An integrally formed fiber-reinforced composite truss and its preparation method

Abstract

The present invention discloses an integrally formed fiber-reinforced composite truss and a preparation method thereof, including an FRP truss with a hollow structure and metal joints arranged at both ends of the FRP truss; polyurethane foam is filled in the FRP truss; the outer wall of the FRP truss is integrally wound with FRP prepreg; the overall quality of this truss is light and the bearing capacity is high.

Description

Technical Field

[0001] The present invention relates to the field of bridge engineering, and particularly to an integrally formed fiber-reinforced composite truss and a preparation method thereof. Background Art

[0002] Military bridges are temporary bridges erected to ensure the smooth passage of troops, weapons, and equipment across obstacles such as rivers, canyons, ditches, and battle-damaged roads. Among many types of military bridges, an important type is the demountable bridge, also known as the prefabricated bridge. Such bridges mostly adopt a truss structure, with truss units made of metal rods, and then multiple truss units are connected and assembled into a truss bridge using simple parts. The traditional truss bridge is made of steel. For example, the ZB-200 steel highway bridge in service in our army, each rod is spliced together by welding. This kind of steel material is heavy, requires a large number of personnel for assembly and erection, and the erection efficiency is not high.

[0003] Fiber Reinforced Polymer (FRP) has the advantages of high strength, light weight, corrosion resistance, and fatigue resistance. It has strong designability, with its strength being several times that of steel tie rods and its density being 1 / 5 of that of steel. It has been widely used in military bridges, aerospace, and civil engineering structures. Developing a truss with light weight, high bearing capacity, and simple and rapid assembly using FRP materials is of great significance. Summary of the Invention

[0004] The object of the present invention is to provide an integrally formed fiber-reinforced composite truss and a preparation method thereof.

[0005] The innovative point of the object of the present invention lies in: using two FRP components with the same structure and integrally formed to be buckled and combined to form an FRP truss, filling polyurethane foam in the middle, setting metal joints at both ends, winding prepreg cloth on the outside, and setting strengthening blocks at the joints to further improve the strength of the joints, with strong designability, high bearing capacity, and light overall mass.

[0006] To achieve the above object of the invention, the technical solution of the present invention is:

[0007] An integrally formed fiber-reinforced composite truss, comprising an FRP truss with a hollow structure and metal joints arranged at both ends of the FRP truss; polyurethane foam is filled in the FRP truss; the outer wall of the FRP truss is integrally wound with FRP prepreg cloth.

[0008] The FRP truss is formed by butt-jointing and splicing two FRP members with exactly the same structure and U-shaped cross-sections for each member; the FRP member includes upper and lower chord members; several vertical web members are evenly arranged between the upper and lower chord members to form several rectangular frames; a diamond-shaped support structure composed of four diagonal web members connected end to end is arranged in each rectangular frame, and the vertices of the support structure are respectively connected to the middle parts of the members of each rectangular frame; the FRP member is integrally formed by vacuum-assisted molding; reinforcing blocks are arranged in the inner cavities at the joints of the upper and lower chord members and the vertical web members and at the joints of the support structure and the members of the rectangular frame, and are fixed by structural adhesive.

[0009] Further, the metal joints are respectively inserted into the two ends of the upper chord member and the lower chord member, and are fixed by structural adhesive and shear pins; one end of the metal joint is a single-ear or double-ear connecting seat, and the end face of the other end is in the shape of a dovetail, serrated or wavy.

[0010] Further, the reinforcing blocks include T-shaped reinforcing blocks arranged in the inner cavities at the joints of the upper and lower chord members and the vertical web members, first K-shaped reinforcing blocks arranged in the inner cavities at the joints of the diagonal web members and the upper and lower chord members, second K-shaped reinforcing blocks arranged in the inner cavities at the joints of the diagonal web members and the vertical web members, and cross-shaped reinforcing blocks.

[0011] Further, the reinforcing blocks are made of solid wood or balsa wood.

[0012] Further, the FRP prepreg is CFRP prepreg, glass fiber prepreg or basalt fiber prepreg; the FRP prepreg can be wound and cured in multiple times according to the designed wall thickness of the truss, and at least 7 layers are wound each time.

[0013] A preparation method for an integrally formed fiber-reinforced composite material truss includes the following steps:

[0014] Step S1: Fabricating the FRP member: including seven steps of preparing the mold, cutting the material, laying the fiber mat and plain cloth, laying the flow guide net and the vacuum bag film, evacuating, resin adsorption and introduction, and curing; laying 6-10 layers of FRP prepreg on a predetermined mold, and curing and integrally forming by vacuum adsorption process. The specific curing temperature and time are determined by the selected FRP prepreg material;

[0015] Step S2: Fabricating the metal joint: selecting a high-strength metal block, machining the metal joint according to the size of the FRP member, machining a connecting seat and opening a through hole at one end of the metal joint, and machining the end face at the other end.

[0016] Step S3: Assemble FRP components, metal joints, and reinforcement blocks and inject polyurethane foam: Control the size of the entire FRP truss by adjusting the axial position of the through-holes of the metal joints. Apply a layer of structural adhesive on the contact surfaces between each metal joint and the FRP components, and also apply a layer of structural adhesive on the contact surfaces between the reinforcement blocks and the FRP components. Apply a certain amount of pressure on the upper and lower FRP components to tightly bond the upper and lower FRP components, metal joints, and reinforcement blocks together; then drill holes in the internal hollow positions to inject polyurethane foam;

[0017] Step S4: Cut FRP prepreg, wind, and cure: Cut prepregs at different angles according to the size requirements of the FRP truss, including prepreg A in the 0° / 90° direction, prepreg B in the 0° direction, prepreg C in the 90° direction, and prepreg D in the ±45° direction; Wind prepregs on the upper and lower chords, vertical web members, and diagonal web members, and lay and wind them in the order of 1 layer of A, 4 layers of B, 1 layer of C, and 1 to 2 layers of D or A; Wind 1 to 2 more layers of prepreg D at the intersections of the members, and wind 1 to 2 more layers of prepreg D or A outside the joints between the FRP components and the metal joints to strengthen the intersections of the members and improve the strength; Place the FRP truss with wound prepregs flat on a flat plate, and lay a release cloth, a flow net, a flow tube, and a vacuum bag according to the vacuum adsorption process flow, and perform vacuum high-temperature curing to form the whole. Slowly raise the temperature to 80°, hold for one hour, raise the temperature to 100°, hold for 1 hour, raise the temperature to 130°, hold for 2 hours, and naturally cool down after complete curing, and demold and cure to form; Wind and cure 3 to 4 times according to this method according to the stress of the FRP truss structure, and finally obtain a cured and formed FRP truss;

[0018] Step S5: Process single and double ear joints on the metal joints; Enlarge the diameter of the through-holes opened in Step S2 according to the structural size requirements; Control the longitudinal and transverse dimensions of the FRP truss by the axial distance of the 4 through-holes, and then cut the through-holes from the outside to the inside according to the design dimensions to process single and double ears.

[0019] Step S6: Process shear pin holes on the metal joints and assemble shear pins, and process bolt holes and assemble high-strength bolts.

[0020] The beneficial effects of the present invention are:

[0021] First: Use two FRP components with the same structure and integrally formed to be buckled and assembled to form an FRP truss, inject polyurethane foam in the middle, set metal joints at both ends, wind FRP prepregs on the outside, and set reinforcement blocks at the intersections of the members to further improve the strength at the intersections of the members. The structure has good integrity, high bearing capacity, and the overall weight of the truss can be reduced by 33%.

[0022] Second: It adopts step-by-step integral curing and forming, and the laying method and the number of laying layers can be optimized according to the stress condition of the FRP truss structure, with strong designability.

[0023] Third: A diamond-shaped support structure is arranged inside the rectangular frame to ensure the stability of the truss structure. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of the present invention.

[0025] Figure 2 It is a schematic structural diagram of the FRP component.

[0026] Figure 3 It is a schematic structural diagram of the FRP component and the reinforcing block.

[0027] Figure 4 Schematic structural diagram of the metal joint.

[0028] In the figure: 100 is the FRP truss, 110 is the FRP component, 111 is the upper chord, 112 is the lower chord, 113 is the vertical web member, 114 is the diagonal web member, 200 is the metal joint, 201 is the shear pin, 301 is the T-shaped reinforcing block, 302 is the first K-shaped reinforcing block, 303 is the second K-shaped reinforcing block, and 304 is the cross-shaped reinforcing block. Detailed Embodiment

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings.

[0030] (Refer to Figure 1 、 Figure 2 ) An integrally formed fiber-reinforced composite material truss, including an FRP truss 100 with a hollow structure and metal joints 200 arranged at both ends of the FRP truss 100; polyurethane foam is filled in the FRP truss 100; the outer wall of the FRP truss 100 is entirely wound with FRP prepreg;

[0031] The FRP truss 100 is formed by snap-fitting two FRP components 110 with exactly the same structure and U-shaped cross-sections of each member; the FRP component 110 includes upper and lower chords 111, 112; several vertical web members 113 are evenly arranged between the upper and lower chords 111, 112 to form several rectangular frames; a diamond-shaped support structure composed of four diagonal web members 114 connected end to end is arranged inside each rectangular frame, and the vertices of the support structure are respectively connected to the middle parts of the various members of the rectangular frame; the FRP component 110 is integrally formed by vacuum hot pressing assistance; reinforcing blocks are arranged in the inner cavities at the joints of the upper and lower chords 111, 112 and the vertical web member 113, and at the joints of the support structure and the various members of the rectangular frame, and are fixed by structural adhesive.

[0032] Further, (refer to Figure 4 ) the metal joints 200 are respectively inserted at both ends of the upper chord 111 and the lower chord 112, and are fixed by structural adhesive and shear pins 201; one end face of the metal joint 200 is in a dovetail shape, or can also be in a serrated shape or a wavy shape, and the other end is a single-ear or double-ear connecting seat. The metal joint 200 is a prior art. Chinese Patent CN114561864A discloses a high-load-bearing integrally formed composite material joint and its manufacturing method. The structure and manufacturing method of the metal joint 200 are disclosed in this patent and will not be elaborated here.

[0033] Further, (refer to Figure 3 ) the reinforcing blocks include a T-shaped reinforcing block 301 arranged in the inner cavity at the connection of the upper and lower chords 111, 112 and the vertical web member 113, a first K-shaped reinforcing block 302 arranged in the inner cavity at the connection of the inclined web member 114 and the upper and lower chords 111, 112, a second K-shaped reinforcing block 303 arranged in the inner cavity at the connection of the inclined web member 114 and the vertical web member 113, and a cross-shaped reinforcing block 304.

[0034] Further, the reinforcing blocks are made of solid wood or balsa wood.

[0035] Further, the FRP prepreg is CFRP prepreg, glass fiber prepreg or basalt fiber prepreg; the FRP prepreg can be wound and cured in multiple times according to the designed wall thickness of the truss, with at least 7 layers wound each time.

[0036] A preparation method of an integrally formed fiber-reinforced composite material truss includes the following steps:

[0037] Step S1: Manufacturing FRP components: including seven steps of preparing a mold, cutting materials, laying glass fiber mats and FRP prepregs, laying a flow guiding net and a vacuum bag film, evacuating, resin adsorption and introduction, and curing; laying 6 - 10 layers of prepregs on a predetermined mold, and curing and integrally forming by a vacuum adsorption process. The specific curing temperature and time are determined by the selected FRP prepreg material;

[0038] Step S2: Manufacturing the metal joints 200; selecting high-strength metal blocks (such as 30CrMnSi metal blocks), machining the metal joints 200 according to the dimensions of the FRP components 110, machining a connecting seat and opening a through hole (generally, the diameter of the through hole is D = 30 mm) at one end of the metal joint 200, and the other end face can be in a dovetail shape, serrated shape, wavy shape, etc. The purpose is to increase the contact area between the end face of the metal joint 200 and the polyurethane foam after filling the polyurethane foam, optimize the force on the metal joint, and improve the firmness;

[0039] Step S3: Assemble the FRP member 110, metal joint 200, reinforcement blocks and inject polyurethane foam: Control the size of the entire FRP truss by adjusting the axial position of the through-hole of the metal joint 200. When assembling, apply a layer of structural adhesive on the contact surfaces of each reinforcement block and the metal joint 200 with the FRP member 110, and apply a certain amount of pressure on the upper and lower FRP members 110 to tightly bond the upper and lower FRP members 110, metal joint 200 and reinforcement blocks together; then drill holes in the internal hollow position to inject polyurethane foam;

[0040] Step S4: Cut the FRP prepreg, wind and cure it: Cut the prepreg at different angles according to the size requirements of the FRP truss 100, including the 0° / 90° direction prepreg A, 0° direction prepreg B, 90° direction prepreg C, and ±45° direction prepreg D; Wind the prepreg on the upper and lower chord members 111, 112, vertical web members 113, and diagonal web members 114, and lay and wind it in the order of 1 layer of A, 4 layers of B, 1 layer of C, and 1 to 2 layers of D or A; Wind 1 to 2 more layers of prepreg D at the intersections of the members; Wind 1 to 2 more layers of prepreg D or A outside the joint between the FRP member 110 and the metal joint 200 to strengthen the intersections of the members and the metal joint 200 and improve the strength; Place the FRP truss 100 wound with the FRP prepreg flat on a flat plate, and lay the release cloth, flow net, flow tube, vacuum bag, etc. according to the vacuum adsorption process flow, evacuate the air and cure it at high temperature to form as a whole. Slowly raise the temperature to 80°, and keep it for one hour; Raise the temperature to 100°, and keep it for 1 hour; Raise the temperature to 130°, and keep it for 2 hours. After complete curing, cool it naturally and demold and cure it; Wind and cure it 3 to 4 times according to this method according to the stress magnitude of the FRP truss 100 structure, and finally obtain the cured and formed FRP truss 100;

[0041] Step S5: Process single and double ear joints on the metal joint 200: Enlarge the diameter of the through-hole opened in Step S2 (from a diameter of 30 mm to a diameter of 50 mm) according to the structural dimension requirements, and control the longitudinal and transverse dimensions of the FRP truss 100 by the axial distance of 4 through-holes; Then use a special cemented carbide tool to cut the through-hole from the outside to the inside (horizontal direction) according to the design dimensions to process single and double ears. Two metal joints on one side are single ears, and two metal joints on the other side are double ears.

[0042] Step S6: Machining shear pin holes and assembling shear pins 201: Use a numerical control machine tool to drill holes. At the position of the metal joint 200, shear pin holes are machined. Among them, 28 shear pin holes are machined on the inner and outer long faces, 14 shear pin holes are machined on the upper and lower short faces, and 2 to 4 bolt holes are machined at the arc of the joint. The diameter of the shear pin hole is 7.8 mm, and the hole depth is 25 mm. Assemble shear pins 201 with a diameter of 8 mm and a length of 25 mm into the shear pin holes to achieve high-strength connection between the wound FRP prepreg and the inner core of the metal joint 200 through interference fit. High-strength bolts are installed at the joint, and a certain pre-tightening force is applied. Of course, the specific number, diameter, and depth of the shear pin holes and bolt holes can be adjusted according to the actual size.

[0043] The described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

Claims

1. An integrally formed fiber-reinforced composite truss, characterized in that: It includes an FRP truss (100) with a hollow structure and metal joints (200) arranged at both ends of the FRP truss (100); polyurethane foam is filled in the FRP truss (100); the outer wall of the FRP truss (100) is entirely wound with FRP prepreg cloth; The FRP truss (100) is formed by snap-fitting two FRP components (110) with exactly the same structure and each rod cross-section being U-shaped; the FRP component (110) includes upper and lower chord bars (111, 112); several vertical web members (113) are evenly arranged between the upper and lower chord bars (111, 112) to form several rectangular frames; a diamond-shaped support structure composed of four diagonal web members (114) connected end to end is arranged in each rectangular frame, and the vertices of the support structure are respectively connected to the middle parts of the various rods of the rectangular frame; the FRP component (110) is integrally formed by vacuum hot pressing assistance; reinforcing blocks are arranged in the inner cavities at the joints of the upper and lower chord bars (111, 112) and the vertical web members (113), and in the inner cavities at the joints of the support structure and the various rods of the rectangular frame, and are fixed by structural adhesive.

2. The integrally formed fiber-reinforced composite truss according to claim 1, wherein: The metal joints (200) are respectively inserted into the two ends of the upper chord bar (111) and the lower chord bar (112), and are fixed by structural adhesive and shear pins (201); one end of the metal joint (200) is a single-ear or double-ear connection seat, and the end face of the other end is dovetail-shaped, serrated or wavy.

3. The integrally formed fiber-reinforced composite truss according to claim 1, characterized in that: The reinforcing blocks include T-shaped reinforcing blocks (301) arranged in the inner cavities at the joints of the upper and lower chord bars (111, 112) and the vertical web members (113), first K-shaped reinforcing blocks (302) arranged in the inner cavities at the joints of the diagonal web members (114) and the upper and lower chord bars (111, 112), second K-shaped reinforcing blocks (303) arranged in the inner cavities at the joints of the diagonal web members (114) and the vertical web members (113), and cross-shaped reinforcing blocks (304); the reinforcing blocks are made of solid wood or balsa wood.

4. A one-piece fiber-reinforced composite truss according to claim 1, characterized in that: The FRP prepreg cloth is CFRP prepreg cloth, glass fiber prepreg cloth or basalt fiber prepreg cloth; the FRP prepreg cloth is wound in several times, and at least 7 layers are wound each time.

5. A method for preparing an integrally formed fiber-reinforced composite truss according to any one of claims 1-4, characterized in that: It includes the following steps: Step S1: Fabricate the FRP component (110): It includes seven steps of preparing the mold, cutting the material, laying the fiber mat and plain cloth, laying the flow guiding net and vacuum bag film, evacuating, resin adsorption and introduction, and curing; 6-10 layers of FRP prepreg cloth are laid on a predetermined mold, and the whole is formed by curing using a vacuum adsorption process. The specific curing temperature and time are determined by the selected FRP prepreg cloth material; Step S2: Fabricate the metal joint (200): Select a high-strength metal block, machine the metal joint (200) according to the size of the FRP component (110), machine a connection seat and a through hole at one end of the metal joint (200), and machine the end face at the other end; Step S3: Assemble the FRP member (110), metal joint (200), reinforcement block and inject polyurethane foam: Control the size of the entire FRP truss by adjusting the axial position of the through-hole of the metal joint (200). When assembling, apply a layer of structural adhesive on the contact surface between each metal joint (200) and the FRP member (110), apply a layer of structural adhesive on the contact surface between each reinforcement block and the FRP member (110), and apply a certain amount of pressure on the upper and lower FRP members (110) to tightly bond the upper and lower FRP members (110), metal joints (200) and reinforcement blocks into one body; then drill holes in the internal hollow position and inject polyurethane foam; Step S4: Cut the FRP prepreg, wind and cure: Cut the prepreg at different angles according to the size requirements of the FRP truss (100), including the 0° / 90° direction prepreg A, 0° direction prepreg B, 90° direction prepreg C, ±45° direction prepreg D; Wind the prepreg on the upper and lower chords (111, 112), vertical web members (113), and diagonal web members (114), and lay and wind them in the order of 1 layer of A, 4 layers of B, 1 layer of C, 1 to 2 layers of D or A; Wind 1 to 2 more layers of prepreg D at the intersections of the members; Wind 1 to 2 more layers of prepreg D or A outside the joint between the FRP member (110) and the metal joint (200) to strengthen the intersections of the members and the metal joint (200) and improve the strength; Place the FRP truss (100) wound with the FRP prepreg flat on a flat plate, and according to the vacuum adsorption process flow, lay the release cloth, flow guide net, flow guide tube, and vacuum bag, evacuate the air and cure it at high temperature to form a whole. Slowly raise the temperature to 80°, hold for one hour, raise the temperature to 100°, hold for 1 hour, raise the temperature to 130°, hold for 2 hours, and naturally cool down after complete curing, and demold and cure to form; Wind and cure 3 to 4 times according to this method according to the force borne by the structure of the FRP truss (100), and finally obtain the cured and formed FRP truss (100); Step S5: Process single and double ear joints on the metal joint (200); Enlarge the diameter of the through-hole opened in Step S2 according to the structural dimension requirements; Control the longitudinal and transverse dimensions of the FRP truss (100) by the axial distance of the 4 through-holes, and then cut the through-hole from the outside to the inside according to the design dimensions to process single and double ears; Step S6: Process shear pin holes on the metal joint (200) and assemble shear pins (201), process bolt holes and assemble high-strength bolts.

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