg length 80 mm). The two sets of automatic resin dispensing modules, the laser displacement sensor-type position sensing unit (position monitoring accuracy ≤ ±0.5 mm), and the controller are connected to communicate with each other. The glue outlets are respectively connected to the two forked input ends of the Y-type impregnation tubes, thus constructing the special winding equipment described in this invention.

[0076] (2) Raw material preparation and pretreatment Prepare HRB400 steel bars with a nominal diameter of 16 mm and a length of 2.50 m. Perform pretreatment—straightening, rust removal, and degreasing—by sequentially passing them through a steel bar straightening machine, a rust remover, and a CO2 surface cleaning machine. Ensure the surface roughness of the steel bar reaches Ra=1.6-6.3 μm and that the surface is free of oil, water stains, and rust residue. Then, fix both ends of the pretreated steel bar onto the continuous fiber winding main unit clamp of a dedicated winding equipment, ensuring a secure and stable clamping. Simultaneously, prepare glass fibers with a linear density of 2400 Tex, thread them through the disposable Y-shaped impregnation tube of the equipment, and fix them to the starting end surface of the steel bar, ensuring smooth continuous fiber routing.

[0077] (3) Equipment parameter preset In the controller's software interface, input the diameter of the reinforcing bar and the axial segmentation parameters, specifically: reinforcing bar diameter 16 mm, segment 1 length 1830 mm, segment 2 length 300 mm, segment 3 length 370 mm, segment 1-2 bending angle 90°, segment 2-3 bending angle 135°. The controller automatically calibrates the axial segment coordinates based on these parameters, using the winding start point as coordinate (0,0), defining straight segment 1 from (0,0) to (1780,0), bent segment 1 from (1780,0) to (1880,0), straight segment 2 from (1880,0) to (2080,0), bent segment 2 from (2080,0) to (2180,0), and straight segment 3 from (2180,0) to (2500,0). The axial segmentation and coordinate calibration of the reinforcing bar are as follows: Figure 9 As shown in (b).

[0078] (4) Differentiated sizing and continuous winding The dedicated winding equipment was started, using the same winding speed and angle parameters as in Example 1: the rotation speed of the rebar body was set to 20 rpm, and the horizontal movement speed of the guide wire head was set to 10 mm / min, maintaining the axial angle between the glass fiber and the rebar body at +86.5°. At the start of winding, the controller triggered the first resin distribution module corresponding to the epoxy resin, setting the resin injection rate to 5 mL / min to supply rigid resin to the straight segment 1 of the rebar body. When the guide wire head moved horizontally to coordinate (1780, 0), the controller automatically shut down the first resin distribution module and triggered the second resin distribution module corresponding to the thermosetting polyurethane, switching the injection rate to 6 mL / min to supply ductile resin to the bent segment 1. When the guide wire head moved to coordinate (1880, 0), the controller automatically switched back to the first resin distribution module, restoring the epoxy resin supply and the 5 mL / min injection rate to supply rigid resin to the straight segment 2. When the guide wire head moved to coordinate (2080, 0), it switched back to the second resin distribution module to supply ductile resin. When the guide wire head moves to coordinate (2180,0), it switches back to supplying rigid resin to the first resin distribution module, supplying rigid resin to straight segment 3. When the guide wire head moves horizontally to coordinate (2500,0), the controller simultaneously shuts down both resin distribution modules and stops all other operating actions of the equipment. Through the above differentiated sizing and continuous winding, a single-layer glass fiber composite coating with an angle of +86.5° to the axial direction of the steel bar and an overall thickness of approximately 0.5 mm is formed on the surface of the steel bar body. The composite coating is evenly distributed along the axial direction of the steel bar body, with a thickness error ≤ ±0.05 mm.

[0079] (5) Composite coating curing treatment The same curing process as in Example 1 was used: the uncured composite-coated steel bars were removed from the continuous fiber winding machine and transferred to an environmental chamber at 25°C and 50% relative humidity. The uncured composite-coated steel bars were kept rotating around the axis at a speed of 20 rpm to prevent resin flow and uneven coating thickness. After 24 hours of constant temperature and humidity curing, the composite coating was completely cured, resulting in straight-shaped composite-coated irregular stirrups.

[0080] (6) Bending and forming process A steel bar bending machine was used to perform dual-scenario bending verification on the cured composite-coated irregular stirrups: a. Delivery inspection scenario: In accordance with the requirements of "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Steel Bars" (GB 1499.2-2024), with a bending head diameter of 4 × 16 mm = 64 mm, a 180° bending test is performed on any preset bending section. After bending, the coating shows no cracking or peeling, which meets the factory quality acceptance standards. b. Construction Scenario: Following the requirements of the "Code for Construction of Concrete Structures" (GB 50666-2011), the irregular bending is completed in steps: First, based on the color difference between rigid and ductile resin, the position and start / end range of bending segment 1 are precisely located, and a 90° bend is performed with an inner diameter of 6 × 16 mm = 96 mm. Second, the position of bending segment 2 is located similarly, and a 135° bend is performed with the same inner diameter. The bending process and the finished product are shown below. Figure 10 As shown.

[0081] It is evident that the composite coatings of both bent sections remain intact, without cracks or peeling. The straight sections of the composite coatings show no crushing or damage. The dimensional accuracy of the shaped stirrups after molding meets the standards and can be directly used in concrete structure construction.

[0082] It should be understood that the application of the present invention is not limited to the examples of the two embodiments described above. For those skilled in the art, parameters such as the diameter of the reinforcing bar, the segment length, the bending angle, the type of resin and continuous fiber can be adjusted according to the actual needs of the project. All improvements or modifications based on the technical solutions of the present invention should fall within the protection scope of the appended claims.

Claims

1. A flexible composite-coated steel bar, characterized in that, It includes the steel bar body and a continuous fiber-reinforced composite material coating covering the outer surface of the steel bar body; The continuous fiber reinforced composite material coating is divided along the axial direction of the steel bar body into at least one straight segment of the continuous fiber reinforced composite material coating and at least one bent segment of the continuous fiber reinforced composite material coating for subsequent bending operations. The straight sections of the continuous fiber reinforced composite material coating are formed by impregnating continuous fibers with rigid resin, and the bent sections of the continuous fiber reinforced composite material coating are formed by impregnating continuous fibers with ductile resin. Wherein, the tensile fracture strain of the rigid resin is <5%, and the tensile fracture strain of the ductile resin is ≥60%.

2. The bendable composite-coated steel bar according to claim 1, characterized in that, The straight section of the continuous fiber reinforced composite material coating and the bent section of the continuous fiber reinforced composite material coating are seamlessly integrated in the axial direction, and both are formed by the same bundle of continuous fibers in a single continuous winding process.

3. The bendable composite-coated steel bar according to any one of claims 1 to 2, characterized in that, The rigid resin and the ductile resin have different colors.

4. The bendable composite-coated steel bar according to any one of claims 1 to 3, characterized in that, The rigid resin is at least one of epoxy resin, epoxy acrylate, vinyl resin, phenolic resin, cyanate ester resin, and bismaleimide resin; The ductile resin is at least one of polyurethane, silicone rubber, nitrile rubber, and carboxyl-terminated nitrile rubber toughened epoxy resin; The continuous fiber is at least one of glass fiber, carbon fiber, basalt fiber, silicon carbide fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, polyester fiber, polypropylene fiber, flax fiber, and bamboo fiber.

5. The bendable composite-coated steel bar according to claim 1, characterized in that, The thickness of the continuous fiber reinforced composite material coating is 0.1-1.2 mm, and it is uniformly distributed along the axial direction of the steel bar body with a thickness error of ≤±0.05 mm.

6. A winding device for producing flexible composite-coated steel bars as described in any one of claims 1 to 5, characterized in that, include: (1) A continuous fiber winding host is used to clamp and drive the steel bar body to rotate, while guiding the continuous fiber to move along the axial direction of the steel bar body for winding; (2) The first resin dispensing module and the second resin dispensing module are used to store and supply rigid resin and ductile resin, respectively; (3) A Y-type impregnation tube has two input ends and one output end. The two input ends are respectively connected to the first resin dispensing module and the second resin dispensing module. The output end is used to guide the continuous fiber through so that the continuous fiber is impregnated with resin during its travel. (4) Position sensing unit, used to obtain the winding position of continuous fiber in the axial direction of the steel bar body in real time; (5) A controller, which is communicatively connected to the continuous fiber winding host, the first resin distribution module, the second resin distribution module and the position sensing unit respectively; wherein, the controller is configured to: acquire preset axial segment position information of the steel bar body; monitor the axial winding position of the continuous fiber on the steel bar body in real time; and automatically control the first resin distribution module and the second resin distribution module to supply corresponding resin to the Y-shaped impregnation tube according to the segment position information and the monitoring position, so as to realize that the continuous fiber is impregnated with different resins according to the different axial positions of the steel bar body during a single continuous winding process.

7. The winding device according to claim 6, characterized in that, The two forked input ends of the Y-shaped impregnation tube are respectively connected to the first resin dispensing module and the second resin dispensing module. The length of the vertical leg section is 50-100 mm, and the Y-shaped impregnation tube is a disposable injection-molded part made of polypropylene or polyethylene.

8. A method for manufacturing the bendable composite-coated steel reinforcement according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Surface pretreatment of the steel reinforcement body; (2) Fix the pretreated steel bar body in the continuous fiber winding host of the winding device according to any one of claims 6 to 7, start the continuous fiber winding host, and make the continuous fiber move along the axial direction of the steel bar body for winding; (3) According to the preset segment position information, when the winding reaches the straight segment position of the steel bar body, the controller controls the first resin distribution module to supply rigid resin to the Y-shaped impregnation tube so that the continuous fiber is impregnated with rigid resin in the straight segment; when the winding reaches the bent segment position of the steel bar body, the controller controls the second resin distribution module to supply ductile resin to the Y-shaped impregnation tube so that the continuous fiber is impregnated with ductile resin in the bent segment. (4) After completing the winding and impregnation, the composite-coated steel bar to be cured is cured to obtain a straight-shaped bendable composite-coated steel bar.

9. A method for bending and forming flexible composite-coated steel bars, characterized in that, Includes the following steps: (1) Provides a straight-shaped bendable composite-coated steel bar prepared by the method described in claim 8; (2) The continuous fiber reinforced composite material coating bending section is bent at an angle of 0°-180°.

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