An interface treatment method for improving the shear strength of a composite member

Abstract

This invention relates to the field of composite material interface modification technology, and discloses a substrate pretreatment method: selecting two sets of substrates matching the composite component, and using 800-2000 grit sandpaper to progressively polish the surfaces of the substrates to be bonded, removing surface burrs, oxide scale, and protruding defects; subsequently, immersing the substrates in a mixed solution of anhydrous ethanol and acetone in a 2:1 volume ratio, and ultrasonically cleaning at 30-40°C for 10-20 minutes to thoroughly remove surface oil, dust, and impurities. This invention employs a multi-synergistic strengthening process of micro-nano composite roughening, chemical activation, and functional transition layer gradient modification, breaking through the limitations of traditional single modification technologies. Through the synergistic effect of four mechanisms—micron-level mechanical interlocking, nano-level interface filling, chemical bonding, and modulus gradient transition—the interfacial bonding strength of the composite component is significantly improved, effectively dispersing shear loads and alleviating interfacial stress concentration. The shear strength of the composite component interface after treatment is increased by more than 40% compared to traditional processes.

Description

Technical Field

[0001] This invention relates to the field of composite material interface modification technology, specifically to an interface treatment method for improving the shear strength of composite components. Background Technology

[0002] Composite components, with their advantages of being lightweight, high-strength, corrosion-resistant, and customizable in performance, are widely used in aerospace, rail transportation, construction engineering, and new energy equipment. Composite components are made of two or more substrates with different physical and chemical properties. The interface, as the core area connecting the different substrates, is a critical part for bearing shear, tensile, and fatigue loads, and its bonding performance directly determines the overall mechanical properties and service life of the composite component.

[0003] Currently, traditional composite component interface treatment processes mostly employ simple grinding, direct adhesive application, and overall curing, which have numerous technical drawbacks. On the one hand, the surface treatment precision of the substrate is low, with a smooth and uneven surface and insufficient roughness. The substrates are only physically bonded together by adhesives, resulting in weak mechanical interlocking and loose interfacial bonding. On the other hand, the modulus and coefficient of thermal expansion of different substrates vary significantly, making it easy for stress concentration to occur at the interface after composite molding. Under shear loads, failure problems such as interface debonding, delamination, and cracking are prone to occur, leading to low shear strength and poor load-bearing stability of the composite components.

[0004] Existing interface modification technologies often rely solely on chemical modification or surface roughening, resulting in limited modification effects. They fail to simultaneously achieve both mechanical interlocking strengthening and chemical bonding enhancement, and lack interfacial modulus gradient transition design, thus failing to effectively mitigate abrupt changes in interfacial stress and exhibiting limited shear strengthening effects. Furthermore, their poor process adaptability and insufficient repeatability make them unsuitable for the high shear resistance and fatigue resistance requirements of high-end equipment for composite components. Therefore, developing a simple, effective, and widely adaptable interface treatment method for composite components is a crucial technical challenge that needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an interface treatment method to improve the shear strength of composite components. This method solves the problems of weak bonding, severe stress concentration, poor shear resistance, and easy delamination failure in traditional interface treatment methods. Through a multi-synergistic strengthening mechanism of mechanical structure interlocking, chemical valence bond bonding, and modulus gradient transition, the interface shear bearing capacity and service stability of composite components are significantly improved.

[0006] This invention provides the following technical solution: an interface treatment method for improving the shear strength of composite components, comprising the following steps: S1. Substrate pretreatment: Select two sets of composite substrates for the composite component, and perform mechanical grinding, degreasing and deoiling, deionized water rinsing and drying in sequence to remove the oxide layer, oil, dust and impurities on the substrate surface and obtain a clean and flat substrate surface to be bonded. S2. Surface micro-nano roughening modification: Laser etching composite chemical roughening treatment is performed on the pretreated substrate surface to be bonded, and a uniformly distributed micro-pit and nano-protrusion composite rough structure is constructed on the substrate surface to increase the specific surface area of ​​the substrate. Then, low temperature activation treatment is performed to introduce hydroxyl and carboxyl active functional groups. S3. Preparation and coating of functional interface transition layer: Prepare silane coupling agent modified composite interface slurry, and uniformly spray / scrape the interface slurry onto the roughened surfaces to be bonded of the two substrates, control the coating thickness to be 2-30 μm, and allow it to stand at room temperature for 5-15 min to level. S4. Composite molding and curing strengthening: The two sets of substrates coated with the interface transition layer are precisely aligned and bonded together. A uniform bonding pressure of 0.2 to 0.5 MPa is applied, and a segmented gradient heating curing process is used for curing. After cooling to room temperature, the interface treatment of the composite component is completed, and a composite component with high shear strength is obtained.

[0007] In step S1, the mechanical polishing is performed using 800-2000 grit sandpaper in stages, the degreasing and oil removal is performed using an anhydrous ethanol and acetone mixed solution for ultrasonic cleaning for 10-20 minutes at a cleaning temperature of 30-40°C, and the drying temperature is 60-80°C for 30-60 minutes.

[0008] In step S2, the laser etching parameters are: laser power 8-15W, scanning speed 200-400mm / s, scanning spacing 50-100μm, and the surface roughness Ra of the substrate after etching is controlled at 1.5-3.5μm; the chemical roughening is performed by immersion in a modified solution of dilute nitric acid and ethanol for 3-8 minutes.

[0009] In particular, in step S2, the low-temperature activation treatment temperature is 40-60°C, the activation time is 20-40 min, the water contact angle of the substrate surface is reduced to below 30° after activation, and the surface active functional group coverage is ≥85%.

[0010] In step S3, the silane coupling agent modified composite interface slurry is composed of the following raw materials in parts by weight: 5-10 parts of silane coupling agent, 20-30 parts of epoxy resin prepolymer, 3-8 parts of nano silica powder, 2-5 parts of carbon nanotube dispersion, and 50-60 parts of anhydrous ethanol.

[0011] Preferably, the silane coupling agent is a KH570 or KH550 type silane coupling agent, the particle size of the nano silica powder is 2-30 nm, and the mass concentration of the carbon nanotube dispersion is 0.5-1.2%.

[0012] In step S3, the interface slurry is pre-cured under UV light for 3-5 minutes after coating to form a preliminary cross-linked structure on the coating surface and prevent the coating from flowing and accumulating.

[0013] In the selected step S4, the segmented gradient temperature curing process is as follows: first, the temperature is raised to 80-100℃ and held for 30 minutes, then the temperature is raised to 120-140℃ and held for 60-90 minutes, and finally the temperature is naturally cooled to room temperature.

[0014] Preferably, the composite component includes any one of metal-resin composite components, carbon fiber reinforced resin composite components, and inorganic board-polymer composite components.

[0015] The present invention has the following beneficial effects: 1. This invention employs a multi-synergistic strengthening process involving micro-nano composite roughening, chemical activation, and functional transition layer gradient modification, overcoming the limitations of traditional single modification techniques. Through the synergistic effect of four mechanisms—micron-level mechanical interlocking, nano-level interface filling, chemical bonding, and modulus gradient transition—the interfacial bonding strength of composite components is significantly improved, effectively dispersing shear loads and alleviating interfacial stress concentration. The shear strength of the treated composite component interface is increased by more than 40% compared to traditional processes, completely solving failure problems such as interface debonding, delamination, and shear cracking.

[0016] 2. This invention achieves precise control over the surface roughness of the substrate, the content of active functional groups, and the thickness of the interface coating by precisely controlling the process parameters of laser etching, chemical roughening, and curing. The process has good repeatability and high stability, and can be adapted to various types of composite components such as metal-resin, fiber-reinforced resin, and inorganic-organic composites, with a wide range of applications.

[0017] 3. The silane coupling agent modified composite interface slurry designed in this invention has the functions of chemical crosslinking, micropore filling and stress transmission. It can effectively match the physical and chemical properties of different substrates, eliminate interface modulus abrupt defects, improve the interface fatigue shear resistance and extend the service life of composite components.

[0018] 4. The present invention has a simple overall process, is easy to operate, does not require large-scale precision equipment, has low energy consumption and no toxic or harmful byproducts, and is suitable for small-batch preparation in the laboratory and large-scale industrial production. It has extremely high engineering application value and promotion prospects. Detailed Implementation

[0019] An interface treatment method for improving the shear strength of composite components includes the following steps: S1. Substrate pretreatment: Select two sets of composite substrates for the composite component, and perform mechanical grinding, degreasing and deoiling, deionized water rinsing and drying in sequence to remove the oxide layer, oil, dust and impurities on the substrate surface and obtain a clean and flat substrate surface to be bonded. In step S1, mechanical polishing is performed by polishing with 800-2000 grit sandpaper in stages, and degreasing and oil removal are performed by ultrasonic cleaning with a mixture of anhydrous ethanol and acetone for 10-20 minutes at a cleaning temperature of 30-40℃. The drying temperature is 60-80℃ and the drying time is 30-60 minutes. S2. Surface micro-nano roughening modification: Laser etching composite chemical roughening treatment is performed on the pretreated substrate surface to be bonded, and a uniformly distributed micro-pit and nano-protrusion composite rough structure is constructed on the substrate surface to increase the specific surface area of ​​the substrate. Then, low temperature activation treatment is performed to introduce hydroxyl and carboxyl active functional groups. In step S2, the laser etching parameters are: laser power 8-15W, scanning speed 200-400mm / s, scanning spacing 50-100μm, and the surface roughness Ra of the substrate after etching is controlled at 1.5-3.5μm; chemical roughening is performed by immersion in a modified solution of dilute nitric acid and ethanol for 3-8 minutes. In step S2, the low-temperature activation treatment temperature is 40-60℃, the activation time is 20-40 min, and after activation, the water contact angle on the substrate surface drops to below 30°, and the surface active functional group coverage is ≥85%. S3. Preparation and coating of functional interface transition layer: Prepare silane coupling agent modified composite interface slurry, and uniformly spray / scrape the interface slurry onto the roughened surfaces to be bonded of the two substrates, control the coating thickness to be 2-30 μm, and allow it to stand at room temperature for 5-15 min to level. In step S3, the silane coupling agent modified composite interface slurry is composed of the following raw materials in parts by weight: 5-10 parts of silane coupling agent, 20-30 parts of epoxy resin prepolymer, 3-8 parts of nano silica powder, 2-5 parts of carbon nanotube dispersion, and 50-60 parts of anhydrous ethanol. The silane coupling agent is KH570 or KH550 type silane coupling agent, the particle size of the nano-silica powder is 2-30 nm, and the mass concentration of the carbon nanotube dispersion is 0.5-1.2%; In step S3, after the interface slurry is coated, it is subjected to UV pre-curing treatment for 3 to 5 minutes to form a preliminary cross-linking structure on the coating surface and avoid coating flow and accumulation. S4. Composite molding and curing strengthening: The two sets of substrates coated with the interface transition layer are precisely aligned and bonded together. A uniform bonding pressure of 0.2 to 0.5 MPa is applied, and a segmented gradient heating curing process is used for curing. After cooling to room temperature, the interface treatment of the composite component is completed, and a composite component with high shear strength is obtained.

[0020] In step S4, the segmented gradient temperature curing process is as follows: first, the temperature is raised to 80-100℃ and held for 30 minutes, then the temperature is raised to 120-140℃ and held for 60-90 minutes, and finally the temperature is naturally cooled to room temperature.

[0021] Composite components include any one of metal-resin composite components, carbon fiber reinforced resin composite components, and inorganic board-polymer composite components.

[0022] To achieve the above objectives, the present invention provides an interface treatment method for improving the shear strength of composite components, comprising the following steps: S1. Substrate Pretreatment: Select two sets of substrates matching the composite components. Use 800-2000 grit sandpaper to progressively sand the surfaces of the substrates to be bonded, removing burrs, oxide scale, and protruding defects. Then, immerse the substrates in a 2:1 volume ratio of anhydrous ethanol and acetone and ultrasonically clean them at 30-40°C for 10-20 minutes to thoroughly remove surface oil, dust, and impurities. After cleaning, rinse repeatedly with deionized water and dry in a 60-80°C oven for 30-60 minutes to obtain a clean, impurity-free substrate surface to be bonded. Progressive sanding ensures uniform surface flatness of the substrates, avoiding localized unevenness that could affect the subsequent interfacial bonding effect. Ultrasonic cleaning and drying thoroughly remove surface contaminants, laying the foundation for subsequent modification treatment.

[0023] S2. Surface Micro / Nano Roughening Modification: The pretreated substrate surface to be bonded is microstructured using laser etching equipment. The laser power is controlled at 8–15W, the scanning speed at 200–400 mm / s, and the scanning spacing at 50–100 μm to construct a uniform micron-scale pit structure on the substrate surface. Subsequently, the etched substrate is immersed in a dilute nitric acid-ethanol mixed modification solution for 3–8 min to perform nanoscale roughening modification, forming a micro / nano composite rough structure. The surface roughness Ra is controlled within the range of 1.5–3.5 μm to maximize the specific surface area and mechanical interlocking potential of the substrate. Finally, the roughened substrate is placed in a low-temperature activation environment of 40–60℃ for 20–40 min to introduce a large number of hydroxyl and carboxyl active functional groups on the substrate surface, thereby improving the chemical bonding ability between the substrate and the interface coating.

[0024] S3. Preparation and Coating of the Functional Interface Transition Layer: Accurately weigh 5-10 parts by weight of KH570 silane coupling agent, 20-30 parts by weight of epoxy resin prepolymer, 3-8 parts by weight of 2-30 nm nano-silica powder, 2-5 parts by weight of 0.5-1.2% carbon nanotube dispersion, and 50-60 parts by weight of anhydrous ethanol. Mix and stir at high speed for 20-30 min, then ultrasonically disperse for 15 min to prepare a uniform and stable composite interface slurry. The silane coupling agent enables chemical bonding between the substrate and the resin system; the nano-silica fills the interfacial micropores and improves interfacial density; and the carbon nanotubes conduct stress and disperse shear loads, achieving multiple reinforcements. The prepared interface slurry is uniformly sprayed or scraped onto the roughened surfaces of both substrates, controlling the coating thickness to 2-30 μm. After leveling at room temperature for 5-15 min, it is pre-cured under UV light for 3-5 min to form a preliminary cross-linked structure, preventing coating flow and uneven thickness.

[0025] S4. Composite Molding and Curing Strengthening: Two sets of substrates coated with the interface transition layer are precisely aligned and bonded together. A uniform surface pressure of 0.2–0.5 MPa is applied using a fixture to ensure a tight, gapless interface. A segmented gradient temperature curing process is then employed: first, the temperature is raised to 80–100℃ and held for 30 minutes to achieve initial cross-linking and shaping of the coating; then, the temperature is raised to 120–140℃ and held for 60–90 minutes to achieve complete cross-linking and curing of the interface coating and full bonding of functional groups. Finally, the temperature is allowed to naturally cool to room temperature in the furnace, the fixture is removed, and the interface treatment of the composite component is complete. The gradient curing process avoids problems such as interface bubbles and residual internal stress caused by rapid heating, ensuring a uniform and stable interface structure. Example

[0026] This embodiment provides an interface treatment method for aluminum alloy-epoxy resin composite components, the specific steps of which are as follows: S1. Substrate Pretreatment: Select aluminum alloy substrate and epoxy resin substrate, and successively polish the aluminum alloy surface to be bonded with 800 grit, 1200 grit and 2000 grit sandpaper; put the two sets of substrates into a mixed solution of anhydrous ethanol and acetone in a volume ratio of 2:1, and ultrasonically clean at 35℃ for 15 minutes to remove surface oil and impurities; rinse with deionized water and dry in a 70℃ oven for 45 minutes for later use.

[0027] S2. Surface micro-nano roughening modification: Laser etching was performed on the surface of the aluminum alloy substrate to be bonded, with a laser power of 12W, a scanning speed of 300mm / s, and a scanning spacing of 80μm; then the substrate was immersed in a dilute nitric acid-ethanol mixture for 5min to complete nano-roughening, and the surface roughness Ra was controlled to be 2.2μm; finally, the substrate was activated at 50℃ for 30min to introduce active functional groups.

[0028] S3. Preparation and coating of functional interface transition layer: Take 8 parts by weight of KH570 silane coupling agent, 25 parts of epoxy resin prepolymer, 5 parts of 30nm nano silica, 3 parts of 1.0% carbon nanotube dispersion, and 55 parts of anhydrous ethanol. Stir at high speed for 25 min and ultrasonically disperse for 15 min to prepare interface slurry. Spray the slurry evenly onto the surfaces of aluminum alloy and epoxy resin to be bonded. The coating thickness is 35μm. Level at room temperature for 10 min and pre-cur under ultraviolet light for 4 min.

[0029] S4. Composite molding and curing reinforcement: The two sets of substrates are precisely bonded together and a uniform pressure of 0.35MPa is applied; segmented curing: heat at 90℃ for 30min, heat at 130℃ for 75min, and then naturally cooled to room temperature to complete the preparation.

[0030] Testing showed that the interfacial shear strength of the aluminum alloy-epoxy resin composite component prepared in this embodiment reached 18.6 MPa, which is 51.2% higher than that of the traditional direct coating and curing process. After 1000 shear fatigue cycles, there was no debonding or cracking at the interface, demonstrating excellent performance stability. Example

[0031] This embodiment provides an interface treatment method for carbon fiber reinforced resin composite components, the specific steps of which are as follows: S1. Substrate pretreatment: Select carbon fiber preform and resin matrix board, gently sand with 1200 grit sandpaper to remove surface floating fibers and impurities, ultrasonically clean with anhydrous ethanol for 12 minutes, and dry at 35℃ for 40 minutes.

[0032] S2. Surface micro-nano roughening modification: Laser etching parameters: laser power 10W, scanning speed 250mm / s, scanning spacing 60μm; chemical roughening immersion for 4min, surface roughness Ra=1.8μm; low temperature activation at 45℃ for 25min.

[0033] S3. Preparation and coating of functional interface transition layer: 6 parts of KH550 silane coupling agent, 22 parts of epoxy resin prepolymer, 4 parts of 25nm nano silica, 2.5 parts of 0.8% carbon nanotube dispersion, and 52 parts of anhydrous ethanol were stirred and dispersed to prepare a slurry; the coating thickness was 25μm, leveling was performed for 8min, and UV pre-curing was performed for 3min.

[0034] S4. Composite molding and curing reinforcement: bonding pressure 0.25MPa; segmented curing: heat preservation at 85℃ for 30min, heat preservation at 125℃ for 60min, and natural cooling for molding.

[0035] Testing revealed that the composite component of this embodiment exhibits an interfacial shear strength of 22.3 MPa, representing a 48.7% improvement over traditional methods. The interface demonstrates high density and exhibits no delamination defects. Example

[0036] This embodiment provides an interface treatment method for inorganic ceramic plate-polyurethane composite components, the specific steps of which are as follows: S1. Substrate pretreatment: The ceramic plate and polyurethane substrate are sanded with 1000-grit sandpaper, ultrasonically cleaned at 40℃ for 18 minutes, and dried at 75℃ for 50 minutes.

[0037] S2. Surface micro / nano roughening modification: laser power 14W, scanning speed 350mm / s, scanning spacing 90μm; chemical roughening immersion for 7min, surface roughness Ra=3.2μm; activation at 55℃ for 35min.

[0038] S3. Preparation and coating of functional interface transition layer: 9 parts of KH570 silane coupling agent, 28 parts of epoxy resin prepolymer, 7 parts of 45nm nano silica, 4.5 parts of 1.2% carbon nanotube dispersion, and 58 parts of anhydrous ethanol; coating thickness 45μm, leveling for 12min, and UV pre-curing for 5min.

[0039] S4. Composite molding and curing reinforcement: bonding pressure 0.45MPa; segmented curing: heat preservation at 95℃ for 30min, heat preservation at 135℃ for 90min, and natural cooling for molding.

[0040] Testing showed that the interfacial shear strength of the composite component in this embodiment reached 15.8 MPa, which is 42.5% higher than that of the traditional process, and the high-temperature shear stability is significantly improved.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An interface treatment method for improving the shear strength of composite components, characterized in that, Includes the following steps: S1. Substrate pretreatment: Select two sets of composite substrates for the composite component, and perform mechanical grinding, degreasing and deoiling, deionized water rinsing and drying in sequence to remove the oxide layer, oil, dust and impurities on the substrate surface and obtain a clean and flat substrate surface to be bonded. S2. Surface micro-nano roughening modification: Laser etching composite chemical roughening treatment is performed on the pretreated substrate surface to be bonded, and a uniformly distributed micro-pit and nano-protrusion composite rough structure is constructed on the substrate surface to increase the specific surface area of ​​the substrate. Then, low temperature activation treatment is performed to introduce hydroxyl and carboxyl active functional groups. S3. Preparation and coating of functional interface transition layer: Prepare silane coupling agent modified composite interface slurry, and uniformly spray / scrape the interface slurry onto the roughened surfaces to be bonded of the two substrates, control the coating thickness to be 2-30 μm, and allow it to stand at room temperature for 5-15 min to level. S4. Composite molding and curing strengthening: The two sets of substrates coated with the interface transition layer are precisely aligned and bonded together. A uniform bonding pressure of 0.2 to 0.5 MPa is applied, and a segmented gradient heating curing process is used for curing. After cooling to room temperature, the interface treatment of the composite component is completed, and a composite component with high shear strength is obtained.

2. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S1, the mechanical polishing is carried out by polishing with 800-2000 grit sandpaper in stages, the degreasing and oil removal is carried out by ultrasonic cleaning with a mixture of anhydrous ethanol and acetone for 10-20 minutes at a cleaning temperature of 30-40℃, and the drying temperature is 60-80℃ for 30-60 minutes.

3. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S2, the laser etching parameters are: laser power 8-15W, scanning speed 200-400mm / s, scanning spacing 50-100μm, and the surface roughness Ra of the substrate after etching is controlled at 1.5-3.5μm; the chemical roughening is performed by immersion treatment in a mixture of dilute nitric acid and ethanol for 3-8 minutes.

4. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S2, the low-temperature activation treatment temperature is 40-60°C, the activation time is 20-40 min, and after activation, the water contact angle on the substrate surface drops to below 30°, and the surface active functional group coverage rate is ≥85%.

5. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S3, the silane coupling agent modified composite interface slurry is composed of the following raw materials in parts by weight: 5-10 parts of silane coupling agent, 20-30 parts of epoxy resin prepolymer, 3-8 parts of nano silica powder, 2-5 parts of carbon nanotube dispersion, and 50-60 parts of anhydrous ethanol.

6. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: The silane coupling agent is KH570 or KH550 type silane coupling agent, the particle size of the nano silica powder is 2-30 nm, and the mass concentration of the carbon nanotube dispersion is 0.5-1.2%.

7. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S3, after the interface slurry is coated, it is subjected to UV pre-curing treatment for 3 to 5 minutes to form a preliminary cross-linking structure on the coating surface and prevent the coating from flowing and accumulating.

8. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: In step S4, the segmented gradient heating and curing process is as follows: first, the temperature is raised to 80-100℃ and held for 30 minutes, then the temperature is raised to 120-140℃ and held for 60-90 minutes, and finally the temperature is naturally cooled to room temperature.

9. The interface treatment method for improving the shear strength of composite components according to claim 1, characterized in that: The composite component includes any one of the following: metal-resin composite component, carbon fiber reinforced resin composite component, and inorganic board-polymer composite component.