Forming method and mold for solid particle integrated fiber reinforced metal laminate

Abstract

The invention provides a forming and forming method and mold for a solid particle integrated fiber-reinforced metal laminate, and relates to the technical field of composite board processing, and the forming and forming method comprises the following steps: paving a pretreated metal board and a fiber-reinforced prepreg to obtain a fiber-reinforced metal laminate sample in a semi-cured state; the sample is positioned and installed in the forming female die, and the center of the sample coincides with the axis of the punch in the forming process; the edge pressing charging barrel and the forming female die are connected through a disc spring, the edge pressing charging barrel is filled with quantitative solid particle media, and a guide ring and a forming punch are assembled; the mold is heated to a prepreg forming temperature interval, and the punch compacts the medium to achieve plastic forming; and synchronously raising the temperature to a curing temperature to complete curing of the prepreg. Forming and curing processes are integrated in a single mold, the problems of interface pollution and thermal stress accumulation of traditional step-by-step manufacturing are solved by utilizing the flexible pressure transfer characteristic of granular media, and high-precision forming and interface combination strengthening machining of complex curved surface components are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite plate processing, and in particular to a forming method and a mould for a solid particle integrated fiber reinforced metal laminate. Background Art

[0002] As an advanced lightweight structural material, fiber-reinforced metal laminates have important application value in strategic emerging industries such as aerospace, new energy vehicles, and high-end equipment manufacturing due to their excellent specific strength, fatigue resistance, and damage tolerance. The traditional forming process of fiber-reinforced metal laminates usually adopts a step-by-step forming process, namely hot pressing forming + autoclave curing or reverse process. This process is not only complicated and inefficient, but also very easy to produce interface contamination and thermal stress accumulation during multiple clamping processes, resulting in a significant reduction in interlayer bonding performance. More prominently, existing technologies are difficult to achieve high-precision forming of complex curved surface components of fiber-reinforced metal laminates, resulting in its current limitation to simple curvature parts such as aircraft skins and door fairings with a curvature radius greater than 500mm. However, its application in complex components such as cylindrical parts and double-curvature wall panels with a curvature radius less than 200mm is severely restricted, resulting in the inability of fiber-reinforced metal laminates to be applied on a large scale in the field of high-end equipment.

[0003] Therefore, it is necessary to propose a forming method and mold for solid particle integrated fiber reinforced metal laminates to achieve the manufacture of high-performance, complex curved fiber reinforced metal laminates. Summary of the Invention

[0004] In order to address the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a forming method and mold for solid particle integrated fiber reinforced metal laminates, which realizes the integration of plastic forming and prepreg curing of fiber reinforced metal laminates in a single mold by synchronously regulating temperature and pressure, and utilizes the fluidity of semi-cured prepregs combined with the flexible pressure transmission of granular media to make the resin synchronously fill the micropores on the metal surface and complete the shape forming; by applying dynamic pressure from the granular medium to the anodized metal sheet and the fiber prepreg in the semi-cured stage, the prepreg matrix resin is forced to fully infiltrate the micropores of the metal surface oxide film, forming a mechanical and chemical composite anchoring effect, thereby enhancing the interface bonding performance between metal and fiber reinforced prepreg; through the flexible pressure transmission of the solid granular medium, the stress concentration in the complex curved surface forming is reduced, and the occurrence of fiber damage is reduced.

[0005] Specifically, in one aspect, the present invention provides a forming method for a solid particle integrated fiber reinforced metal laminate, which comprises the following steps: S1. Laying the pretreated metal sheet and the fiber-reinforced prepreg, and heating and pressurizing the selected materials to form a preliminary bonding layer and obtain a semi-cured fiber-reinforced metal laminate sample; S2. Apply lubricant to the die forming area and the surface of the specimen, and use a positioning ring that matches the specimen size to position the specimen in the forming die so that the center of the specimen coincides with the punch axis during the forming process; S3. Use disc springs to connect the edge-holding barrel and the forming die, fill the edge-holding barrel with a fixed amount of solid granular medium, and assemble the guide ring and forming punch. The number of disc springs is related to the required edge-holding force and the bearing capacity of the disc springs. The calculation expression for the number of disc springs N is: ; ; Among them, F R is the rated load of a single disc spring, E is the elastic modulus of the disc spring, ν is the Poisson's ratio of the disc spring, t is the thickness of the disc spring, h0 is the inner cone height of the disc spring, D is the outer diameter of the disc spring, d is the inner diameter of the disc spring, r is the fillet radius of the disc spring edge, F BHF is the blank holding force required for forming, n is the safety factor; S4. Install heating rods in the forming die and perform heat insulation coating on the die. Use thermocouples in the circumferential array of heating rods to monitor the temperature of the die forming area in real time. S5. Control the temperature of the forming zone to the optimal forming range of the prepreg. The press drives the punch to compact the solid particle medium. The press utilizes its flexible pressure transmission characteristics to make the semi-cured sample flow along the mold surface to form. S6. Adjust the temperature control system according to the selected prepreg so that its temperature rises stepwise to the curing temperature and is cured under pressure, so that the resin fills the micropores of the metal oxide film and cures, forming a mechanical and chemical composite anchoring effect, thereby completing the forming and curing of the fiber-reinforced metal laminate in the same set of molds.

[0006] Preferably, in step S3, the disc spring is subjected to the pressure F of the nut during the pre-tightening stage. nut Compressed to the initial compression amount x1, at this time the disc spring reaction force F pre-spring =F nut =k eff x1 acts on the blank holder to provide the initial blank holder force; as the punching progresses, the sheet metal flange area wrinkles and exerts an upward force F on the blank holder. wrinkle , causing the blank holder to move upward, further compressing the disc spring to x2=x1+△x; at this time, the disc spring reaction force increases to F spring =k eff x2, this increased disc spring reaction force is converted into dynamic blank holder force through the blank holder ring, F blank =F spring The dynamic blank holding force suppresses the wrinkling and deformation of the sheet in real time, forming a multi-mode blank holding force with closed-loop feedback.

[0007] Preferably, in step S1, the pretreatment of the metal sheet specifically includes the following steps: S11. Degrease the surface of the metal sample using an organic solvent to remove oil stains and surface impurities; S12. Remove the surface oxide layer and residual contaminants with an alkaline solution, and rinse the sample thoroughly with deionized water until the surface is neutral; S13. Perform acid etching activation treatment with an acidic solution and wash with deionized water until there is no chemical residue on the surface.

[0008] Preferably, in step S1, the pretreatment of the metal sheet further includes the following steps: S14, using the metal sample as an anode to form an electrolysis system with the cathode, wherein the cathode material and the metal sample form a dissimilar metal electrode pair; S15, applying a DC electric field in the electrolyte and controlling the current density to form a uniform oxide film on the metal surface; S16. After oxidation, immediately rinse with deionized water and then dry.

[0009] Preferably, in step S3, the particle size of the solid granular medium is 0.15 mm ± 0.05 mm, and the Rockwell hardness reaches 48-55 HRC.

[0010] Preferably, the mass m of the solid particle medium is calculated as: ; Where ρ is the density of the solid granular medium, V granule is the volume of the required solid particle medium, V mold is the volume of the edge-pressing barrel, η is the filling rate of the solid particle medium, R is the radius of the barrel, and H is the height of the barrel.

[0011] Preferably, in step S3, the solid particle medium is non-metallic particles with a melting point above 1000°C.

[0012] Preferably, in step S5, the displacement of the press is stopped after the sample is attached to the die or reaches the target shape, and the press load is maintained to provide the pressure required for the product curing stage. At the same time, the optimal forming temperature is between the softening temperature and the curing temperature of the matrix resin in the fiber prepreg.

[0013] Preferably, the cathode is made of an inert conductive material, and the surface area of ​​the cathode is larger than that of the anode; and the electrolysis parameters satisfy the positive correlation between the current density and the oxide film growth rate.

[0014] The second aspect of the present invention provides a mold for the aforementioned method of integrating solid particles into a fiber-reinforced metal laminate, which includes a forming die, a heating reserved hole, a pressure barrel, a disc spring, a positioning ring, a punch and a guide ring; the pressure barrel is elastically connected to the forming die through an array of disc springs, the positioning ring is arranged between the pressure barrel and the forming die, the punch and the pressure barrel are in a clearance fit, and the guide ring is arranged between the pressure barrel and the punch to seal the particles and guide the punch vertically downward.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The forming method of the solid particle integrated fiber reinforced metal laminate of the present invention realizes the integration of plastic forming of the fiber reinforced metal laminate and prepreg curing in a single mold by synchronously regulating temperature and pressure. The fluidity of the semi-cured prepreg is combined with the flexible pressure transmission of the particle medium to enable the resin to synchronously fill the micropores on the metal surface and complete the shape forming, thereby reducing secondary clamping and transfer links and avoiding interface contamination and thermal stress accumulation.

[0016] The present invention provides a forming method for a solid particle integrated fiber reinforced metal laminate. Dynamic pressure from a particle medium is applied to an anodized metal sheet and a fiber prepreg in a semi-cured stage, forcing the prepreg matrix resin to fully infiltrate the micropores of the metal surface oxide film, thereby forming a mechanical and chemical composite anchoring effect, enhancing the interface bonding performance between the metal and the fiber reinforced prepreg, and improving the mechanical properties and durability of the composite laminate.

[0017] Compared with the high impact force and stress concentration problems of traditional rigid punches, the forming method of the solid particle integrated fiber reinforced metal laminate of the present invention reduces stress concentration in complex curved surface forming and reduces the occurrence of fiber damage through the flexible pressure transmission of solid particle media, provides uniform pressure distribution during the curing process, ensures resin filling integrity and interlayer bonding strength, and is suitable for the manufacture of high-precision, complex-shaped laminates. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention provides a forming method for the solid particle integrated fiber reinforced metal laminate; Figure 2 This is a process flow chart of a specific embodiment of the forming method of the solid particle integrated fiber reinforced metal laminate of the present invention; Figure 3 It is a front view of the overall structure of the mold of the present invention; Figure 4 This is a structural cross-sectional view of the mold of the present invention before stamping; Figure 5 This is a cross-sectional view of the structure of the mold after stamping of the present invention; Figure 6A physical picture of the non-metallic solid particle medium used in the present invention; Figure 7 This is a physical picture of the product obtained by stamping and forming the solid granular medium according to the present invention; Figure 8 This is a picture of the product after stamping with a rigid punch; Figure 9 The microscopic morphology of the product obtained by the forming method of the present invention is shown in FIG.

[0019] Main reference numerals: 1. Forming die; 11. Heating reserved hole; 2. Edge pressing barrel; 3. Disc spring; 4. Positioning ring; 5. Punch; 6. Guide ring. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] like Figures 1-9 As shown, the present invention provides a forming method for solid particle integrated fiber reinforced metal laminate, which comprises the following steps: S1. Lay the pretreated metal sheet and fiber-reinforced prepreg, and heat and pressurize the selected materials to form a preliminary bonding layer and obtain a semi-cured fiber-reinforced metal laminate sample, retaining the deformation capacity required for subsequent forming.

[0022] S11. Use organic solvent to degrease the surface of the metal sample to remove oil stains and surface impurities.

[0023] S12. Remove the surface oxide layer and residual contaminants with an alkaline solution, and rinse the sample thoroughly with deionized water until the surface is neutral.

[0024] S13. Perform acid etching activation treatment with an acidic solution and wash with deionized water until there is no chemical residue on the surface.

[0025] S14. The metal sample is used as an anode to form an electrolysis system with the cathode, and the cathode material and the metal sample constitute a dissimilar metal electrode pair.

[0026] The cathode is made of inert conductive material and has a larger surface area than the anode; the electrolyte composition is adapted to the type of metal substrate; and the electrolysis parameters satisfy the positive correlation between current density and oxide film growth rate.

[0027] S15. Apply a DC electric field in the electrolyte and control the current density to form a uniform oxide film on the metal surface.

[0028] S16. After oxidation, immediately rinse with deionized water and then dry.

[0029] The fiber direction of the fiber-reinforced prepreg needs to be at a certain angle to the rolling direction of the metal sample according to product requirements, and multiple layers of prepreg can be laid according to product performance requirements.

[0030] S2. Apply lubricant to the die forming area and the surface of the specimen, and use a positioning ring that matches the specimen size to position the specimen in the forming die so that the center of the specimen coincides with the punch axis during the forming process.

[0031] The outer diameter of the locating ring and the locating groove of the die form a first matching structure to provide radial positioning constraint; the inner diameter of the locating ring and the specimen form a second matching structure to allow axial detachable connection; the first matching structure has a higher coaxiality accuracy level than the second matching structure.

[0032] S3. Use a disc spring to connect the edge pressing barrel and the forming die, fill the edge pressing barrel with a fixed amount of solid granular medium. The particle size of the particles is 0.15mm±0.05mm, and the Rockwell hardness reaches 48~55HRC, and assemble the guide ring and forming punch.

[0033] The number of disc springs depends on the required blanking force and the bearing capacity of the disc springs. The calculation expression for the number of disc spring groups N is: ; ; Among them, F R is the rated load of a single disc spring, E is the elastic modulus of the disc spring, ν is the Poisson's ratio of the disc spring, t is the thickness of the disc spring, h0 is the inner cone height of the disc spring, D is the outer diameter of the disc spring, d is the inner diameter of the disc spring, r is the fillet radius of the disc spring edge, F BHF is the blank holding force required for forming, and n is the safety factor.

[0034] The calculation expression of the mass m of solid particle medium is: ; Where ρ is the density of the solid granular medium, V granule is the volume of the required solid particle medium, V mold is the volume of the edge-pressing barrel, η is the filling rate of the solid particle medium, R is the radius of the barrel, and H is the height of the barrel.

[0035] During the pre-tightening stage, the disc spring is subjected to the pressure F from the nut. nut Compressed to the initial compression amount x1, at this time the disc spring reaction force F pre-spring =F nut =k eff ·x1 acts on the blank holder to provide the initial blank holder force. As the punching progresses, the sheet metal flange area wrinkles and exerts an upward force F on the blank holder. wrinkle, causing the blank holder to move upward, thereby further compressing the disc spring to x2=x1+△x. At this time, the disc spring reaction force increases to F spring =k eff x2, this increased disc spring reaction force is converted into dynamic blank holder force through the blank holder ring, F blank =F spring This force suppresses the wrinkling and deformation of the sheet metal in real time, forming a closed-loop feedback multi-mode blank holding force control system.

[0036] Through the uniform pressure transmission characteristics and friction effect of solid particle media, fiber damage is reduced during the forming stage, overcoming the stress concentration of traditional rigid molds that causes premature fracture of the specimen. The particle medium is non-metallic particles with a melting point above 1000°C, which solves the problem that special forming cannot be carried out at high temperatures. Compared with special forming processes such as hydraulic forming or pneumatic forming, solid particle media can provide greater punching force, which can achieve full mold fit for parts with more complex shapes and higher processing accuracy.

[0037] S4. A heating rod is set in the forming die and the die is thermally insulated. The temperature of the die forming area is monitored in real time by thermocouples in the circumferential array of heating rods to ensure that the temperature gradient in the forming area is ≤3°C / mm.

[0038] S5. Control the temperature of the forming zone to the optimal forming range of the prepreg. The press drives the punch to compact the solid particle medium. The press utilizes its flexible pressure transmission characteristics to make the semi-cured sample flow and form along the mold surface.

[0039] The displacement of the press is stopped after the sample is attached to the die or reaches the target shape, but the press load is kept unloaded, thereby greatly suppressing the rebound of the sample and providing the pressure required for the product curing stage. The optimal forming temperature should be between the softening temperature and curing temperature of the matrix resin in the fiber prepreg.

[0040] S6. Adjust the temperature control system according to the selected prepreg, so that its temperature rises stepwise to the curing temperature, and maintains pressure to cure, so that the resin fills the micropores of the metal oxide film and cures, forming a mechanical and chemical composite anchoring effect, and completing the forming and curing of the fiber reinforced metal laminate in the same set of molds.

[0041] Preferably, on the other hand, the present invention provides a mold for solid particle integrated forming of a fiber-reinforced metal laminate, which includes a forming die 1, a heating reserved hole 11, a side clamping barrel 2, a disc spring 3, a positioning ring 4, a punch 5 and a guide ring 6; the side clamping barrel 2 is elastically connected to the forming die 1 through an array of disc springs 3, and the positioning ring 4 is arranged between the side clamping barrel 2 and the forming die 1. The positioning ring 4 prevents the center from deviating from the central axis of the punch 5, resulting in unqualified product shape, and the thickness of the positioning ring 4 can be greater than the test sample. The punch 5 is slidably engaged with the side clamping barrel 2, and the punch 5 and the side clamping barrel 2 are in a clearance fit, so that the punch 5 can slide freely in the side clamping barrel 2 without touching the inner wall of the barrel. The guide ring 6 is arranged between the side clamping barrel 2 and the punch 5, and has the functions of sealing particles to prevent splashing and guiding the punch 5 to descend vertically. The heating reserved hole 11 is arranged on the peripheral side of the forming die 1.

[0042] The forming method and mold of a solid particle integrated fiber reinforced metal laminate of the present invention are further described below with reference to the embodiments.

[0043] The metal used in this embodiment is aluminum alloy, and the fiber prepreg is a satin-woven glass-reinforced fiber prepreg with a thermosetting matrix.

[0044] S1. Use precision CNC wire cutting technology to cut the aluminum alloy substrate into the geometric shape required by the preformed blank to obtain an aluminum alloy specimen of standard size, and then perform acid and alkali cleaning on its surface.

[0045] S2. The cleaned aluminum alloy sample is anodized, and then washed with deionized water and dried.

[0046] S3. Cut the fiber-reinforced prepreg according to the shape of the preformed blank, and then fit it with the aluminum alloy sample obtained by the S2 process according to the shape, and make the rolling direction of the aluminum alloy parallel to the 0° direction of the glass fiber prepreg.

[0047] S4. Place the bonded glass fiber reinforced aluminum alloy laminate sample into a vacuum bag, evacuate the bag, and place it in a vacuum drying oven. Use a vacuum pump to maintain the vacuum bag in the vacuum drying oven at 0.1 MPa. Then raise the temperature to 70°C and keep it warm for half an hour to improve the fluidity of the matrix in the prepreg and better fill the micropores and pits on the surface of the surface-treated metal sheet, thereby preliminarily improving its bonding performance and preventing it from undergoing a curing reaction that reduces the forming performance of the glass fiber reinforced aluminum alloy laminate sample.

[0048] S5. Apply high-temperature forming lubricant to the forming area of ​​the forming die 1 and the upper and lower surfaces of the glass fiber reinforced aluminum alloy laminate sample prepared in S4, and then place the sample in the forming die 1, and use a positioning ring 4 to cooperate with the sample to position the sample.

[0049] S6, such as Figure 3-Figure 5 As shown, the edge-holding barrel 2 and the forming die 1 are connected by disc springs 3, nuts and studs, the solid granular medium is quantitatively weighed using an electronic scale and loaded into the edge-holding barrel 2, the guide ring 6 is assembled and a punch 5 of a suitable shape is installed.

[0050] Solid particle medium forming molds have a simple structure, are economical and practical, and are easy to use. They not only overcome the stress concentration of traditional rigid molds that causes premature fracture of the specimen, but also do not require expensive sealing components and pressure supply systems required for hydraulic and pneumatic forming. Moreover, the particle medium is a non-metallic particle with a melting point of 1000°C and above, which can meet the forming requirements of the product at various temperatures and solve the problems of hydraulic and pneumatic forming at high temperatures and low product precision.

[0051] The number of disc springs 3 depends on the required blanking force and the load-bearing capacity of the disc springs 3. The calculation expression for the number of disc spring groups N is: ; ; This shows that the number of disc springs 3 should be at least 26 (calculated value 25.76). Given that this mold uses six studs for fastening, the total number of disc springs 3 must be a multiple of 6; also, disc springs 3 must be used in pairs. Therefore, this embodiment ultimately uses 36 disc springs 3, evenly distributed between each stud, meaning six disc springs 3 are installed on each stud.

[0052] like Figure 6 As shown, the particle size here is 0.15mm±0.05mm, the Rockwell hardness reaches 48~55HRC, and there is no bonding phenomenon under high pressure conditions. The appearance is smooth and round, with good filling capacity and flow performance, and the chemical properties are stable, high temperature resistant, and non-corrosive to the workpiece. The calculation expression of the mass m of the solid particle medium is: ; Where ρ is the density of the solid granular medium, V granule is the required volume of solid particle medium, V mold is the volume of the edge pressing barrel 2, η is the filling rate of the solid particle medium, R is the radius of the barrel, and H is the height of the barrel.

[0053] S7. Install the heating rod in the heating reserved hole 11 of the forming die 1, and then use high-performance thermal insulation cotton to cover the entire mold to reduce heat loss in the forming area. Then use the thermocouples in the circular array of heating rods to monitor the temperature of the mold forming area in real time to ensure that the temperature gradient of the forming area is ≤3℃ / mm, so as to prevent the material from causing stress concentration, uneven structure or abnormal phase change due to local temperature difference in the subsequent forming process.

[0054] S8. Control the temperature control system so that the heating rod heats the mold to 100°C at a heating rate of 5°C / min and maintains a constant temperature. Then control the press to move downward at a constant speed of 6 mm / min to drive the punch downward to compact the solid particle medium and provide load to form the specimen into the target product shape.

[0055] S9. After the product is formed, the press is controlled not to be unloaded and remains constant to provide the pressure required for product solidification. At the same time, the temperature control system is controlled to heat the heating rod to 120°C at a heating rate of 5°C / min and keep the temperature for 90 minutes to complete the glass fiber reinforced aluminum alloy laminate product, thereby achieving the target product performance.

[0056] Specifically, in step S1, acid-base washing specifically includes the following steps: S11. Use organic solvents such as acetone or ethanol to clean the surface of the aluminum alloy sample to remove surface oil and impurities.

[0057] S12. Place the aluminum alloy sample in a 100g / l sodium hydroxide solution for alkaline washing for 3 to 5 minutes to remove the surface oxide layer and residual contaminants, and then rinse the sample thoroughly with deionized water until there is no residual alkaline solution on the sample surface.

[0058] S13. Place the aluminum alloy sample in a 20% vol nitric acid solution for acid etching activation for 90 to 120 seconds until the sample surface becomes white and bright. Finally, rinse thoroughly with deionized water until there is no chemical residue on the sample surface.

[0059] In step S1, the organic solvent, sodium hydroxide and nitric acid solution and their concentrations should be selected and prepared according to the 2024-T3 aluminum alloy.

[0060] Specifically, step S2 includes the following steps: S21. Construct an anodizing system, connect the aluminum alloy sample to the anode of the anodizing device, and connect the lead plate to the cathode of the anodizing device.

[0061] S22. Place the two electrodes in a phosphoric acid solution with a concentration of 300g / l, turn on the power of the device within 1 minute, and then increase the DC voltage between the plates from 0V to 10±1V within 2 minutes. Then, allow the aluminum alloy sample to undergo an anodic oxidation reaction for 20±1 minutes until a uniform oxide film is formed on the metal surface.

[0062] S23. After the anodizing is completed, remove the sample from the phosphoric acid solution within 1 minute, rinse it thoroughly with deionized water, and dry it in a drying oven to ensure that there is no chemical residue on the surface of the aluminum alloy sample.

[0063] Specifically, in step S2, the lead plate is a material selected based on the 2024-T3 aluminum alloy, which has good conductivity, corrosion resistance, and does not produce contamination ions, and its surface area is larger than that of the aluminum alloy sample; the phosphoric acid solution and its concentration, voltage, and reaction time are selected based on the 2024-T3 aluminum alloy.

[0064] In step S3, the 0° direction of the glass fiber reinforced prepreg needs to be parallel to the rolling direction of the 2024-T3 aluminum alloy sample, and the entire sample is a "sandwich structure", namely aluminum alloy, prepreg, and aluminum alloy, so as to meet the product usage requirements.

[0065] In step S5, the outer diameter of the locating ring 4 and the locating groove of the forming die 1 should satisfy the H7 / g6 fit, and the inner diameter of the locating ring 4 and the sample should satisfy the G7 / h6 fit, so as to ensure that the axis of the sample always coincides with the axis of the punch 5 during the forming process, and no unbalanced load will occur, resulting in an asymmetric shape of the formed product.

[0066] In step S8, the optimal forming temperature of 100°C is determined by a high-temperature uniaxial tensile test. At this temperature, the elongation is maximum, and this temperature is between the softening temperature and the curing temperature of the matrix in the prepreg; the press speed of 6 mm / min is the optimal deformation speed determined by numerical simulation.

[0067] In step S9, the curing temperature of 120°C and the curing time of 90 minutes are determined by the thermosetting matrix resin in the glass fiber prepreg; at the same time, the press must not be unloaded during the entire curing process. After the prepreg is cured and firmly bonded to the metal layer, the heating system can be turned off and the press can be unloaded, the mold can be disassembled, and the product can be taken out.

[0068] like Figure 7 As shown in the figure, the product obtained by the solid granular medium stamping test, because the granular medium is a flexible medium with a certain fluidity, it can fully contact with the surface of the fiber reinforced laminate to dynamically adapt to the deformation of the laminate, and evenly transmit pressure to guide the uniform flow of the material. At the same time, this uniform stress distribution avoids local stress concentration, thereby reducing the risk of rupture. Figure 8 As shown in the figure, the product obtained by the rigid punch stamping test, the shape of the rigid punch is fixed and cannot adapt to the flow characteristics of the material. At the same time, the contact between the rigid punch and the material is local, especially at the rounded corners of the punch, which is prone to stress concentration and causes the layer to rupture.

[0069] like Figure 9 The figure shows the microscopic morphology of the product after stamping using solid particle media. It can be found that the fiber prepreg and the aluminum alloy sheet form a continuous interface at the micro level. There is no obvious gap or void between the two, and the bonding is good, and the interface bonding strength is high.

[0070] The present invention also provides a multi-mode blank holding force control method. When the elastic blank holding force control system of the disc spring 3 is used, the disc spring 3 is subjected to the pressure F of the nut during the pre-tightening stage. nut Compressed to the initial compression amount x1, at this time the disc spring 3 reaction force F pre-spring =F nut =k eff ·x1 acts on the blank holder to provide the initial blank holder force. As the punching progresses, the sheet metal flange area wrinkles and exerts an upward force F on the blank holder. wrinkle , causing the blank holder to move upward, thereby further compressing the disc spring 3 to x2=x1+△x. At this time, the reaction force of the disc spring 3 increases to F spring =k eff x2, the increased reaction force of disc spring 3 is converted into dynamic blank holder force through the blank holder ring, F blank =F spring This force suppresses the wrinkling and deformation of the sheet in real time, forming a closed-loop feedback control system, which is suitable for products with complex forming processes and high product quality requirements.

[0071] Among them, F nut F is the nut pre-tightening force; pre-spring is the initial reaction force of disc spring 3; k eff F is the stiffness of disc spring 3 (its value increases nonlinearly with the increase of compression); wrinkle is the effect of sheet wrinkling and the normal force of the blank holder; △x is the displacement of the blank holder caused by sheet wrinkling; F spring F is the real-time reaction force of disc spring 3; blank It is the real-time blank holding force, and its value is greater than the initial blank holding force.

[0072] In addition, by adjusting the thickness of the positioning ring, the pressure gap can be controlled, thereby optimizing the fluidity of the material during the forming process and simplifying the mold structure, which is suitable for products with relatively simple forming structures and low precision requirements. Therefore, the flexible selection or combination of disc springs and pressure gap control can not only better meet the forming requirements of different products, but also take into account flexibility and economy, significantly improving the quality and efficiency of stamping. Compared with special forming processes such as hydraulic forming / pneumatic forming, the solid particle medium used can provide greater punching force, which can achieve full mold attachment of more complex shaped parts and higher processing accuracy. At the same time, the melting point of the solid particle medium is higher than 1000°C, which solves the problem that special forming cannot be carried out at high temperatures. The prepreg used in the embodiment is a glass fiber reinforced prepreg, and its matrix resin is a thermosetting resin, but it does not mean that the method of the present invention is limited to this. The method and its mold can also meet the needs of fiber reinforced prepregs with a matrix of thermoplastic resin. When using thermoplastic fiber prepregs, it is necessary to change the forming temperature, curing temperature, and curing time according to the parameters related to the matrix resin in the prepreg, so as to be more conducive to intelligent manufacturing.

[0073] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for forming a solid particle integrated fiber reinforced metal laminate, characterized by: It includes the following steps: S1. Laying the pretreated metal sheet and the fiber-reinforced prepreg, and heating and pressurizing the selected materials to form a preliminary bonding layer and obtain a semi-cured fiber-reinforced metal laminate sample; S2. Apply lubricant to the die forming area and the surface of the specimen, and use a positioning ring that matches the specimen size to position the specimen in the forming die so that the center of the specimen coincides with the punch axis during the forming process; S3. Use disc springs to connect the edge-holding barrel and the forming die, fill the edge-holding barrel with a fixed amount of solid granular medium, and assemble the guide ring and forming punch. The number of disc springs is related to the required edge-holding force and the bearing capacity of the disc springs. The calculation expression for the number of disc springs N is: ； ； Among them, F R is the rated load of a single disc spring, E is the elastic modulus of the disc spring, ν is the Poisson's ratio of the disc spring, t is the thickness of the disc spring, h0 is the inner cone height of the disc spring, D is the outer diameter of the disc spring, d is the inner diameter of the disc spring, r is the fillet radius of the disc spring edge, F BHF is the blank holding force required for forming, n is the safety factor; S4. Install heating rods in the forming die and perform heat insulation coating on the die. Use thermocouples in the circumferential array of heating rods to monitor the temperature of the die forming area in real time. S5. Control the temperature of the forming zone to the optimal forming range of the prepreg. The press drives the punch to compact the solid particle medium. The press utilizes its flexible pressure transmission characteristics to make the semi-cured sample flow along the mold surface to form. S6. Adjust the temperature control system according to the selected prepreg so that its temperature rises stepwise to the curing temperature and is cured under pressure, so that the resin fills the micropores of the metal oxide film and cures, forming a mechanical and chemical composite anchoring effect, thereby completing the forming and curing of the fiber-reinforced metal laminate in the same set of molds.

2. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S3, the disc spring is subjected to the pressure F of the nut during the pre-tightening stage. nut Compressed to the initial compression amount x1, at this time the disc spring reaction force F pre-spring =F nut =k eff x1 acts on the blank holder to provide the initial blank holding force; As the stamping progresses, the sheet metal flange area wrinkles and exerts an upward force F on the blank holder. wrinkle , causing the blank holder to move upward, further compressing the disc spring to x2=x1+△x; at this time, the disc spring reaction force increases to F spring =k eff x2, this increased disc spring reaction force is converted into dynamic blank holder force through the blank holder ring, F blank =F spring The dynamic blank holding force suppresses the wrinkling and deformation of the sheet in real time, forming a multi-mode blank holding force with closed-loop feedback.

3. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S1, the pretreatment of the metal sheet specifically includes the following steps: S11. Degrease the surface of the metal sample using an organic solvent to remove oil stains and surface impurities; S12. Remove the surface oxide layer and residual contaminants with an alkaline solution, and rinse the sample thoroughly with deionized water until the surface is neutral; S13. Perform acid etching activation treatment with an acidic solution and wash with deionized water until there is no chemical residue on the surface.

4. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S1, the pretreatment of the metal sheet specifically further includes the following steps: S14, using the metal sample as an anode to form an electrolysis system with the cathode, wherein the cathode material and the metal sample form a dissimilar metal electrode pair; S15, applying a DC electric field in the electrolyte and controlling the current density to form a uniform oxide film on the metal surface; S16. After oxidation, immediately rinse with deionized water and then dry.

5. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S3 , the particle size of the solid granular medium is 0.15 mm ± 0.05 mm, and the Rockwell hardness reaches 48-55 HRC.

6. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: The calculation expression of the mass m of solid particle medium is: ； Where ρ is the density of the solid granular medium, V granule is the volume of the required solid particle medium, V mold is the volume of the edge-pressing barrel, η is the filling rate of the solid particle medium, R is the radius of the barrel, and H is the height of the barrel.

7. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S3, the solid particle medium is non-metallic particles with a melting point of above 1000°C.

8. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 1, characterized in that: In step S5, the displacement of the press is stopped after the sample is attached to the die or reaches the target shape, and the press load is maintained to provide the pressure required for the product curing stage. At the same time, the optimal forming temperature is between the softening temperature and the curing temperature of the matrix resin in the fiber prepreg.

9. The forming method of solid particle integrated fiber reinforced metal laminate according to claim 4, characterized in that: The cathode is made of inert conductive material, and the surface area of ​​the cathode is larger than that of the anode; the electrolysis parameters satisfy the positive correlation between current density and oxide film growth rate.

10. A mold for use in the forming method of the solid particle integrated fiber reinforced metal laminate according to any one of claims 1 to 9, characterized in that: It includes a forming die, a heating reserved hole, a pressure barrel, a disc spring, a positioning ring, a punch and a guide ring; the pressure barrel is elastically connected to the forming die through an array of disc springs, the positioning ring is arranged between the pressure barrel and the forming die, the punch and the pressure barrel are clearance-fitted, and the guide ring is arranged between the pressure barrel and the punch to seal the particles and guide the punch to move vertically downward.

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