Metal-inlay composite heterogeneous structural member and composite forming method thereof

Abstract

This invention discloses a metal-embedded composite material heterogeneous structural component and its composite molding method, aiming to solve the problems of low interfacial bonding strength and large thermal strain in heterogeneous structures. The invention includes: sequentially degreasing, roughening, and plasma activation treatments on the interfacing surfaces of the metal and composite materials to construct a dual-mechanism combination of mechanical interlocking and chemical activation; employing a specific cyclic symmetrical layup method, combined with a pre-compacting and segmented hot-pressing process, to precisely constrain the metal component, reduce porosity, and offset thermal stress; and using a combination of co-bonding and secondary bonding processes to embed the metal component within the composite material during the curing stage, followed by secondary bonding after demolding and machining. This invention effectively overcomes the challenges of integrated molding of metal and composite materials, significantly reducing overall weight and ensuring reliability under complex conditions such as load-bearing, thermal conductivity, and impact resistance, providing a solid guarantee for the lightweight design and manufacturing of high-end equipment such as aerospace.

Description

Technical Field

[0001] This invention relates to the field of advanced composite material molding technology, specifically to a metal-embedded composite material heterogeneous structural component and its composite molding method. Background Technology

[0002] With the increasing urgency of lightweight structural requirements in high-end equipment manufacturing fields such as aerospace and new energy vehicles, carbon fiber reinforced composite materials are widely used due to their high specific strength and high specific stiffness. However, the performance of single composite materials is often limited under specific working conditions such as localized wear resistance, impact resistance, and high thermal conductivity. Therefore, combining metal components such as titanium alloys and aluminum alloys with composite materials to form metal-composite heterostructures has become an ideal solution that balances complex working conditions and lightweighting. These heterostructures retain the significant weight reduction advantage of composite materials while fully utilizing the excellent impact resistance, wear resistance, and high thermal conductivity of metal materials. Currently, the main methods for achieving the connection of metal and composite heterostructures include mechanical joining, adhesive bonding, and welding.

[0003] However, existing methods still face severe technical bottlenecks in practical applications. Mechanical connections require opening holes in the composite material, which not only cuts continuous fibers and easily causes severe stress concentration, but also introduces additional weight to the fasteners. The high temperatures of welding processes can easily cause thermal degradation and damage to the composite matrix. Conventional single-layer adhesive bonding processes often suffer from low mold positioning accuracy, high curing porosity, and difficulty in controlling interface bonding quality when dealing with complex heterogeneous components with multiple nested layers. Existing surface treatments before adhesive bonding are limited, resulting in uncontrollable micro-roughness and high surface chemical inertness, leading to low adhesive strength and high porosity at heterogeneous interfaces, making them prone to delamination failure under complex working conditions. Without specific surface treatment processes and refined layup control, heterogeneous interfaces are highly susceptible to debonding and delamination failure under service loads.

[0004] Therefore, in the lightweight design and manufacturing of complex structural components such as aerospace, there is an urgent need to develop a new composite molding process to overcome key technical bottlenecks such as low interfacial bonding strength of multiple materials and numerous defects in integrated molding, so as to achieve highly reliable and integrated manufacturing of high-performance metal-composite heterostructures. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a metal-embedded composite material heterogeneous structural component and its composite molding method, offering an efficient solution for the surface treatment process and refined layup molding control of metal and composite material heterogeneous structural components.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for composite molding of a metal-embedded composite material heterogeneous structural component, wherein the structural component includes a composite material matrix and a metal component embedded in the composite material matrix, the composite material matrix being a fiber-reinforced resin-based composite material, and the method includes the following steps:

[0008] S1. Pretreatment of metal parts: The mating surfaces of the metal parts are degreased, roughened and activated in sequence.

[0009] Degreasing treatment: The mating surfaces are wiped with isopropanol, alcohol or acetone solvent to remove surface contaminants;

[0010] Roughening treatment: Sandblasting, shot peening, sandpaper or grinding wheel are used to construct a micro-nano rough structure on the mating surface of the metal parts;

[0011] Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface;

[0012] S2. Prepreg Laying: Interlocking holes are made on each layer of fiber prepreg. The n layers of fiber prepreg are laid layer by layer through the interlocking holes and aligned with the metal parts, n>1, to form a prefabricated substrate. After the n layers of fiber prepreg are aligned and laid, the interlocking holes are connected to form an interlocking groove, and the shape of the interlocking groove matches the shape of the interlocking surface of the metal parts.

[0013] S3. Co-bonding and hot-press curing: The pre-made substrate is vacuum-sealed and then cured according to the preset temperature and pressure curve. The curing temperature is 120~190℃ and the curing pressure is 0.4~0.8MPa. Under these temperature and pressure conditions, the heat and pressure are maintained for more than 3 hours, and the total curing cycle is 8-10 hours.

[0014] S4. Demolding and Machining: Demolding and secondary processing of the cured precast substrate to obtain the finished product of metal-embedded composite material heterostructure.

[0015] Preferably, the roughening treatment controls the surface roughness of the mating surfaces of the metal parts to Ra1.0-Ra3.0;

[0016] The roughening process is carried out by sandblasting. The abrasive used for sandblasting is alumina or silicon carbide. The abrasive particle size of the metal parts is 80-220 mesh, and the sandblasting pressure is 3-5 bar.

[0017] As a preferred embodiment, the activation treatment introduces hydroxyl, carboxyl, carbonyl, or amino functional groups into the mating surfaces of the metal parts;

[0018] The activation process speed is 20-40 mm / s, the nozzle height is 20-35 mm, the processing power is 700-1000 W, and the air pressure is 2-3 bar.

[0019] Preferably, the composite matrix is ​​a carbon fiber reinforced resin matrix composite; the thickness of each layer of carbon fiber prepreg is 0.1-0.2 mm;

[0020] The laying sequence adopts a preset cyclic symmetrical layup configuration. This configuration is generated through finite element analysis and optimization design iteration, with specific structural features, boundary conditions and load conditions as input parameters. The cyclic symmetrical layup configuration includes +45°, -45°, 0° or 90°.

[0021] For each preset number of prepreg layers laid, a pre-vacuum compaction operation is performed for 10-30 minutes.

[0022] Preferably, a combination mold is used to position the metal part in step S2;

[0023] The combined mold includes a right tooling, a left tooling, a base, and a fixing device. The right and left toolings are respectively equipped with metal positioning parts for fixing the metal parts. The fiber prepreg is laid on the corresponding areas of the base, the right tooling, and the left tooling. After the laying is completed, the right tooling, the left tooling, and the base are fixed by the fixing device to compact the fiber prepreg.

[0024] Preferably, the metal parts are made of titanium alloy, aluminum alloy or aluminum-magnesium alloy.

[0025] The metal parts have protrusions, and the fitting grooves have matching grooves to increase the contact area between the metal parts and the prepreg.

[0026] As a preferred option, a zoned hot pressing process is adopted, with the structural components designed and laid in zones.

[0027] The precast substrates prepared in each zone are first subjected to hot pressing at a temperature of 50~60℃ and a pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for 0.5h. Then, the precast substrates in all zones are subjected to hot pressing and curing again at a curing temperature of 120~190℃ and a curing pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for more than 3h under these conditions. The total curing cycle is 8-10h.

[0028] A composite molding method for a metal-embedded composite material heterogeneous structural component, wherein the heterogeneous structural component includes a composite material matrix and a metal component embedded in the composite material matrix, the composite material matrix being a fiber-reinforced resin-based composite material; the method includes the following steps:

[0029] S1. Pretreatment of metal parts: The mating surfaces of the metal parts are degreased, roughened and activated in sequence.

[0030] Degreasing treatment: The mating surfaces are wiped with isopropanol, alcohol or acetone solvent to remove surface contaminants;

[0031] Roughening treatment: Sandblasting, shot peening, sandpaper or grinding wheel are used to construct a micro-nano rough structure on the mating surface of the metal parts;

[0032] Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface;

[0033] S2. Pretreatment of composite matrix: A fitting groove for the metal part is opened on the composite matrix, and the shape of the fitting groove matches the metal part;

[0034] Degreasing treatment: The fitting groove is cleaned with isopropanol, alcohol or acetone solvent to remove surface contaminants;

[0035] Roughening treatment: Sandblasting, shot blasting, sandpaper or grinding wheel are used; the composite matrix is ​​roughened only on the surface resin without damaging the internal reinforcing fibers;

[0036] Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface;

[0037] S3. Secondary bonding: Apply structural adhesive to the mating surface of the metal parts and the mating groove of the composite matrix after surface pretreatment, and then embed the metal parts into the mating groove.

[0038] S4. Curing and Molding: Molding is carried out under preset temperature and curing pressure; the curing temperature is 50-75℃, the curing pressure is 0.1-0.3MPa, and the temperature and pressure are maintained for more than 6 hours, and the total curing cycle is 7-8 hours.

[0039] Preferably, the surface roughness of the metal fitting surface is Ra1.0-Ra3.0; the surface roughness of the composite matrix fitting groove is Ra0.5-Ra1.0.

[0040] The roughening process adopts sandblasting. The abrasive used for sandblasting is alumina or silicon carbide. The abrasive particle size of metal parts is 80-220 mesh, and the sandblasting pressure is 3-5 bar. The abrasive particle size of composite matrix is ​​120-220 mesh, and the sandblasting pressure is 1-2 bar.

[0041] The activation treatment introduces hydroxyl, carboxyl, carbonyl or amino functional groups into the interlocking surfaces of the metal parts; the activation treatment speed for both the metal parts and the composite matrix is ​​20-40 mm / s, the nozzle height is 20-35 mm, the treatment power is 700-1000 W, and the air pressure is 2-3 bar.

[0042] The adhesive layer thickness is 0.15-0.2mm.

[0043] A metal-embedded composite heterogeneous structural component, the structural component comprising a composite matrix and a metal component embedded in the composite matrix, wherein the composite matrix is ​​a fiber-reinforced resin-based composite material, and the metal component is embedded in the composite matrix using the method described in claims 1-9.

[0044] The present invention has the following beneficial effects:

[0045] 1. This invention employs a metal-embedded heterogeneous structure design, combining the high specific strength and high specific stiffness of composite materials with the impact resistance, high thermal conductivity, and wear resistance of metallic materials. While ensuring equivalent service performance, it can reduce weight by 20%-30% compared to traditional pure titanium alloy structures, meeting the lightweight requirements of high-end equipment such as aerospace.

[0046] 2. This invention employs a degreasing-roughening-plasma activation composite surface treatment process. This process first removes surface contaminants through degreasing, then roughens the surface to create a microstructure with a roughness of Ra1.0-Ra3.0, and finally utilizes plasma activation to introduce oxygen- or nitrogen-containing polar functional groups such as hydroxyl (-OH), carboxyl (-COOH), carbonyl (-C=O), or amino (-NH2) groups onto the roughened surface. This dual mechanism of mechanical interlocking and chemical activation significantly enhances surface hydrophilicity and chemical activity, ensuring that subsequent adhesives can deeply penetrate the microstructure, thereby forming a high-strength, low-porosity, high-quality interface. After this treatment, the co-bonding strength of the final metal / composite heterostructure is increased to 30-40 MPa, and the secondary bonding strength reaches 40-50 MPa, representing a 30%-40% improvement compared to conventional processes, significantly enhancing the bonding quality and reliability of the interface.

[0047] 3. This invention strictly controls the adhesive layer thickness within the optimal range of 0.15-0.20 mm, and optimizes the stress distribution at the secondary bonding interface in conjunction with the aforementioned surface treatment process. This solution enables the secondary bonding strength of metal and composite materials to reach 40-50 MPa, improving performance by 30%-40% compared to conventional methods, and ensuring the connection stability of complex nested parts.

[0048] 4. This invention overcomes the problems of stress concentration and structural weight increase caused by traditional mechanical connections by first co-bonding the main body, then mechanically precisely grooving, and finally bonding the inserts a second time. At the same time, it avoids thermal degradation damage caused by high welding temperature, and realizes high-precision and high-strength manufacturing of complex nested structures of metal and composite materials.

[0049] 5. This invention achieves a two-way synergy between high-precision constraint of tooling and mold and structural layup optimization. Precise spatial constraint of the metal inserts is achieved under high temperature and pressure, and combined with pre-vacuuming and venting processes and segmented hot pressing processes, the internal porosity of the thick-walled structure is significantly reduced. On the other hand, by strictly constraining the metal parts within the critical load-bearing area, and combining finite element optimization design, the main composite material adopts a specific [+45 / 0 / -45 / 0 / +45 / 90 / -45 / 0 / +45 / 90]s cyclic symmetrical layup. This not only effectively offsets the curing thermal stress between heterogeneous materials and ensures molding accuracy, but also achieves an overall weight reduction of 20%-30% compared to traditional pure metal structures while maintaining equivalent service performance. Attached Figure Description

[0050] Figure 1 This is an assembly drawing of a metal-embedded composite material heterostructure component in one embodiment.

[0051] Figure 2 This is an exploded view of a metal-embedded composite material heterostructure component in one embodiment.

[0052] Figure 3 This is a mold assembly drawing of a metal-embedded composite material heterostructure component in one embodiment.

[0053] Figure 4 This is an exploded view of a mold for a metal-embedded composite material heterostructure component in one embodiment.

[0054] Figure 5 This is a process flow diagram of the composite molding method in the embodiment.

[0055] Figure 6 This is a schematic diagram of the composite molding method in the embodiment.

[0056] Figure 7 This is a diagram showing the layup sequence of the carbon fiber prepreg in the embodiment.

[0057] Figure 8 This is a surface morphology diagram of a composite matrix after sandblasting.

[0058] Figure 9 This is a surface morphology diagram of a metal part after sandblasting.

[0059] Figure 10 This is a diagram showing the atomic percentage of the surface of a metal part before and after plasma treatment.

[0060] Figure 11 This is a diagram showing the surface atomic percentage of the composite matrix before and after plasma treatment.

[0061] Figure 12 It is a load-displacement curve of the interfacial shear strength of metal / composite materials under various processes.

[0062] Wherein: 1-Composite matrix, 2-Outer ring of bushing, 3-Bushing base, 4-Metal ring, 5-Right tooling, 6-Left tooling, 7-Right C-shaped positioning block, 8-Left C-shaped positioning block, 9-Base, 10-Positioning screw, 11-Right prepreg, 12-Left prepreg, 13-Base plate prepreg, 14-Groove prepreg. Detailed Implementation

[0063] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0064] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0065] like Figures 1-7 As shown, a metal-embedded composite material heterostructure includes a composite material matrix 1 and a metal component embedded in the composite material matrix 1.

[0066] Since different regions of the structural components require different service performance, this application adopts a split design for the structural components, aiming to achieve structural lightweighting and meet the needs of complex working conditions in high-end equipment fields such as aerospace.

[0067] The composite matrix 1 is made of fiber-reinforced resin matrix composite material, preferably carbon fiber-reinforced resin matrix composite material. This material has the characteristics of high specific strength, high specific stiffness and low density, and is suitable for the main load-bearing skeleton and lightweight area of ​​structural components.

[0068] The preferred materials for metal parts are titanium alloy, aluminum alloy, or aluminum-magnesium alloy. These materials have excellent wear resistance, impact resistance, and high thermal conductivity, making them suitable for high-load connection areas, stress concentration areas, assembly ends that require frequent disassembly, and areas subject to impact or heat concentration in structural components.

[0069] In this embedded design, metal components are typically pre-embedded at the joints of the composite material, forming a locally reinforced embedded body. This split-type composite design can fully leverage the advantages of each dissimilar material, balancing overall lightweighting with high local reliability, thereby meeting the differentiated mechanical performance and functional requirements of different areas of the structural component.

[0070] This application provides two molding process paths for embedding metal parts into a composite matrix 1: co-bonding and secondary bonding, to adapt to different manufacturing needs.

[0071] Co-bonding is suitable for manufacturing scenarios requiring high-precision integrated molding of structural components and streamlined assembly processes. In this process, the metal parts are pre-positioned during the composite material layup stage, and then simultaneously placed in a can for thermo-pressing and curing with the prepreg / resin matrix. This process offers high production efficiency and is particularly suitable for mass production and integrated manufacturing of complex curved structures, but it places stringent requirements on the positioning accuracy of the pre-embedded parts in the mold.

[0072] The secondary bonding process is suitable for scenarios requiring extremely high dimensional accuracy and precise assembly, or for large metal inserts that are prone to thermal deformation under the high temperature and pressure of an autoclave. This process is also applicable to later-stage local structural reinforcement and repair maintenance of cured composite material components. It involves first curing the composite matrix 1 and precisely machining the fitting groove, then bonding and curing the metal parts. This effectively avoids the risk of insert displacement during the co-curing process, resulting in superior dimensional controllability and assembly accuracy.

[0073] (a) The specific process of co-bonding is as follows.

[0074] S1. Pretreatment of metal parts: The mating surfaces of the metal parts (i.e. the contact surfaces with the carbon fiber prepreg) are sequentially degreased, roughened, and activated to significantly improve the interfacial bonding force between the metal and the resin matrix / adhesive.

[0075] Specifically, the degreasing process involves repeatedly wiping the mating surfaces of the metal parts with isopropanol, alcohol, or acetone to remove surface oil and grease.

[0076] The roughening process specifically involves sandblasting (with abrasive particles of 80-220 mesh and a sandblasting pressure of 3-5 bar), shot peening, sandpaper, or grinding with a grinding wheel to construct a micro-nano rough structure on the mating surface of the metal parts, so that the surface roughness of the mating surface of the metal parts after the treatment reaches Ra1.0-Ra3.0.

[0077] The activation treatment specifically involves air, oxygen, or nitrogen plasma treatment at a speed of 20-40 mm / s, a nozzle height of 20-35 mm, a power of 700-1000 W, and a pressure of 2-3 bar. This introduces oxygen- or nitrogen-containing polar functional groups such as hydroxyl (-OH), carboxyl (-COOH), carbonyl (-C=O), or amino (-NH2) onto the intercalated surface of the metal parts, thereby significantly improving the surface hydrophilicity and chemical activity, ensuring that the resin of the composite material can effectively wet into the microstructure of the metal.

[0078] In this embodiment, the roughening treatment adopts sandblasting process, and the sandblasting abrasive is alumina (or silicon carbide). The abrasive particle size of metal sandblasting is 120 mesh, and the sandblasting pressure is controlled at 4 bar. After the treatment, the surface roughness of the titanium alloy mating surface reaches Ra1.2. The activation treatment adopts air plasma treatment with a processing speed of 26 mm / s, a nozzle height of 25 mm, a processing power of 750 W, and an air pressure of 2.5 bar.

[0079] S2. Prepreg Laying: Interlocking holes are made in each layer of fiber prepreg. n layers of fiber prepreg are laid layer by layer through these interlocking holes, aligning with the metal component, where n > 1, to form a prefabricated substrate. After the n layers of fiber prepreg are laid, the interlocking holes connect to form an interlocking groove, which matches the shape of the interlocking surface of the metal component. The thickness of each layer of fiber prepreg is 0.1-0.2 mm. During the entire laying process, to reduce internal porosity, a pre-vacuum compaction operation is performed after each preset number of prepreg layers are laid, lasting 10-30 minutes.

[0080] In the integrated molding of complex heterogeneous components, metal parts are prone to slippage when the resin flows at high temperatures, resulting in low positioning accuracy. Furthermore, the one-time laying of thick-walled composite materials is prone to internal pores. At the same time, existing composite / metal heterogeneous structures lack layup optimization for the differences in thermal expansion coefficients of heterogeneous materials, which easily leads to thermal stress coupling and warping deformation during the curing process, resulting in poor structural stability and limited weight reduction effect.

[0081] In this embodiment, the carbon fiber prepreg used has a single-layer thickness of 0.1 mm. To optimize stress distribution, reduce warpage, and achieve better mechanical properties, the composite matrix 1 adopts a preset cyclic symmetrical layup configuration. This configuration is generated iteratively through finite element analysis and optimization design, using specific structural features, boundary conditions, and load conditions as input parameters, thereby achieving precise matching between the composite layup configuration and specific application scenarios. Figure 7 As shown, the preferred cyclic symmetrical layup configuration is +45°, -45°, 0°, or 90°. A pre-vacuum compaction operation is performed after every 5-10 layers of prepreg, with each compaction lasting 20 minutes.

[0082] Furthermore, in step S2, a special combination mold is used to precisely position the metal parts. The combination mold includes a right tooling 5, a left tooling 6, a base 9, and a fixing device. The right tooling 5 and the left tooling 6 are respectively equipped with metal positioning parts for fixing the metal parts. The carbon fiber prepreg is laid on the corresponding areas of the base 9, the right tooling 5, and the left tooling 6. After the laying is completed, the right tooling 5, the left tooling 6, and the base 9 are fixed by the fixing device to compact the carbon fiber prepreg.

[0083] In this embodiment, the metal parts include a metal bushing, which includes an outer bushing ring 2 and a bushing base 93. The outer bushing ring 2 and the bushing base 93 are respectively fitted onto the metal positioning parts of the right tooling 5 and the left tooling 6. The carbon fiber prepreg is divided into right prepreg 11, left prepreg 12, base plate prepreg 13, and grooved prepreg 14. During installation, the right prepreg 11 is laid in the corresponding area of ​​the right tooling 5, the left prepreg 12 is laid in the corresponding area of ​​the left tooling 6, the base plate prepreg 13 is laid in the area of ​​the base 9, and the grooved prepreg 14 precisely fills the gap between the left and right prepregs 11. The fixing device includes a right C-shaped positioning block 7, a left C-shaped positioning block 8, and a positioning screw 10, which fix the right tooling 5, the left tooling 6, and the base 9, respectively. The outer bushing ring 2 and the bushing base 93 are respectively provided with sockets and inserts, and the fitting and positioning are achieved by using a socket connection method.

[0084] The metal parts are also provided with protrusions, and the fitting grooves are provided with matching grooves to increase the contact area between the metal parts and the prepreg.

[0085] S3. Co-bonding and hot-press curing: The pre-made substrate is vacuum-sealed and placed in a hot-pressing device, and then cured and molded according to the preset temperature and pressure curve. The curing temperature is 120~190℃, the curing pressure is 0.4~0.8MPa, and the temperature and pressure are maintained for more than 3 hours under these conditions. The total curing cycle is 8-10 hours.

[0086] For complex heterogeneous components, this application adopts a zoned hot-pressing process, that is, the heterogeneous components are designed and laid in zones; the precast substrate prepared in each zone is first hot-pressed, with a curing temperature of 50~60℃ and a curing pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for 0.5h; then the precast substrate in all zones is hot-pressed and cured again, with a curing temperature of 120~190℃ and a curing pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for more than 3h under these conditions, and the total curing cycle is 8-10h.

[0087] In this embodiment, the part is placed in a hot press and heated to 55°C for half an hour while maintaining a vacuum of ≤-0.085 MPa. The pressure is 0.65 MPa, the pressure increase rate is 0.02-0.05 MPa / min, the heating rate is 1.0°C / min~2.0°C / min, the pressure drops to 0, and the temperature drops below 30°C to end the curing process and remove the product. Before the second curing, perform a vacuum tightness retest, evacuate to -0.085 MPa and maintain above for 10 minutes. The heating rate is 1.0℃ / min~2.0℃ / min, and the temperature is raised to 120℃. Hold at this temperature for 1 hour. After the holding period, the temperature is raised to 175-185℃ at a rate of 1.0℃ / min~2.0℃ / min, preferably 180℃, and held at this temperature for more than 2 hours. After the holding period, the temperature is lowered at a rate of 1.0℃ / min~2.0℃ / min. When the temperature of the thermocouple with the fastest cooling rate drops below 60℃, the curing process is complete and the product is removed.

[0088] During this curing process, the resin matrix undergoes a full cross-linking reaction and is cured in synergy with the pre-coated adhesive, effectively eliminating interfacial pores and enabling high-strength co-bonding between the metal parts and the composite matrix 1.

[0089] S4. Demolding and Machining: Demolding and secondary processing of the cured precast substrate to obtain the finished product of metal-embedded composite material heterostructure.

[0090] In this embodiment, after the autoclave cools and depressurizes, the solidified precast substrate is demolded, and then the precast substrate is precision machined to remove excess flash and form the final outline.

[0091] (ii) The specific process of secondary bonding is as follows.

[0092] The composite matrix 1 is made of fiber-reinforced resin-based composite material, preferably carbon fiber-reinforced resin-based composite material. The composite matrix 1 can be formed by laying and curing n layers of carbon fiber prepreg. The metal parts are preferably made of titanium alloy, aluminum alloy or aluminum-magnesium alloy.

[0093] S1. Pretreatment of metal parts: The mating surfaces of the metal parts are degreased, roughened and activated in sequence.

[0094] Degreasing treatment: The mating surfaces are wiped with isopropanol, alcohol or acetone solvent to remove surface contaminants;

[0095] Roughening treatment: Sandblasting, shot blasting, sandpaper or grinding wheel are used to control the surface roughness of the mating surfaces of the metal parts to Ra1.0-Ra3.0; sandblasting is preferred for roughening treatment. The abrasive used for sandblasting is alumina or silicon carbide. The abrasive particle size of the metal parts is 80-220 mesh, and the sandblasting pressure is 3-5 bar.

[0096] Activation treatment: The roughened surface of the mating surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups such as hydroxyl (-OH), carboxyl (-COOH), carbonyl (-C=O) or amino (-NH2) on the roughened surface of the metal part, thereby significantly improving the surface hydrophilicity and chemical activity, ensuring that the resin of the composite material can effectively wet into the interior of the metal microstructure;

[0097] S2. Pretreatment of composite matrix 1: A fitting groove for the metal part is opened on the composite matrix 1, and the shape of the fitting groove matches the metal part; this design of first forming the main body and then opening the groove effectively releases the thermal stress generated by the first curing.

[0098] Referring to step S1, the interlocking groove of the composite matrix 1 is subjected to degreasing, roughening and activation treatment;

[0099] Degreasing treatment: The fitting groove is cleaned with isopropanol, alcohol or acetone solvent to remove surface contaminants;

[0100] Roughening treatment: The roughening is carried out by sandblasting, shot blasting, sandpaper or grinding wheel; the surface roughness of the interlocking groove of the composite matrix 1 is Ra0.5-Ra1.0; when roughening the composite matrix 1, only the surface resin is roughened and the internal reinforcing fibers are not damaged; the abrasive particle size of the composite matrix is ​​120-220 mesh, and the sandblasting pressure is 1-2 bar;

[0101] Activation treatment: The surface of the interlocking groove is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups such as hydroxyl (-OH), carboxyl (-COOH), carbonyl (-C=O) or amino (-NH2) into the interlocking groove, thereby significantly improving the surface hydrophilicity and chemical activity, ensuring that the subsequent adhesive can effectively penetrate into the interior of the microstructure.

[0102] The activation treatment speed for both metal parts and composite matrix is ​​20-40 mm / s, the nozzle height is 20-35 mm, the treatment power is 700-1000 W, and the air pressure is 2-3 bar.

[0103] S3. Secondary bonding: Apply structural adhesive to the mating surfaces of the pre-treated metal parts and the mating grooves of the composite materials, controlling the adhesive layer thickness to be 0.15-0.2mm, and then embed the metal parts into the mating grooves.

[0104] S4. Curing and Molding: Molding is carried out under preset temperature and curing pressure. The curing temperature is 50-75℃, and the curing pressure is 0.1-0.3MPa. Under these temperature and pressure conditions, the temperature and pressure are maintained for more than 6 hours, and the total curing cycle is 7-8 hours.

[0105] In this embodiment, the metal part includes a metal ring 4. A bottom groove for accommodating the metal ring 4 is machined into the bottom of the composite matrix 1. The sandblasting pressure is 1.5 Bar, and the abrasive mesh size is 220 mesh, ensuring that the surface roughness is maintained at Ra0.5-Ra1.0, only roughening the surface resin without damaging the internal reinforcing fibers. The metal ring 44, treated with S1, is coated with structural adhesive. In this embodiment, the adhesive layer thickness is controlled at 0.15 mm. It is embedded into the bottom groove of the composite matrix 11 by secondary bonding. The adhesive is cured at 0.2 MPa, a curing temperature of 75°C, a pressure increase rate of 0.05 MPa / min, and a heating rate of 1-2°C / min, thereby effectively optimizing the stress distribution at the secondary bonding interface and the connection stability of complex nested parts. Finally, the overall heterogeneous structural part is subjected to final finishing and dimensional inspection, thus completing the preparation.

[0106] Compared to the untreated state, the molding method of this embodiment improves the interfacial bonding strength between the metal and composite materials by 20% to 30% and the interfacial bonding strength by 30% to 40% compared to existing methods. While achieving a significant weight reduction of 20% to 30%, it effectively solves the technical problems of weak interfacial bonding between metal and composite materials and numerous molding defects.

[0107] To address the requirements of complex metal / composite heterogeneous material nested structures, this embodiment provides a co-bonding + secondary bonding combined process. In this process, the metal component is directly co-bonded and embedded into the composite material during the curing stage; after demolding, the composite component is precision machined, and then the metal component is re-bonded. This co-bonding + secondary bonding combined process effectively solves the challenge of integrated molding of complex nested structures. It addresses the problems of traditional metal-composite material heterogeneous structure connections, which often rely on single mechanical connections (requiring openings, leading to continuous fiber cutting, severe stress concentration, and the introduction of fastener weight), welding (causing thermal degradation damage to the composite matrix at high temperatures), or single conventional bonding (prone to debonding in multi-layered complex nested structures).

[0108] Figure 8The evolution of the microstructure and roughness of the composite material surface after sandblasting is shown. The core of composite material surface treatment lies in balancing the contradiction between removing the weak boundary layer and avoiding fiber damage. The untreated CFRP surface exhibits typical resin enrichment characteristics and is relatively smooth (Ra=0.58μm). This low-energy surface is not conducive to adhesive wetting and bonding. To prevent high-energy impact from causing fracture or delamination damage to the carbon fibers, mild process parameters (220-mesh fine abrasive, 1 bar low air pressure) were used in the experiment. The three-dimensional morphology after treatment shows that the smooth resin skin was effectively peeled off, exposing a rougher and denser microstructure. The roughness Ra was significantly increased to 1.02μm, while the resin thickness on the surface of the carbon fiber prepreg with a nominal thickness of 0.1mm was about 5-10μm. This indicates that the low-pressure fine sandblasting process successfully increased the specific surface area of ​​the composite material surface without damaging the load-bearing fibers, providing abundant micropores and grooves for the adhesive, thereby helping to form an effective mechanical interlocking structure.

[0109] Figure 9 The evolution of the microstructure and roughness of metal surfaces after sandblasting is shown. For titanium alloy substrates, with 120-mesh abrasive, the surface roughness exhibits a clear linear increase (Ra increases from 0.49 μm to 1.08 μm) as the sandblasting pressure increases from 1 bar to 4 bar. At low pressure (1 bar), the abrasive kinetic energy is insufficient, producing only shallow scratches; however, as the pressure increases to 4 bar, the high-energy abrasive grains induce intense plastic deformation and cutting action on the metal substrate, forming a deep and uniformly distributed peak-valley structure. This high-roughness surface not only significantly increases the physical contact area and enhances the mechanical interlocking force, but also removes the oxide layer and contaminants from the surface, activating the metal surface and giving it higher surface free energy, which is beneficial for improving the bonding strength between the adhesive layer and the substrate interface.

[0110] Figure 10The effects of plasma treatment on the chemical composition and activity of metal surfaces are illustrated. The titanium alloy surface underwent a drastic surface cleaning and oxide layer activation process before and after treatment. Before treatment, a high C1s signal of 38.94% was detected on the titanium alloy surface, mainly due to hydrocarbon contaminants adsorbed from the air covering the metal substrate. After plasma bombardment, the C1s content sharply decreased to 18.67%, indicating that surface organic contaminants were effectively removed. Simultaneously, the O1s content increased significantly from 41.90% to 64.22%, becoming the dominant element on the surface. This suggests that plasma not only removed impurities but also promoted the growth and densification of the oxide film on the titanium alloy surface, potentially forming more chemically active TiO2 and Ti-OH structures. Although the relative atomic percentage of Ti2p apparently decreased due to the surge in oxygen content (from 15.37% to 9.93%), the significant increase in the surface oxygen-to-titanium ratio confirms the activation of the metal surface oxidation state; such oxygen-rich surfaces are typically accompanied by higher surface activity.

[0111] Figure 11 The effects of plasma on the surface chemical composition and activity of composite materials are shown. Based on X-ray photoelectron spectroscopy (XPS) full-spectrum scanning data, the modification effect of atmospheric pressure low-temperature plasma on carbon fiber reinforced composites is illustrated in the figure. Plasma treatment produced significant chemical etching and oxidation of the resin matrix on the CFRP surface. Before treatment, the C1s peak (284.8 eV) on the CFRP surface had extremely high intensity, accounting for 76.39% of the atoms, while the O1s peak (531.1 eV) accounted for only 23.61%, exhibiting strong inert characteristics. After plasma treatment, the C1s content decreased significantly to 58.73%, while the O1s content surged to 41.27%, and the O / C atomic ratio jumped from 0.31 to 0.70. This significant change indicates that high-energy particles in the plasma (such as free radicals, electrons, and metastable ions) initiated the oxidation reaction, grafting a large number of oxygen-containing polar functional groups (such as hydroxyl -OH, carboxyl -COOH, or carbonyl C=O) onto the surface. The introduction of these polar groups significantly increases the surface energy and polar component of the composite material surface, improves surface wettability, and provides favorable thermodynamic conditions for the subsequent wetting and spreading of adhesives.

[0112] Figure 12The effects of sandblasting and plasma composite processes on the bonding performance of metal / composite materials are illustrated. Comparative analysis of load-displacement curves based on the interfacial shear strength of the metal / composite materials shows that surface treatment has a decisive influence on interfacial bonding performance. The untreated group exhibits significantly low strength (10–22 MPa), indicating that adhesive layer control alone cannot overcome the weak boundary layer and low wettability of the original surface. Although plasma treatment alone increases the strength to approximately 30 MPa through chemical activation, its ductility in the subsequent yielding stage is limited due to the smoothness of the surface morphology. In contrast, sandblasting alone, thanks to the mechanical interlocking effect brought about by micro-roughness, significantly improves the strength by approximately 40 MPa. Most notably, the sandblasting + plasma composite process achieves the optimal synergistic enhancement effect, with the shear strength reaching a peak of approximately 45 MPa, an increase of approximately 100% compared to the maximum value of the untreated group. This composite mechanism not only utilizes sandblasting to construct deep mechanical anchoring points, but also ensures the full wetting and chemical bonding of the adhesive in the micro-rough structure through plasma cleaning and activation. Thus, through the dual mechanism of mechanical interlocking and chemical connection, it delays interface failure to the maximum extent, giving the joint the highest load-bearing capacity and fracture toughness.

[0113] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for composite molding of metal-embedded composite material heterogeneous structural parts, characterized in that, The structural component includes a composite material matrix and a metal component embedded in the composite material matrix. The composite material matrix is ​​a fiber-reinforced resin-based composite material. The method includes the following steps: S1. Pretreatment of metal parts: The mating surfaces of the metal parts are degreased, roughened and activated in sequence. Degreasing treatment: The mating surfaces are wiped with isopropanol, alcohol or acetone solvent to remove surface contaminants; Roughening treatment: Sandblasting, shot peening, sandpaper or grinding wheel are used to construct a micro-nano rough structure on the mating surface of the metal parts; Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface; S2. Prepreg Laying: Interlocking holes are made on each layer of fiber prepreg. The n layers of fiber prepreg are laid layer by layer through the interlocking holes and aligned with the metal parts, n>1, to form a prefabricated substrate. After the n layers of fiber prepreg are aligned and laid, the interlocking holes are connected to form an interlocking groove, and the shape of the interlocking groove matches the shape of the interlocking surface of the metal parts. S3. Co-bonding and hot-press curing: The pre-made substrate is vacuum-sealed and then cured according to the preset temperature and pressure curve. The curing temperature is 120~190℃ and the curing pressure is 0.4~0.8MPa. Under these temperature and pressure conditions, the substrate is kept at the temperature and pressure for more than 3 hours.

2. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, Roughening treatment controls the surface roughness of the mating surfaces of metal parts to Ra1.0-Ra3.0; The roughening process is carried out by sandblasting. The abrasive used for sandblasting is alumina or silicon carbide. The abrasive particle size of the metal parts is 80-220 mesh, and the sandblasting pressure is 3-5 bar.

3. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, Activation treatment introduces hydroxyl, carboxyl, carbonyl, or amino functional groups into the mating surfaces of metal parts; The activation process speed is 20-40 mm / s, the nozzle height is 20-35 mm, the processing power is 700-1000 W, and the air pressure is 2-3 bar.

4. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, The composite matrix is ​​a carbon fiber reinforced resin matrix composite; the thickness of each layer of carbon fiber prepreg is 0.1-0.2 mm; The laying sequence adopts a preset cyclic symmetrical layup configuration. This configuration is generated through finite element analysis and optimization design iteration, with specific structural features, boundary conditions and load conditions as input parameters. The cyclic symmetrical layup configuration includes +45°, -45°, 0° or 90°. For each preset number of prepreg layers laid, a pre-vacuum compaction operation is performed for 10-30 minutes.

5. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, In step S2, a combination mold is used to position the metal part; The combined mold includes a right tooling, a left tooling, a base, and a fixing device. The right and left toolings are respectively equipped with metal positioning parts for fixing the metal parts. The fiber prepreg is laid on the corresponding areas of the base, the right tooling, and the left tooling. After the laying is completed, the right tooling, the left tooling, and the base are fixed by the fixing device to compact the fiber prepreg.

6. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, The preferred materials for metal parts are titanium alloy, aluminum alloy, or aluminum-magnesium alloy; The metal parts have protrusions, and the fitting grooves have matching grooves to increase the contact area between the metal parts and the prepreg.

7. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 1, characterized in that, The structural components are designed and laid in sections using a zoned hot pressing process. The precast substrates prepared in each zone are first subjected to hot pressing at a temperature of 50~60℃ and a pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for 0.5h. Then, the precast substrates in all zones are subjected to hot pressing and curing again at a curing temperature of 120~190℃ and a curing pressure of 0.4~0.8MPa, and the temperature and pressure are maintained for more than 3h under these conditions.

8. A composite molding method for a metal-embedded composite material heterogeneous structural component, characterized in that, The heterogeneous structural component includes a composite material matrix and a metal component embedded in the composite material matrix, wherein the composite material matrix is ​​a fiber-reinforced resin-based composite material; the method includes the following steps: S1. Pretreatment of metal parts: The mating surfaces of the metal parts are degreased, roughened and activated in sequence. Degreasing treatment: The mating surfaces are wiped with isopropanol, alcohol or acetone solvent to remove surface contaminants; Roughening treatment: Sandblasting, shot peening, sandpaper or grinding wheel are used to construct a micro-nano rough structure on the mating surface of the metal parts; Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface; S2. Pretreatment of composite matrix: A fitting groove for the metal part is opened on the composite matrix, and the shape of the fitting groove matches the metal part; Degreasing treatment: The fitting groove is cleaned with isopropanol, alcohol or acetone solvent to remove surface contaminants; Roughening treatment: Sandblasting, shot blasting, sandpaper or grinding wheel are used; the composite matrix is ​​roughened only on the surface resin without damaging the internal reinforcing fibers; Activation treatment: The interlocking surface is treated with air, oxygen or nitrogen plasma to introduce oxygen- or nitrogen-containing polar functional groups into the interlocking surface; S3. Secondary bonding: Apply structural adhesive to the mating surface of the metal parts and the mating groove of the composite matrix after surface pretreatment, and then embed the metal parts into the mating groove. S4. Curing and molding: Molding is carried out under preset temperature and curing pressure; the curing temperature is 50-75℃, the curing pressure is 0.1-0.3MPa, and the temperature and pressure are maintained for more than 6 hours.

9. The method for composite molding of a metal-embedded composite material heterogeneous structural component according to claim 8, characterized in that, The surface roughness of the mating surfaces of metal parts is Ra1.0-Ra3.0; the surface roughness of the mating grooves of composite material matrices is Ra0.5-Ra1.

0. The roughening process adopts sandblasting. The abrasive used for sandblasting is alumina or silicon carbide. The abrasive particle size of metal parts is 80-220 mesh, and the sandblasting pressure is 3-5 bar. The abrasive particle size of composite matrix is ​​120-220 mesh, and the sandblasting pressure is 1-2 bar. The activation treatment introduces hydroxyl, carboxyl, carbonyl or amino functional groups into the interlocking surfaces of the metal parts; the activation treatment speed for both the metal parts and the composite matrix is ​​20-40 mm / s, the nozzle height is 20-35 mm, the treatment power is 700-1000 W, and the air pressure is 2-3 bar. The adhesive layer thickness is 0.15-0.2mm.

10. A metal-embedded composite material heterogeneous structural component, characterized in that, The structural component includes a composite material matrix and a metal component embedded in the composite material matrix. The composite material matrix is ​​a fiber-reinforced resin-based composite material, and the metal component is embedded in the composite material matrix using the method described in claims 1-9.

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