A thermoplastic FRP reinforcement cage and its preparation method

Abstract

The present invention discloses a thermoplastic FRP reinforcement cage and a method for preparing the same. The method employs a double melting method and uses thermoplastic LCP fiber composite tapes to allow the thermoplastic FRP longitudinal bars, thermoplastic FRP stirrups, and thermoplastic LCP fiber composite tapes to interpenetrate and fully fuse at the joints through melting, thereby improving the structural integrity and mechanical properties of the joints and facilitating increased strength at the joints where the thermoplastic FRP longitudinal bars and stirrups are connected.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and more particularly to a thermoplastic FRP reinforcement cage and a preparation method thereof. Background Art

[0002] Fiber reinforced polymer (FRP) is an emerging material with excellent properties such as light weight, high strength, and good durability. Using it as FRP bars in concrete structures can fundamentally solve the durability problems of traditional reinforced concrete structures. Based on the differences in the resins used in the FRP molding process, FRP can be divided into thermosetting FRP and thermoplastic FRP. Thermosetting FRP is currently the most commonly used material in bridge engineering, but it has disadvantages such as low fracture toughness, long curing cycles, poor environmental adaptability, and difficulty in recycling. In addition, once thermosetting FRP is cured and formed, the corresponding product shape cannot be changed. This makes the molding of thermosetting FRP stirrups more difficult, reducing the convenience and efficiency of FRP bars in actual engineering. Thermoplastic FRP not only has the mechanical properties advantages of thermosetting FRP, but also has good toughness, strong environmental adaptability, easy recycling, excellent impact resistance and secondary molding characteristics. When it is made into thermoplastic FRP bars and assembled into thermoplastic FRP reinforcement cages for use in components such as concrete piers or concrete beams, it can not only improve the efficiency of actual projects, but also improve the durability of concrete structures.

[0003] However, when thermoplastic FRP cages are prepared using thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups made of thermoplastic FRP and used in components such as concrete piers or concrete beams, it is found that the nodes where the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected are weak, making the thermoplastic FRP cages prone to damage at the nodes, thereby reducing the service life of the thermoplastic FRP cages.

[0004] Therefore, it is of great significance to develop a method for preparing thermoplastic FRP cages that can improve the strength of the nodes where thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected. Summary of the Invention

[0005] The primary purpose of the present invention is to overcome the problem of poor strength at the nodes where thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected in the prior art, and to provide a method for preparing a thermoplastic FRP reinforcement cage.

[0006] Another object of the present invention is to provide a thermoplastic FRP cage.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] A method for preparing a thermoplastic FRP reinforcement cage comprises the following steps:

[0009] S1. Place the thermoplastic FRP longitudinal bars inside the thermoplastic FRP stirrups so that the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups are in contact and connected;

[0010] S2. Perform a melting process at the contact joints between the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups to fuse the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups together to form a node;

[0011] S3. Using thermoplastic LCP (Liquid Crystal Polyester, liquid crystal polymer) fiber composite tape to tie the node;

[0012] S4 is melt-treated the thermoplastic LCP fiber composite tape, so that it is combined with the node to obtain the thermoplastic FRP cage;

[0013] The thermoplastic LCP fiber composite tape is composed of fiber layers containing liquid crystal polyarylate fibers in a laminated structure, and the layers are bonded together by resin; the width of the thermoplastic LCP fiber composite tape is 2 to 5 cm.

[0014] The present invention adopts a double melting method and selects thermoplastic LCP fiber composite tapes, so that the thermoplastic FRP longitudinal bars, thermoplastic FRP stirrups and thermoplastic LCP fiber composite tapes penetrate and fully fuse with each other at the nodes by melting, thereby improving the structural integrity of the nodes and the mechanical properties of the nodes, which is beneficial to improving the strength of the nodes where the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected.

[0015] When the width of the thermoplastic LCP fiber composite tape is within the range of 2 to 5 cm, the contact area between the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups can be increased, thereby better utilizing the restraint performance of the thermoplastic LCP fiber composite tape through binding, which is beneficial to improving the structural integrity of the node and also beneficial to improving the mechanical properties of the node. Therefore, the strength of the node where the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups are connected can be better improved.

[0016] However, when the width of the thermoplastic LCP fiber composite tape is too wide, the thermoplastic LCP fiber composite tape will be kinked and wrinkled during the binding process, which is not conducive to the restraint performance, affects the structural integrity of the node, reduces the mechanical properties of the node, and cannot better improve the strength of the node where the thermoplastic FRP longitudinal reinforcement and the thermoplastic FRP stirrups are connected.

[0017] Specifically, the width of the thermoplastic LCP fiber composite tape is 4 to 5 cm.

[0018] Specifically, the fiber layer containing liquid crystal polyarylate fibers is made by weaving liquid crystal polyarylate fibers, or is made by weaving liquid crystal polyarylate fibers and auxiliary fibers.

[0019] Furthermore, the auxiliary fibers are one or more of carbon fibers, basalt fibers or glass fibers.

[0020] In the present invention, the weaving can be a two-dimensional weaving method or a three-dimensional weaving method, wherein the two-dimensional weaving structure is one of plain weave, twill or satin weave, and the three-dimensional weaving structure is one of three-dimensional four-directional, three-dimensional five-directional, three-dimensional six-directional or three-dimensional seven-directional.

[0021] All resins used in the art can be used in the present invention, such as epoxy resin, phenolic resin and polyester resin.

[0022] Liquid crystal polyarylate fibers used in the art can be used in the present invention, such as series, Kingfa Technology's Vicryst TM series, Walter's series, PRET series of Pulite, Mitsubishi Chemical of Japan series and so on.

[0023] Specifically, the number of fiber layers in the thermoplastic LCP fiber composite tape is 2 to 8.

[0024] Furthermore, the number of fiber layers in the thermoplastic LCP fiber composite tape is 6 to 8.

[0025] Specifically, the thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups are one or more of thermoplastic carbon fiber reinforced composite (CFRTP) bars, thermoplastic basalt fiber reinforced composite (BFRTP) bars, thermoplastic glass fiber reinforced composite (GFRTP) bars or thermoplastic aramid fiber reinforced composite (AFRTP) bars.

[0026] In the present invention, thermoplastic carbon fiber reinforced composite material (CFRTP) ribs are a composite material prepared with carbon fiber as reinforcement and thermoplastic resin as matrix; thermoplastic basalt fiber reinforced composite material (BFRTP) ribs are a composite material prepared with basalt fiber as reinforcement and thermoplastic resin as matrix; thermoplastic glass fiber reinforced composite material (GFRTP) ribs are a composite material prepared with glass fiber as reinforcement and thermoplastic resin as matrix; thermoplastic aramid fiber reinforced composite material (AFRTP) ribs are a composite material prepared with aramid fiber as reinforcement and thermoplastic resin as matrix; the thermoplastic resin used is one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate or polyamide.

[0027] Furthermore, the thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups are one or more of CFRTP bars, BFRTP bars or AFRTP bars.

[0028] The joint strength of thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups varies depending on the type of thermoplastic FRP longitudinal bars and stirrups. Compared to GFRTP bars, the joint strength is higher when CFRTP bars, BFRTP bars, or AFRTP bars are used. This is likely because the interpenetration and fusion between the CFRTP bars, BFRTP bars, or AFRTP bars and the thermoplastic LCP fiber composite tapes is stronger than that between the GFRTP bars and the thermoplastic LCP fiber composite tapes.

[0029] Specifically, the shape of the thermoplastic FRP stirrups is one of circular, spiral or rectangular.

[0030] Specifically, the diameter of the thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups is 1 to 2 cm.

[0031] Specifically, the binding refers to cross-reciprocating winding.

[0032] Specifically, the number of the binding circles is 3 to 6 circles.

[0033] A thermoplastic FRP reinforcement cage is prepared by the above preparation method.

[0034] The thermoplastic FRP reinforcement cage of the present invention can be used in concrete components.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention adopts a double melting method and selects thermoplastic LCP fiber composite tapes, so that the thermoplastic FRP longitudinal bars, thermoplastic FRP stirrups and thermoplastic LCP fiber composite tapes penetrate and fully fuse with each other at the nodes by melting, thereby improving the structural integrity of the nodes and the mechanical properties of the nodes, which is beneficial to improving the strength of the nodes where the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the preparation method of the thermoplastic FRP cage in Example 1;

[0038] Figure 2 Schematic diagram of the structure of the thermoplastic FRP cage in Example 1;

[0039] Figure 3 Schematic diagram of the structure of the thermoplastic FRP cage of Example 11;

[0040] Figure 4 Schematic diagram of the structure of the thermoplastic FRP cage of Example 12;

[0041] Figures 1 to 4 Among them, 1-thermoplastic FRP longitudinal reinforcement, 2-thermoplastic FRP stirrups, 3-thermoplastic LCP fiber composite tape, 4-electric heating equipment. DETAILED DESCRIPTION

[0042] The present invention is further described below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Experimental methods in the following examples where specific conditions are not specified are generally performed in accordance with conventional conditions in the art or the conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed in the present invention.

[0043] In the embodiments and comparative examples of the present invention, the thermoplastic resins used in the CFRTP bars, BFRTP bars, AFRTP bars and GFRTP bars are all polypropylene; the liquid crystal polyarylate fibers are from Ningbo Jujia New Material Technology Co., Ltd. JA280 in the series, and its molding temperature is 285℃.

[0044] Example 1

[0045] This embodiment provides a thermoplastic FRP cage, the preparation method of which includes the following steps: Figure 1 As shown:

[0046] S1. The thermoplastic FRP longitudinal reinforcement 1 is placed inside the thermoplastic FRP stirrup 2 so that the thermoplastic FRP longitudinal reinforcement 1 and the thermoplastic FRP stirrup 2 are in contact and connected;

[0047] S2. Using electric heating equipment 4 in the contact connection of the thermoplastic FRP longitudinal reinforcement 1 and the thermoplastic FRP stirrup 2 is melted, so that the thermoplastic FRP longitudinal reinforcement 1 and the thermoplastic FRP stirrup 2 are fused together to form a node;

[0048] S3. Using a thermoplastic LCP (Liquid Crystal Polyester, liquid crystal polymer) fiber composite tape 3 by cross-winding and reciprocating binding the node, and tightening it so that the inner surface of the thermoplastic LCP fiber composite tape 3 is in close contact with the outer surface of the thermoplastic FRP longitudinal reinforcement 1 and the thermoplastic FRP stirrup 2;

[0049] S4 using an electric heating device 4 of the thermoplastic LCP fiber composite material 3 with a melt treatment, so that it is combined with the node to obtain the thermoplastic FRP cage, such as Figure 2 As shown;

[0050] in:

[0051] The thermoplastic LCP fiber composite tape is composed of fiber layers containing liquid crystal polyarylate fibers through a laminated structure, and the layers are bonded by epoxy resin, and the number of fiber layers is 4;

[0052] The fiber layer containing liquid crystal polyarylate fibers is made by weaving liquid crystal polyarylate fibers, and the weaving adopts a two-dimensional weaving method with a twill structure;

[0053] The number of binding circles is 4; the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are both thermoplastic carbon fiber reinforced composite (CFRTP) bars; the shape of the thermoplastic FRP stirrups is circular; the diameters of the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are both 2 cm; the width of the thermoplastic LCP fiber composite tape is 3 cm.

[0054] Examples 2 to 4 and Comparative Examples 1 to 2

[0055] Examples 2 to 4 and Comparative Examples 1 to 2 provide different thermoplastic FRP reinforcement cages. The difference between their preparation methods and those of Example 1 is only that the width of the thermoplastic LCP fiber composite tape is different. The rest is consistent with Example 1, as shown in the following table:

[0056] Table 1 Width of thermoplastic LCP fiber composite tapes of Examples 1 to 4 and Comparative Examples 1 to 2

[0057] Width of thermoplastic LCP fiber composite tape / cm Example 1 3 Example 2 2 Example 3 4 Example 4 5 Comparative Example 1 8 Comparative Example 2 1

[0058] Examples 5 to 7

[0059] Examples 5 to 7 provide different thermoplastic FRP reinforcement cages. The difference between their preparation methods and those of Example 1 is only in the different types of thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups. The rest is consistent with Example 1, as shown in the following table:

[0060] Table 2 Types of thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups in Examples 1 and 5-7

[0061] Types of Thermoplastic FRP Longitudinal Rebars and Thermoplastic FRP Stirrups Example 1 CFRTP bars Example 5 BFRTP bars Example 6 AFRTP ribs Example 7 GFRTP bars

[0062] Examples 8 to 10

[0063] Examples 8 to 10 provide different thermoplastic FRP reinforcement cages. The difference between their preparation methods and those of Example 1 is only that the number of fiber layers in the thermoplastic LCP fiber composite tape is different. The rest is consistent with Example 1, as shown in the following table:

[0064] Table 3 Number of fiber layers in Examples 1 and 8 to 10

[0065] Number of fiber layers / layers Example 1 4 Example 8 2 Example 9 6 Example 10 8

[0066] Example 11

[0067] This embodiment provides a thermoplastic FRP reinforcement cage. The difference between its preparation method and that of embodiment 1 is that the shape of the thermoplastic FRP stirrup is spiral. The obtained thermoplastic FRP reinforcement cage is as follows: Figure 3 As shown, the rest are consistent with Example 1.

[0068] Example 12

[0069] This embodiment provides a thermoplastic FRP reinforcement cage. The difference between its preparation method and that of embodiment 1 is that the shape of the thermoplastic FRP stirrup is rectangular. The obtained thermoplastic FRP reinforcement cage is as follows: Figure 4 As shown, the rest are consistent with Example 1.

[0070] Comparative Example 3

[0071] This comparative example provides a thermoplastic FRP reinforcement cage. The only difference between its preparation method and that of Example 1 is that step S2 is not performed, and the rest is the same as that of Example 1.

[0072] Comparative Example 4

[0073] This comparative example provides a thermoplastic FRP reinforcement cage, the preparation method of which differs from that of Example 1 only in that no thermoplastic LCP fiber composite tape is used, namely:

[0074] S1. Place the thermoplastic FRP longitudinal reinforcement 1 inside the thermoplastic FRP stirrup 2 so that the thermoplastic FRP longitudinal reinforcement 1 and the thermoplastic FRP stirrup 2 are in contact and connected, with the connection point being a node;

[0075] S2. The nodes are heated to 450°C by an electric heating device 4 for melting, cooling and solidifying to obtain a thermoplastic FRP reinforcement cage;

[0076] The rest are consistent with Example 1.

[0077] Comparative Example 5

[0078] This comparative example provides a thermoplastic FRP reinforcement cage. The only difference in its preparation method from Example 1 is that a thermoplastic carbon fiber reinforced composite material (CFRTP) tape is used instead of a thermoplastic LCP fiber composite tape. Moreover, the difference between the thermoplastic carbon fiber reinforced composite material (CFRTP) tape and the CFRTP reinforcement is only the shape of the material. The CFRTP tape is a strip with a width of 3 cm. The rest is consistent with Example 1.

[0079] Comparative Example 6

[0080] This comparative example provides a thermoplastic FRP reinforcement cage. The only difference between its preparation method and that of Example 1 is that a single-layer fiber layer containing liquid crystal polyarylate fibers is used instead of the thermoplastic LCP fiber composite tape. The rest is the same as that of Example 1.

[0081] Performance Testing

[0082] The strength of the thermoplastic reinforcement cages of each embodiment and each comparative example was tested at the nodes. The specific testing process was as follows: a tensile force was applied to the nodes of the thermoplastic reinforcement cages of each embodiment and each comparative example using an MTS1000 universal testing machine. The test was stopped when the stirrups and longitudinal bars were completely separated, thereby measuring the strength of the nodes of different thermoplastic reinforcement cages.

[0083] The test results are as follows:

[0084] Table 4 Node strength test results of Examples 1 to 4 and Comparative Examples 1 to 2

[0085] Width of thermoplastic LCP fiber composite tape / cm Node strength / MPa Example 1 3 45 Example 2 2 35 Example 3 4 52 Example 4 5 56 Comparative Example 1 8 26 Comparative Example 2 1 19

[0086] It can be seen from Table 4 that when the width of the thermoplastic LCP fiber composite tape is in the range of 2 to 5 cm, the strength of the node where the thermoplastic FRP longitudinal reinforcement and the thermoplastic FRP stirrups are connected can be improved.

[0087] When the width of the thermoplastic LCP fiber composite tape is within the range of 2 to 5 cm, the contact area between the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups can be better increased, thereby better utilizing the restraint performance of the thermoplastic LCP fiber composite tape through binding, which is beneficial to improving the structural integrity of the node and also beneficial to improving the mechanical properties of the node. Therefore, the strength of the node where the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups are connected can be better improved.

[0088] In Comparative Example 1, the thermoplastic LCP fiber composite tape may be too wide, causing kinks and wrinkles in the thermoplastic LCP fiber composite tape during the binding process, which is not conducive to the restraint performance, affects the structural integrity of the node, reduces the mechanical properties of the node, and cannot better improve the strength of the node where the thermoplastic FRP longitudinal reinforcement and the thermoplastic FRP stirrups are connected.

[0089] Table 5 Node strength test results of Examples 1 and 5 to 7

[0090] Types of Thermoplastic FRP Longitudinal Rebars and Thermoplastic FRP Stirrups Node strength / MPa Example 1 CFRTP bars 45 Example 5 BFRTP bars 48 Example 6 AFRTP ribs 40 Example 7 GFRTP bars 35

[0091] It can be seen from Table 5 that the strength at the node is higher when CFRTP bars, BFRTP bars or AFRTP bars are used compared with GFRTP bars. This may be because the degree of mutual penetration and fusion between CFRTP bars, BFRTP bars or AFRTP bars and thermoplastic LCP fiber composite tapes is stronger than that between GFRTP bars and thermoplastic LCP fiber composite tapes.

[0092] Table 6 Number of fiber layers in Examples 1 and 8 to 10

[0093] Number of fiber layers / layers Node strength / MPa Example 1 4 45 Example 8 2 37 Example 9 6 52 Example 10 8 55

[0094] It can be seen from Table 6 that when the number of fiber layers in the thermoplastic LCP fiber composite tape is in the range of 2 to 8 layers, especially in the range of 6 to 8 layers, the strength of the nodes where the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected can be better improved.

[0095] Table 7 Node strength test results of Example 1 and Comparative Examples 3 to 6

[0096]

[0097] As can be seen from Table 7, the absence of step S2 or the thermoplastic LCP fiber composite tape, as well as the use of CFRTP tape or a single layer of fiber layer containing liquid crystal polyarylate fibers instead of the thermoplastic LCP fiber composite tape, will significantly reduce the strength of the node where the thermoplastic FRP longitudinal bars and thermoplastic FRP stirrups are connected.

[0098] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a thermoplastic FRP reinforcement cage, characterized in that: The steps include: S1. Place the thermoplastic FRP longitudinal bars inside the thermoplastic FRP stirrups so that the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups are in contact and connected; S2. Perform a melting process at the contact joints between the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups to fuse the thermoplastic FRP longitudinal bars and the thermoplastic FRP stirrups together to form a node; S3 using thermoplastic LCP fiber composite tape tying the node; S4 is melt-treated the thermoplastic LCP fiber composite tape, so that it is combined with the node to obtain the thermoplastic FRP cage; The thermoplastic LCP fiber composite tape is composed of fiber layers containing liquid crystal polyarylate fibers in a laminated structure, and the layers are bonded by resin; the width of the thermoplastic LCP fiber composite tape is 2 to 5 cm; the number of fiber layers in the thermoplastic LCP fiber composite tape is 2 to 8; The thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups are one or more of CFRTP bars, BFRTP bars or AFRTP bars.

2. The preparation method according to claim 1, characterized in that The width of the thermoplastic LCP fiber composite tape is 4 to 5 cm.

3. The preparation method according to claim 1, characterized in that: The thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups are one or more of CFRTP bars, BFRTP bars, GFRTP bars or AFRTP bars.

4. The preparation method according to claim 1, characterized in that The shape of the thermoplastic FRP stirrups is one of circular, spiral or rectangular.

5. The preparation method according to claim 1, characterized in that: The fiber layer containing liquid crystal polyarylate fibers is made by weaving liquid crystal polyarylate fibers, or is made by weaving liquid crystal polyarylate fibers and auxiliary fibers.

6. The preparation method according to claim 1, characterized in that: The number of fiber layers in the thermoplastic LCP fiber composite tape is 6 to 8.

7. The preparation method according to claim 1, characterized in that: The diameter of the thermoplastic FRP longitudinal bars and / or thermoplastic FRP stirrups is 1 to 2 cm.

8. A thermoplastic FRP reinforcement cage prepared by the preparation method according to any one of claims 1 to 7.

Images