Composite material and co-bonding method thereof

Abstract

The invention discloses a composite material and a co-bonding method thereof, and relates to the technical field of composite material forming. The composite material co-bonding method comprises the steps of pre-assembly, honeycomb dehumidification, pre-leveling, skin checking, heat sealing and pressing, pre-bonding, skin wet laying and co-bonding forming. The composite material co-bonding method disclosed by the invention has the advantages of simple process and low cost, and compared with secondary bonding in the prior art, the composite material co-bonding process disclosed by the invention is easier to realize industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming, and more particularly, to a composite material and a co-bonding method thereof. Background Art

[0002] Due to its excellent properties such as high specific strength, high specific modulus, and corrosion resistance, composite materials have been widely used in the fields of aerospace, automotive manufacturing, shipbuilding industry, etc. However, the connection technology of composite materials has always been one of the key issues restricting its further development. Traditional mechanical connection methods will introduce stress concentration and reduce the overall performance of the structure, while the bonding technology can effectively avoid this problem. However, the existing bonding technology is very complex, with multiple bondings, and the entire process flow is cumbersome, resulting in high costs and being unfavorable for industrial production.

[0003] Therefore, how to achieve a bonding technology with simple process and low cost has always been an objective that the industry urgently needs to improve. Summary of the Invention

[0004] The main object of the present invention is to provide a co-bonding method for composite materials to solve the technical problem in the prior art that a bonding technology with simple process and low cost cannot be achieved.

[0005] To achieve the above object, according to the first aspect of the present invention, a co-bonding method for composite materials is provided, including the following steps:

[0006] Pre-assembly step: perform overall fitting of the parts before co-bonding and make bonding positioning holes.

[0007] Honeycomb dehumidification step: position the honeycomb and the radome on the bonding tooling and perform honeycomb dehumidification after assembly.

[0008] Pre-leveling step: pre-bond the honeycomb and the radome using foaming adhesive, and lay a film on the radome and level it in the plate area where the radome is bonded to the skin.

[0009] Skin verification step: lay isolation films, adhesive films, and isolation films on the lower skin in sequence, and perform verification after assembling all the parts.

[0010] Hot sealing and pressing step: determine the matching situation between the parts according to the state of the adhesive film, perform adhesive film compensation on the areas with matching problems, and perform hot sealing and pressing on the skin after compensation.

[0011] Pre-bonding step: prepare for pre-bonding by assembling all the parts. During pre-bonding, confirm the step difference between the honeycomb and the radome, and confirm that the fit clearance of each part is consistent with the assembled state during verification. Then send the parts into the autoclave for pre-curing.

[0012] The steps of wet laying the skin: Check and confirm that the gap between the honeycomb and the radome is flush, compensate for the positions lacking glue. After the compensation is completed, stick a glue film on the entire surface of the honeycomb, wet lay prepreg, lay auxiliary materials in sequence, and place rubber dam strips around.

[0013] The steps of co-bonding and forming: Apply a preset pressure and temperature to the bonded parts after bagging to perform co-bonding and forming.

[0014] Furthermore, the preparation method further includes the following steps: The step of forming parts. Design a part forming tooling, lay the prepreg on the forming tooling, lay auxiliary materials in the order of release film, Teflon cloth, breather felt, and vacuum bag, seal the periphery with rubber dam strips, and use the autoclave forming process to cure the parts. After curing, remove the auxiliary materials to obtain the parts.

[0015] Furthermore, the preparation method further includes the following steps: The step of designing a forming mold. Design and manufacture a bonding mold according to the shape and size of the variable-curved surface composite material part.

[0016] Furthermore, the preparation method further includes the following steps: The surface treatment step. Clean and roughen the composite material base that needs to be bonded.

[0017] Furthermore, the preparation method further includes the following steps: The post-treatment step. After co-bonding and forming, cool and demold the bonded parts.

[0018] Furthermore, the glue film is a composite glue film of resin and carrier. The main material of the resin includes one of epoxy resin, bismaleimide resin, polyimide resin, and acrylate resin. The material of the carrier is nylon, and the structural form of the carrier is fabric or non-woven fabric.

[0019] Furthermore, in the co-bonding and forming step, the initial vacuum is -0.050 Mpa, and vacuum is pumped throughout the process.

[0020] Furthermore, in the co-bonding and forming step, the temperature parameters are set as follows: Start heating at a heating rate of 1.5 ± 0.5 °C / minute to 150 ± 5 °C, and keep the temperature constant for 30 - 40 minutes; then heat at a heating rate of 1.5 ± 0.5 °C / minute to 180 ± 5 °C, and keep the temperature constant for 120 - 130 minutes; finally heat at a heating rate of 1.5 ± 0.5 °C / minute to 195 - 200 °C, and keep the temperature constant for 240 - 245 minutes. After the constant temperature ends, start cooling at a rate of ≤ 1.5 °C / minute to 50 °C.

[0021] Further, in the co-bonding forming step, the pressure parameters are set as follows: After pressurization starts for 20 minutes and the pressure rises to 0.35 ± 0.02 Mpa, after heat preservation at 180 °C ends, the pressure decreases by 0.1 MPa in 30 minutes. When the temperature of the bonded part is lower than 60 °C, the pressure is removed in 10 minutes.

[0022] According to the second aspect of the present invention, a composite material prepared by the above method is provided.

[0023] Applying the co-bonding method of the composite material disclosed in the present invention has the advantages of simple process and low cost. Moreover, compared with the secondary bonding of the prior art, the co-bonding process of the composite material of the present invention is easier to realize industrial production. Description of the Drawings

[0024] Figure 1 It is a flowchart of the co-bonding method of the composite material in the embodiment of the present invention. Detailed Embodiments

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0026] In the description of the present invention, it should be understood that orientation words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal", and "top, bottom" generally refer to the orientation or position relationship shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, so they cannot be construed as limiting the protection scope of the present invention; the orientation words "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0027] As described in the background art of the present invention, there is a technical problem in the prior art that a bonding technique that is simple in process and low in cost cannot be achieved. To solve the above technical problem, in a typical embodiment of the present invention, a co-bonding method of a composite material is provided, and its flowchart is as Figure 1 shown, including the following steps:

[0028] Pre-assembly step, perform overall repair on the parts before co-bonding, and make bonding positioning holes;

[0029] Honeycomb dehumidification step, position the honeycomb and the radome on the bonding tooling, and perform honeycomb dehumidification after assembly;

[0030] Pre-leveling step: pre-bond the honeycomb and the radome using foaming adhesive, and lay a film adhesive on the radome and level it in the panel area where the radome is bonded to the skin;

[0031] Skin verification step: lay an isolation film, a film adhesive, and an isolation film on the lower skin in sequence, and verify after assembling all parts;

[0032] Hot sealing and pressing step: determine the matching condition between the parts according to the state of the film adhesive, compensate the film adhesive for the areas with matching problems, and perform hot sealing and pressing on the skin after the compensation is completed;

[0033] Pre-bonding step: prepare all parts for pre-bonding, confirm the step difference between the honeycomb and the radome during pre-bonding, and confirm that the fit clearance of each part is consistent with the assembled state during verification, then send the parts into a hot press for pre-curing;

[0034] Skin wet laying step: check and confirm that the gap between the honeycomb and the radome is flush, compensate for the positions with lack of adhesive, and after the compensation is completed, stick a film adhesive on the entire surface of the honeycomb, wet lay prepreg, lay auxiliary materials in sequence, and place glue-blocking strips around;

[0035] Co-bonding and forming step: apply a preset pressure and temperature to the bonded parts after bagging to perform co-bonding and forming.

[0036] The co-bonding method of composite materials disclosed by the present invention has the advantages of simple process and low cost, and compared with the secondary bonding of the prior art, the co-bonding process of the composite materials of the present invention is easier to realize industrial production.

[0037] The following further describes the present invention in detail.

[0038] In this embodiment, before the pre-assembly step, there are also component forming steps, design of forming molds steps, and surface treatment steps.

[0039] Component forming steps: Design a tooling for component forming, lay prepreg on the said tooling, lay auxiliary materials in the order of release film, PTFE cloth, breather felt, and vacuum bag, seal the periphery with rubber sealing strips, and cure the component using an autoclave molding process. After curing, remove the auxiliary materials to obtain the component. In this embodiment, with the aid of a tooling mold, according to the designed structure, use prepreg laying to manufacture a whole composite bonded structure blank, sequentially place auxiliary materials in the order of release film, PTFE cloth, breather felt, and vacuum bag, use a sealing rubber strip to seal the edge of the composite bonded structure blank for laying process auxiliary materials, perform vacuum bag encapsulation and execute the autoclave curing process for prepreg curing. After curing is completed, open the mold and take out the auxiliary materials, and the preparation of the whole composite bonded structure component is completed. Among them, components are connected by installing process nails through process holes. The bonded parts are prepared through processes such as honeycomb dehumidification, pre-leveling, pre-foaming, lower skin calibration, hot sealing and pressing, pre-bonding, honeycomb stabilization, upper skin hot pressing, and co-bonding.

[0040] Designing the forming mold steps: Design and manufacture a bonding mold according to the shape and size of the variable-curved surface composite component. Among them, it is difficult for traditional bonding processes to achieve precise forming of complex curved surface components, which limits their application scope. However, the designing the forming mold steps of the present invention can achieve precise forming of complex curved surface components. By precisely controlling the curved surface shape and heating temperature of the mold, it is ensured that the composite material can closely adhere to the mold surface during the curing process. When laying wet materials for co-bonding, the prepreg is processed in blocks to reduce the surface tension of the material sheet during curing, and high-precision fitting forming of complex curved surface structures is achieved.

[0041] In this embodiment, the variable-curved surface forming technology is adopted to achieve precise forming of complex curved surface components and expand the application scope of the co-bonding process.

[0042] Surface treatment steps: Clean and roughen the composite material base to be bonded. Among them, cleaning and roughening the composite material base to be bonded removes oil stains and dust on the surface, increases the surface roughness, and improves the bonding strength.

[0043] Pre-assembly steps: Perform overall fitting of the components before co-bonding and make bonding positioning holes. In this embodiment, for the pre-assembly steps of co-bonding, visually inspect the overall smooth surface of the components by irradiating with light to observe whether there are scratches that damage the fibers on the surface, use type inspection positioning to perform overall fitting of the components before co-bonding, and make bonding positioning holes.

[0044] Honeycomb dehumidification steps: Position the honeycomb and the radome (such as the skeleton of the radome) on the bonding tooling and perform honeycomb dehumidification after assembly.

[0045] Pre-leveling step: Use foaming adhesive to pre-bond the honeycomb and the radome, and in the panel area where the radome is bonded to the skin, lay a film adhesive on the radome and level it.

[0046] In this embodiment, the film adhesive is a composite film adhesive of resin and carrier. The main material of the resin includes one of epoxy resin, bismaleimide resin, polyimide resin, and acrylate resin. The material of the carrier is nylon, and the structural form of the carrier is fabric or non-woven fabric.

[0047] Skin verification step: Lay an isolation film, a film adhesive, and an isolation film on the lower skin in sequence, and verify after assembling all the parts. Among them, lay an isolation film, a film adhesive, and an isolation film on the lower skin in sequence to protect the film adhesive with the isolation film to prevent the adhesive from overflowing onto the skin and other parts. Verify after assembling all the parts to check the matching situation between each part to ensure the bonding quality. In this embodiment, according to the designed structure, with the aid of the bonding tooling for positioning, combine the cured structural unit parts and the honeycomb assembly with the film adhesive, use the isolation film to block the film adhesive area, and perform the hot pressing verification process to verify the assembly and cooperation relationship of the parts.

[0048] Hot sealing and pressing step: After verification, determine the matching situation between the parts according to the state of the film adhesive, perform film adhesive compensation on the areas with problems in matching, and perform hot sealing and pressing on the skin after the compensation is completed.

[0049] Pre-bonding step: After confirming that the state of the skin film adhesive is correct, prepare for pre-bonding by assembling all the parts. When pre-bonding, confirm the step difference between the honeycomb and the radome (such as the skeleton of the radome), and confirm that the fitting clearance of each part is consistent with the assembled state during verification, and send the parts into the autoclave for pre-curing.

[0050] In this embodiment, after the hot pressing verification structure, open the mold to check the film adhesive. For the areas where the film adhesive has bubbles or the cell imprints are not obvious, perform compensation. After compensation, perform pre-bonding, reassemble the parts, and perform the autoclave pre-bonding and curing process for the bonded parts, that is, send the parts into the autoclave for pre-curing.

[0051] Skin wet laying step: After the pre-bonding step is completed, use a feeler gauge to check and confirm that the gap between the honeycomb and the radome (such as the skeleton of the radome) is flush, perform compensation on the positions lacking adhesive, and after the compensation is completed, stick a film adhesive on the entire surface of the honeycomb, wet lay the prepreg, lay the auxiliary materials in sequence, and place a rubber strip for blocking glue around to prepare for curing.

[0052] In this embodiment, the function of the skin wet laying step is to prevent the honeycomb from being crushed and stabilize the honeycomb. In addition, laying the film adhesive and prepreg on the honeycomb can increase the compressive capacity of the honeycomb.

[0053] Co - bonding forming step: Apply a preset pressure and temperature to the bonded parts after bagging for co - bonding forming. Among them, after stabilization (i.e., the skin wet - laying step), start the last step of co - bonding. Lay the adhesive film and lay the pre - impregnated wet material on the adhesive film, and perform the co - bonding curing process to complete the final co - bonding process.

[0054] In this embodiment, the co - bonding curing process parameters include vacuum, temperature, and pressure. Among them, the initial vacuum is - 0.050 Mpa, and vacuum is pumped throughout the process.

[0055] In this embodiment, in the co - bonding forming step, the temperature parameters are set as follows: Start heating at a heating rate of 1.5 ± 0.5 °C / minute to 150 ± 5 °C, and keep the temperature constant for 30 - 40 minutes; then heat at a heating rate of 1.5 ± 0.5 °C / minute to 180 ± 5 °C, and keep the temperature constant for 120 - 130 minutes; finally, heat at a heating rate of 1.5 ± 0.5 °C / minute to 195 - 200 °C, and keep the temperature constant for 240 - 245 minutes. After the constant - temperature ends, start cooling at a rate of ≤ 1.5 °C / minute to 50 °C.

[0056] In this embodiment, in the co - bonding forming step, the pressure parameters are set as follows: Start pressurizing for 20 minutes until the pressure rises to 0.35 ± 0.02 Mpa. After the heat preservation at 180 °C ends, the pressure decreases by 0.1 Mpa in 30 minutes. When the temperature of the bonded part is lower than 60 °C, remove the pressure in 10 minutes.

[0057] In this embodiment, the co - bonding forming step has the advantages of high interfacial bonding strength and small residual stress. By precisely controlling the core temperature gradient, the interfacial stress is effectively reduced, and the interfacial strength is improved. By optimizing the design of the core temperature gradient curve, the residual stress is effectively reduced, and the dimensional stability and fatigue life of the component are improved. In the prior art, due to problems such as the thermal expansion and contraction effect of materials, the cross - linking and curing of resins, the difference in the coefficient of thermal expansion between composite parts and forming molds, and the thermal conduction efficiency inside, the existing co - bonding autoclave forming process still has deficiencies such as low interfacial bonding strength, large residual stress, and unstable bonding quality. For example, due to the different coefficients of thermal expansion of the adhesive and the composite material, interfacial stress is easily generated during the curing process, resulting in a decrease in the bonding force; due to the different coefficients of thermal expansion of the components of the composite material, temperature changes during the curing process will cause residual stress in the composite material, affecting the storage stability and fatigue life of the component; due to the difficulty of precisely controlling the temperature field in the traditional curing process, the temperature distribution at the bonding interface is uneven, affecting the bonding quality.

[0058] In this embodiment, according to the types of composite materials and the characteristics of the adhesive film, the curing temperature, time and pressure parameters are optimized to ensure the sufficient curing of the bonding interface, the bonding strength, and to reduce the residual stress of the composite parts after co-bonding.

[0059] In this embodiment, the preparation method further includes the following steps: a post-treatment step, after co-bonding and forming, cooling and demolding the bonded part.

[0060] The present invention also provides a composite material prepared by the above method.

[0061] In the composite co-bonding method of the embodiment of the present invention, by precisely controlling the core temperature gradient in the bonding process and combining with the forming technology of variable curved surfaces, the mechanical properties and process stability of composite components can be significantly improved, and it is applicable to fields such as aerospace, automobile manufacturing, and rail transit. The embodiment of the present invention provides a composite co-bonding process based on the design of the core temperature gradient and the forming of variable curved surfaces. This process can effectively improve the interfacial bonding strength, reduce the residual stress, improve the bonding quality, and achieve the precise forming of complex curved surface components.

[0062] In addition, applying the composite co-bonding method disclosed in the present invention has the advantages of simple process and low cost. Moreover, compared with the secondary bonding of the prior art, the composite co-bonding process of the present invention is more easily realized for industrial production.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite material co-bonding method, characterized in that: The steps include: Pre-assembly step, the parts are overall repaired before being glued together, and the gluing positioning holes are made; The honeycomb dehumidification step is to position the honeycomb and the antenna cover on the bonding tool, and dehumidify the honeycomb after assembly; A pre-leveling step, using a foam adhesive to pre-bond the honeycomb and the radome, and in the panel area where the radome is bonded to the skin, applying an adhesive film to the radome and leveling it; Skin verification step: laying the isolation film, adhesive film, and isolation film on the lower skin in sequence, and verifying all parts after they are assembled; A heat sealing and pressing step, determining the matching status between the parts according to the state of the adhesive film, performing adhesive film compensation on the area where the matching problem exists, and heat sealing and pressing the skin after the compensation is completed; Pre-gluing step, assembling all parts to prepare for pre-gluing, confirming the step difference between the honeycomb and the antenna cover during pre-gluing, and confirming that the matching clearance of each part is consistent with the assembly state during verification, and sending the parts into the autoclave for pre-curing; Skin wet laying step: check and confirm that the gap between the honeycomb and the radome is flush, compensate for the glue shortage position, and after the compensation is completed, apply glue film to the entire surface of the honeycomb, wet lay prepreg, lay auxiliary materials in sequence, and place blocking strips around; In the co-bonding and molding step, a preset pressure and temperature are applied to the bagged bonded parts for co-bonding and molding.

2. The composite material co-bonding method according to claim 1, characterized in that: The preparation method further comprises the following steps: Parts molding steps include designing parts molding tooling, laying prepreg on the molding tooling, laying auxiliary materials in the order of isolation film, polytetrafluoroethylene cloth, breathable felt, and vacuum bag, sealing with rubber strips on all sides, curing the parts by autoclave molding process, and removing the auxiliary materials after curing to obtain the parts.

3. The composite material co-bonding method according to claim 1, characterized in that: The preparation method further comprises the following steps: The molding mold is designed and manufactured according to the shape and size of the variable-curved composite material component.

4. The composite material co-bonding method according to claim 1, characterized in that: The preparation method further comprises the following steps: The surface treatment step is to clean and roughen the composite material base to be bonded.

5. The composite material co-bonding method according to claim 1, characterized in that: The preparation method further comprises the following steps: The post-processing step is to cool and demould the bonded parts after the co-bonding molding.

6. The composite material co-bonding method according to claim 1, characterized in that: The adhesive film is a composite adhesive film of a resin and a carrier, the main material of the resin includes one of epoxy resin, bismaleimide resin, polyimide resin, and nitrile resin, the material of the carrier is nylon, and the structural form of the carrier is fabric or non-woven fabric.

7. The composite material co-bonding method according to claim 1, characterized in that: In the co-bonding molding step, the initial vacuum is -0.050 MPa, and the vacuum is applied throughout the entire process.

8. The composite material co-bonding method according to claim 1, characterized in that: In the co-bonding molding step, the temperature parameters are set as follows: initially, the temperature is increased to 150±5°C at a heating rate of 1.5±0.5°C / min, and the temperature is maintained constant for 30 to 40 minutes; then, the temperature is increased to 180±5°C at a heating rate of 1.5±0.5°C / min, and the temperature is maintained constant for 120 to 130 minutes; finally, the temperature is increased to 195-200°C at a heating rate of 1.5±0.5°C / min, and the temperature is maintained constant for 240-245 minutes, and after the constant temperature is ended, the temperature is lowered to 50°C at a rate of ≤1.5°C / min.

9. The composite material co-bonding method according to claim 1, characterized in that: In the co-bonding step, the pressure parameters are set as follows: after the pressure is increased to 0.35±0.02Mpa for 20 minutes after the start of pressurization, the pressure is reduced by 0.1MPa in 30 minutes after the 180°C insulation is completed, and when the temperature of the bonded part is lower than 60°C, the pressure is removed in 10 minutes.

10. A composite material, characterized in that: The composite material is prepared by the composite material co-bonding method according to any one of claims 1 to 9.

Images