Steel-fiber reinforced polymer composite bar and method of making same

Abstract

The application relates to the technical field of composite bars, in particular to a steel-FRP composite bar and a preparation method thereof, which comprises a three-section structure of an outer layer, a middle layer and an inner layer; the outer layer is composed of high-modulus alkali-free glass fibers and fluorocarbon resin; the middle layer is composed of high-modulus alkali-free glass fibers and epoxy resin; and the inner layer is composed of modified resin mixed with elastomer particles. The application develops a winding structure with gradually changed fiber angles, and the winding angle of the glass fibers gradually changes from 90 DEG (longitudinal reinforcement) to 30 DEG (circumferential reinforcement) from the inner layer to the outer layer, so that the composite bar can meet the requirements of high axial tensile resistance and transverse shear resistance, and is suitable for complex stress scenes such as bridge bearing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite bars, in particular to a steel-FRP composite bar and a preparation method thereof. BACKGROUND

[0002] With the development of modern civil engineering structures towards large span, heavy load, high-rise and deep sea, etc. extreme environment, the strength, durability and lightweight of building materials have been put forward unprecedentedly high requirements. As the most important bearing material in concrete structure, the corrosion resistance of steel bar has become a fatal weakness that affects the safety and service life of the structure. Especially in harsh environments such as bridges, ports, coastal buildings and roads using deicing salt, the performance degradation of concrete structures caused by steel bar corrosion and the surge in maintenance costs have become increasingly prominent.

[0003] To meet this challenge, fiber reinforced polymer (FRP) bars have emerged and are considered as one of the ideal materials to replace traditional steel bars. FRP bars have attracted attention due to their excellent corrosion resistance, high tensile strength and lightweight. However, there are also obvious shortcomings in the material itself: first, most FRP bars are linear elastic materials, lack of yield platform similar to steel, and show brittle failure characteristics, which makes the structure lack enough warning before failure; second, its shear strength and elastic modulus are usually lower than steel, and its application in complex stress state is limited; in addition, the fatigue performance and anchoring performance of FRP bars still need to be further improved.

[0004] In the prior art, the common composite form is mainly to simply wrap a layer of FRP material outside the steel core. However, this simple "core-shell" structure has significant defects. First, steel and FRP are two materials with very different properties, and the interface bonding reliability is the key to the performance of the composite bar. Under the action of long-term load and environment, the interface is easy to become a weak link, leading to debonding failure and failing to realize the synergistic work of the two materials. Then, the single FRP shell often cannot meet the multiple performance requirements of axial tensile, lateral shear, corrosion resistance, etc. For example, the fiber arrangement focusing on axial enhancement will weaken the ring constraint and shear resistance. Many existing designs fail to finely design the orientation and distribution of fibers from the microstructure, resulting in that the material performance cannot be maximized, and the material cannot meet the requirements of complex multi-dimensional stress scenarios such as bridge bearing.

[0005] Therefore, there is an urgent need in the art for a new type of steel-FRP composite bar and a preparation method thereof, which is reasonably designed, has a firm interface, can fully utilize the advantages of steel and FRP, and can meet the requirements of complex multi-dimensional stress. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a steel-FRP composite bar and a preparation method thereof.

[0007] To achieve the above object, the present application provides the following technical solutions:

[0008] A steel-FRP composite bar comprises a three-section structure of an outer layer, a middle layer and an inner layer; the outer layer is composed of high-modulus alkali-free glass fiber and modified fluorocarbon resin; the middle layer is composed of high-modulus alkali-free glass fiber and epoxy resin; and the inner layer is modified resin with elastic particles;

[0009] The preparation of the modified fluorocarbon resin comprises the following steps:

[0010] S11. Pre-treat nano-silicon dioxide by mixing 3-5 parts of nano-silicon dioxide and 1-2 parts of silane coupling agent at 60°C under ultrasonic dispersion at a frequency of 40 kHz for 25-30 min to obtain pre-treated nano-silicon dioxide;

[0011] S12. Add 90-100 parts of fluorocarbon resin and 15-20 parts of N-methyl pyrrolidone into a reaction kettle, and stir at a speed of 150-200 r / min at 80°C for 10-15 min to obtain a resin mixture;

[0012] S13. Add the pre-treated nano-silicon dioxide obtained in step S11 and 5-8 parts of a toughening agent into the resin mixture obtained in step S12, and stir at a speed of 150-200 r / min for 45-50 min;

[0013] S14. Cool the mixture obtained in step S13 to 50°C, add 8-10 parts of toluene diisocyanate, stir uniformly, and then vacuum degas for 20-30 min to obtain modified fluorocarbon resin.

[0014] Preferably, the preparation of the high-modulus alkali-free glass fiber comprises the following steps:

[0015] S21. Pre-treat nano-aluminum oxide by mixing 2-3 parts of KH-560, 4-6 parts of nano-aluminum oxide and 10-12 parts of deionized water, and ultrasonic dispersion at a frequency of 40 kHz for 25-30 min to obtain pre-treated nano-aluminum oxide;

[0016] S22. Add 0.5-1 parts of titanate coupling agent, 0.3-0.5 parts of sodium molybdate and 3-5 parts of water-based polyurethane dispersion into the pre-treated nano-aluminum oxide obtained in step S21, and ultrasonic dispersion at a frequency of 40 kHz for 25-30 min to obtain a high-modulus modifier;

[0017] S23. Uniformly dip the high-modulus modifier obtained in step S22 through a coating tank, dry at 90-100°C for 10-15 min, and then heat treat at 230-250°C for 15-20 min to obtain high-modulus alkali-free glass fiber after cooling.

[0018] Preferably, the preparation of the elastomer particle modified resin comprises the following steps:

[0019] S31. Mix 10-15 parts of nitrile rubber particles, 5-7 parts of polyurethane prepolymer and 2-4 parts of compatibilizer by mass fraction, and mill at 80-85°C for 8-10 min to obtain an elastomer particle modifier;

[0020] 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;

[0021] S33. Cool the modified resin mixture obtained in step S32 to 40°C, add 25-30 parts of 651 low molecular weight polyamide and stir until uniform, then vacuum degassing for 20-25 min to obtain an elastomer particle modified resin.

[0022] Preferably, the silane coupling agent in step S11 is selected from KH-550.

[0023] Preferably, the toughening agent in step S13 is selected from thermoplastic polyurethane elastomer.

[0024] Preferably, the titanate coupling agent in step S22 is selected from NDZ-201.

[0025] Preferably, the compatibilizer in step S31 is selected from maleic anhydride grafted POE.

[0026] A method for preparing a steel-FRP composite bar, for preparing the above steel-FRP composite bar.

[0027] A method for preparing a steel-FRP composite bar, comprising the following preparation steps:

[0028] S1. The steel wire is coated with a layer of elastomer particle modified resin through the inner layer glue slot, and then enters the middle layer winding area. High modulus alkali-free glass fiber is wound onto the inner layer resin at an angle of 75-85° through a fiber winding machine, and at the same time, the fiber is fully impregnated with epoxy resin through the middle layer glue slot;

[0029] S2. After passing through the middle layer glue slot, enter the outer layer winding area. High modulus alkali-free glass fiber is wound onto the middle layer at an angle of 30-45° through a fiber winding machine, and at the same time, the fiber is fully impregnated with modified fluorocarbon resin through the outer layer glue slot;

[0030] S3. After passing through the outer layer glue slot, add the mold, preliminarily compact and remove the bubbles, enter the heating and curing oven for curing, and during the curing process, pull the composite bar forward at a speed of 0.2-0.5 m / min through a slow traction device, and finally obtain a steel-FRP composite bar.

[0031] Preferably, the curing in step S3 adopts a stepwise heating method: the first stage is 80 DEG C for 25-30 min; the second stage is 120 DEG C for 50-60 min; and the third stage is 150 DEG C for 25-30 min.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] 1. The application develops a "fiber angle gradient" winding structure: from the inner layer to the outer layer, the glass fiber winding angle gradually transitions from 90 DEG (longitudinal reinforcement) to 30 DEG (hoop reinforcement), so that the composite bar meets the requirements of high axial tensile strength and transverse shear resistance, and is suitable for complex stress scenarios such as bridge bearing.

[0034] 2. The elastomer particle modified resin as a buffer and transition layer effectively improves the interface bonding between the steel wire and the fiber reinforced layer, absorbs impact and vibration, and delays crack propagation; the high modulus alkali-free glass fiber provides excellent axial tensile strength and stiffness to support the main bearing function; the modified fluorocarbon resin has high corrosion resistance and toughness, enhances the hoop constraint and shear resistance, and protects the internal structure from external erosion. The three work together to form a gradient structure, achieving balanced improvement of axial tensile strength, transverse shear resistance and impact resistance, especially suitable for complex multi-directional stress scenarios such as bridges and offshore platforms. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The preparation process flow chart of the steel-FRP composite bar of the application is shown in the figure;

[0036] Figure 2 The preparation process flow chart of the modified fluorocarbon resin of the application is shown in the figure;

[0037] Figure 3 The preparation process flow chart of the high modulus alkali-free glass fiber of the application is shown in the figure;

[0038] Figure 4 The preparation process flow chart of the elastomer particle modified resin of the application is shown in the figure;

[0039] Figure 5 The cross-sectional SEM image of the steel-FRP composite bar obtained in Example 1 of the application is shown in the figure;

[0040] Figure 6 The SEM image of the high modulus alkali-free glass fiber obtained in Example 1 of the application is shown in the figure. DETAILED DESCRIPTION

[0041] The present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0042] Please refer to Figures 1-6 The present application provides a technical solution:

[0043] Embodiment 1

[0044] A preparation method of a steel-FRP composite bar:

[0045] Before preparing the steel-FRP composite bar, the modified fluorocarbon resin, the high-modulus alkali-free glass fiber and the elastomer particle modified resin are prepared:

[0046] The preparation of the modified fluorocarbon resin comprises the following steps:

[0047] S11. 30 g of nanometer silicon dioxide and 10 g of silane coupling agent (KH-550) are ultrasonically dispersed at a frequency of 40 kHz for 25 min at 60°C to obtain pretreated nanometer silicon dioxide;

[0048] S12. 900 g of fluorocarbon resin and 150 g of N-methyl pyrrolidone are added to a reaction kettle, and stirred at a speed of 150 r / min for 10 min at 80°C to obtain a resin mixture;

[0049] S13. The pretreated nanometer silicon dioxide obtained in step S11 and 50 g of a toughening agent (thermoplastic polyurethane elastomer) are added to the resin mixture obtained in step S12, and stirred at a speed of 150 r / min for 45 min;

[0050] S14. The mixture obtained in step S13 is cooled to 50°C, 80 g of toluene diisocyanate is added, and after stirring uniformly, vacuum degassing is performed for 20 min to obtain a modified fluorocarbon resin.

[0051] The preparation of the high-modulus alkali-free glass fiber comprises the following steps:

[0052] S21. 20 g of KH-560, 40 g of nanometer alumina and 100 g of deionized water are mixed, and ultrasonically dispersed at a frequency of 40 kHz for 25 min to obtain pretreated nanometer alumina;

[0053] S22. 5 g of a titanate coupling agent (NDZ-201), 3 g of sodium molybdate and 30 g of a water-based polyurethane dispersion are added to the pretreated nanometer alumina obtained in step S21, and ultrasonically dispersed at a frequency of 40 kHz for 25 min to obtain a high-modulus modifier.

[0054] S23. The high modulus modifier obtained in step S22 was coated on 800 g of alkali-free glass fiber by dip coating, dried by hot air at 90 °C for 10 min, and then heat treated at 230 °C for 15 min. After cooling, the high modulus alkali-free glass fiber was obtained.

[0055] The preparation of the elastomer particle modified resin comprises the following steps:

[0056] S31. 100 g of nitrile rubber particles, 50 g of polyurethane prepolymer, and 20 g of compatibilizer (maleic anhydride grafted POE) were mixed and masticated at 80 °C for 8 min to obtain an elastomer particle modifier;

[0057] S32. 800 g of E-51 epoxy resin was heated to 60 °C, and the elastomer particle modifier obtained in step S31 was added. The mixture was stirred at 300 r / min for 50 min to obtain a modified resin mixture;

[0058] S33. The modified resin mixture obtained in step S32 was cooled to 40 °C, and 250 g of curing agent (651 low molecular weight polyamide) was added and stirred uniformly. After vacuum degassing for 20 min, the elastomer particle modified resin was obtained.

[0059] The preparation of the steel-FRP composite bar comprises the following steps:

[0060] S1. The steel wire was coated with a layer of elastomer particle modified resin by passing through the inner layer glue tank, and then passed through the middle layer winding area. High modulus alkali-free glass fiber was wound onto the inner layer resin at an angle of 85° by a fiber winding machine, and was fully impregnated with epoxy resin while winding;

[0061] S2. After passing through the middle layer glue tank, the high modulus alkali-free glass fiber was wound onto the middle layer at an angle of 45° by a fiber winding machine, and was fully impregnated with modified fluorocarbon resin while winding;

[0062] S3. After passing through the outer layer glue tank, the composite bar was added to the mold, and was preliminarily compacted and bubble-free. The composite bar was then cured in a heating and curing oven (first stage: 80 °C for 25 min; second stage: 120 °C for 50 min; third stage: 150 °C for 25 min). During the curing process, the composite bar was pulled forward at a speed of 0.2 m / min by a slow pulling device. Finally, the steel-FRP composite bar was obtained.

[0063] Example 2

[0064] A method for preparing a steel-FRP composite bar comprises the following steps:

[0065] Before preparing the steel-FRP composite bar, the modified fluorocarbon resin, high modulus alkali-free glass fiber, and elastomer particle modified resin were prepared.

[0066] The preparation of the modified fluorocarbon resin comprises the following steps:

[0067] S11. 50 g of nano-silicon dioxide is dispersed with 20 g of silane coupling agent (KH-550) at 60°C for 30 min at a frequency of 40 kHz to obtain pretreated nano-silicon dioxide;

[0068] S12. 1000 g of fluorocarbon resin and 200 g of N-methyl pyrrolidone are added to a reaction kettle, stirred at 80°C at a speed of 200 r / min for 15 min to obtain a resin mixture;

[0069] S13. The pretreated nano-silicon dioxide obtained in step S11 and 80 g of a toughening agent (thermoplastic polyurethane elastomer) are added to the resin mixture obtained in step S12, and stirred at a speed of 200 r / min for 50 min;

[0070] S14. The mixture obtained in step S13 is cooled to 50°C, 100 g of toluene diisocyanate is added, stirred uniformly, and then vacuum degassed for 30 min to obtain a modified fluorocarbon resin.

[0071] The preparation of high-modulus alkali-free glass fiber comprises the following steps:

[0072] S21. 30 g of KH-560, 60 g of nano-alumina, and 120 g of deionized water are mixed and dispersed at a frequency of 40 kHz for 30 min to obtain pretreated nano-alumina;

[0073] S22. 10 g of titanate coupling agent (NDZ-201), 5 g of sodium molybdate, and 50 g of water-based polyurethane dispersion are added to the pretreated nano-alumina obtained in step S21, and ultrasonic dispersion is carried out at a frequency of 40 kHz for 30 min to obtain a high-modulus modifier;

[0074] S23. 1000 g of alkali-free glass fiber is uniformly immersed with the high-modulus modifier obtained in step S22 through a coating tank, dried by hot air at 100°C for 15 min, and then heat-treated at 250°C for 20 min to obtain high-modulus alkali-free glass fiber after cooling.

[0075] The preparation of elastomer particle modified resin comprises the following steps:

[0076] S31. 150 g of butyl nitrile rubber particles, 70 g of polyurethane prepolymer, and 40 g of a compatibilizing agent (maleic anhydride grafted POE) are mixed and milled at 85°C for 10 min to obtain an elastomer particle modifier;

[0077] S32.1000g E-51 epoxy resin is heated to 60℃, and the elastomer particle modifier obtained in step S31 is added. Stirring is performed at a rotation speed of 400 r / min for 60 min to obtain a modified resin mixture;

[0078] S33. The modified resin mixture obtained in step S32 is cooled to 40℃, and 300g of a curing agent (651 low molecular weight polyamide) is added. After uniform stirring, vacuum degassing is performed for 25 min to obtain an elastomer particle modified resin.

[0079] The preparation of the steel-FRP composite bar includes the following steps:

[0080] S1. The steel wire is coated with a layer of elastomer particle modified resin through the inner layer glue slot, and then enters the middle layer winding area. High modulus alkali-free glass fiber is wound onto the inner layer resin at an angle of 75° by a fiber winding machine. At the same time, the fiber is fully impregnated with epoxy resin through the middle layer glue slot;

[0081] S2. After passing through the middle layer glue slot, the high modulus alkali-free glass fiber is wound onto the middle layer at an angle of 30° by a fiber winding machine through the outer layer glue slot, and is fully impregnated with modified fluorocarbon resin at the same time;

[0082] S3. After passing through the outer layer glue slot, the mold is added, and the composite bar is preliminarily compacted and bubble-free. The composite bar is pulled forward at a speed of 0.5 m / min by a slow traction device during the curing process, and finally the steel-FRP composite bar is obtained.

[0083] Example 3

[0084] A method for preparing a steel-FRP composite bar:

[0085] Before preparing the steel-FRP composite bar, the modified fluorocarbon resin, high modulus alkali-free glass fiber and elastomer particle modified resin are prepared:

[0086] The preparation of the modified fluorocarbon resin includes the following steps:

[0087] S11. 40g of nano-silicon dioxide is dispersed with 15g of silane coupling agent (KH-550) at 60℃ for 27 min at a frequency of 40kHz to obtain pretreated nano-silicon dioxide;

[0088] S12. 950g of fluorocarbon resin and 170g of N-methyl pyrrolidone are added to a reaction kettle. Stirring is performed at a rotation speed of 170 r / min for 13 min at 80℃ to obtain a resin mixture;

[0089] S13. Add the pretreated nanosilica obtained in step S11 and 60 g of a toughening agent (thermoplastic polyurethane elastomer) to the resin mixture obtained in step S12, and stir at a rotation speed of 170 r / min for 47 min;

[0090] S14. Cool the mixture obtained in step S13 to 50℃, add 90 g of toluene diisocyanate, stir uniformly, and vacuum degas for 25 min to obtain a modified fluorocarbon resin.

[0091] The preparation of high-modulus alkali-free glass fiber includes the following steps:

[0092] S21. Mix 25 g of KH-560, 50 g of nanometer alumina, and 110 g of deionized water, and ultrasonically disperse at a frequency of 40 kHz for 27 min to obtain pretreated nanometer alumina;

[0093] S22. Add 7 g of titanate coupling agent (NDZ-201), 4 g of sodium molybdate, and 40 g of water-based polyurethane dispersion to the pretreated nanometer alumina obtained in step S21, and ultrasonically disperse at a frequency of 40 kHz for 27 min to obtain a high-modulus modifier;

[0094] S23. Uniformly dip coat 900 g of alkali-free glass fiber with the high-modulus modifier obtained in step S22 through a coating tank, dry at 95℃ by hot air for 13 min, and then heat treat at 240℃ for 17 min to obtain high-modulus alkali-free glass fiber after cooling.

[0095] The preparation of elastomer particle modified resin includes the following steps:

[0096] S31. Mix 130 g of nitrile rubber particles, 60 g of polyurethane prepolymer, and 30 g of a compatibilizing agent (maleic anhydride grafted POE), and mill at 83℃ for 9 min to obtain an elastomer particle modifier;

[0097] S32. Heat 900 g of E-51 epoxy resin to 60℃, add the elastomer particle modifier obtained in step S31, and stir at a rotation speed of 350 r / min for 55 min to obtain a modified resin mixture;

[0098] S33. Cool the modified resin mixture obtained in step S32 to 40℃, add 260 g of a curing agent (651 low molecular weight polyamide), stir uniformly, and vacuum degas for 23 min to obtain an elastomer particle modified resin.

[0099] The preparation of steel-FRP composite bar includes the following steps:

[0100] S1. The steel wire passes through the inner layer rubber tank, the surface is uniformly coated with a layer of elastomer particle modified resin, and then enters the middle layer winding area. High modulus alkali-free glass fiber is wound on the inner layer resin at an angle of 80° by a fiber winding machine. At the same time of winding, it passes through the middle layer rubber tank and is fully impregnated with epoxy resin;

[0101] S2. After passing through the middle layer rubber tank, it enters the outer layer winding area. High modulus alkali-free glass fiber is wound on the middle layer at an angle of 40° by a fiber winding machine. At the same time of winding, it passes through the outer layer rubber tank and is fully impregnated with modified fluorocarbon resin;

[0102] S3. After passing through the outer layer rubber tank, it is added to the mold, preliminarily compacted and bubble-free, and then enters the heating and curing oven for curing (the first stage is 80°C for 27 min; the second stage is 120°C for 55 min; the third stage is 150°C for 27 min). During the curing process, the composite bar is pulled forward at a speed of 0.3 m / min by a slow traction device. Finally, the steel-FRP composite bar is obtained.

[0103] Comparative Example 1

[0104] Comparative Example 1 and Example 1 have the following differences. The only difference between this comparative example and Example 1 is that the elastomer particle modified resin is replaced by E-51 epoxy resin. The remaining steps are exactly the same in Comparative Example 1 and Example 1.

[0105] Comparative Example 2

[0106] Comparative Example 2 and Example 1 have the following differences. The only difference between this comparative example and Example 1 is that the high modulus alkali-free glass fiber is replaced by ordinary alkali-free glass fiber. The remaining steps are exactly the same in Comparative Example 2 and Example 1.

[0107] Comparative Example 3

[0108] Comparative Example 3 and Example 1 have the following differences. The only difference between this comparative example and Example 1 is that the modified fluorocarbon resin is replaced by ordinary fluorocarbon resin. The remaining steps are exactly the same in Comparative Example 3 and Example 1.

[0109] Performance Test:

[0110] The tensile properties, shear properties and corrosion resistance of the steel-FRP composite bars obtained in Examples 1-3 and Comparative Examples 1-3 are tested according to GB / T 30022-2013 "Test Method for Basic Mechanical Properties of Fiber Reinforced Composite Bars", ASTM D4475-21 "Standard Test Method for Determining Apparent Horizontal Shear Strength of Pultruded Plastic Rods by Short Beam Method", and GB / T 10125-2021 "Salt Spray Test Standard". The results are shown in Table 1 below:

[0111] Table 1 Performance Test Results

[0112]

[0113] From the data in Table 1, the steel-FRP composite bar obtained in Example 1 is superior to the comparative example in tensile properties, shear properties and corrosion resistance, which shows that the synergistic effect of the modified fluorocarbon resin, high modulus alkali-free glass fiber and elastomer particle modified resin effectively improves the interfacial bonding between the steel wire and the fiber reinforced layer, provides excellent axial tensile strength and stiffness, has high corrosion resistance and toughness, enhances the hoop constraint and shear resistance, protects the internal structure from external erosion, is suitable for modern civil engineering applications requiring high durability and complex stress, and has important engineering application value.

[0114] Figure 1 is a schematic diagram of the steel-FRP composite bar of the present application. Figure 5 Figure 2 is a schematic diagram of the steel-FRP composite bar of the present application. Figure 6 Figures 3 and 4 are SEM images of the steel-FRP composite bar and high modulus alkali-free glass fiber obtained in Example 1, respectively.

[0115] Figure 5 is a schematic diagram of the steel-FRP composite bar of the present application. Figure 5 In Figure 5, 1 is a steel wire; 2 is an inner layer: elastomer particle modified resin as a buffer and transition layer, effectively improving the interfacial bonding between the steel wire and the fiber reinforced layer, absorbing impact and vibration, and delaying crack propagation; 3 is a middle layer: high modulus alkali-free glass fiber providing excellent axial tensile strength and stiffness, supporting the main load bearing function; 4 is an outer layer: high modulus alkali-free glass fiber and modified fluorocarbon resin synergistically providing corrosion resistance and toughness, enhancing hoop constraint and shear resistance, and protecting the internal structure from external erosion. As can be seen in the figure, the middle layer and the outer layer are wrapped in the outer layer material under the condition of heating and curing, further improving the overall durability, environmental erosion resistance and adhesion to concrete of the composite bar, and realizing a high-strength, high-durability and lightweight composite bar material.

[0116] Figure 6 is a schematic diagram of the steel-FRP composite bar of the present application. Figure 6 As can be seen in Figure 6, the high modulus alkali-free glass fiber is composed of oriented reinforcing fibers, providing the material with longitudinal tensile strength and stiffness.

[0117] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, 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. 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. 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.

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

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

4. The steel-FRP composite reinforcement according to claim 1, characterized in that, The titanate coupling agent in step S22 is selected from NDZ-201.

5. The steel-FRP composite reinforcement according to claim 1, characterized in that, The compatibilizer in step S31 is selected from maleic anhydride-grafted POE.

6. 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 1-5 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.

7. The method for preparing a steel-FRP composite reinforcement according to claim 6, 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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