A composite material electrothermal curing system and method

Abstract

The application discloses a composite material electrothermal curing system and method, relates to the technical field of composite material electrothermal curing, and comprises the following: a laminate which is laminated by prepreg and an electrically conductive heating layer embedded between the prepreg layers; an electrode assembly which is electrically connected with the carbon nanotube film and is used for leading an external power supply into the carbon nanotube film; a temperature acquisition module which at least comprises a first thermocouple arranged at a central region of the laminate, a second thermocouple arranged at an edge region of the laminate and a third thermocouple arranged on the surface of a mold; a pressure loading module which is used for applying pressure to the laminate; and a control unit which is in communication connection with the temperature acquisition module, the electrode assembly and the pressure loading module respectively; and the application can solve the problems that the existing composite material curing equipment is highly dependent, temperature uniformity is insufficient and the forming quality is difficult to be stably controlled.

Description

Technical Field

[0001] This invention relates to the field of electrothermal curing technology for composite materials, and specifically to an electrothermal curing system and method for composite materials. Background Technology

[0002] Fiber-reinforced resin matrix composites, with their excellent specific strength and specific modulus, have become key materials for aerospace and high-end equipment. Traditional curing processes mainly rely on autoclaves or ovens for external heating, which has inherent drawbacks such as large equipment size, high energy consumption, and long heat conduction paths leading to large temperature differences between the inside and outside of thick-walled components.

[0003] In recent years, the technology of introducing carbon nanotube (CNT) films into the interlayer of prepregs as an in-situ electrothermal functional layer has attracted much attention due to its rapid heating speed and high energy utilization. However, in practical engineering applications, this technology still faces severe challenges: First, temperature field uniformity is difficult to control: CNT films generate concentrated heat, and the composite material edges dissipate heat quickly, resulting in a significant center-edge temperature difference within the layup; simultaneously, the exothermic peak of the resin in the crosslinking reaction superimposed with the electrothermal input makes local temperature easily runaway, seriously affecting the consistency of the mechanical properties of the component. Second, the thermo-mechanical process matching degree is low: during the curing process, the viscosity of the resin exhibits complex nonlinear characteristics with temperature changes. Existing processes mostly use constant pressure or manual pressure adjustment based on experience, which cannot provide the optimal compaction pressure during the flow and wetting stage when the resin viscosity is lowest, nor can it accurately increase the pressure before the resin gels, often leading to excessive porosity or excessive resin loss. Finally, there is a lack of adaptive control methods: existing technologies mostly rely on simple on / off power control at a single temperature feedback point, which cannot perform zoned power compensation for temperature distribution differences in large-area or thick components, limiting the application of this technology in the manufacture of large and complex components. Summary of the Invention

[0004] To address the problems of existing technologies, this invention provides a composite material electrothermal curing system and method. By introducing carbon nanotube films as interlayer electrothermal functional layers into the composite material layup structure, and combining temperature acquisition results from multiple points such as the central region, edge region, and mold surface, the input power of different electrothermal regions is dynamically adjusted. Simultaneously, based on the changes in resin heating and softening, flow wetting, gelation, and cross-linking curing stages, the vacuum compaction and external pressure loading processes are synergistically controlled, thereby solving the problems of strong dependence on existing composite material curing equipment, insufficient temperature uniformity, and difficulty in stable control of molding quality.

[0005] The technical solution of the present invention is as follows: In a first aspect of the invention, a composite material electrothermal curing system is provided, comprising: The laminate is composed of a prepreg and a conductive and heating layer embedded between the prepreg layers; An electrode assembly, electrically connected to the conductive heating layer, is used to introduce external power into the carbon nanotube film. The temperature acquisition module includes at least a first thermocouple disposed in the central region of the laminate, a second thermocouple disposed in the edge region of the laminate, and a third thermocouple disposed on the surface of the mold. A pressure loading module is used to apply pressure to the laminate; The control unit is communicatively connected to the temperature acquisition module, the electrode assembly, and the pressure loading module, respectively. The control unit is configured to: adjust the input power of the electrode assembly based on the temperature difference collected by the first thermocouple and the second thermocouple to reduce the temperature difference between the central region and the edge region; and simultaneously, identify the curing stage based on the temperature data collected by the third thermocouple, and adjust the output pressure of the pressure loading module according to the curing stage.

[0006] In some embodiments of the present invention, the carbon nanotube film is divided into a central electrothermal region and at least one edge electrothermal region; the electrode assembly includes a central electrothermal region aluminum foil electrode and an edge electrothermal region aluminum foil electrode, the two electrodes being respectively connected to a multi-channel power supply.

[0007] In some embodiments of the present invention, the laminate is placed in a vacuum bag, the vacuum bag is sealed to the upper surface of the mold, and the vacuum bag is connected to a pressure loading module.

[0008] In some embodiments of the present invention, the pressure loading module employs a vacuum pump, which is connected to the vacuum bag via a vacuum tube.

[0009] In some embodiments of the present invention, the laminate is placed in a vacuum bag, the vacuum bag is sealed to the upper surface of the mold, and the vacuum bag and the mold are placed in a sealed pressure vessel.

[0010] In some embodiments of the present invention, the pressure loading module includes a vacuum pump and an air compressor. The vacuum pump is connected to the vacuum bag via a vacuum tube, and the air compressor is connected to the inflation port on the sealed pressure vessel via a pipe.

[0011] In a second aspect of the invention, a method for electrothermal curing of composite materials is provided, comprising the following steps: Lay the prepreg and conductive heating layer in the design sequence, connect the conductive heating layer to the electrode assembly and arrange the thermocouples, and then seal it in a vacuum bag. Vacuum the vacuum bag to remove the interlayer gas, so that the prepreg layers can be initially bonded; By applying electricity to the conductive heating layer, and based on the temperature difference feedback between the central and edge regions of the laminate, the input power of different electrothermal zones is dynamically adjusted so that the laminate heats up according to the preset curing curve. Based on the changes in the resin curing stage, the external loading pressure is adjusted synchronously, with the pressure being increased to the target value before the resin gel point and maintained until the end of the cooling stage.

[0012] In some embodiments of the present invention, the input power of different electrothermal zones is dynamically adjusted based on the temperature difference feedback between the central region and the edge region of the laminate, specifically including: Obtain the temperature of the central region and the edge region of the laminate, and determine whether the difference between the two is greater than the temperature difference threshold. When the difference between the two is greater than the temperature difference threshold, the power in the low-temperature region is increased and the power in the high-temperature region is decreased. When the difference between the two is less than or equal to the temperature difference threshold, the power in the central region and the edge region is adjusted according to the target curing curve.

[0013] In some embodiments of the present invention, the temperature difference threshold is 3-5°C; During the heating process, the actual heating rate is calculated and compared with the preset heating rate. When the actual heating rate exceeds the preset range, the output power of the electrode assembly is dynamically adjusted to maintain a stable heating rate.

[0014] In some embodiments of the present invention, the curing stage includes a vacuum pre-compaction stage, a low-pressure heating stage, a resin flow and wetting stage, a pre-gel pressurization stage, a heat preservation and curing stage, and a cooling stage. Based on the changes in the resin curing stage, the external loading pressure is adjusted synchronously, specifically including: During the vacuum pre-compaction stage, the interlayer gas is removed by vacuuming, allowing the prepreg layers to initially adhere. During the low-pressure heating phase, maintain a low external pressure; During the resin flow and impregnation stage, the pressure inside the pressure tank is gradually increased; During the pre-gelation pressurization phase, the pressure is increased to the target pressure and maintained. Maintain stable pressure during the heat preservation and curing stage; During the cooling phase, the pressure is released slowly.

[0015] One or more technical solutions of the present invention have the following beneficial effects: (1) The composite material curing system of the present invention achieves in-situ heating and curing of thermosetting resin-based composite materials based on the interlayer electrothermal effect of carbon nanotube films. During the heating process, the synergistic pressurization effect can efficiently expel interlayer entrained gas with extremely low energy consumption, promoting the tight adhesion of the prepreg. Since the heat source is built-in, the heat is transferred from the inside to the outside. Combined with the uniform binding of the vacuum bag film, the resin flow and accumulation are effectively suppressed, and the temperature difference at different positions of the mold is stably controlled within 5°C. This mode of equipment is lightweight and simple in structure, and is particularly suitable for thin-walled components, irregularly shaped parts, and in-situ curing. While ensuring the densification of the components, it also improves the energy utilization rate.

[0016] (2) The composite material curing system of the present invention, after introducing an air compressor to implement external positive pressure, constructs a two-way pressure difference environment of "internal vacuum and external positive pressure", which significantly enhances the compaction driving force. Compared with single vacuum compaction, this mode can effectively overcome the flow resistance inside thick-walled components, promote the deep wetting of fiber bundles by low viscosity resin, and completely eliminate interlayer dry spots and micropores. Experiments show that by using carbon nanotube film layer heating while applying external pressure, the interlayer shear strength and compressive strength are greatly improved, effectively suppressing curing deformation and warping, and meeting the stringent requirements of large-size, thick-section high-performance components for internal quality and dimensional accuracy.

[0017] (3) The composite material curing method of the present invention achieves multi-dimensional synergistic optimization of thermo-mechanical parameters through "temperature difference feedback adjustment + curing stage identification". On the one hand, the power of each electrothermal zone is dynamically adjusted based on the temperature difference between the center and the edge, which solves the problem of uneven thermal field caused by rapid heat dissipation at the edge; on the other hand, the six-stage pressure loading curve is accurately matched according to the thermorheological characteristics of resin softening, flow and gelation, which solves the problem of resin loss or pore residue caused by constant pressure loading. This method not only strictly controls the temperature difference within the threshold of 3~5℃, but also continuously iterates the process parameters through data model, which greatly improves the process adaptability and batch stability of molding components of different specifications, and finally obtains composite material components with extremely low porosity, dense interior and excellent mechanical properties. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the composite material electrothermal curing system of the present invention; Figure 2 This is a schematic diagram of the electrothermal structure of the partitioned carbon nanotube film of the present invention; Figure 3 This is a schematic diagram of the electrothermal curing part of the composite material electrothermal curing system of the present invention; Figure 4 This is a schematic diagram of the overall structure of the sealed pressure vessel of the present invention; Figure 5 This is a schematic diagram of the structure of the sealed pressure vessel tank body and the cover plate of the present invention. Figure 6 This is a schematic diagram of the interface on the sealed pressure vessel cover plate of the present invention; Figure 7 This is a schematic diagram of the temperature and power variation curves during the electrothermal curing process under vacuum compaction conditions according to the present invention. Figure 8 This is a schematic diagram of the temperature and power variation curves during the electrothermal curing process under external pressure loading conditions according to the present invention. Figure 9 This is a flowchart of the temperature control process for the electrothermal curing method of the composite material of the present invention; Figure 10 This is a schematic diagram of the staged pressure loading control curve of the present invention.

[0019] In the diagram: 1. Cover plate; 2. Sealing ring; 3. Flange; 4. Bolt hole; 5. Vacuum bag; 6. Prepreg; 601. Upper prepreg; 602. Lower prepreg; 7. Carbon nanotube film; 8. Copper foil electrode; 9. Thermocouple; 10. Thermocouple acquisition interface; 11. Gas filling interface; 12. Vacuum interface; 13. Temperature acquisition module; 14. Control unit; 15. Positive power interface; 16. Negative power interface; 17. Air compressor; 18. Vacuum pump; 19. Conductive silver paint; 20. Mold; 21. Vacuum tube; 22. Sealing strip; 23. DC power supply; 24. Sealed pressure vessel. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] Example 1 A conductive heating layer refers to an interlayer electrothermal functional layer with electrothermal conversion capabilities. In a typical embodiment of this invention, a composite material electrothermal curing system is proposed, using a carbon nanotube film as the conductive heating layer as an example. Figure 1 As shown, it includes: The laminate is formed by stacking a prepreg 6 and a carbon nanotube film 7 embedded between the layers of the prepreg 6. The prepreg 6 contains an uncured thermosetting resin matrix, and the carbon nanotube film 7 serves as a built-in heating element. When electricity is applied, it generates Joule heat through its conductive network, thereby achieving direct heating of the interior of the laminate. The electrode assembly is electrically connected to the carbon nanotube film 7 and is used to introduce an external power source into the carbon nanotube film 7 to provide a stable and controllable current input to the carbon nanotube film 7. The temperature acquisition module 13 includes at least a first thermocouple 9 disposed in the central region of the laminate, a second thermocouple 9 disposed in the edge region of the laminate, and a third thermocouple 9 disposed between the surface of the mold 20 and the prepreg, for real-time acquisition of the temperature change of the interface, thereby characterizing the temperature state of the prepreg during the curing process and determining the curing stage of the prepreg accordingly. The pressure loading module is used to apply pressure to the laminate to compact the prepreg 6, remove excess resin and air bubbles during the curing process, and control the resin flow. The control unit 14 is communicatively connected to the temperature acquisition module 13, the electrode assembly and the pressure loading module, respectively, and is used to receive sensor signals and issue control commands. The control unit 14 is configured to: calculate the temperature difference between the center and edge regions of the laminate in real time based on the temperature difference collected by the first thermocouple 9 and the second thermocouple 9, and adjust the input power of the electrode assembly based on this temperature difference feedback. By differentiating the power distribution, the temperature difference between the center and edge regions is reduced, thereby suppressing the temperature gradient and achieving uniform heating. At the same time, based on the temperature data collected by the third thermocouple 9, the state of the prepreg in the curing process is determined, and the curing stage of the prepreg is determined accordingly. Based on the different requirements of the curing stage, the output pressure of the pressure loading module is dynamically adjusted to achieve coordinated and precise control of the heating and pressurization processes.

[0023] Specifically, the prepreg 6-layer composite is formed by stacking multiple layers of glass fiber / epoxy resin prepreg 6, with a carbon nanotube film 7 embedded between the prepreg 6 layers, preferably located in the central region of the composite structure. The carbon nanotube film 7 is connected to the copper foil electrode 8 via conductive silver paint 19. The conductive silver paint 19 is used to achieve a low contact resistance electrical connection between the carbon nanotube film 7 and the copper foil electrode 8, forming a stable conductive interface between them, thereby reducing interface contact resistance and improving current transmission efficiency. The specific application method is as follows: first, the conductive silver paint is uniformly coated on the surface of the copper foil electrode; then, the copper foil electrode and the carbon nanotube film are aligned and bonded together, and appropriate pressure is applied so that the conductive silver paint fully fills the microscopic gaps at the interface under pressure, forming a continuous conductive path, thereby achieving a reliable electrical connection between the copper foil electrode and the carbon nanotube film. The copper foil electrode 8 is connected to an external DC power supply 23 via a wire to form a closed circuit. When energized, the carbon nanotube film 7 generates Joule heat under the action of current, heating the epoxy resin in the adjacent prepreg 6 in situ.

[0024] The electrothermal zones of the carbon nanotube film 7 can be arranged along the length, width, or center-edge direction of the composite material, and each electrothermal zone is equipped with at least one temperature detection point. The control unit 14 adjusts the output voltage or output current of the corresponding power channel according to the real-time temperature feedback of each electrothermal zone, thereby achieving local compensation heating when the heat dissipation in the edge area is faster or there are differences in local contact resistance, suppressing local overheating and improving the overall temperature uniformity.

[0025] In this embodiment, as Figure 2 As shown, the carbon nanotube film 7 is divided into a central heating zone and at least one edge heating zone to achieve independent heating control in each zone. The electrode assembly includes aluminum foil electrodes for the central heating zone and aluminum foil electrodes for the edge heating zone. Both types of electrodes are connected to a multi-channel power supply, allowing the central and edge zones to receive electrical energy inputs of different power levels, thus enabling independent temperature regulation. The control unit 14 adjusts the input power of the central and edge heating zones based on the temperature difference collected by the thermocouples 9 in the central and edge regions, ensuring that the laminate maintains a small center-edge temperature difference during heating and heat preservation.

[0026] It should be noted that the division between the central heating zone and the edge heating zone is achieved by setting up independent electrode connections and power supply circuits for each zone, enabling independent power input and control. Specifically, the central heating zone and the edge heating zone correspond to different conductive heating paths, each connected to a multi-channel power supply system via independent copper foil electrodes. The control system adjusts the output power of each channel based on the temperature feedback signals from different zones, thereby achieving independent control of the zoned heating. Therefore, "zoned" is based on the functional division of the heating control unit. Alternatively, physical insulation can be used for zoning, for example, by placing insulating material between the central heating zone and the edge heating zone to achieve physical insulation between the two zones.

[0027] In one embodiment of this example, such as Figure 3 As shown, the laminate is placed in a vacuum bag 5. The vacuum bag 5 is airtightly connected to the upper surface of the mold 20 via a sealing strip 22. The vacuum bag 5 is connected to a pressure loading module to apply a vacuum negative pressure to the laminate during the curing process, assisting in the removal of interlayer gases and volatiles. The pressure loading module uses a vacuum pump 18, which is connected to the vacuum bag 5 via a vacuum tube 21. By evacuating the air from the vacuum bag 5, a uniform negative pressure environment is formed on the surface of the laminate, achieving initial compaction and gas removal.

[0028] Specifically, during use, a layer of release film is first laid on the surface of the metal mold 20, the laminate is placed on the release film, and another layer of release film is laid on the upper surface of the laminate. Then, a breathable felt is used to cover the laminate and its upper and lower release films, and the entire packaged assembly is placed in a vacuum bag 5. After sealing with a sealing strip 22, it is connected to the vacuum pump 18 to keep the laminate in a vacuum compacted state during the curing process. Thermocouples 9 are respectively placed in the central and edge areas of the mold 20 to detect temperature changes during the molding process. The temperature signal is transmitted to the computer control unit 14 via the temperature acquisition module 13. The computer control unit 14 adjusts the output of the DC power supply 23 according to the preset curing temperature curve. During curing, the vacuum pump 18 is first started to create a negative pressure environment inside the vacuum bag 5 and compact the laminate. Then, the DC power supply 23 is turned on to gradually heat the carbon nanotube film 7. The control unit 14 adjusts the input voltage or current according to the real-time temperature measurement results to make the actual temperature as close as possible to the target curing curve. After the temperature reaches the preset insulation temperature, it is maintained for a period of time to complete the cross-linking and curing of the resin; after the insulation is completed, heating is stopped and the material is allowed to cool naturally or at a controlled rate to finally obtain the cured composite material component.

[0029] During the molding process, the temperatures of both the edge and center regions increased with the increase of their respective input power, and the overall temperature change trend was consistent with the input power change trend, indicating that the carbon nanotube film 7 can achieve a stable electrothermal response according to the power supply adjustment. After temperature field control treatment, during the molding and curing stage, the maximum temperature difference between the edge and center regions was controlled within 5 ℃, indicating that this electrothermal curing method can effectively improve the temperature uniformity during the molding process.

[0030] like Figure 7 As shown, the total electrical energy consumption during the experiment can be obtained by integrating the power-time curve during the molding process. The calculated electrical energy consumption for this experiment was 0.0597 kW·h. This result indicates that the electrothermal curing method achieves effective curing of the composite material while maintaining low energy consumption, which is beneficial for improving the energy utilization efficiency of the curing process.

[0031] In this embodiment, by using the carbon nanotube film 7 as the internal electrothermal layer, heat can be transferred to the resin region more quickly compared to traditional external heating methods. Simultaneously, vacuum compaction facilitates interlayer degassing, resin flow, and component densification. Experiments show that this method can achieve stable electrothermal curing of the composite material and maintain the temperature difference at different locations on the mold 20 within a small range.

[0032] Example 2 This embodiment provides an electrothermal curing system with external pressure loading, such as... Figure 1 Combination Figure 4-6 As shown, the laminate is placed in a vacuum bag 5. The vacuum bag 5 and the upper surface of the mold 20 are airtightly connected by a sealing strip 22. The vacuum bag 5 and the mold 20 are placed together in a sealed pressure vessel 24, which can withstand high internal pressure. The pressure loading module includes a vacuum pump 18 and an air compressor 17. The vacuum pump 18 is connected to the vacuum bag 5 through a vacuum tube 21 and is used to evacuate the inside of the vacuum bag 5. The air compressor 17 is connected to the air inlet 11 on the sealed pressure vessel 24 through a pipe and is used to inject compressed gas or air into the pressure vessel, thereby establishing and maintaining the required pressurized environment inside the vessel and applying uniform positive pressure to the laminate. By adjusting the output pressure of the air compressor 17, the internal pressure of the pressure vessel can be controlled to meet the pressure requirements under different curing process conditions.

[0033] Specifically, the tank body and cover plate 1 of the sealed pressure vessel 24 are sealed and installed using flange 3 and bolts with sealing ring 2. The cover plate 1 is provided with bolt holes 4, thermocouple acquisition interface 10, gas filling interface 11, vacuum interface 12, positive power supply structure, and negative power supply interface. The laminate is placed inside the pressure vessel after being sealed in a vacuum bag 5. Compressed gas is introduced into the container through an external gas source to apply external pressure to the laminate. The carbon nanotube film 7 is still connected to the DC power supply 23 through copper foil electrode 8, and the thermocouple 9 is arranged near the laminate and connected to the temperature acquisition module 13.

[0034] During the curing process, the vacuum bag 5 is first evacuated to allow the laminate to undergo initial degassing and pre-compaction under negative pressure. Then, external positive pressure is applied to the pressure vessel, allowing the laminate to achieve a higher compaction effect under the combined action of internal negative pressure and external positive pressure. The external pressure loading process is regulated by the control unit 14 according to the resin curing stages: a low external pressure is maintained during the initial heating stage; when the temperature rises to the range where the resin viscosity decreases and has good fluidity, the internal pressure of the pressure vessel is gradually increased to promote resin impregnation of the fiber bundles and expel residual gas; when the resin enters the pre-gel stage, the pressure is increased to the target pressure and maintained; subsequently, the power output is adjusted according to the target curing temperature curve to heat the carbon nanotube film 7 and complete resin curing.

[0035] Compared with Example 1, the pressure conditions in Example 2 are higher, which can further promote resin impregnation of fiber bundles, inhibit pore formation, enhance interlayer bonding, and improve the surface quality and internal density of the molded parts.

[0036] During the molding process, the power input voltage is adjusted based on the real-time collected temperature values ​​to ensure that the composite material layup temperature rises, holds, and cures according to the preset curing curve of the prepreg 6. Dynamic control of the input voltage allows for stable control of the curing temperature process. During the curing stage, the temperature difference between the edge and center areas of the mold 20 is controlled within 5°C, indicating that this pressurized electrothermal curing method has good temperature uniformity.

[0037] like Figure 8 As shown, by integrating the power-time curve during the molding process, the electrical energy consumed in this experiment was found to be 0.131 kW·h. Compared with the electrothermal curing method that only uses vacuum bag 5 for pressure application, this method increases energy consumption by about 54% due to the introduction of pressure tank pressurization conditions, but the overall energy consumption is still at a low level. It can ensure the pressure curing effect and temperature uniformity while taking into account good energy utilization efficiency.

[0038] Example 3 This embodiment provides a method for electrothermal curing of composite materials, using the composite material electrothermal curing system described in Embodiments 1 and 2, including the following steps: Before curing, the control unit sets the initial heating rate, central region power, edge region compensation power, and pressure loading program based on the prepreg type, layup thickness, initial resistance of the carbon nanotube film, and target curing temperature curve.

[0039] The prepreg and carbon nanotube film are laid out in the design sequence, the carbon nanotube film is connected to the electrode assembly and thermocouples are arranged, and then vacuum bag is sealed to ensure that each component is accurately positioned, reliably connected and tightly sealed.

[0040] During curing, the vacuum pump is first started to evacuate the vacuum bag and remove the interlayer gas, so that the prepreg layers are initially bonded, eliminating the initial layup gaps and creating good contact conditions for subsequent heating and curing. Subsequently, a multi-channel DC power supply is activated to power the carbon nanotube film, causing the central and edge electrothermal zones to heat up separately. Based on the temperature difference feedback between the central and edge regions of the laminate, the input power of different electrothermal zones is dynamically adjusted to ensure that the laminate heats up uniformly and stably according to the preset curing curve, avoiding local overheating or excessively rapid heating.

[0041] The specific adjustment process is as follows: Figure 9 As shown, the temperature Tc of the central region and the temperature Te of the edge region of the laminate are acquired in real time, the difference ΔT between the two is calculated in real time, and it is determined whether the difference is greater than the preset temperature difference threshold ΔTmax. When the difference between the two is ΔT, it is greater than the temperature difference threshold Tmax. The input power of the electric heating zone corresponding to the low temperature zone is increased, while the input power of the electric heating zone corresponding to the high temperature zone is reduced to actively compensate for the temperature difference and promote the uniformity of the temperature field. When the difference between the two is less than or equal to the temperature difference threshold, the power of the central region and the edge region is adjusted synchronously according to the preset target curing curve so that the overall heating process follows the predetermined process path.

[0042] Furthermore, the temperature difference threshold can be determined based on the thickness of the composite material, the number of layups, and the resin system, and is preferably 3-5℃. This range aims to balance temperature control accuracy and system response stability. During the heating process, the actual heating rate is continuously calculated and compared with the preset heating rate. When the actual heating rate exceeds the set range, the control unit reduces the power output to avoid local overheating of the carbon nanotube film and excessive resin temperature. When the actual heating rate is lower than the set range, the control unit increases the power output to ensure that the composite material is heated stably according to the preset curing regime.

[0043] In terms of pressure control, the external loading pressure is adjusted synchronously according to the changes in the resin curing stage. The pressure is increased to the target value before the resin gel point and maintained until the end of the cooling stage to ensure that the resin flows fully, wets the fiber and completes compaction before gelation. After gelation, the pressure is maintained to control the porosity and stabilize the resin shape.

[0044] like Figure 10 As shown, the curing stage includes a low-pressure heating stage, a resin flow and wetting stage, a pre-gelling pressurization stage, a heat preservation and curing stage, and a cooling stage. During the vacuum pre-compaction stage, the vacuum pump is started first to expel the interlayer gas, so that the prepreg layers can be initially bonded. During the low-pressure heating stage, i.e. the initial curing stage, maintain a low external pressure to avoid fiber layer slippage or local resin extrusion due to excessive pressure before the resin has softened. During the resin flow impregnation stage, as the resin viscosity decreases, the pressure inside the pressure tank is gradually increased or the vacuum level is adjusted to promote resin impregnation of the fiber bundles and the removal of interlayer gas. During the pre-gelation pressurization stage, that is, before the resin undergoes a gelation reaction, the pressure is increased to the target pressure and maintained to enhance the interlayer compaction effect. During the heat preservation and curing stage, the target pressure is maintained to provide a stable pressure environment for resin cross-linking and curing, thus ensuring the performance of the composite material. During the cooling phase, external pressure is slowly and gradually removed as the temperature decreases to reduce porosity, delamination, warping, and springback defects.

[0045] In another preferred embodiment, the control unit further includes a curing process data processing module. This module records the layup thickness, initial resistance of the carbon nanotube film, input voltage, input current, central region temperature, edge region temperature, pressure changes, curing time, energy consumption, and post-curing quality evaluation results for each curing process. The control unit can establish a process parameter recommendation model based on historical curing data to predict the initial input power, edge compensation power, heating rate, pressure loading timing, and holding time for different layup structures. During subsequent curing processes, the system generates an initial control scheme based on the recommended parameters and makes corrections using real-time temperature and pressure feedback, thereby improving the adaptability and stability of the curing process for composite materials of different specifications.

[0046] Using the above methods, the composite material can simultaneously achieve target temperature tracking, center-edge temperature difference control, heating rate control, and pressure loading timing optimization during the curing process. Compared with single-area energization and constant pressure loading, this embodiment can further improve curing temperature uniformity, enhance resin wetting effect, reduce porosity and delamination defects, and improve the molding quality and process repeatability of composite material components.

[0047] The electrothermal curing method for composite materials provided in this embodiment has the characteristics of short heating path, high energy utilization, fast temperature response, and suitability for local or zoned heating. It can be used for curing and molding thermosetting resin-based composite materials such as epoxy resin, bismaleimide resin, phenolic resin, cyanate ester resin, and polyimide resin.

[0048] It should be noted that this invention uses carbon nanotube thin films as an example to illustrate the partitioned electrothermal curing structure, but the scope of protection of this invention is not limited to this specific material. Any technical solution that employs a similar structural form, i.e., introducing a conductive heating layer with electrothermal conversion function into a composite material laminate structure and performing partitioned electrothermal control to achieve composite material curing, should fall within the scope of protection of this invention.

[0049] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A composite material electrothermal curing system, characterized by, include: The laminate is composed of a prepreg and a conductive and heating layer embedded between the prepreg layers; An electrode assembly, electrically connected to the conductive heating layer, is used to introduce external power into the carbon nanotube film. The temperature acquisition module includes at least a first thermocouple disposed in the central region of the laminate, a second thermocouple disposed in the edge region of the laminate, and a third thermocouple disposed on the surface of the mold. A pressure loading module is used to apply pressure to the laminate; The control unit is communicatively connected to the temperature acquisition module, the electrode assembly, and the pressure loading module, respectively. The control unit is configured to: adjust the input power of the electrode assembly based on the temperature difference collected by the first thermocouple and the second thermocouple to reduce the temperature difference between the central region and the edge region; and simultaneously, identify the curing stage based on the temperature data collected by the third thermocouple, and adjust the output pressure of the pressure loading module according to the curing stage.

2. The composite material electrothermal curing system as described in claim 1, characterized in that, The conductive heating layer is made of carbon nanotube film, which is divided into a central heating region and at least one edge heating region; the electrode assembly includes a central heating region aluminum foil electrode and an edge heating region aluminum foil electrode, and the two types of electrodes are respectively connected to a multi-channel power supply.

3. The composite electrothermal curing system of claim 1, wherein, The laminate is placed in a vacuum bag, which is sealed to the upper surface of the mold and connected to the pressure loading module.

4. The composite electrothermal curing system of claim 3, wherein, The pressure loading module uses a vacuum pump, which is connected to the vacuum bag via a vacuum tube.

5. The composite electrothermal curing system of claim 1, wherein, The laminate is placed in a vacuum bag, which is sealed to the upper surface of the mold. The vacuum bag and the mold are placed in a sealed pressure vessel.

6. The composite electrothermal curing system of claim 5, wherein, The pressure loading module includes a vacuum pump and an air compressor. The vacuum pump is connected to the vacuum bag via a vacuum tube, and the air compressor is connected to the inflation port on the sealed pressure vessel via a pipe.

7. A method of electrothermal curing of a composite material using the electrothermal curing system according to any one of claims 1 to 6, characterized in that, Includes the following steps: Lay the prepreg and conductive heating layer in the design sequence, connect the conductive heating layer to the electrode assembly and arrange the thermocouples, and then seal it in a vacuum bag. Vacuum the vacuum bag to remove the interlayer gas, so that the prepreg layers can be initially bonded; By applying electricity to the conductive heating layer, and based on the temperature difference feedback between the central and edge regions of the laminate, the input power of different electrothermal zones is dynamically adjusted so that the laminate heats up according to the preset curing curve. Based on the changes in the resin curing stage, the external loading pressure is adjusted synchronously, with the pressure being increased to the target value before the resin gel point and maintained until the end of the cooling stage.

8. The composite electrothermal curing method of claim 7, wherein, Based on the temperature difference feedback between the central and edge regions of the laminate, the input power of different electrothermal zones is dynamically adjusted, specifically including: Obtain the temperature of the central region and the edge region of the laminate, and determine whether the difference between the two is greater than the temperature difference threshold. When the difference between the two is greater than the temperature difference threshold, the power in the low-temperature region is increased and the power in the high-temperature region is decreased. When the difference between the two is less than or equal to the temperature difference threshold, the power in the central region and the edge region is adjusted according to the target curing curve.

9. The method for electrothermal curing of composite materials as described in claim 8, characterized in that, The temperature difference threshold is 3-5℃; During the heating process, the actual heating rate is calculated and compared with the preset heating rate. When the actual heating rate exceeds the preset range, the output power of the electrode assembly is dynamically adjusted to maintain a stable heating rate.

10. The composite electrothermal curing method of claim 7, wherein, The curing stage includes a vacuum pre-compaction stage, a low-pressure heating stage, a resin flow and wetting stage, a pre-gel pressurization stage, a heat preservation and curing stage, and a cooling stage. Based on the changes in the resin curing stage, the external loading pressure is adjusted synchronously, specifically including: During the vacuum pre-compaction stage, the interlayer gas is removed by vacuuming, allowing the prepreg layers to initially adhere. During the low-pressure heating phase, maintain a low external pressure; During the resin flow and impregnation stage, the pressure inside the pressure tank is gradually increased; During the pre-gelation pressurization phase, the pressure is increased to the target pressure and maintained. Maintain stable pressure during the heat preservation and curing stage; During the cooling phase, the pressure is released slowly.

Images