Continuous hot pressing-hot stamping forming method for thermoplastic prepreg protected by double steel belts
The continuous hot pressing-hot stamping molding method using double steel strips to protect thermoplastic prepregs solves the problems of wrinkle control and porosity control in traditional hot stamping technology, enabling efficient manufacturing of complex thermoplastic composite components and improving production efficiency and forming quality.
Patent Information
- Application Number
- CN202511344136.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2025-11-14
AI Technical Summary
Traditional hot stamping technology in the aerospace industry suffers from problems such as difficulty in wrinkle control, difficulty in pore control, and mismatch between the hot die pressing plate and the hot stamping forming cycle, resulting in long forming cycles and low production efficiency.
A continuous hot pressing-hot stamping molding method using double steel strips to protect thermoplastic prepregs is adopted. Through a progressive continuous hot pressing and hot stamping integrated process, the steel strips apply normal constraints to the composite layers. Combined with the heat transfer and insulation properties of the steel strips and the non-stick properties of the mold, the interlayer porosity is eliminated and deformation is controlled, thus shortening the molding cycle.
It effectively reduces the risk of wrinkling in composite components, eliminates interlayer porosity, shortens the molding cycle, improves production efficiency, and enables low-defect and high-efficiency manufacturing of complex thermoplastic composite components.
Smart Images
Figure CN120941772A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of composite material molding and relates to a continuous hot pressing-hot stamping molding method for thermoplastic prepreg protected by double steel strips. Background Technology
[0002] Carbon fiber reinforced thermoplastic composites have widely replaced metal materials in many aircraft components due to their advantages such as high strength and toughness, short molding cycle, environmental friendliness and recyclability, resistance to damp heat, weldability, and secondary molding capabilities. These materials are mainly used in the forming and manufacturing of small and medium-sized components such as leading edge ribs, pylons, beams, and corner plates of aircraft wings. Currently, hot stamping technology for thermoplastic composites is difficult to meet the stringent airworthiness standards and regulations of civil aircraft, as well as the stringent international market competition, which imposes stringent requirements on the mechanical properties, precision, lifespan, reliability, and cost of main load-bearing structures, thus hindering their widespread application in main load-bearing structures.
[0003] In thermoplastic composite systems, carbon fibers themselves lack plastic deformation capabilities. During hot stamping, the material primarily undergoes macroscopic deformations such as in-plane shearing, bending, and interlaminar slip. These deformation mechanisms have limitations, posing significant challenges to the effective control of the hot stamping process. Furthermore, the long cycle time of laminated molding cannot match the pace of rapid hot stamping, ultimately limiting the forming cycle to the molding process and failing to fully leverage the technological advantages of short-process, high-efficiency manufacturing of thermoplastic composites.
[0004] The inventors have drawn inspiration from the progressive hot stamping process of thin metal sheets to provide a new approach to the hot stamping of thermoplastic prepregs. This method optimizes the traditional hot stamping process, offering a new research direction for continuous hot pressing-hot stamping. Furthermore, the inventors have adopted wrinkle suppression methods from metal stamping to achieve deformation control and wrinkle suppression, using double steel strips to sandwich the prepreg and optimizing the structural design, allowing the hot stamping technology to manufacture more complex geometries. However, this technology still cannot solve the problems of porosity between the metal and thermoplastic composite layers, poor bonding performance, and the long process flow and low production efficiency of the two-step hot stamping process.
[0005] The inventors proposed a new process that is expected to overcome the control problem of wrinkling in traditional hot stamping by means of the coupling and interaction between the double steel strip and the thermoplastic composite. Furthermore, by eliminating interlayer porosity through progressive continuous hot pressing and then directly hot stamping, the process flow can be shortened and efficiency improved, ultimately achieving low-defect and high-efficiency manufacturing of complex thermoplastic composite components. Summary of the Invention
[0006] The problem this invention aims to solve is the potential problems of traditional hot stamping in the aerospace industry, including the difficulty in controlling wrinkles and pores, as well as the mismatch between the hot die pressing plate and the hot stamping forming cycle, resulting in a long forming cycle.
[0007] To solve the above-mentioned technical problems, the present invention provides a continuous hot pressing-hot stamping molding method for thermoplastic prepregs with double steel strip protection, comprising the following steps:
[0008] Step 1): Install multiple molding dies with heating tubes and a stamping die on the press in sequence to form multiple molding stations and a stamping station. Heat all molding dies to the target temperature and keep the temperature constant.
[0009] Step 2): Lay a layer of adhesive film on the steel plate, and then lay multiple layers of carbon fiber prepreg on the adhesive film. The stacking order of the carbon fiber prepreg can be set according to different needs. Lay another layer of adhesive film on the carbon fiber prepreg, and then lay another steel plate to assemble a double steel strip thermoplastic prepreg.
[0010] Step 3): Transfer the double steel strip thermoplastic prepreg to the molding die of the first molding station for molding; after completion, the double steel strip thermoplastic prepreg is transferred to the molding die of the next molding station under the drive of the feeding device for molding, and then sequentially passes through the molding dies of the set molding process for molding; the heat transfer and heat preservation effect of the steel plate makes the thermoplastic prepreg reach the required temperature;
[0011] Step 4): The double steel strip thermoplastic prepreg that has been molded does not require cooling. It is transferred to the stamping die at the stamping station by the feeding device for stamping and forming, and then held under pressure and cooled.
[0012] Step 5): After the double steel strip thermoplastic prepreg has been stamped, the laser cutting edge is used to remove the cutting allowance to ensure its dimensional accuracy. After the cutting edge is completed, the steel plates on both sides can be removed.
[0013] Preferably, all molding processes and stamping processes have the same time and pressure.
[0014] More preferably, the molding process takes 5-10 minutes.
[0015] Preferably, the steel plate in step 2) is made of SPCE steel or DC04 steel.
[0016] Preferably, the anti-stick film in step 2) is made of anti-stick PI film.
[0017] Preferably, the carbon fiber prepreg (3) in step 2) is a unidirectional carbon fiber prepreg.
[0018] Preferably, the carbon fiber prepreg (3) in step 2) includes carbon fiber raw material and resin powder material, wherein the resin powder material is at least one of polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polyamide-6.
[0019] Preferably, a release agent is applied between the steel plate and the molding die before molding.
[0020] Utilizing the design concept of progressive dies, this invention sets up multiple stations in a specific sequence within a single press. During one stroke of the press, multiple stamping processes are completed simultaneously at different stations, allowing for the concurrent molding of multiple sheet metal parts. This enables the blanks to gradually transform into qualified stamped parts as they are continuously fed in. The heating temperature at each station can be set independently, and the pressure at each station is consistent. The heating and melting temperature must not be lower than the pre-solidification temperature.
[0021] This invention replaces traditional molding and hot stamping processes with a laminated structure of metal sheet and thermoplastic prepreg and an integrated continuous hot pressing-hot stamping process. The process employs double steel strips to protect the thermoplastic prepreg laminate through rapid contact heating and melting, progressive multi-stage heat preservation and pressure holding, hot stamping forming, and in-mold pressure holding and cooling. This process leverages the continuous and efficient advantages of progressive stamping to integrate prepreg layer bonding and hot stamping forming into a single process, shortening the production cycle to 5-10 minutes per piece. Furthermore, the double steel strips apply normal gradient stress and constraint to the composite material, effectively mitigating wrinkling. The heat transfer, heat preservation, and non-stick properties of the steel strips facilitate continuous hot pressing to eliminate interlayer porosity and achieve continuous consolidation. The steel strip / composite laminate configuration allows for design-adjustable control of the stress state of the composite layers, enabling defect control.
[0022] Compared with existing traditional molding and hot stamping processes, the advantages of this invention are as follows:
[0023] (1) The continuous hot pressing-hot stamping molding method for double steel strip protected thermoplastic prepreg described in this invention can reduce the risk of wrinkling of composite components by applying normal constraints to the composite layer by steel strip;
[0024] (2) The heat transfer, heat preservation, and non-stick properties of steel strips can be used to facilitate continuous hot pressing to eliminate interlayer pores and achieve continuous consolidation.
[0025] (3) The process of using progressive continuous hot pressing to eliminate the interlayer pores of the prepreg material and then directly hot stamping can shorten the forming cycle and improve efficiency.
[0026] (4) The outstanding advantage of the new process of this invention is that it utilizes the coupled deformation of steel strip and thermoplastic composite to achieve defect control, uses the "high plasticity" and "high rigidity" of steel strip to coordinate the deformation of composite and suppress wrinkling of components, and uses the "heat transfer and insulation" and "force transfer and pressurization" effects of steel strip to achieve continuous progressive hot pressing to eliminate interlayer porosity. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the double steel strips protecting the thermoplastic prepreg in this invention;
[0028] Figure 2 This is a schematic diagram of the continuous hot pressing and hot stamping integrated mold in this invention;
[0029] Figure 3 A process flow diagram of the continuous hot pressing-hot stamping molding method for double steel strip protected thermoplastic prepreg provided by the present invention;
[0030] Figure 4 The hot pressing-hot stamping temperature curve provided in Example 2;
[0031] Figure 5 The porosity curve provided in Example 2 is a hot-pressing-hot-stamping curve. Detailed Implementation
[0032] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.
[0033] Examples 1-4 provide a continuous hot pressing-hot stamping molding method for thermoplastic prepregs with double steel strip protection (e.g., Figure 3 (As shown), including the following steps:
[0034] Step 1): Prepare the molding die: Install three molding dies 5 with heating tubes 5 and one stamping die 9 on the press 6 in sequence to form multiple molding stations and one stamping station (e.g., Figure 2 (As shown), heat all the molding dies 5 to the target temperature and keep the temperature constant;
[0035] Step 2): Lay a layer of adhesive film 2 on steel plate 1, then lay multiple layers of carbon fiber prepreg 3 on the adhesive film 2, and then lay another layer of adhesive film 2 on the carbon fiber prepreg 3. Then lay another steel plate 1 on top, assembling it into a double-strand thermoplastic prepreg 8 (e.g., Figure 1 (as shown);
[0036] Step 3): Transfer the double steel strip thermoplastic prepreg 8 to the molding die 5 of the first molding station and preheat and melt it; apply release agent between the steel plate 1 and the molding die 5 before molding;
[0037] Step 4): The preheated double steel strip thermoplastic prepreg 8 is transferred to the molding die 5 at the second molding station under the drive of the feeding device 7 for molding pre-consolidation; a release agent is applied between the steel plate 1 and the molding die 5 before molding.
[0038] Step 5): The double steel strip thermoplastic prepreg 8, which has completed the molding pre-consolidation, is transferred to the molding die 5 of the third molding station under the drive of the feeding device 7 for continuous pre-consolidation.
[0039] Step 6): The double steel strip thermoplastic prepreg 8, which has completed continuous pre-consolidation, is transferred to the stamping die 9 of the stamping station via the feeding device 7 for stamping and forming without cooling, and is then held under pressure and cooled.
[0040] Step 7): After the double steel strip thermoplastic prepreg 8 has been stamped, the cutting allowance is removed by laser cutting to ensure its dimensional accuracy. After the cutting is completed, the steel plates 1 on both sides can be removed.
[0041] Example 1
[0042] Prepare DC04 ultra-low carbon cold-rolled carbon steel and carbon fiber reinforced PEEK unidirectional prepreg. First, lay a layer of polyimide release film on the bottom steel plate, then lay 14 layers of prepreg on the release film, with a prepreg thickness of 2mm. Then lay another layer of release film, and finally lay a steel plate on top with a steel plate thickness of 1mm. This produces the required double steel strip thermoplastic prepreg.
[0043] Place the prepared double steel strip thermoplastic prepreg in the first molding station and position it; apply release agent between the molding die and the preform; set the temperature / pressure to 400℃ / 3MPa; since it is an integrated design, the time for each preform at each station is set to 5 minutes.
[0044] The material is preheated and melted, then transported to the second molding station by the drive of the feeding device for molding, then transported to the third molding station by the drive of the feeding device for molding, and finally transported to the stamping station by the drive of the feeding device for stamping and pressure holding and cooling.
[0045] After hot stamping, the parts are laser-cut to remove the steel strip and obtain the final component.
[0046] Example 2
[0047] Prepare DC04 ultra-low carbon cold-rolled carbon steel and carbon fiber reinforced PEEK unidirectional prepreg. First, lay a layer of polyimide release film on the bottom steel plate, then lay 14 layers of prepreg on the release film, with a prepreg thickness of 2mm. Then lay another layer of release film, and finally lay a steel plate on top, with a steel plate thickness of 1mm. This produces the required double steel strip thermoplastic prepreg.
[0048] Place the prepared double steel strip thermoplastic prepreg in the first molding station and position it; apply release agent between the molding die and the preform; set the pressure to 5 MPa and the working time for each station to ten minutes.
[0049] Preheating and melting are performed at a temperature of 400℃. The material is then transferred to the second molding station by the drive of the feeding device for molding at a temperature of 370℃. The material is then transferred to the third molding station by the drive of the feeding device for molding at a temperature of 370℃. Finally, the material is transferred to the stamping station by the drive of the feeding device for stamping and pressure holding and cooling.
[0050] After hot stamping, the parts are laser-cut to remove the steel strip and obtain the final component.
[0051] Example 3
[0052] Prepare DC04 ultra-low carbon cold-rolled carbon steel and carbon fiber reinforced PPS unidirectional prepreg. First, lay a layer of polyimide release film on the bottom steel plate, then lay 20 layers of prepreg on the release film, with a prepreg thickness of 3mm. Then lay another layer of release film, and finally lay a steel plate on top, with a steel plate thickness of 1mm. This produces the required double steel strip thermoplastic prepreg.
[0053] Place the prepared double steel strip thermoplastic prepreg in the first molding station and position it; apply release agent between the molding die and the preform; set the pressure to 8 MPa and the working time of the station to fifteen minutes.
[0054] The preheating and melting temperature is set to 380℃. Driven by the feeding device, the material is transferred to the second molding station at a temperature of 350℃ for molding. Finally, driven by the feeding device, the material is transferred to the stamping station for stamping and pressure holding and cooling.
[0055] After hot stamping, the parts are laser-cut to remove the steel strip and obtain the final component.
[0056] Example 4
[0057] Prepare DC04 ultra-low carbon cold-rolled carbon steel and carbon fiber reinforced PA-6 unidirectional prepreg. First, lay a layer of polyimide release film on the bottom steel plate, then lay 20 layers of prepreg on the release film, with a prepreg thickness of 3mm. Next, lay another layer of release film, and finally lay a steel plate on top, with a steel plate thickness of 1.5mm. This produces the required double-strand thermoplastic prepreg.
[0058] Place the prepared double steel strip thermoplastic prepreg in the first molding station and position it; apply release agent between the molding die and the preform; set the temperature and pressure to 400℃ / 5MPa; set the time for the preform at each station to ten minutes.
[0059] The material is preheated and melted, then transported to the second molding station by the drive of the feeding device for molding. It is then transported to the third molding station by the drive of the feeding device for molding, then to the fourth molding station by the drive of the feeding device for molding, and finally to the stamping station by the drive of the feeding device for stamping and pressure holding and cooling.
[0060] After hot stamping, the parts are laser-cut to remove the steel strip and obtain the final component.
Claims
1. A method for continuous hot pressing-hot stamping molding of thermoplastic prepreg with double steel strip protection, characterized in that, Includes the following steps: Step 1): Install multiple molding dies (5) with heating tubes (5) and a stamping die (9) on the press (6) in sequence to form multiple molding stations and a stamping station. Heat all the molding dies (5) to the target temperature and keep the temperature constant. Step 2): Lay a layer of adhesive film (2) on the steel plate (1), lay multiple layers of carbon fiber prepreg (3) on the adhesive film (2), lay another layer of adhesive film (2) on the carbon fiber prepreg (3), and then lay another steel plate (1) to assemble a double steel strip thermoplastic prepreg (8). Step 3): Transfer the double steel strip thermoplastic prepreg (8) to the molding die (5) of the first molding station for molding; after completion, the double steel strip thermoplastic prepreg (8) is transferred to the molding die (5) of the next molding station under the drive of the feeding device (7) for molding, and then passes through the molding die (5) of the set molding process for molding in sequence; Step 4): The double steel strip thermoplastic prepreg (8) that has been molded does not need to be cooled down. It is transferred to the stamping die (9) of the stamping station through the feeding device (7) for stamping and forming, and then held under pressure and cooled. Step 5): After the double steel strip thermoplastic prepreg (8) is stamped, the laser cutting edge is used to remove the cutting allowance to ensure its dimensional accuracy. After the cutting edge is completed, the steel plates on both sides (1) are removed.
2. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 1, characterized in that, All molding and stamping processes have the same time and pressure.
3. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 2, characterized in that, The molding process takes 5-10 minutes.
4. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 1, characterized in that, The steel plate (1) in step 2) is made of SPCE steel or DC04 steel.
5. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 1, characterized in that, The anti-stick film (2) in step 2) is made of anti-stick PI film.
6. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 1, characterized in that, In step 2), the carbon fiber prepreg (3) is a unidirectional carbon fiber prepreg.
7. The continuous hot pressing-hot stamping molding method for double-steel-strip protected thermoplastic prepreg as described in claim 1 or 6, characterized in that, In step 2), the carbon fiber prepreg (3) includes carbon fiber raw materials and resin powder materials, wherein the resin powder materials are at least one of polyether ether ketone, polyphenylene sulfide, and polyamide-6.
8. The continuous hot pressing-hot stamping molding method for thermoplastic prepreg with double steel strip protection as described in claim 1, characterized in that, Before molding, a release agent is applied between the steel plate (1) and the molding die (5).