Vehicle body carbon fiber bonding method

Abstract

The invention relates to the technical field of automobile body manufacturing, and particularly discloses an automobile body carbon fiber bonding method. Comprising the following four steps: pretreatment of a bonding base material, preparation and coating of an adhesive, precise bonding and pressurized curing, and detection and finishing after bonding. Wherein the mode of combining high-pressure inert gas purging, ultrasonic cleaning, plasma etching activation and gradient cooling drying is adopted in pretreatment, and the wettability of a bonding surface is improved; the adhesive is a composite modified epoxy adhesive and has high strength and weather resistance; a mode of combining precise positioning with step-by-step pressurization and step heating is adopted in fitting and curing, so that the bonding quality is ensured; and accurate identification and finishing of bonding defects are realized through detection and finishing. The device solves the problems of insufficient bonding strength, low glue layer control precision, low automation degree and the like in the prior art, is high in bonding strength, good in stability and high in production efficiency, meets the large-scale production requirements of automobiles, and can be widely applied to bonding of carbon fiber components of automobile bodies.

Description

Technical Field

[0001] This invention relates to the field of automotive body manufacturing technology, specifically to a method for bonding carbon fiber in automotive bodies. Background Technology

[0002] With the rapid development of the new energy vehicle industry, lightweighting of vehicle bodies has become a key path to improve driving range and reduce energy consumption. Carbon fiber composite materials, due to their excellent properties such as high specific strength, low density, corrosion resistance, and fatigue resistance, are widely used in the manufacturing of automotive body structural components. During the assembly of carbon fiber components for the vehicle body, it is inevitable to bond carbon fibers to each other and to the metal substrate of the vehicle body. The quality of the bonding directly determines the overall strength, safety, and service life of the vehicle body structure.

[0003] Currently, existing carbon fiber bonding methods for car bodies suffer from the following technical challenges: First, the bonding interface is susceptible to impurities such as oil, dust, and moisture, leading to insufficient bonding strength and potential failures like debonding and peeling after long-term use. Second, traditional bonding processes use a single adhesive, making it difficult to balance bonding strength, curing efficiency, and weather resistance, thus failing to adapt to the complex operating environment of automotive bodies. Third, the adhesive layer thickness is difficult to control precisely during bonding; excessive thickness can cause bubbles and cracking, while insufficient thickness prevents effective bonding, and the lack of real-time monitoring and feedback mechanisms makes it difficult to ensure bonding consistency. Fourth, existing bonding systems have low automation levels, relying heavily on manual operation, resulting in low bonding accuracy and efficiency, failing to meet the needs of large-scale production, and the introduction of human error further affects bonding quality.

[0004] To address the aforementioned issues, there is an urgent need to design a novel carbon fiber bonding method for automotive bodies. This method should enable efficient pretreatment of the bonding interface, precise control of the adhesive layer, real-time monitoring of the bonding process, and automated operation. This would improve bonding strength and stability, meet the long-term usage requirements of automotive bodies, and simultaneously increase production efficiency and reduce production costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for bonding carbon fiber in car bodies, so as to achieve high-strength, long-lasting and precise bonding between carbon fiber components and metal substrates, and between carbon fiber components, while improving the automation level and production efficiency of bonding operations, and adapting to the needs of large-scale automobile production.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for bonding carbon fiber in a car body, comprising the following steps: Step 1: Pretreatment of bonding substrate: Select the vehicle body substrate to be bonded, which includes carbon fiber components and / or metal substrates; perform surface cleaning, plasma etching activation, and gradient cooling drying on the bonding surface of the vehicle body substrate in sequence; Step 2: Adhesive preparation and coating: Prepare composite modified epoxy adhesive, and apply the adhesive to the pretreated bonding surface using a high-precision anilox roller coating method. After coating, perform vacuum degassing. Step 3: Precise bonding and pressure curing: The car body substrate to be bonded is precisely bonded using a positioning fixture, and curing is carried out by step-by-step pressure application and stepped temperature increase. Step 4: Post-bonding inspection and finishing: Perform visual and strength inspections on the bonded joints. After passing the inspections, finish and remove any excess adhesive.

[0007] Furthermore, in step 1, the surface cleaning is carried out by a combination of high-pressure inert gas purging and anhydrous ethanol ultrasonic cleaning. The high-pressure inert gas is a mixture of argon and nitrogen with a volume ratio of 3:1, the purging pressure is 0.2-0.3 MPa, and the purging time is 15-20 s. The ultrasonic cleaning frequency is 40 kHz, and the cleaning time is 3-5 min.

[0008] Further, in step 1, the power of the plasma etching activation is 180-220W, the etching time is 8-12s, and the vacuum degree inside the equipment during the etching process is -0.095~-0.098MPa; the gradient cooling drying is first dried at a constant temperature of 80℃ for 10-15min, and then gradually cooled to room temperature at a rate of 10℃ every 5min, and the moisture content of the bonding surface after drying is ≤0.1%.

[0009] Further, in step 2, the composite modified epoxy adhesive comprises, by weight parts: 60-70 parts epoxy resin, 10-15 parts hydroxyl-terminated polybutadiene rubber, 5-8 parts nano-alumina, 8-12 parts curing agent, 1-2 parts accelerator, and 2-3 parts coupling agent; the nano-alumina has a particle size of 50-80 nm, the curing agent is an aliphatic amine curing agent, the accelerator is an imidazole accelerator, and the coupling agent is KH-550.

[0010] Furthermore, in step 2, the rotation speed of the anilox roller coating is 30-40 r / min, the coating pressure is 0.15-0.2 MPa, and the adhesive layer thickness is controlled at 0.18-0.22 mm; the vacuum degree of the vacuum degassing is -0.09 MPa, and the degassing time is 3-5 min.

[0011] Furthermore, in step 3, the positioning error of the precise bonding is ≤ ±0.05mm, and the bonding speed is 5-10mm / s; the step-by-step pressure curing includes: pre-pressing 0.05MPa and holding for 5min; the first stage of heating to 60℃ and holding for 30min with a pressure of 0.15MPa; the second stage of heating to 100℃ and holding for 60min with a pressure of 0.25MPa; and finally, gradient cooling to room temperature while maintaining pressure until curing is complete.

[0012] Furthermore, in step 4, the strength test includes tensile shear strength test and peel strength test, with tensile shear strength ≥35MPa and peel strength ≥7.0kN / m; the surface flatness of the bonded joint after trimming is ≤0.03mm / m.

[0013] The advantages of this invention compared to the prior art are: This invention utilizes a pretreatment method combining plasma etching activation and gradient cooling drying to effectively remove impurities and moisture from the bonding surface, forming a uniform micro-rough structure and introducing polar functional groups, significantly improving the surface energy and wettability of the bonding surface. Simultaneously, a composite modified epoxy adhesive is used, possessing high strength, high toughness, and excellent weather resistance. Combined with a step-by-step pressure application and stepped temperature increase curing method, this ensures the adhesive is fully cured, reducing adhesive layer defects.

[0014] This invention employs a high-precision anilox roller coating method, which can precisely control the adhesive layer thickness, ensuring that the adhesive layer is uniform, continuous, bubble-free, and without missing adhesive. At the same time, it achieves precise bonding to the vehicle body substrate, avoiding uneven adhesive layer distribution caused by misalignment or tilting, and significantly improving the consistency of bonding quality.

[0015] The present invention achieves fully automated operation of the entire bonding process, including pretreatment, adhesive preparation and coating, bonding and curing, and inspection and finishing, without the need for manual intervention, effectively reducing human error and shortening the bonding cycle. The bonding time of a single carbon fiber component for the car body is short, which is suitable for the needs of large-scale automobile production and reduces production costs. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0017] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0018] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0019] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0020] The specific implementation process of the carbon fiber bonding method for a car body according to the present invention is as follows: Step 1: Pretreatment of bonding substrate Select a vehicle body substrate to be bonded, the vehicle body substrate including carbon fiber components and / or metal substrates; pre-treat the bonding surface of the vehicle body substrate, the pre-treatment process including: surface cleaning, plasma etching activation, and gradient cooling drying, as follows: Step 1.1 Surface cleaning: Use high-pressure inert gas (a mixture of argon and nitrogen in a volume ratio of 3:1) to blow away surface dust and impurities. The blowing pressure is controlled at 0.2-0.3 MPa and the blowing time is 15-20 seconds. Then, use anhydrous ethanol to ultrasonically clean the bonding surface at a frequency of 40 kHz for 3-5 minutes to remove oil and residual impurities. After cleaning, allow the ethanol on the surface to drain naturally. Step 1.2 Plasma Etching Activation: The drained car body substrate is placed in a plasma etching equipment. Low-temperature plasma is used to etch and activate the bonding surface. The plasma power is controlled at 180-220W and the etching time is 8-12s. During the etching process, the vacuum degree inside the equipment is maintained at -0.095~-0.098MPa. Through plasma etching, a uniform micro-rough structure is formed on the bonding surface. At the same time, polar functional groups such as hydroxyl and carboxyl groups are introduced to improve the surface energy and wettability of the bonding surface. Step 1.3 Gradient cooling and drying: The plasma-etched car body substrate is placed in a gradient drying oven and dried at a constant temperature of 80℃ for 10-15 minutes to remove residual moisture from the bonding surface. Then, the temperature is gradually reduced to room temperature (25±2℃) at a rate of 10℃ every 5 minutes to avoid stress deformation of the bonding surface due to rapid cooling. The moisture content of the bonding surface after drying is controlled below 0.1%.

[0021] Step 2: Adhesive preparation and coating Step 2.1 Adhesive Preparation: Prepare a composite modified epoxy adhesive, the components of which, by mass parts, include: 60-70 parts epoxy resin, 10-15 parts hydroxyl-terminated polybutadiene rubber, 5-8 parts nano-alumina (particle size 50-80nm), 8-12 parts curing agent (aliphatic amine curing agent), 1-2 parts accelerator (imidazolium accelerator), and 2-3 parts coupling agent (KH-550); the preparation process is as follows: first, the epoxy resin and hydroxyl-terminated polybutadiene... Rubber mixtures were stirred at 80℃ and 500 rpm for 30 min to obtain a mixed matrix. Nano-alumina and a coupling agent were then added to the mixed matrix, and the mixture was stirred at 100℃ and 800 rpm for 45 min to ensure uniform dispersion of the nanoparticles. Finally, the mixture was cooled to 50℃, a curing agent and an accelerator were added, and the mixture was stirred for 20 min to obtain a composite modified epoxy adhesive. This adhesive has high strength, high toughness and excellent weather resistance. Step 2.2 Adhesive Coating: Using a high-precision anilox roller coating method, the prepared composite modified epoxy adhesive is coated onto the pretreated bonding surface. During the coating process, the anilox roller speed is controlled at 30-40 r / min, and the coating pressure is 0.15-0.2 MPa to ensure a uniform and continuous adhesive layer with a thickness of 0.18-0.22 mm. After coating, vacuum adsorption is used to remove air bubbles from the adhesive layer surface. The vacuum degree is -0.09 MPa, and the adsorption time is 3-5 min to ensure that the adhesive layer is free of air bubbles and has no missing adhesive.

[0022] Step 3: Precise bonding and pressure curing Step 3.1 Precise bonding: The car body substrate (carbon fiber component and metal substrate, or carbon fiber component and carbon fiber component) coated with adhesive is precisely positioned using a positioning fixture. The positioning error is controlled within ±0.05mm. During the bonding process, the bonding surfaces are kept parallel and aligned to avoid misalignment or tilting. The bonding speed is controlled at 5-10mm / s to reduce the extrusion and loss of adhesive layer. Step 3.2 Stepwise pressure curing: Curing is carried out using a stepwise pressure application combined with stepped temperature increase, as detailed below: Step 3.2.1 Pre-pressure venting: After bonding, apply a pre-pressure of 0.05MPa and maintain it for 5 minutes to expel the air remaining in the adhesive layer. During the pre-pressure process, use an infrared thermometer to monitor the temperature of the bonding surface in real time and keep the temperature at room temperature. Step 3.2.2 Stepwise Heating and Curing: After pre-pressing, begin stepwise heating. First stage: Heat to 60℃ at a rate of 5℃ / min, hold for 30min, and apply a pressure of 0.15MPa to allow the adhesive to initially wet the bonding surface. Second stage: Heat to 100℃ at a rate of 3℃ / min, hold for 60min, and apply a pressure of 0.25MPa to allow the adhesive to fully cure. Third stage: Cool to room temperature at a rate of 2℃ / min while maintaining constant pressure until the adhesive is completely cured. The crosslinking density of the cured adhesive layer is ≥1.2×10³mol / m³.

[0023] Step 4: Post-bonding inspection and finishing Step 4.1 Appearance Inspection: Use high-definition vision inspection equipment to perform appearance inspection on the bonded joints to check for defects such as delamination, bubbles, cracks, and glue overflow. If defects are found, rework is required. Step 4.2 Strength test: Randomly select bonded samples and conduct tensile shear strength test and peel strength test. Tensile shear strength ≥35MPa, peel strength ≥7.0kN / m. If the test results do not meet the standards, the parameters of pretreatment, glue application, curing and other links need to be checked and the bonding should be repeated. Step 4.3 Finishing: For bonded joints that pass the appearance inspection and strength test, use a special tool to remove the excess adhesive layer. After finishing, the surface flatness of the bonded joint is controlled within 0.03mm / m to ensure that it meets the vehicle body assembly requirements.

[0024] The present invention and its embodiments have been described above. This description is not restrictive. If a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the spirit of the present invention, such design should fall within the protection scope of the present invention.

Claims

1. A method for bonding carbon fiber in a car body, characterized in that: Includes the following steps: Step 1: Pretreatment of bonding substrate: Select the vehicle body substrate to be bonded, which includes carbon fiber components and / or metal substrates; perform surface cleaning, plasma etching activation, and gradient cooling drying on the bonding surface of the vehicle body substrate in sequence; Step 2: Adhesive preparation and coating: Prepare composite modified epoxy adhesive, and apply the adhesive to the pretreated bonding surface using a high-precision anilox roller coating method. After coating, perform vacuum degassing. Step 3: Precise bonding and pressure curing: The car body substrate to be bonded is precisely bonded using a positioning fixture, and curing is carried out by step-by-step pressure application and stepped temperature increase. Step 4: Post-bonding inspection and finishing: Perform visual and strength inspections on the bonded joints. After passing the inspections, finish and remove any excess adhesive.

2. The method for bonding carbon fiber in a car body according to claim 1, characterized in that: In step 1, the surface cleaning is carried out by a combination of high-pressure inert gas purging and anhydrous ethanol ultrasonic cleaning. The high-pressure inert gas is a mixture of argon and nitrogen with a volume ratio of 3:1, the purging pressure is 0.2-0.3 MPa, and the purging time is 15-20 s. The ultrasonic cleaning frequency is 40 kHz and the cleaning time is 3-5 min.

3. The method for bonding carbon fiber in a car body according to claim 2, characterized in that: In step 1, the plasma etching activation power is 180-220W, the etching time is 8-12s, and the vacuum degree inside the equipment during the etching process is -0.095~-0.098MPa; the gradient cooling drying is first dried at a constant temperature of 80℃ for 10-15min, and then gradually cooled to room temperature at a rate of 10℃ every 5min, and the moisture content of the bonding surface after drying is ≤0.1%.

4. The method for bonding carbon fiber in a car body according to claim 3, characterized in that: In step 2, the composite modified epoxy adhesive comprises, by weight parts: 60-70 parts epoxy resin, 10-15 parts hydroxyl-terminated polybutadiene rubber, 5-8 parts nano-alumina, 8-12 parts curing agent, 1-2 parts accelerator, and 2-3 parts coupling agent; the nano-alumina has a particle size of 50-80 nm, the curing agent is an aliphatic amine curing agent, the accelerator is an imidazole accelerator, and the coupling agent is KH-550.

5. The method for bonding carbon fiber in a car body according to claim 4, characterized in that: In step 2, the rotation speed of the anilox roller coating is 30-40 r / min, the coating pressure is 0.15-0.2 MPa, and the adhesive layer thickness is controlled at 0.18-0.22 mm; the vacuum degree of the vacuum degassing is -0.09 MPa, and the degassing time is 3-5 min.

6. The method for bonding carbon fiber in a car body according to claim 5, characterized in that: In step 3, the positioning error of the precise fitting is ≤ ±0.05mm, and the fitting speed is 5-10mm / s; The stepwise pressure curing process includes: pre-pressurization of 0.05 MPa for 5 minutes; first stage heating to 60°C for 30 minutes with a pressure of 0.15 MPa; second stage heating to 100°C for 60 minutes with a pressure of 0.25 MPa; and finally, gradual cooling to room temperature while maintaining pressure until curing is complete.

7. The method for bonding carbon fiber in a car body according to claim 6, characterized in that: In step 4, the strength test includes tensile shear strength test and peel strength test. The tensile shear strength is ≥35MPa and the peel strength is ≥7.0kN / m. The surface flatness of the bonded joint after trimming is ≤0.03mm / m.