A device and method for bonding composite material circular tube and closed-cell foam core material

Abstract

The present invention discloses a device for adhesively connecting a composite material circular tube and a closed-cell foam core material, comprising: a thickness gauge, which is axially movably arranged in the composite material circular tube, and one end of the thickness gauge is provided with a first through hole, and the other end is provided with an open accommodating cavity connected to the first through hole; wherein the closed-cell foam core material is arranged in the open accommodating cavity; an upper pressure head, one end of which is movably arranged in the open accommodating cavity and abuts against one end of the closed-cell foam core material, and the other end passes through the first through hole; a lower pressure head, which is engaged in the composite material circular tube and abuts against the other end of the thickness gauge; a one-way valve, which is arranged at the axis of the lower pressure head and is used to inject glue into the thickness gauge. The present invention also discloses a method for adhesively connecting a composite material circular tube and a closed-cell foam core material, and the thickness of the glue layer is made as uniform as possible by controlling the rotational withdrawal speed and the injection speed of the thickness gauge.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive connection of composite material round tubes, and more specifically, to an adhesive connection device and method for composite material round tubes and closed-cell foam core materials. Background Art

[0002] Since the development of automobile lightweight technology, thin-walled tubes have been widely used in various parts of the car body due to their remarkable crash resistance and energy absorption capacity. Compared with traditional metal thin-walled tubes, composite thin-walled tubes have the advantages of light weight, energy absorption, and high specific energy absorption. However, their stress fluctuates violently during deformation, and their ability to withstand non-axial loads is weak. To address this problem, many projects fill metal core materials such as foam or honeycomb into hollow thin-walled tubes, and their mechanical properties have been effectively improved.

[0003] However, the most important thing in the preparation of foam-filled composite thin-walled tubes is to achieve effective bonding between the core material and the outer thin-walled tube, and to ensure the integrity of the foam core structure as much as possible during the bonding process. When the foam core material is a closed-cell structure, adhesive bonding is often used to reduce costs and simplify the process.

[0004] Adhesive bonding refers to the use of adhesives to achieve the connection between the foam core material and the inner wall of the composite thin-walled tube. First, the inner wall of the thin-walled tube and the outer wall of the core material must be polished to increase the effective bonding area. After the bonding is completed, the glue layer is kept at room temperature or a certain temperature for a period of time to solidify. However, the current composite material round tube bonding process still has great defects. If the glue is applied first and then filled, the glue layer will be destroyed during the filling process, and the adhesive in the holes on the surface of the foam core material is difficult to achieve a connection effect; if the glue is applied first and then filled, the process is difficult, and the thickness of the glue layer is difficult to control and is prone to unevenness. Regardless of the processing sequence, due to the sensitivity of the composite material to the warm environment and its tubular structure, it is difficult to heat and pressurize the glue layer when it is cured, and due to the lack of effective sealing and measures to reduce glue overflow, glue tumors are easily generated, which reduces the connection strength. Therefore, it is very necessary to develop a new bonding method and device suitable for composite round tubes and closed-cell foam core materials. Summary of the invention

[0005] The purpose of the present invention is to design and develop a bonding connection device for a composite material round tube and a closed-cell foam core material. The closed-cell foam core material is fixed by the combination of an upper pressure head and a lower pressure head. The bonding surface pretreatment and bonding are achieved by the combination of a thickness gauge and a one-way valve. At the same time, damage to the thin-walled tube wall of the composite material and the complete structure of the foam core material is avoided, thereby improving the connection strength.

[0006] The present invention also designs and develops a method for gluing a composite material circular tube to a closed-cell foam core material, by controlling the axial withdrawal speed of the thickness gauge, thereby controlling the glue injection speed and the thickness of the glue layer, so that the thickness of the glue layer is more uniform.

[0007] The technical solution provided by the present invention is:

[0008] A bonding connection device for a composite material round tube and a closed-cell foam core material, comprising:

[0009] A thickness gauge is axially movable in the composite material circular tube, and one end of the thickness gauge is provided with a first through hole, and the other end is provided with an open receiving cavity connected to the first through hole, and the outer wall of the thickness gauge and the inner wall of the open receiving cavity are both sandblasted;

[0010] Wherein, the closed-cell foam core material is arranged in the open accommodating cavity;

[0011] An upper pressing head, one end of which is movably disposed in the open accommodating cavity and abuts against one end of the closed-cell foam core material, and the other end of which passes through the first through hole;

[0012] A lower pressure head, which is engaged in the composite material round tube and abuts against the other end of the thickness gauge;

[0013] A one-way valve is arranged at the axis of the lower pressure head and is used for injecting glue into the thickness gauge.

[0014] Preferably, the upper pressure head comprises:

[0015] A pressing block, which is a cylindrical structure and is movably disposed in the open accommodating cavity, and is used to cooperate with the lower pressing head to limit the movement of the closed-cell foam core material;

[0016] The long axis is coaxially and vertically arranged with the pressing block, and the long axis can rotatably pass through the first through hole.

[0017] Preferably, the pressing head further comprises:

[0018] A second through hole, which is arranged at the axis of the lower pressure head;

[0019] A plurality of rubber guide grooves are radially arranged at equal intervals on the surface of the lower pressure head close to the thickness gauge;

[0020] Wherein, the one-way valve and the second through hole are interference fit.

[0021] Preferably, it also includes:

[0022] A first groove, which is annularly arranged on the circumference of the pressing block;

[0023] A first sealing ring is arranged in the first groove.

[0024] Preferably, it also includes:

[0025] A second groove, which is annularly arranged on the circumference of the lower pressure head;

[0026] A second sealing ring is arranged in the second groove.

[0027] Preferably, it also includes:

[0028] A plurality of pressure sensors are evenly arranged on the surface of the pressing block close to the lower pressing head, and are used to detect the change of the radial pressure value of the rubber layer;

[0029] A controller is connected to the plurality of pressure sensors, the upper pressure head, the thickness gauge and the glue injection device, and is used for receiving data and transmitting commands.

[0030] A method for bonding a composite material round tube and a closed-cell foam core material, using the bonding device for bonding a composite material round tube and a closed-cell foam core material, comprises the following steps:

[0031] Step 1, placing the closed-cell foam core material in the accommodating cavity after low-temperature treatment and clamping it with an upper pressure head and a lower pressure head, and then leaving it to stand;

[0032] Step 2: when the multiple pressure sensors detect that the closed-cell foam core material squeezes the thickness gauge, the thickness gauge is axially withdrawn in a direction away from the closed-cell foam core material, and glue is injected between the closed-cell foam core material and the composite material round tube;

[0033] Step 3: When the pressure reaches 2MPa, stop injecting glue and let it stand at room temperature until the glue layer solidifies. After the upper and lower pressure heads are reset, the bonding connection is completed.

[0034] Preferably, the difference between the outer diameter of the thickness gauge and the aperture of the open accommodating cavity is twice the thickness of the glue layer.

[0035] Preferably, the speed of the glue injection satisfies:

[0036]

[0037] Where V i is the injection speed, ω i is the correction factor, T is the ambient temperature, F d is the pressure value, D b is the length of the closed-cell foam core, ρ is the density of the adhesive, V d is the axial withdrawal speed of the thickness gauge.

[0038] Preferably, the axial withdrawal speed of the thickness gauge satisfies:

[0039]

[0040] Where φ is the correction factor, D ois the length of the thickness gauge, f is the friction between the thickness gauge and the composite material tube, N is the initial volume of the closed-cell foam core, and R is the diameter of the composite material tube.

[0041] The beneficial effects of the present invention are:

[0042] (1) The present invention designs and develops a bonding connection device for a composite material circular tube and a closed-cell foam core material. The foam core material has a special structure. In order to ensure a sufficient effective bonding area, a higher requirement is placed on the fullness of the adhesive layer. The good sealing of the bonding area can not only eliminate the formation of glue tumors at the bonding site, but also allow the adhesive layer to fill the entire bonding area under pressure.

[0043] (2) The present invention designs and develops a bonding connection device for a composite material circular tube and a closed-cell foam core material. The composite material is a brittle material, and the pore structure of the foam core material is prone to local collapse and cracking. The device described in the present invention avoids damage to the intact structure of the composite material thin-walled tube and the foam core material, and is also suitable for bonding metal thin-walled tubes and ordinary solid core materials, and has a wide range of applications.

[0044] (3) The present invention designs and develops a bonding connection device for a composite material circular tube and a closed-cell foam core material. The foam core material recovers its volume at room temperature and applies uniform radial pressure to the adhesive layer. At the same time, the grinding of the bonding surface by the thickness gauge not only improves the surface quality of the bonding surface and increases the effective bonding area, but also generates friction heat, which accelerates the recovery of the foam core material volume and heats the entire curing process, thereby effectively achieving the heating and pressurization of the adhesive layer.

[0045] (4) The present invention designs and develops a method for bonding a composite material circular tube and a closed-cell foam core material. By controlling the axial withdrawal speed of the thickness gauge, the glue injection speed and the thickness of the glue layer are controlled to make the thickness of the glue layer as uniform as possible, thereby realizing the integration of the bonding surface pretreatment and the glue injection equipment, and simplifying the bonding process steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a schematic cross-sectional structural diagram of a device for bonding a composite material circular tube and a closed-cell foam core material.

[0047] Figure 2 It is a schematic diagram of the cross-sectional structure of the thickness gauge of the present invention.

[0048] Figure 3 It is a schematic diagram of the main structure of the upper pressure head described in the present invention.

[0049] Figure 4 It is a schematic structural diagram of the pressing head described in the present invention.

[0050] Figure 5It is a schematic structural diagram of the adhesive connection device of the composite material circular tube and the closed-cell foam core material of the present invention when the adhesive connection is completed. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below so that those skilled in the art can implement it according to the description.

[0052] like Figure 1 As shown, the present invention provides a bonding connection device for a composite material circular tube and a closed-cell foam core material, which specifically includes: a composite material circular tube 110, a closed-cell foam core material 120, an upper pressure head 130, a thickness gauge 140, a lower pressure head 150, a one-way valve 160, a first sealing ring 170 and a second sealing ring 180, wherein the composite material circular tube 110, the thickness gauge 140 and the closed-cell foam core material 120 are coaxially arranged in sequence from the outside to the inside at the part to be bonded.

[0053] like Figure 2 As shown, the thickness gauge 140 is an overall cylindrical structure and is axially movable in the composite material round tube 110. One end of the thickness gauge 140 is provided with a first through hole 141, and the other end is provided with an open accommodating cavity 142 connected to the first through hole 141. The closed-cell foam core material 120 is arranged in the open accommodating cavity 142.

[0054] The inner wall of the open accommodating cavity 142 and the outer wall of the thickness gauge 140 are both subjected to corresponding sandblasting treatment to obtain a sand texture effect with a certain degree of roughness. The specific roughness is determined according to the specific implementation process and the bonding material.

[0055] One end of the upper pressure head 130 is movably arranged in the open accommodating cavity 142 and abuts against one end of the closed-cell foam core material 120, and the other end passes through the first through hole 141; the lower pressure head 150 is engaged in the composite material circular tube 110 and abuts against the other end of the thickness gauge 140, and the upper pressure head 130 and the lower pressure head 150 relatively squeeze and limit the freedom of the closed-cell foam core material 120; the one-way valve 160 is arranged at the axis of the lower pressure head 150, and is used to inject glue into the thickness gauge 140.

[0056] In this embodiment, the one-way valve 160 is a straight-through plug-in one-way valve, which ensures that the adhesive can only be injected into the bonding area and cannot flow back.

[0057] The overall height of the thickness gauge 140 is 35-50 mm more than the height of the closed-cell foam core 120. The outer diameter of the thickness gauge 140 is the same as the inner diameter of the composite material circular tube 110. The aperture of the first through hole 141 is 11 mm and the height is 25-40 mm. The difference between the outer diameter of the thickness gauge 140 and the aperture of the open accommodating cavity 142 is theoretically twice the expected thickness of the glue layer (for example, if the glue layer thickness is 2 mm and the inner diameter of the composite material circular tube 110 is 40 mm, then the aperture of the open accommodating cavity 142 is 36 mm).

[0058] like Figure 3 As shown, the upper pressure head 130 includes: a pressure block 131 and a long axis 132. The pressure block 131 is a cylindrical structure and is movably arranged in the open accommodating cavity 142, and is used to cooperate with the lower pressure head 150 to limit the movement of the closed-cell foam core material 120; the long axis 132 is coaxially and vertically arranged with the pressure block 131, and the long axis 132 coaxially and rotatably passes through the first through hole 141.

[0059] The shaft diameter of the long axis 132 is 10 mm, the height of the pressing block 131 is 10 mm, the outer diameter of the pressing block 131 is the same as the aperture of the open accommodating cavity 142, a first groove 133 is machined on the circumference of the outer side surface of the pressing block 131, a first sealing ring 170 is installed in the first groove 133, the depth of the first groove 133 is 4 mm, and the width is 6 mm, and a plurality of pressure sensors 134 are evenly arranged on the outer side surface of the pressing block 131 close to the closed-cell foam core material 120, which are used to detect the change in the radial pressure value of the rubber layer, so that the controller can determine whether the rubber layer is full and pressurized.

[0060] like Figure 4 As shown, the lower pressure head 150 is a cylindrical structure as a whole, with an outer diameter the same as the inner diameter of the composite material circular tube 110 and a height of 10mm. A second through hole 152 is opened in the middle, and the second through hole 152 is a stepped hole, with a large hole diameter of 5mm and a height of 7mm, and a small hole diameter of 2mm and a height of 2mm. The one-way valve 160 is arranged at the large hole, and the one-way valve 160 is interference fit with the large hole. A plurality of rubber guide grooves 153 are radially machined on the end surface of the lower pressure head 150 in contact with the closed-cell foam core material 120. The rubber guide grooves 153 are semicircular straight grooves with a cross-sectional radius of 1mm. A second groove 151 is machined on the circumference of the outer side surface of the lower pressure head 150, and a second sealing ring 180 is installed in the second groove 151. The depth of the second groove 151 is 5mm and the width is 6mm.

[0061] In this embodiment, the first sealing ring 170 and the second sealing ring 180 are both common O-rings.

[0062] In this embodiment, the surfaces of the upper pressure head 130 and the lower pressure head 150 are sprayed with an anti-stick and wear-resistant coating to ensure that they can be easily peeled off from both sides of the closed-cell foam core material 120 and returned to their original positions after the bonding is completed; the size of the first sealing ring 170 and the second sealing ring 180 should ensure the sealing ability during the entire bonding process, and their material should not be easily adhered to by adhesives.

[0063] The present invention also includes: a controller (not shown in the figure), which is connected to the multiple pressure sensors 134, the upper pressure head 130, the thickness gauge 140 and the glue injection equipment, and is used to receive the detection data of the pressure sensor 134, control the status of the upper pressure head 130 and the thickness gauge 140 and the glue injection speed.

[0064] The present invention designs and develops a bonding connection device for a composite material circular tube and a closed-cell foam core material, which realizes the integration of bonding surface pretreatment and glue injection equipment, and simplifies the bonding process steps; the foam core material recovers its volume at room temperature, which will apply uniform radial pressure to the glue layer, and at the same time, the friction heat generated by the thickness gauge grinding the bonding surface accelerates the recovery of the foam core material volume, and also plays a heating role in the entire curing process, effectively realizing the heating and pressurization of the glue layer; the foam core material has a special structure, and in order to ensure sufficient effective bonding area, higher requirements are put forward on the fullness of the glue layer. Good sealing of the bonding area can not only eliminate the formation of glue nodules at the bonding site, but also allow the glue layer to fill the entire bonding area under pressure.

[0065] The method for bonding a composite material round tube and a closed-cell foam core material of the present invention uses the bonding device for bonding a composite material round tube and a closed-cell foam core material, and comprises the following steps:

[0066] Step 1: Place the closed-cell foam core material at low temperature in advance to shrink its volume, take it out and place it in the open receiving cavity of the thickness gauge, clamp it with the upper and lower pressure heads to limit all degrees of freedom of the end face of the closed-cell foam core material;

[0067] Step 2: Let it stand for a while, and wait for the closed-cell foam core material to recover its volume as the temperature rises, which will produce a certain squeezing effect on the inner wall of the thickness gauge. The controller controls the thickness gauge to rotate and axially withdraw in the direction away from the closed-cell foam core material, and at the same time, glue is injected into the area to be glued from the one-way valve. In this process, the sand grains on the outer wall of the thickness gauge and the inner wall of the open accommodating cavity will grind the inner wall of the composite material circular tube and the outer wall of the closed-cell foam core material. The upper pressure head and the lower pressure head are kept in a clamped state to prevent the closed-cell foam core material from moving with the thickness gauge.

[0068] Wherein, the speed of the glue injection satisfies:

[0069]

[0070] Where V i is the injection speed, ωi is the correction coefficient, the correction coefficient range is [0.5-0.78], T is the ambient temperature, F d is the pressure value, D b is the length of the closed-cell foam core, ρ is the density of the adhesive, V d is the axial withdrawal speed of the thickness gauge;

[0071] The axial withdrawal speed of the thickness gauge meets the following requirements:

[0072]

[0073] Where φ is the correction factor, and the range of the correction factor is [1.1-1.43], D o is the length of the thickness gauge, f is the friction between the thickness gauge and the composite material tube, N is the initial volume of the closed-cell foam core, and R is the diameter of the composite material tube;

[0074] Step 3: If Figure 5 As shown, the adhesive continuously fills the gap between the composite material circular tube wall and the closed-cell foam core material, and is blocked from overflowing by the first sealing ring and the second sealing ring. When the pressure sensor detects that the pressure value reaches 2MPa, the glue injection is stopped and the adhesive is left to stand at room temperature until the glue layer 190 is cured, the upper pressure head and the lower pressure head return to their positions, and the adhesive connection is completed.

[0075] At room temperature, the diameter of the closed-cell foam core material should not be larger than the inner diameter of the composite material round tube; the difference between the outer diameter of the thickness gauge and the aperture of the open accommodating cavity is theoretically twice the final adhesive layer thickness, which is generally 0.1-2 mm.

[0076] The invention designs and develops a method for gluing and connecting a composite material circular tube and a closed-cell foam core material. The thickness of the glue layer is controlled by a thickness gauge to make the thickness of the glue layer as uniform as possible. The composite material is a brittle material, and the pore structure of the foam core material is prone to local collapse and cracks. The method avoids damage to the complete structure of the composite material thin-walled tube and the foam core material. The method is also suitable for gluing metal thin-walled tubes and ordinary solid core materials, and has a wide range of applications.

[0077] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A bonding connection device for a composite material round tube and a closed-cell foam core material, characterized in that: include: A thickness gauge is axially movable in the composite material circular tube, and one end of the thickness gauge is provided with a first through hole, and the other end is provided with an open accommodating cavity connected to the first through hole, and the outer wall of the thickness gauge and the inner wall of the open accommodating cavity are both sandblasted; Wherein, the closed-cell foam core material is arranged in the open accommodating cavity; An upper pressing head, one end of which is movably disposed in the open accommodating cavity and abuts against one end of the closed-cell foam core material, and the other end of which passes through the first through hole; A lower pressure head, which is engaged in the composite material round tube and abuts against the other end of the thickness gauge; A one-way valve, which is arranged at the axis of the lower pressure head and is used to inject glue into the thickness gauge; A plurality of pressure sensors are evenly arranged on the surface of the pressing block close to the lower pressing head, and are used to detect the change of the radial pressure value of the rubber layer; A controller connected to the plurality of pressure sensors, the upper pressure head, the thickness gauge and the glue injection device, and used for receiving data and transmitting commands; The upper pressure head comprises: The pressing block is a cylindrical structure and is movably disposed in the open accommodating cavity, and is used to cooperate with the lower pressing head to limit the movement of the closed-cell foam core material.

2. The adhesive connection device for composite material round tube and closed-cell foam core material according to claim 1, characterized in that: The upper pressure head also includes: The long axis is coaxially and vertically arranged with the pressing block, and the long axis can rotatably pass through the first through hole.

3. The adhesive connection device for composite material round tube and closed-cell foam core material according to claim 2, characterized in that: The lower pressure head also includes: A second through hole, which is arranged at the axis of the lower pressure head; A plurality of rubber guide grooves are radially arranged at equal intervals on the surface of the lower pressure head close to the thickness gauge; Wherein, the one-way valve and the second through hole are interference fit.

4. The adhesive connection device for composite material round tube and closed-cell foam core material according to claim 3, characterized in that: The adhesive connection device for the composite material round tube and the closed-cell foam core material also includes: A first groove, which is annularly arranged on the circumference of the pressing block; A first sealing ring is arranged in the first groove.

5. The adhesive connection device for composite material round tube and closed-cell foam core material according to claim 4, characterized in that: The adhesive connection device for the composite material round tube and the closed-cell foam core material also includes: A second groove, which is annularly arranged on the circumference of the lower pressure head; A second sealing ring is arranged in the second groove.

6. A method for bonding a composite material round tube to a closed-cell foam core, using the bonding device for bonding a composite material round tube to a closed-cell foam core as claimed in any one of claims 1 to 5, characterized in that: The steps include: Step 1, placing the closed-cell foam core material in the accommodating cavity after low-temperature treatment and clamping it with an upper pressure head and a lower pressure head, and then leaving it to stand; Step 2: when the multiple pressure sensors detect that the closed-cell foam core material squeezes the thickness gauge, the thickness gauge is axially withdrawn in a direction away from the closed-cell foam core material, and glue is injected between the closed-cell foam core material and the composite material round tube; Step 3: When the pressure reaches 2MPa, stop injecting glue and let it stand at room temperature until the glue layer solidifies. After the upper and lower pressure heads are reset, the bonding connection is completed.

7. The method for bonding a composite material round tube and a closed-cell foam core material as claimed in claim 6, characterized in that: The difference between the outer diameter of the thickness gauge and the aperture of the open accommodating cavity is twice the thickness of the adhesive layer.

8. The method for bonding a composite material round tube and a closed-cell foam core material as claimed in claim 7, characterized in that: The speed of the injection meets the following requirements: Where V i is the injection speed, ω i is the correction factor, T is the ambient temperature, F d is the pressure value, D b is the length of the closed-cell foam core, ρ is the density of the adhesive, V d It is the axial withdrawal speed of the thickness gauge.

9. The method for bonding a composite material round tube and a closed-cell foam core material as claimed in claim 8, characterized in that: The axial withdrawal speed of the thickness gauge satisfies: Where φ is the correction factor, D o is the length of the thickness gauge, f is the friction between the thickness gauge and the composite material tube, N is the initial volume of the closed-cell foam core, and R is the diameter of the composite material tube.

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