Steel-FRP composite bar and preparation method thereof

Abstract

The invention relates to the technical field of composite bars, in particular to a steel-FRP composite bar and a preparation method thereof.The steel-FRP composite bar comprises a three-section structure including an outer layer, a middle layer and an inner layer; the outer layer is formed by compounding high-modulus alkali-free glass fibers and fluorocarbon resin; the middle layer is formed by matching high-modulus alkali-free glass fibers with epoxy resin; and the inner layer is doped with elastomer particle modified resin. The winding structure with the gradually-changed fiber angle is developed, the winding angle of the glass fiber is gradually transited from 90 degrees (longitudinal reinforcement) to 30 degrees (circumferential reinforcement) from the inner layer to the outer layer, the composite rib can meet the requirements for high axial tensile strength and transverse shear resistance at the same time, and the composite rib is suitable for complex stress scenes such as bridge bearing.

Description

Technical Field

[0001] This invention relates to the field of composite reinforcement technology, specifically to a steel-FRP composite reinforcement and its preparation method. Background Technology

[0002] As modern civil engineering structures evolve towards large spans, heavy loads, towering structures, and extreme environments such as deep seas, unprecedented demands are placed on the strength, durability, and lightweighting of building materials. As the most crucial load-bearing material in concrete structures, the susceptibility of steel reinforcement to corrosion has become a fatal weakness affecting structural safety and service life. Particularly in harsh environments such as bridges, ports, coastal buildings, and highways using de-icing salt, the performance degradation of concrete structures and the surge in maintenance costs caused by steel corrosion are becoming increasingly prominent.

[0003] To address this challenge, fiber-reinforced polymer (FRP) bars have emerged and are considered one of the ideal materials to replace traditional steel bars. FRP bars have attracted considerable attention due to their excellent corrosion resistance, high tensile strength, and lightweight properties. However, the material itself also has significant shortcomings: First, most FRP bars are linear elastic materials, lacking a yield plateau similar to steel, exhibiting brittle failure characteristics, which means that structures lack sufficient warning before failure; second, their shear strength and modulus of elasticity are generally lower than those of steel, limiting their application under complex stress states; furthermore, the fatigue performance and anchorage performance of FRP bars still need further improvement.

[0004] In existing technologies, the common composite form mainly involves simply wrapping a steel core with a layer of FRP material. However, this simple "core-shell" structure has significant drawbacks. First, steel and FRP are two materials with vastly different properties, and the reliability of their interfacial bonding is crucial to the performance of the composite reinforcement. Under long-term loads and environmental conditions, the interface is prone to becoming a weak point, leading to debonding failure and preventing the two materials from working synergistically. Second, a single FRP shell often cannot simultaneously meet multiple performance requirements such as axial tensile strength, transverse shear strength, and corrosion resistance. For example, a fiber arrangement that focuses on axial reinforcement weakens circumferential restraint and shear resistance. Many existing designs fail to refine the fiber orientation and distribution at the microstructural level, resulting in the material's performance not being maximized and failing to meet the multi-dimensional performance requirements of complex stress scenarios such as bridge load-bearing.

[0005] Therefore, there is an urgent need in this field for a novel steel-FRP composite reinforcement with a reasonable design, a robust interface, the ability to fully leverage the advantages of both steel and FRP, and the capacity to meet complex multidimensional stress requirements, as well as its preparation method. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a steel-FRP composite reinforcement and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A steel-FRP composite reinforcement includes a three-section structure consisting of an outer layer, a middle layer, and an inner layer; the outer layer is made of high-modulus alkali-free glass fiber and modified fluorocarbon resin; the middle layer is made of high-modulus alkali-free glass fiber and epoxy resin; and the inner layer is made of resin modified with elastomer particles. The preparation of modified fluorocarbon resin includes the following steps: S11. By mass, 3-5 parts of nano-silica and 1-2 parts of silane coupling agent are ultrasonically dispersed at 60℃ and 40kHz for 25-30 minutes to obtain pretreated nano-silica. S12. Add 90-100 parts of fluorocarbon resin and 15-20 parts of N-methylpyrrolidone to a reaction vessel, and stir at 150-200 r / min for 10-15 min at 80℃ to obtain a resin mixture. S13. Add the pretreated nano-silica obtained in step S11 and 5-8 parts of toughening agent to the resin mixture obtained in step S12 and stir at a speed of 150-200 r / min for 45-50 min. S14. Cool the mixture obtained in step S13 to 50°C, add 8-10 parts of toluene diisocyanate, stir evenly, and then degas under vacuum for 20-30 minutes to obtain modified fluorocarbon resin.

[0008] Preferably, the preparation of high-modulus alkali-free glass fibers includes the following steps: S21. By mass, mix 2-3 parts KH-560, 4-6 parts nano alumina and 10-12 parts deionized water, and ultrasonically disperse at a frequency of 40kHz for 25-30min to obtain pretreated nano alumina. S22. Add 0.5-1 parts of titanate coupling agent, 0.3-0.5 parts of sodium molybdate and 3-5 parts of waterborne polyurethane dispersion to the pretreated nano alumina obtained in step S21, and ultrasonically disperse at a frequency of 40 kHz for 25-30 min to obtain a high modulus modifier. S23. 80-100 parts of alkali-free glass fiber are uniformly dipped into the high modulus modifier obtained in step S22 through a coating tank, dried with hot air at 90-100℃ for 10-15 min, and then heat-treated at 230-250℃ for 15-20 min. After cooling, high modulus alkali-free glass fiber is obtained.

[0009] Preferably, the preparation of the elastomer particle modified resin includes the following steps: S31. By weight, 10-15 parts of nitrile rubber granules, 5-7 parts of polyurethane prepolymer and 2-4 parts of compatibilizer are mixed and kneaded at 80-85℃ for 8-10 minutes to obtain elastomer granule modifier. S32. Heat 80-100 parts of E-51 epoxy resin to 60°C, add the elastomer particle modifier obtained in step S31, and stir at a speed of 300-400 r / min for 50-60 min to obtain a modified resin mixture. S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 25-30 parts of 651 low molecular weight polyamide, stir evenly, and then degas under vacuum for 20-25 minutes to obtain elastomer particle modified resin.

[0010] Preferably, the silane coupling agent in step S11 is selected from KH-550.

[0011] Preferably, the toughening agent in step S13 is selected from thermoplastic polyurethane elastomer.

[0012] Preferably, the titanate coupling agent in step S22 is selected from NDZ-201.

[0013] Preferably, the compatibilizer in step S31 is selected from maleic anhydride-grafted POE.

[0014] A method for preparing steel-FRP composite reinforcement, used to prepare the aforementioned steel-FRP composite reinforcement.

[0015] A method for preparing steel-FRP composite reinforcement includes the following preparation steps: S1. After the steel wire is passed through the inner layer glue tank and coated with a layer of elastomer particle modified resin evenly, it enters the middle layer winding area. The high modulus alkali-free glass fiber is wound onto the inner layer resin at a large angle of 75-85° through the fiber winding machine. At the same time, it passes through the middle layer glue tank and is fully impregnated by epoxy resin. S2. After passing through the middle layer adhesive tank, it enters the outer layer winding area. The high-modulus alkali-free glass fiber is wound onto the middle layer at an angle of 30-45° using a fiber winding machine. At the same time, it passes through the outer layer adhesive tank and is fully impregnated by the modified fluorocarbon resin. S3. After passing through the outer adhesive groove, the material is added to the mold, initially compacted and air bubbles are removed, and then it enters the heating curing oven for curing. During the curing process, the composite reinforcement is pulled forward at a speed of 0.2-0.5 m / min by a slow traction device, and finally steel-FRP composite reinforcement is obtained.

[0016] Preferably, the curing in step S3 adopts a stepped heating method: the first stage is 80℃ for 25-30 min; the second stage is 120℃ for 50-60 min; and the third stage is 150℃ for 25-30 min.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention develops a “gradual fiber angle” winding structure: from the inner layer to the outer layer, the glass fiber winding angle gradually transitions from 90° (longitudinal reinforcement) to 30° (circumferential reinforcement), so that the composite reinforcement can simultaneously meet the requirements of high axial tensile strength and transverse shear resistance, and is suitable for complex stress scenarios such as bridge load-bearing.

[0018] 2. The elastomeric particles modified resin of this invention serve as a buffer and transition layer, effectively improving the interfacial bonding between the steel wire and fiber reinforcement layer, absorbing impact and vibration, and delaying crack propagation; high-modulus alkali-free glass fiber provides excellent axial tensile strength and stiffness, supporting the main load-bearing function; modified fluorocarbon resin possesses high corrosion resistance and toughness, enhancing circumferential restraint and shear resistance, protecting the internal structure from external erosion. The synergistic effect of these three components forms a gradient structure, achieving a balanced improvement in axial tensile strength, transverse shear strength, and impact resistance, making it particularly suitable for complex multi-directional stress scenarios such as bridges and offshore platforms. Attached Figure Description

[0019] Figure 1 This is a process flow diagram for the preparation of the steel-FRP composite reinforcement of the present invention; Figure 2 This is a process flow diagram for preparing the modified fluorocarbon resin of the present invention; Figure 3 This is a process flow diagram for preparing the high-modulus alkali-free glass fiber of the present invention; Figure 4 This is a process flow diagram for preparing the elastomer particle-modified resin of the present invention. Figure 5 This is a cross-sectional SEM image of the steel-FRP composite reinforcement obtained in Example 1 of the present invention; Figure 6 This is a SEM image of the high-modulus alkali-free glass fiber obtained in Example 1 of the present invention. Detailed Implementation

[0020] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Please see Figures 1-6 The present invention provides a technical solution: Example 1 A method for preparing steel-FRP composite reinforcement: Before preparing the steel-FRP composite reinforcement, modified fluorocarbon resin, high-modulus alkali-free glass fiber, and elastomer particles are first prepared: The preparation of modified fluorocarbon resin includes the following steps: S11. Disperse 30g of nano-silica and 10g of silane coupling agent (KH-550) at 60℃ and 40kHz for 25min to obtain pretreated nano-silica. S12. Add 900g of fluorocarbon resin and 150g of N-methylpyrrolidone to the reactor and stir at 150r / min for 10min at 80℃ to obtain a resin mixture. S13. Add the pretreated nano-silica obtained in step S11 and 50g toughening agent (thermoplastic polyurethane elastomer) to the resin mixture obtained in step S12 and stir at 150r / min for 45min. S14. Cool the mixture obtained in step S13 to 50°C, add 80g of toluene diisocyanate, stir evenly, and then degas under vacuum for 20 minutes to obtain modified fluorocarbon resin.

[0022] The preparation of high-modulus alkali-free glass fibers includes the following steps: S21. Mix 20g KH-560, 40g nano alumina and 100g deionized water, and ultrasonically disperse at a frequency of 40kHz for 25min to obtain pretreated nano alumina; S22. Add 5g of titanate coupling agent (NDZ-201), 3g of sodium molybdate and 30g of aqueous polyurethane dispersion to the pretreated nano alumina obtained in step S21, and ultrasonically disperse at a frequency of 40kHz for 25min to obtain a high modulus modifier. S23. 800g of alkali-free glass fiber is uniformly coated with the high modulus modifier obtained in step S22 through a coating tank, dried with hot air at 90℃ for 10min, heat-treated at 230℃ for 15min, and then cooled to obtain high modulus alkali-free glass fiber.

[0023] The preparation of elastomer particle-modified resin includes the following steps: S31. Mix 100g of nitrile rubber granules, 50g of polyurethane prepolymer and 20g of compatibilizer (maleic anhydride grafted POE), and knead at 80℃ for 8min to obtain elastomer granule modifier. S32. Heat 800g of E-51 epoxy resin to 60℃, add the elastomer particle modifier obtained in step S31, and stir at 300r / min for 50min to obtain the modified resin mixture. S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 250g of curing agent (651 low molecular weight polyamide), stir evenly, and then degas under vacuum for 20 minutes to obtain elastomer particle modified resin.

[0024] The preparation of steel-FRP composite reinforcement includes the following steps: S1. The steel wire is passed through the inner layer glue tank, and after the surface is uniformly coated with a layer of elastomer particle modified resin, it enters the middle layer winding area. The high modulus alkali-free glass fiber is wound onto the inner layer resin at a large angle of 85° through the fiber winding machine. At the same time, it passes through the middle layer glue tank and is fully impregnated by epoxy resin. S2. After passing through the middle layer adhesive tank, it enters the outer layer winding area. The high-modulus alkali-free glass fiber is wound onto the middle layer at a 45° angle using a fiber winding machine. At the same time, it passes through the outer layer adhesive tank and is fully impregnated by the modified fluorocarbon resin. S3. After passing through the outer adhesive tank, the material is added to the mold, initially compacted and air bubbles are removed, and then placed in a heating curing oven for curing (the first stage is 80℃ for 25 minutes; the second stage is 120℃ for 50 minutes; the third stage is 150℃ for 25 minutes). During the curing process, the composite reinforcement is pulled forward at a speed of 0.2 m / min by a slow traction device, and finally the steel-FRP composite reinforcement is obtained.

[0025] Example 2 A method for preparing steel-FRP composite reinforcement: Before preparing the steel-FRP composite reinforcement, modified fluorocarbon resin, high-modulus alkali-free glass fiber, and elastomer particles are first prepared: The preparation of modified fluorocarbon resin includes the following steps: S11. 50g of nano silica and 20g of silane coupling agent (KH-550) are ultrasonically dispersed at 60℃ and 40kHz for 30min to obtain pretreated nano silica. S12. Add 1000g of fluorocarbon resin and 200g of N-methylpyrrolidone to the reactor and stir at 200r / min for 15min at 80℃ to obtain a resin mixture. S13. Add the pretreated nano-silica obtained in step S11 and 80g of toughening agent (thermoplastic polyurethane elastomer) to the resin mixture obtained in step S12 and stir at 200r / min for 50min. S14. Cool the mixture obtained in step S13 to 50°C, add 100g of toluene diisocyanate, stir evenly, and then degas under vacuum for 30 minutes to obtain modified fluorocarbon resin.

[0026] The preparation of high-modulus alkali-free glass fibers includes the following steps: S21. Mix 30g KH-560, 60g nano alumina and 120g deionized water, and ultrasonically disperse at a frequency of 40kHz for 30min to obtain pretreated nano alumina; S22. Add 10g of titanate coupling agent (NDZ-201), 5g of sodium molybdate and 50g of aqueous polyurethane dispersion to the pretreated nano alumina obtained in step S21, and ultrasonically disperse at a frequency of 40kHz for 30min to obtain a high modulus modifier. S23. 1000g of alkali-free glass fiber is uniformly coated with the high modulus modifier obtained in step S22 through a coating tank, dried with hot air at 100℃ for 15min, heat-treated at 250℃ for 20min, and then cooled to obtain high modulus alkali-free glass fiber.

[0027] The preparation of elastomer particle-modified resin includes the following steps: S31. Mix 150g of nitrile rubber granules, 70g of polyurethane prepolymer and 40g of compatibilizer (maleic anhydride grafted POE), and knead at 85°C for 10min to obtain an elastomer granule modifier. S32. Heat 1000g of E-51 epoxy resin to 60℃, add the elastomer particle modifier obtained in step S31, and stir at 400r / min for 60min to obtain the modified resin mixture. S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 300g of curing agent (651 low molecular weight polyamide), stir evenly, and then degas under vacuum for 25 minutes to obtain elastomer particle modified resin.

[0028] The preparation of steel-FRP composite reinforcement includes the following steps: S1. After the steel wire is passed through the inner layer glue tank and coated with a layer of elastomer particle modified resin evenly, it enters the middle layer winding area. The high modulus alkali-free glass fiber is wound onto the inner layer resin at a large angle of 75° through the fiber winding machine. At the same time, it passes through the middle layer glue tank and is fully impregnated by epoxy resin. S2. After passing through the middle layer adhesive tank, it enters the outer layer winding area. The high-modulus alkali-free glass fiber is wound onto the middle layer at a 30° angle using a fiber winding machine. At the same time, it passes through the outer layer adhesive tank and is fully impregnated by the modified fluorocarbon resin. S3. After passing through the outer adhesive tank, the material is added to the mold, initially compacted and air bubbles are removed, and then placed in a heating curing oven for curing (the first stage is 80℃ for 30 minutes; the second stage is 120℃ for 60 minutes; the third stage is 150℃ for 30 minutes). During the curing process, the composite reinforcement is pulled forward at a speed of 0.5 m / min by a slow traction device, and finally the steel-FRP composite reinforcement is obtained.

[0029] Example 3 A method for preparing steel-FRP composite reinforcement: Before preparing the steel-FRP composite reinforcement, modified fluorocarbon resin, high-modulus alkali-free glass fiber, and elastomer particles are first prepared: The preparation of modified fluorocarbon resin includes the following steps: S11. 40g of nano-silica and 15g of silane coupling agent (KH-550) were ultrasonically dispersed at 60℃ and 40kHz for 27min to obtain pretreated nano-silica. S12. Add 950g of fluorocarbon resin and 170g of N-methylpyrrolidone to the reactor and stir at 170r / min for 13min at 80℃ to obtain a resin mixture. S13. Add the pretreated nano-silica obtained in step S11 and 60g of toughening agent (thermoplastic polyurethane elastomer) to the resin mixture obtained in step S12 and stir at 170r / min for 47min. S14. Cool the mixture obtained in step S13 to 50°C, add 90g of toluene diisocyanate, stir evenly, and then degas under vacuum for 25 minutes to obtain modified fluorocarbon resin.

[0030] The preparation of high-modulus alkali-free glass fibers includes the following steps: S21. Mix 25g KH-560, 50g nano alumina and 110g deionized water, and ultrasonically disperse at a frequency of 40kHz for 27min to obtain pretreated nano alumina; S22. Add 7g of titanate coupling agent (NDZ-201), 4g of sodium molybdate and 40g of aqueous polyurethane dispersion to the pretreated nano alumina obtained in step S21, and ultrasonically disperse at a frequency of 40kHz for 27min to obtain a high modulus modifier. S23. 900g of alkali-free glass fiber is uniformly dipped into the high modulus modifier obtained in step S22 through a coating tank, dried with hot air at 95℃ for 13min, and then heat-treated at 240℃ for 17min. After cooling, high modulus alkali-free glass fiber is obtained.

[0031] The preparation of elastomer particle-modified resin includes the following steps: S31. Mix 130g of nitrile rubber granules, 60g of polyurethane prepolymer and 30g of compatibilizer (maleic anhydride grafted POE), and knead at 83℃ for 9min to obtain elastomer granule modifier. S32. Heat 900g of E-51 epoxy resin to 60℃, add the elastomer particle modifier obtained in step S31, and stir at 350r / min for 55min to obtain a modified resin mixture. S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 260g of curing agent (651 low molecular weight polyamide), stir evenly, and then degas under vacuum for 23 minutes to obtain elastomer particle modified resin.

[0032] The preparation of steel-FRP composite reinforcement includes the following steps: S1. The steel wire is passed through the inner layer glue tank, and after the surface is uniformly coated with a layer of elastomer particle modified resin, it enters the middle layer winding area. The high modulus alkali-free glass fiber is wound onto the inner layer resin at a large angle of 80° through the fiber winding machine. At the same time, it passes through the middle layer glue tank and is fully impregnated by epoxy resin. S2. After passing through the middle layer adhesive tank, it enters the outer layer winding area. The high-modulus alkali-free glass fiber is wound onto the middle layer at a 40° angle using a fiber winding machine. At the same time, it passes through the outer layer adhesive tank and is fully impregnated by the modified fluorocarbon resin. S3. After passing through the outer adhesive tank, the material is added to the mold, initially compacted and air bubbles are removed, and then placed in a heating curing oven for curing (the first stage is 80℃ for 27 minutes; the second stage is 120℃ for 55 minutes; the third stage is 150℃ for 27 minutes). During the curing process, the composite reinforcement is pulled forward at a speed of 0.3 m / min by a slow traction device, and finally the steel-FRP composite reinforcement is obtained.

[0033] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the elastomer particle modified resin in this comparative example is replaced with E-51 epoxy resin. The remaining steps are exactly the same in Comparative Example 1 and Example 1.

[0034] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the high-modulus alkali-free glass fiber is replaced with ordinary alkali-free glass fiber in this comparative example. The remaining steps are exactly the same in Comparative Example 2 and Example 1.

[0035] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the modified fluorocarbon resin in this comparative example is replaced with ordinary fluorocarbon resin, while the other steps are exactly the same in Comparative Example 3 and Example 1.

[0036] Performance testing: The tensile properties, shear properties, and corrosion resistance of the steel-FRP composite bars obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to GB / T 30022-2013 "Test Methods for Basic Mechanical Properties of Fiber Reinforced Composite Reinforced Bars", ASTM D4475-21 "Standard Test Method for Determination of Apparent Horizontal Shear Strength of Pultruded Reinforced Plastic Rods by Short Beam Method", and GB / T 10125-2021 "Salt Spray Test Standard". The results are shown in Table 1 below: Table 1 Performance Test Results As shown in Table 1, the steel-FRP composite reinforcement obtained in Example 1 is superior to the comparative example in terms of tensile properties, shear properties, and corrosion resistance. This demonstrates that the present invention effectively improves the interfacial bonding between the steel wire and the fiber reinforcement layer through the synergistic effect of modified fluorocarbon resin, high-modulus alkali-free glass fiber, and elastomer particle-modified resin, providing excellent axial tensile strength and stiffness, high corrosion resistance and toughness, enhanced circumferential restraint and shear resistance, and protection of the internal structure from external erosion. It is suitable for modern civil engineering applications requiring high durability and complex stress, and has significant engineering application value.

[0037] Appendix Figure 5 and attached Figure 6 The images shown are cross-sectional SEM images of the steel-FRP composite reinforcement obtained in Example 1 and SEM images of high-modulus alkali-free glass fiber, respectively.

[0038] Appendix Figure 5 1 represents the steel wire; 2 represents the inner layer: elastomeric particles modified resin act as a buffer and transition layer, effectively improving the interfacial bonding between the steel wire and the fiber reinforcement layer, absorbing impact and vibration, and delaying crack propagation; 3 represents the middle layer: high-modulus alkali-free glass fiber provides excellent axial tensile strength and stiffness, supporting the main load-bearing function; 4 represents the outer layer: high-modulus alkali-free glass fiber and modified fluorocarbon resin work synergistically to provide corrosion resistance and toughness, enhance circumferential restraint and shear resistance, and protect the internal structure from external erosion. As shown in the figure, under heat curing conditions, the middle layer material is encased within the outer layer material, further improving the overall durability, environmental erosion resistance, and bonding performance with concrete of the composite reinforcement, achieving a high-strength, high-durability, and lightweight composite reinforcement.

[0039] Appendix Figure 6 As can be seen, high-modulus alkali-free glass fiber is composed of oriented reinforcing fibers, providing the material with longitudinal tensile strength and stiffness.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A steel-FRP composite reinforcement bar, characterized in that, It comprises a three-section structure consisting of an outer layer, a middle layer, and an inner layer; the outer layer is made of high-modulus alkali-free glass fiber and modified fluorocarbon resin composite; the middle layer is made of high-modulus alkali-free glass fiber combined with epoxy resin; and the inner layer incorporates elastomer particles to modify the resin. The preparation of the modified fluorocarbon resin includes the following steps: S11. By mass, 3-5 parts of nano-silica and 1-2 parts of silane coupling agent are ultrasonically dispersed at 60℃ and 40kHz for 25-30 minutes to obtain pretreated nano-silica. S12. Add 90-100 parts of fluorocarbon resin and 15-20 parts of N-methylpyrrolidone to a reaction vessel, and stir at 150-200 r / min for 10-15 min at 80℃ to obtain a resin mixture. S13. Add the pretreated nano-silica obtained in step S11 and 5-8 parts of toughening agent to the resin mixture obtained in step S12 and stir at a speed of 150-200 r / min for 45-50 min. S14. Cool the mixture obtained in step S13 to 50°C, add 8-10 parts of toluene diisocyanate, stir evenly, and then degas under vacuum for 20-30 minutes to obtain modified fluorocarbon resin.

2. The steel-FRP composite reinforcement according to claim 1, characterized in that, The preparation of the high-modulus alkali-free glass fiber includes the following steps: S21. By mass, mix 2-3 parts KH-560, 4-6 parts nano alumina and 10-12 parts deionized water, and ultrasonically disperse at a frequency of 40kHz for 25-30min to obtain pretreated nano alumina. S22. Add 0.5-1 parts of titanate coupling agent, 0.3-0.5 parts of sodium molybdate and 3-5 parts of waterborne polyurethane dispersion to the pretreated nano alumina obtained in step S21, and ultrasonically disperse at a frequency of 40 kHz for 25-30 min to obtain a high modulus modifier. S23. 80-100 parts of alkali-free glass fiber are uniformly dipped into the high modulus modifier obtained in step S22 through a coating tank, dried with hot air at 90-100℃ for 10-15 min, and then heat-treated at 230-250℃ for 15-20 min. After cooling, high modulus alkali-free glass fiber is obtained.

3. The steel-FRP composite reinforcement according to claim 1, characterized in that, The preparation of the elastomer particle modified resin includes the following steps: S31. By weight, 10-15 parts of nitrile rubber granules, 5-7 parts of polyurethane prepolymer and 2-4 parts of compatibilizer are mixed and kneaded at 80-85℃ for 8-10 minutes to obtain elastomer granule modifier. S32. Heat 80-100 parts of E-51 epoxy resin to 60°C, add the elastomer particle modifier obtained in step S31, and stir at a speed of 300-400 r / min for 50-60 min to obtain a modified resin mixture. S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 25-30 parts of 651 low molecular weight polyamide, stir evenly, and then degas under vacuum for 20-25 minutes to obtain elastomer particle modified resin.

4. The steel-FRP composite reinforcement according to claim 1, characterized in that, The silane coupling agent in step S11 is selected from KH-550.

5. The steel-FRP composite reinforcement according to claim 1, characterized in that, The toughening agent in step S13 is selected from thermoplastic polyurethane elastomer.

6. A steel-FRP composite reinforcement according to claim 2, characterized in that, The titanate coupling agent in step S22 is selected from NDZ-201.

7. A steel-FRP composite reinforcement according to claim 3, characterized in that, The compatibilizer in step S31 is selected from maleic anhydride-grafted POE.

8. A method for preparing steel-FRP composite reinforcement, characterized in that, The method for preparing the steel-FRP composite reinforcement according to any one of claims 1-7 comprises the following steps: S1. After the steel wire is passed through the inner layer glue tank and coated with a layer of elastomer particle modified resin evenly, it enters the middle layer winding area. The high modulus alkali-free glass fiber is wound onto the inner layer resin at a large angle of 75-85° through the fiber winding machine. At the same time, it passes through the middle layer glue tank and is fully impregnated by epoxy resin. S2. After passing through the middle layer adhesive tank, it enters the outer layer winding area. The high-modulus alkali-free glass fiber is wound onto the middle layer at an angle of 30-45° using a fiber winding machine. At the same time, it passes through the outer layer adhesive tank and is fully impregnated by the modified fluorocarbon resin. S3. After passing through the outer adhesive groove, the material is added to the mold, initially compacted and air bubbles are removed, and then it enters the heating curing oven for curing. During the curing process, the composite reinforcement is pulled forward at a speed of 0.2-0.5 m / min by a slow traction device, and finally steel-FRP composite reinforcement is obtained.

9. The method for preparing a steel-FRP composite reinforcement according to claim 8, characterized in that, The curing process in step S3 adopts a stepped heating method: the first stage is 80℃ for 25-30 min; the second stage is 120℃ for 50-60 min; and the third stage is 150℃ for 25-30 min.

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