Anchoring body for a fiber-reinforced thermoplastic resin-based composite rod

Abstract

The application discloses an anchoring body for a fiber reinforced thermoplastic resin base composite material rod, belonging to the field of civil engineering anchoring technology, comprising an FRTP rod, a centering ring, an anchoring steel pipe and a fixing cover, the anchoring section of the FRTP rod is located in the anchoring steel pipe, at high temperature, the FRTP prepreg tape is softened and wound on the anchoring section of the FRTP rod in a clockwise direction to form a plurality of FRTP conical gradient structures, the inner cavity of the anchoring steel pipe is provided with a plurality of recesses with variable cross-section conical gradient along the axial direction, the FRTP conical gradient structure is arranged in the recess, and the anchoring section is fixed and sealed in the inner part of the anchoring steel pipe through an epoxy resin filling agent. The anchoring efficiency and the anchoring strength are improved, and the problem that the anchoring efficiency of the FRTP rod is reduced under an erosive environment and under repeated fatigue load is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering anchoring, specifically relating to an anchoring body for fiber-reinforced thermoplastic resin-based composite rods (FRTP bars). Background Technology

[0002] Fiber-reinforced thermoplastic resin matrix composites (FRTPs) are widely used in civil engineering due to their excellent properties such as high toughness, impact resistance, easy repair, short molding cycle, and recyclability. Compared with steel bars, FRTP bars have advantages such as high strength, corrosion resistance, and fatigue resistance. Compared with thermosetting reinforcement materials, thermoplastic reinforcement materials have advantages such as easy repair and recyclability. Therefore, when applied as a new type of reinforcement material in civil engineering, it will inject new vitality into the development of this field. However, due to the special properties of the material, traditional anchoring methods cannot achieve good anchoring effects. Therefore, it is necessary to develop a new type of anchoring material based on FRTP materials. Summary of the Invention

[0003] Based on the above shortcomings, the purpose of this invention is to provide an anchor body for fiber-reinforced thermoplastic resin-based composite rods (FRTP bars), which effectively solves the problem of reduced anchorage efficiency of FRTP bars under corrosive environments and repeated fatigue loads.

[0004] The technical solution adopted in this invention is as follows: An anchor body for fiber-reinforced thermoplastic resin-based composite rods, comprising FRTP bars, a centering ring, an anchoring steel pipe, and a fixing cap. The end of the anchoring steel pipe is threadedly connected to the fixing cap. The interior of the anchoring steel pipe is hollow. The anchoring section of the FRTP bar is located inside the anchoring steel pipe. At high temperature, the FRTP prepreg tape is softened and wound clockwise around the anchoring section of the FRTP bar. During the winding process, an epoxy resin layer is evenly applied to the surface of the FRTP bar and the FRTP prepreg tape, forming no less than four FRTP conical gradient structures in the anchoring section of the FRTP bar. Each FRTP conical gradient structure has equal gradient, equal length, and equal thickness. The maximum diameter of the hole is the same as that of the FRTP conical gradient structure. The inner cavity of the anchoring steel pipe has a corresponding number of variable cross-section tapered gradient grooves along the axial direction. The length of the groove at the end of the anchoring steel pipe is slightly smaller than the length of the FRTP tapered gradient structure, while the length of each of the remaining grooves is the same as the length of the FRTP tapered gradient structure. Each FRTP tapered gradient structure is placed in the groove. Except for the FRTP tapered gradient structure at the end, the two ends of each FRTP tapered gradient structure are aligned with the two ends of the corresponding groove. A centering ring is installed at the top of the anchoring steel pipe. One end of the FRTP rib passes through the center hole of the centering ring, so that the anchoring section of the FRTP rib is coaxial with the anchoring steel pipe. The gaps between the anchoring steel pipe, the FRTP rib, the fixing cap, and the centering ring are all filled with epoxy resin filler for sealing.

[0005] Furthermore, the angle between the inner wall of the groove and the axial center line of the anchoring steel pipe gradually decreases from the top of the anchoring steel pipe.

[0006] Furthermore, a release agent is sprayed onto the inner wall of the anchoring steel pipe to reduce the adhesion between the inner wall of the anchoring steel pipe and the FRTP tapered gradient structure.

[0007] Furthermore, one end of the FRTP bar extends 5-15mm beyond the top of the anchoring steel pipe.

[0008] Furthermore, the inner end face of the fixing cover has a recessed hole at its center, and the other end of the FRTP rib is located in and in contact with the recessed hole.

[0009] Furthermore, the epoxy resin filler contains iron sand.

[0010] The present invention has the following advantages and beneficial effects:

[0011] (1) Considering the characteristics of thermoplastic prepreg tape softening by heating and cooling to form a mold, multiple tapered gradient segments are wound onto the surface of the FRTP reinforcement, which not only increases the anchoring efficiency but also greatly improves the transverse shear resistance of the FRTP reinforcement. The epoxy resin layer applied to the surface of the FRTP prepreg tape during the winding process also has a positive effect on improving the bonding performance between the thermoplastic resin and the fiber surface.

[0012] (2) Multiple variable cross-section grooves are designed inside the anchoring steel pipe, and an appropriate amount of release agent is sprayed in each groove to improve the force transmission performance of the three components: FRTP reinforcement, epoxy resin filler and anchoring steel pipe. When the FRTP reinforcement is subjected to an external axial load, the axial force on the FRTP reinforcement will be transmitted to the external anchoring steel pipe in the form of extrusion pressure through the epoxy resin filler. When the inner wall of the anchoring steel pipe is designed with a variable cross-section, the anchoring steel pipe will transmit the extrusion pressure to different positions of the steel pipe, so that the entire anchoring system is uniformly stressed and the anchoring efficiency is improved.

[0013] (3) The anchorage length of the FRTP bar is slightly longer than the length of the anchoring steel pipe. When the FRTP bar is subjected to axial force, the surface of the multiple tapered gradient sections of the FRTP bar will effectively contact the bottom surface of the anchoring steel pipe, which improves the anchorage efficiency and can better transmit the external load to the anchoring steel pipe through the epoxy resin filler.

[0014] (4) A non-penetrating circular hole is left in the center of the bottom inner wall of the fixed cover, which coincides with the bottom surface of the FRTP bar. Together with the centering ring on the top surface of the anchoring steel pipe, the FRTP bar is always in the middle position of the anchoring system, avoiding the eccentric force of the entire anchoring system caused by the offset of the FRTP bar. The gap of a certain length left between the bottom surface of the anchoring steel pipe and the bottom surface of the fixed cover means that when the epoxy resin filler fills the gap, it will not only help to enhance the connection strength of the FRTP bar, the anchoring steel pipe and the fixed steel pipe, but also have a certain positive effect on the force transmission of the entire anchoring system.

[0015] (5) Add a certain proportion of iron sand to the epoxy resin filler, mix evenly, and then use a pressure injector to inject the prepared epoxy resin filler into the gap between the FRTP reinforcement and the anchoring steel pipe. Since the addition of iron sand changes the stiffness of the epoxy resin filler, the injection process should be divided into multiple stages according to the number of grooves set in the anchoring steel pipe. The stiffness of the epoxy resin filler can be changed by changing the amount of iron sand added in each stage. The entire injection process should be continuous. After the epoxy resin is fully impregnated in the current stage, the next stage of injection can be carried out.

[0016] (6) In summary, the present invention is a new type of anchor body designed for FRTP bars under corrosive environment and repeated fatigue load. The entire anchor body is simple in design, has reasonable stress distribution, is easy to process, has good economy and wide applicability. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of the anchor body used in the fiber-reinforced thermoplastic resin-based composite rod of the present invention.

[0018] Figure 2 This is a schematic diagram of the top surface structure of the anchor body for the fiber-reinforced thermoplastic resin-based composite rod of the present invention;

[0019] Figure 3 A schematic diagram of the side structure of FRTP prepreg tape wrapped with FRTP reinforcement;

[0020] Figure 4 A schematic diagram of the top structure of FRTP prepreg tape wrapped with FRTP reinforcement.

[0021] In the diagram: 1-FRTP reinforcement, 2-centering ring, 3-FRTP prepreg tape, 4-epoxy resin filler, 5-anchoring steel pipe, 6-fixing cap. Detailed Implementation

[0022] The invention will be further described below with reference to the accompanying drawings:

[0023] Example 1

[0024] like Figure 1-4As shown, an anchor body for a fiber-reinforced thermoplastic resin-based composite rod includes an FRTP bar 1, a centering ring 2, an anchoring steel pipe 5, and a fixing cap 6. The anchoring steel pipe is hollow inside, and the end of the anchoring steel pipe 5 is threadedly connected to the fixing cap 6. The anchoring section of the FRTP bar 1 is located inside the anchoring steel pipe 5. At high temperature, the FRTP prepreg tape 3 is softened and wound clockwise around the anchoring section of the FRTP bar 1. During the winding process, an epoxy resin layer is evenly applied to the surfaces of the FRTP bar 1 and the FRTP prepreg tape 3, forming four FRTP conical gradient structures in the anchoring section of the FRTP bar 1. Each FRTP conical gradient structure has equal gradient, equal length, and equal thickness. The maximum diameter of the hole is the same as that of the FRTP conical gradient structure. The inner cavity of the anchoring steel pipe 5 has four variable cross-section conical gradient grooves along the axial direction. The length of the groove at the end of the anchoring steel pipe 5 is slightly less than the length of the FRTP conical gradient structure. The length of each of the remaining grooves is the same as the length of the FRTP conical gradient structure. The angle between the inner wall of the groove and the axial centerline of the anchoring steel pipe 5 gradually decreases from the top of the anchoring steel pipe 5. Each FRTP conical gradient structure is placed in the groove. Except for the FRTP conical gradient structure at the end, the two ends of each FRTP conical gradient structure are aligned with the two ends of the corresponding groove. A centering ring 2 is installed at the top of the anchoring steel pipe 5. One end of the FRTP rib 1 passes through the center hole of the centering ring 2. The center hole is coaxial with the anchoring steel pipe 5, so that the anchoring section of the FRTP rib 1 is coaxial with the anchoring steel pipe 5. Epoxy resin filler 4 is filled in the gaps between the anchoring steel pipe 5, the FRTP rib 1, the fixing cap 6, and the centering ring 2. A release agent is sprayed on the inner wall of the anchoring steel pipe 5 to reduce the adhesion between the inner wall of the anchoring steel pipe 5 and the FRTP conical gradient structure. One end of the FRTP rib 1 extends 5-15mm beyond the top of the anchoring steel pipe 5. The fixing cap 6 has a recessed hole at its center on its inner end face, and is coaxial with the anchoring steel pipe 5. The other end of the FRTP rib 1 is located within and in contact with the recessed hole. The epoxy resin filler 4 contains iron sand.

[0025] Its production method is as follows:

[0026] First, a certain length of FRTP reinforcement 1 is selected as the anchoring section of the system. FRTP prepreg tape 3 is wound around its surface. Utilizing the characteristics of FRTP prepreg tape 3—heat softening and cooling molding—four identical, uniformly thick FRTP conical gradient structures are wound onto the surface of FRTP reinforcement 1. This winding process enhances the transverse shear resistance of FRTP reinforcement 1. During the heating and winding process of FRTP prepreg tape 3, an epoxy resin layer is uniformly applied to the surfaces of FRTP reinforcement 1 and FRTP prepreg tape 3. Under high temperature, the epoxy resin penetrates into the thermoplastic resin, enhancing the adhesion between the thermoplastic resin and the fiber surface. Second, the cut length of the anchoring steel pipe 5... The length of the anchorage section should be slightly less than that of the FRTP reinforcement 1, ensuring that the end of the FRTP reinforcement 1 extends 5-15mm beyond the anchoring steel pipe 5 to enhance the anchoring efficiency of the anchor body. For ease of processing, the anchoring steel pipe 5 is composed of two parts, upper and lower, with its inner wall consisting of four variable cross-section grooves. Starting from the top of the anchoring steel pipe 5, the length of the first three variable cross-section grooves should match the length of the FRTP conical gradient structure formed by the above winding. The length of the fourth variable cross-section groove should be slightly less than the length of the FRTP conical gradient structure. Starting from the top of the anchoring steel pipe 5, the angle between the inner wall of each variable cross-section groove and the horizontal line decreases progressively, ensuring that the FRTP reinforcement 1 can withstand axial force. To better transfer this force to the anchoring steel pipe 5, the outer end of the anchoring steel pipe 5 should have a certain length of thread, and the upper end of the outer wall of the fixing cap 6 should also have a certain length of thread to facilitate connection via threads. Additionally, the bottom of the fixing cap 6 should have a certain thickness to ensure that when the epoxy resin filler completely fills the gap between the FRTP reinforcement 1 and the anchoring steel pipe 5, the epoxy resin filler will not flow out through the bottom of the fixing cap 6 to the outside of the anchoring system. When the anchoring steel pipe 5 and the fixing cap 6 are connected together by threads, a certain gap should be left between their bottoms, and a partially penetrating circular hole should be left on the inner end face of the fixing cap, with a diameter equal to that of the FRTP prepreg tape 1. The maximum diameter of the conical gradient segments formed by the winding is the same. During the assembly of the anchor body, the centering ring 2 at the top of the anchoring steel pipe 1 is used to fix the position of the FRTP bar 1, so that it is always coaxial with the anchoring steel pipe 5. When the anchor body is assembled, the bottom surface of the FRTP bar 1 should be in complete contact with the surface of the circular hole left on the fixing cover 6. Finally, an appropriate amount of release agent is sprayed on the inner wall of the anchoring steel pipe 5 to prevent the epoxy resin from bonding too strongly with the inner wall of the anchoring steel pipe 5, which would affect the anchoring efficiency of the entire anchor body for the FRTP bar 1. Then, the prepared epoxy resin filler is injected into the gap between the FRTP bar and the anchoring steel pipe from the top of the anchoring steel pipe 5 using a pressure injector, and the filling is uniform.

[0027] The anchorage length of the FRTP reinforcement depends on the magnitude of the axial force it experiences. The anchorage length should be considered based on the actual axial force on the rod. Otherwise, the anchorage efficiency will be greatly reduced. When considering the anchorage length of the FRTP reinforcement, the end of the rod should extend 10±5mm beyond the anchoring steel pipe and make effective contact with the anchoring steel pipe. When the FRTP reinforcement is subjected to axial tension, it can better transfer the external load to the anchoring steel pipe through the epoxy resin filler. In addition, when cutting the rod to consider the anchorage length of the FRTP reinforcement, attention should be paid to the cutting angle and details to avoid excessive cutting defects that cause local stress concentration, thereby affecting the overall anchorage efficiency of the anchorage system.

[0028] When wrapping FRTP prepreg tape around FRTP reinforcement bars, the process should be carried out at a certain high temperature. Firstly, a high-temperature environment helps soften the FRTP prepreg tape, improving winding efficiency. Secondly, applying an epoxy resin layer to the surfaces of both the FRTP prepreg tape and the FRTP reinforcement bars at a high temperature promotes fusion and improves the interfacial adhesion between the bars and the prepreg tape. This temperature range should ensure that the FRTP prepreg tape softens without affecting processing quality. Furthermore, the entire winding process should be uniform and continuous; otherwise, the stress-bearing and force-transfer performance of the wound section will be affected, thus impacting the anchoring efficiency of the anchoring system.

[0029] The anchor body adopts a "variable gradient extrusion-bonding" mode. Under the condition that the FRTP prepreg tape is wound with a uniform thickness, the inner wall of the anchor steel pipe is cut into 4 variable gradient grooves. Starting from the top of the anchor steel pipe, the groove gradient gradually becomes gentler. When the FRTP bar is subjected to external load, the variable gradient design will be more conducive to converting the external load into the extrusion force on the bar and transferring it to the outer anchor steel pipe, which greatly improves the integrity and force transmission of the anchoring system.

[0030] To enhance the anchoring strength of the entire anchor body, an appropriate amount of release agent should be sprayed onto the inner wall of the anchoring steel pipe. This prevents the adhesion between the FRTP winding section and the epoxy resin layer from being too weak when the entire system is subjected to external loads, which would affect the working efficiency of the "variable gradient extrusion-bonding" mode. Applying a release agent appropriately to the inner wall of the anchoring steel pipe reduces the adhesion between the inner wall of the steel pipe and the FRTP winding section, which can better leverage the variable gradient advantage of the anchoring system and greatly improve the overall anchoring capacity.

[0031] When the anchoring steel pipe and the fixing cap are connected by threads, the bottom end of the FRTP reinforcement coincides with the bottom surface of the non-penetrating circular hole on the end face of the fixing cap. Then, a centering ring is placed on top of the anchoring steel pipe. The outer wall of the centering ring should coincide with the inner wall of the anchoring steel pipe, and the inner wall of the centering ring should coincide with the outer wall of the FRTP reinforcement. This ensures that the FRTP reinforcement is always coaxial with the anchoring steel pipe, avoiding eccentric stress on the entire anchoring system due to the offset of the FRTP reinforcement. In addition, a certain length of gap is left between the bottom surface of the anchoring steel pipe and the bottom surface of the fixing steel pipe. When the epoxy resin filler fills the gap, it not only enhances the connection strength of the FRTP reinforcement, the anchoring steel pipe, and the fixing steel pipe, but also has a positive effect on the force transmission of the entire anchoring system.

[0032] A certain proportion of iron sand is added to the epoxy resin filler. After mixing evenly, the prepared epoxy resin filler is injected into the gap between the FRTP bar and the anchoring steel pipe through the injection port at the top of the FRTP bar anchoring section using a pressure injector. Since the addition of iron sand changes the stiffness of the epoxy resin filler, the injection process should be carried out in four stages according to the number of grooves set in the anchoring steel pipe. The stiffness of the epoxy resin filler is changed by changing the amount of iron sand added in each stage. The entire injection process should be continuous. After the epoxy resin has fully impregnated the surface in one stage, the next stage of injection can be carried out.

Claims

1. An anchor body for a fiber-reinforced thermoplastic resin-based composite rod, comprising a FRTP bar (1), a centering ring (2), an anchoring steel pipe (5), and a fixing cap (6), wherein the end of the anchoring steel pipe (5) is threadedly fastened to the fixing cap (6), the interior of the anchoring steel pipe is hollow, and the anchoring section of the FRTP bar (1) is located inside the anchoring steel pipe (5), characterized in that: At high temperature, the FRTP prepreg tape (3) is softened and wound clockwise around the anchoring section of the FRTP bar (1). During the winding process, the epoxy resin layer is evenly applied to the surface of the FRTP bar (1) and the FRTP prepreg tape (3), forming no less than 4 FRTP conical gradient structures in the anchoring section of the FRTP bar (1). Each of the FRTP conical gradient structures is of equal gradient, equal length, and equal thickness. The center of the inner end face of the fixing cap (6) has a recessed hole and is coaxial with the anchoring steel pipe (5). The other end of the FRTP bar (1) is located in the recessed hole and in contact with it. The recessed hole has the same maximum diameter as the FRTP conical gradient structure. The inner cavity of the anchoring steel pipe (5) has a corresponding number of variable cross-section conical gradient grooves along the axial direction. (5) The length of the end groove is slightly less than the length of the FRTP conical gradient structure, and the length of each other groove is the same as the length of the FRTP conical gradient structure. Each FRTP conical gradient structure is placed in the groove. Except for the end FRTP conical gradient structure, the two ends of each FRTP conical gradient structure are aligned with the two ends of the corresponding groove. The top of the anchoring steel pipe (5) is equipped with a centering ring (2). One end of the FRTP bar (1) passes through the center hole of the centering ring (2). The center hole is coaxial with the anchoring steel pipe (5), so that the anchoring section of the FRTP bar (1) is coaxial with the anchoring steel pipe (5). The gaps between the anchoring steel pipe (5), the FRTP bar (1), the fixing cap (6), and the centering ring (2) are all filled with epoxy resin filler (4) for sealing.

2. The anchor body for a fiber-reinforced thermoplastic resin-based composite rod according to claim 1, characterized in that: The angle between the inner wall of the groove and the axial center line of the anchoring steel pipe (5) gradually decreases from the top of the anchoring steel pipe (5).

3. The anchor body for a fiber-reinforced thermoplastic resin-based composite rod according to claim 1, characterized in that: A release agent is sprayed on the inner wall of the anchoring steel pipe (5) to reduce the adhesion between the inner wall of the anchoring steel pipe (5) and the FRTP tapered gradient structure.

4. The anchor body for a fiber-reinforced thermoplastic resin-based composite rod according to claim 1, characterized in that: The length of one end of the FRTP bar (1) extending beyond the top of the anchoring steel pipe (5) is 5-15mm.

5. An anchor body for a fiber-reinforced thermoplastic resin-based composite rod according to any one of claims 1-4, characterized in that: The epoxy resin filler (4) contains iron sand.

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