Composite material section rigidity variable connecting joint and connecting method

Abstract

The application discloses a composite material section variable stiffness connecting node and a connecting method. The composite material section variable stiffness connecting node comprises a fiber reinforced composite material rod, a metal lining connected with one end of the fiber reinforced composite material rod, splicing plates distributed on both sides of the fiber reinforced composite material rod and a locking assembly. The fiber reinforced composite material rod and the metal lining are both hollow tubes with square cross sections. The connection between the metal lining and the fiber reinforced composite material rod is a gradually changing thickness connection. The inner wall of one end of the fiber reinforced composite material rod is provided with a first connecting inclined surface. The outer wall of the metal lining is provided with a second connecting inclined surface matched with the first connecting inclined surface. A glue layer is arranged between the first connecting inclined surface and the second connecting inclined surface. The metal lining, the fiber reinforced composite material rod and the splicing plates are provided with through holes for mounting the locking assembly. The application has the effects of high connecting node strength, good damage ductility and uniform bolt load distribution.

Description

Technical Field

[0001] This invention relates to the field of civil engineering structural components, and in particular to a composite material profile variable stiffness connection node and connection method. Background Technology

[0002] Currently, bridge structures face a significant problem in harsh environments such as marine, humid, and saline-alkali lands: steel corrosion. Researchers have implemented numerous methods to prevent this corrosion, but all have limitations. Fiber-reinforced polymer (FRP) composites, with their advantages of high strength, lightweight, corrosion resistance, and fatigue resistance, have gained increasing attention in civil engineering. Besides the extensive use of FRP sheets and reinforcing bars in structural reinforcement and repair, all-FRP new structures composed of pultruded FRP profiles are also receiving growing attention in the engineering community, especially in truss structures and large-span spatial structures, where they offer significant advantages in weight reduction and improved durability. Currently, the main connection methods for FRP profile structures include adhesive bonding, bolting, and a hybrid of adhesive and bolt connections. Bolting, with its advantages of convenient installation, disassembly, high reliability, and ease of quality inspection, is the most commonly used connection method.

[0003] Weak FRP joints are a key factor limiting the development of FRP trusses. Existing truss connection nodes cannot achieve efficient connections for FRP profiles (connection efficiency is only 20%~30%), resulting in the ineffective utilization of the high strength of FRP profiles, low material utilization, and failure to effectively realize the lightweight and economic advantages of the designed structure. Furthermore, the anisotropy of FRP makes the joints prone to localized splitting failure due to stress concentration, and the failure is brittle, compromising structural safety. In addition, FRP bolted joints also suffer from uneven load distribution among different bolts, leading to premature failure of some bolts and structural failure.

[0004] Therefore, a new node connection scheme is needed to solve the above problems by preventing premature failure of nodes in composite truss structures, improving ductility, and suppressing uneven load distribution. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing composite truss structure square tube components, such as premature node failure, poor ductility, and uneven load distribution, and to propose a composite material profile variable stiffness connection node and connection method that is reliable, high-strength, and has good ductility.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a variable stiffness connection node for composite material profiles, comprising a fiber-reinforced composite material rod, a metal liner inserted into one end of the fiber-reinforced composite material rod, splicing plates distributed on both sides of the fiber-reinforced composite material rod, and a locking assembly. Both the fiber-reinforced composite material rod and the metal liner are hollow tubular components with a square cross-section. The connection between the metal liner and the fiber-reinforced composite material rod is a thickness-gradient connection. A first connecting slope is provided on the inner wall of one end of the fiber-reinforced composite material rod, and a second connecting slope adapted to the first connecting slope is provided on the outer wall of the metal liner. An adhesive layer is bonded between the first connecting slope and the second connecting slope. Through holes for installing the locking assembly are provided in the metal liner, the fiber-reinforced composite material rod, and the splicing plates.

[0007] Furthermore, the cutting slopes of the first and second connecting bevels are ≤10%. By making certain cuts, and ensuring that the cut surfaces are flat, the wall thickness gradually changes. Since the wall thickness variation of the metal liner is consistent with the wall thickness variation of the fiber-reinforced composite rod, this type of joint is versatile and its length can be freely adjusted.

[0008] Furthermore, the outer wall dimension of the metal liner is smaller than the inner wall dimension of the fiber-reinforced composite rod. This results in a localized thickening of the joint area, thereby increasing the strength of the joint.

[0009] Furthermore, the metal liner has a positioning protrusion at one end facing the fiber-reinforced composite rod, which facilitates better positioning when the metal liner is inserted into the fiber-reinforced composite rod.

[0010] Furthermore, the metal liner and the splicing plate are made of relatively corrosion-resistant aluminum alloy or stainless steel.

[0011] Furthermore, the thickness of the splicing plate is at least half the wall thickness of the fiber-reinforced composite rod. As an example, the splicing plate can be rectangular. The specific shape of the splicing plate can be adjusted according to the actual engineering application.

[0012] Furthermore, the adhesive layer is made of epoxy resin. As an example, Olin polyurethane-modified epoxy resin DER791 can be used.

[0013] Furthermore, the thickness of the adhesive layer is set to 1~2mm.

[0014] Furthermore, there are several through holes, and the through holes are arranged in rows with equal spacing.

[0015] Preferably, the distance between the opening position of the through hole and the end of the fiber-reinforced composite rod is greater than four times the diameter of the through hole, and the distance between the through holes is greater than four times the diameter of the through hole.

[0016] Furthermore, the locking component is a bolt and nut assembly.

[0017] Secondly, the present invention also provides a connection method for the above-mentioned composite material profile variable stiffness connection node, comprising the following steps: 1) Cut the inner wall of one end of the fiber-reinforced composite rod to form a first connecting bevel, and cut the outer wall of the metal liner to form a second connecting bevel; 2) Grind the first and second connecting bevels, wipe the bonding area with a surface cleaner and apply adhesive material, insert the metal liner and fiber-reinforced composite rod, and form an adhesive layer between the first and second connecting bevels. 3) Place splicing plates on both sides of the assembly obtained in step 2) and align them to make holes; 4) Use locking components to connect the splicing plate, the assembly from step 2), and the components to be connected.

[0018] Compared with the prior art, the present invention provides a variable stiffness connection node and connection method for composite material profiles, which has the following beneficial effects: 1. Uniform bolt load distribution. In this invention, both the fiber-reinforced composite rods and the metal liner in the joint connection area have variable cross sections. The cross-sectional stiffness changes with the length of the rod. This variable stiffness design can effectively suppress the excessively high load ratio at the row of bolts furthest from the end of the rod, making the load distribution more uniform among the bolts, thereby improving the joint performance.

[0019] 2. High joint strength. Simple fiber-reinforced composite materials have low joint strength and are prone to brittle fracture due to their weak shear properties. The joint part of this invention uses a combination of fiber-reinforced composite material and metal, with local thickening, which utilizes the high shear strength of the metal material, thereby significantly improving the strength of the joint.

[0020] 3. Good fracture ductility. Fiber-reinforced composite materials are linear elastic materials, and the failure of the joints is also brittle. The joint part of this invention uses a combination of fiber-reinforced composite materials and metal, which utilizes the high ductility of the metal material to improve the ductility of the joint.

[0021] 4. By utilizing fiber-reinforced composite materials to protect easily corroded metal parts, the joints exhibit good corrosion resistance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a half-sectional view of the present invention; Figure 3 This is a structural schematic diagram of a fiber-reinforced composite rod. Figure 4 This is a schematic diagram of the metal liner structure; Figure 5 This is an exploded view of the part of the present invention.

[0024] Reference numerals: 1. Fiber-reinforced composite rod; 11. First connecting bevel; 2. Metal liner; 21. Second connecting bevel; 22. Positioning protrusion; 3. Splicing plate; 4. Locking assembly; 5. Adhesive layer; 6. Through hole. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0026] refer to Figures 1-5 This embodiment provides a variable stiffness connection node for composite material profiles, including a fiber-reinforced composite material rod 1, a metal liner 2 inserted into one end of the fiber-reinforced composite material rod 1, splicing plates 3 distributed on both sides of the fiber-reinforced composite material rod 1, and a locking assembly 4 for connection and fixation. Both the fiber-reinforced composite material rod 1 and the metal liner 2 are hollow tubular components with a square cross-section. The connection between the metal liner 2 and the fiber-reinforced composite material rod 1 is a thickness-gradient connection. A first connecting slope 11 is provided on the inner wall of one end of the fiber-reinforced composite material rod 1, and a second connecting slope 21 adapted to the first connecting slope 11 is provided on the outer wall of the metal liner. An adhesive layer 5 is bonded between the first connecting slope 11 and the second connecting slope 21. Through holes 6 for installing the locking assembly 4 are provided in the metal liner 2, the fiber-reinforced composite material rod 1, and the splicing plate 3.

[0027] In some specific embodiments, the cutting slopes of the first connecting slope 11 and the second connecting slope 21 are ≤10%. By making a certain cut, and ensuring that the cut surface is flat, the wall thickness gradually changes. Thus, the end of the fiber-reinforced composite rod has a concave frustum-shaped insertion interface, and the metal liner has a corresponding frustum-shaped insertion joint. Since the wall thickness variation of the metal liner is consistent with the wall thickness variation of the fiber-reinforced composite rod, this type of joint is versatile and its length can be freely adjusted.

[0028] In some specific embodiments, the outer wall dimension of the metal liner 2 is smaller than the inner wall dimension of the fiber-reinforced composite rod 1. This results in a localized thickening of the joint area, thereby increasing the strength of the joint.

[0029] In some specific implementation methods, such as Figure 4 As shown, the metal liner 2 has a positioning protrusion 22 at one end facing the fiber-reinforced composite rod 1, which facilitates a better positioning effect when the metal liner is inserted into the fiber-reinforced composite rod.

[0030] In some specific embodiments, the metal liner 2 and the splicing plate 3 are made of relatively corrosion-resistant aluminum alloy or stainless steel.

[0031] In some specific embodiments, the thickness of the splicing plate 3 is at least half the wall thickness of the fiber-reinforced composite rod 1. As an example, the splicing plate can be rectangular. The specific shape of the splicing plate can be adjusted according to the actual engineering application.

[0032] In some specific embodiments, the adhesive layer 5 is an epoxy adhesive. As an example, Olin polyurethane-modified epoxy resin DER791 can be used.

[0033] In some specific embodiments, the thickness of the adhesive layer 5 is set to 1~2mm.

[0034] In some specific implementation methods, refer to Figure 1 and Figure 5 The unit has a plurality of through holes 6, which are arranged in rows at equal intervals. Preferably, the distance between the opening position of the through hole and the end of the fiber-reinforced composite material rod is greater than four times the diameter of the through hole, and the distance between the through holes is greater than four times the diameter of the through hole.

[0035] In some specific embodiments, the locking component 4 is a bolt and nut assembly.

[0036] refer to Figures 1-5 The connection method for the variable stiffness connection node of the composite material profile includes the following steps: 1) Cut the inner wall of one end of the fiber-reinforced composite rod 1 to form a first connecting slope 11, and cut the outer wall of the metal liner 2 to form a second connecting slope 21; 2) Grind the first connecting bevel 11 and the second connecting bevel 21 until the fibers are visible. The grinding thickness is about 0.1 mm. Then, use a surface cleaner (such as Eagle Gold Cleaner) to wipe the surface of the bonding area and apply the adhesive material. Connect the metal liner 2 to the fiber reinforced composite rod 1. After the adhesive material between the first connecting bevel 11 and the second connecting bevel 21 is bonded and cured, an adhesive layer 5 is formed. 3) Place splicing plates 3 on both sides of the assembly obtained in step 2) and align them to make holes; 4) Use locking component 4 to connect splicing plate 3, the assembly in step 2), and the components to be connected.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0038] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A variable stiffness connection node for composite material profiles, characterized in that: The device includes a fiber-reinforced composite rod, a metal liner inserted into one end of the fiber-reinforced composite rod, splicing plates distributed on both sides of the fiber-reinforced composite rod, and a locking assembly. Both the fiber-reinforced composite rod and the metal liner are hollow tubular components with a square cross-section. The connection between the metal liner and the fiber-reinforced composite rod is a gradually changing thickness connection. The inner wall of one end of the fiber-reinforced composite rod is provided with a first connecting slope, and the outer wall of the metal liner is provided with a second connecting slope adapted to the first connecting slope. An adhesive layer is bonded between the first connecting slope and the second connecting slope. The metal liner, the fiber-reinforced composite rod, and the splicing plates are provided with through holes for installing the locking assembly.

2. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The cutting slopes of the first connecting slope and the second connecting slope are ≤10%.

3. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The outer wall dimension of the metal liner is smaller than the inner wall dimension of the fiber-reinforced composite rod.

4. The composite material profile variable stiffness connection node according to claim 3, characterized in that: The metal liner has a positioning protrusion at one end facing the fiber-reinforced composite rod.

5. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The metal liner and the splicing plate are made of aluminum alloy or stainless steel.

6. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The thickness of the splicing plate is at least half the wall thickness of the fiber-reinforced composite rod.

7. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The adhesive layer is made of epoxy resin; the thickness of the adhesive layer is set to 1~2mm.

8. The composite material profile variable stiffness connection node according to claim 1, characterized in that: There are several through holes, and the through holes are arranged in rows with equal spacing.

9. The composite material profile variable stiffness connection node according to claim 1, characterized in that: The locking component is a bolt and nut assembly.

10. A connection method for a composite material profile variable stiffness connection node as described in claim 1, characterized in that, Includes the following steps: 1) Cut the inner wall of one end of the fiber-reinforced composite rod to form a first connecting bevel, and cut the outer wall of the metal liner to form a second connecting bevel; 2) Grind the first and second connecting bevels, wipe the bonding area with a surface cleaner and apply adhesive material, insert the metal liner and fiber-reinforced composite rod, and form an adhesive layer between the first and second connecting bevels. 3) Place splicing plates on both sides of the assembly obtained in step 2) and align them to make holes; 4) Use locking components to connect the splicing plate, the assembly from step 2), and the components to be connected.

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