Hot air pressure-diaphragm synergistic forming method for resin-based fiber composite material

Abstract

The invention relates to the technical field of composite material manufacturing, in particular to a resin-based fiber composite material hot air pressure-diaphragm synergistic forming method which comprises the following steps: cutting prepreg, paving multiple layers, paving diaphragms on the upper surface and the lower surface of the prepreg, placing the prepreg in a forming area of a lower mold, fixing the prepreg, and closing and sealing an upper mold and the lower mold; a heating system is started, the mold is preheated, and meanwhile pressurized gas is heated; vacuumizing the vacuum cavity, and introducing heated pressurized gas into the high-pressure gas cavity at the same time; the diaphragm-prepreg assembly deforms and is attached to the molded surface, and gradient temperature-changing pressure-maintaining curing is carried out; the input of the pressurized gas is stopped, the heating device is stopped, the gas pressure reducing and recycling device is started, the gas in the high-pressure gas cavity is subjected to pressure reduction and then recycled, the mold is opened and taken after the mold is cooled, the hot air pressure-diaphragm collaborative forming component is obtained and cut, and a finished product component is obtained. Through the synergistic effect of hot air pressure and the diaphragm, the porosity of a finished component is reduced.

Description

Technical Field

[0001] This invention relates to the field of composite material manufacturing technology, and in particular to a method for hot air pressure-diaphragm co-molding of resin-based fiber composite materials. Background Technology

[0002] Currently, the main molding methods for resin-based fiber composite materials in this field include: autoclave molding, vacuum bag molding, injection molding, diaphragm molding, and compression molding. Autoclave molding involves sequentially laying prepreg into a curved mold and then placing it in an autoclave for curing. However, this method has high initial equipment investment and maintenance costs, a long curing cycle, low equipment utilization, and high energy consumption and cost. Vacuum bag molding involves laying prepreg on the mold surface, covering it with a flexible vacuum bag, and creating negative pressure to obtain a component conforming to the mold shape. However, insufficient molding pressure results in high porosity in the molded component, making it difficult to meet the high-performance production requirements. Injection molding involves injecting molten polymer into a mold, then holding it at a constant temperature and pressure before cooling, such as resin transfer molding (RTM) and high-pressure resin transfer molding (HP-RTM). However, this process requires precise control of injection pressure, speed, and other parameters, which can easily cause defects such as rough surface, internal bubbles, and shrinkage cavities in the product. Diaphragm molding uses vacuum negative pressure to deform and bond a preheated elastic diaphragm and prepreg to a mold. However, due to insufficient local pressure provided by vacuum negative pressure, diaphragm molding is often used as a pre-forming step in autoclave processes. Compression molding involves placing a prepared molding compound into a mold, closing the mold, and then curing it. However, insufficient pressure uniformity can easily lead to defects such as fiber buckling and wrinkling. Currently, out-of-autoclave (OOA) processes have been a key focus of research and development in the field of composite material molding. However, most of these processes result in lower molding quality and performance compared to autoclave molding, and there is a lack of methods for molding composite materials under high hot pressure.

[0003] Chinese Patent Publication No. CN108327313A discloses a continuous molding apparatus and method for resin-based composite materials, comprising: a molding mold, into which the resin-based composite material is placed; a vacuum device, into which the resin-based composite material placed in the molding mold is sealed and then vacuumed and compacted; and a zoned temperature-controlled curing device, which cures the resin-based composite material after the vacuuming operation; wherein the zoned temperature-controlled curing device consists of at least two constant temperature components, the temperature of which is set in a stepped manner, and the molding mold, the vacuum device, and the zoned temperature-controlled curing device form a circulation system; it can be seen that this invention has the problem of relying solely on vacuum negative pressure molding, resulting in insufficient pressure and high porosity of the molded component. Summary of the Invention

[0004] Therefore, the present invention provides a hot air pressure-diaphragm co-molding method for resin-based fiber composite materials to overcome the problem of high porosity of components caused by relying solely on vacuum negative pressure molding in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials, comprising: Step S1: Cut the prepreg of the resin-based fiber composite material according to the shape of the mold; Step S2: The prepreg is laid in multiple layers. A non-porous diaphragm is laid on the upper surface of the prepreg, and a porous diaphragm is laid on the lower surface of the prepreg to obtain a diaphragm-prepreg assembly. Step S3: Place the diaphragm-prepreg assembly on the molding area of ​​the upper surface of the lower mold and fix it. Close the upper mold and the lower mold. The molding areas of the upper mold and the lower mold are provided with silicone sealing frames to seal the upper and lower cavities formed by the mold cavity and the surface of the diaphragm-prepreg assembly in a planar manner. Step S4: Start the heating system to preheat the diaphragm-prepreg assembly inside the mold, and at the same time, introduce pressurized gas into the electric heating assembly for heating; Step S5: Vacuum the vacuum cavity formed by the lower mold and the lower surface of the diaphragm-prepreg assembly, and at the same time introduce the heated pressurized gas into the high-pressure gas cavity formed by the upper mold and the upper surface of the diaphragm-prepreg assembly. Step S6: Under the combined effect of high pressure-vacuum loading and high temperature environment, the diaphragm-prepreg assembly deforms and adheres to the molding surface of the lower mold cavity, and gradient temperature and pressure are maintained for a specified time according to the resin characteristics for curing. Step S7: After the specified time is reached, the input of the pressurized gas is turned off, the electric heating component is turned off and the gas depressurization and recovery device is turned on to recover the pressurized gas in the high-pressure gas chamber. After the mold is cooled down, the mold is opened and the part is taken out to obtain the hot gas pressure-diaphragm co-molded component. Step S8: Cut the hot air pressure-diaphragm co-molding component to remove excess material edges and burrs, and obtain the finished component.

[0006] Furthermore, the resin-based fiber composite material uses thermoplastic resin or thermosetting resin.

[0007] Furthermore, in step S2, both the non-porous diaphragm and the porous diaphragm are made of polytetrafluoroethylene heat-resistant film material.

[0008] Further, in step S4, Oil channels are provided on the mold, and the heat transfer oil is heated by a mold temperature controller to preheat the diaphragm-prepreg assembly inside the mold; The pressurized gas is heated electrically, and the heating temperature of the pressurized gas is the same as the preheating temperature. Furthermore, in step S4, the pressurizing gas is an inert gas with an adjustable pressure range of 0–70 MPa; The target heating temperature for heating the pressurized gas is determined based on the target viscosity, wherein the target viscosity is 1.2 times the viscosity of the resin at the first temperature, and the first temperature is the thermal degradation temperature of the prepreg.

[0009] Furthermore, step S5 also includes: First, the vacuum degree of the lower mold vacuum chamber is evacuated to ≤50mbar, and then the pressure in the high-pressure gas chamber is increased to the target hot-pressing pressure at a rate of 0.15MPa / s, while the vacuum degree of the vacuum chamber is evacuated to ≤5mbar. The target hot-pressing pressure is determined based on the service performance of the prepreg.

[0010] Further, in step S5, the service performance equivalent is determined based on the shrinkage rate and adhesion of the prepreg, and the target hot-pressing pressure is determined based on the service performance equivalent.

[0011] Further, in step S7, the gas pressure reduction and recovery device includes a gas storage tank connected to the high-pressure gas chamber. A pressure reducing valve is installed on the outside of the gas storage tank. After the specified time is reached, the input of the pressurized gas is shut off, the electric heating component is turned off, and the valve of the pressure reducing valve of the gas pressure reduction and recovery device is opened to reduce the pressure of the high-pressure gas chamber and recover the pressurized gas in the high-pressure gas chamber at the same time.

[0012] Furthermore, in step S7, the cooling method is gradient cooling, which lowers the temperature to three gradients: 80% of the curing temperature, 50% of the curing temperature, and room temperature. Each gradient is held for 5 minutes to suppress defects such as deformation, cracking, and springback of the part.

[0013] Further, in step S4, for thermosetting resin-based fiber composite materials, the preheating temperature is lower than the resin gel temperature of the prepreg; for thermosetting resin-based fiber composite materials, the preheating temperature is lower than the resin gel temperature of the prepreg; for thermoplastic resin-based fiber composite materials, the preheating temperature is higher than the resin melting temperature of the prepreg.

[0014] Compared with existing technologies, the beneficial effect of this invention lies in constructing a non-autoclave molding process based on a "small autoclave," namely, a pneumatic-diaphragm co-molding method. A sealed cavity is formed using a mold, hot pressurized gas is added, and the mold is precisely temperature-controlled to create a thermal environment similar to an autoclave.

[0015] Furthermore, the composite material employs a double-diaphragm vacuum negative pressure method, effectively improving its molding performance. Applying pressurized gas effectively eliminates defects such as interfacial pores, bubbles, and delamination. The pressure range of the pressurized gas is 0–70 MPa, adjustable as needed, while traditional autoclaves operate at only around 1 MPa. The porosity of the molded component can reach less than 1%, avoiding the high porosity phenomenon caused by insufficient pressure. This enables the manufacture of composite material components with performance equivalent to autoclave processes, while significantly reducing costs and energy consumption and facilitating automation. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the hot air pressure-diaphragm co-molding method for resin-based fiber composite materials in an embodiment of the present invention; Figure 2 This is a plan view of the resin-based fiber composite material hot air pressure-diaphragm co-molding device in an embodiment of the present invention; Figure 3 This is a schematic plan view of the diaphragm-prepreg assembly of the resin-based fiber composite hot air pressure-diaphragm co-molding device in an embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of the resin-based fiber composite material hot air pressure-diaphragm co-molding device in an embodiment of the present invention; Figure 5 This is a flowchart of step S7, cooling and demolding, in the hot air pressure-diaphragm co-molding method for resin-based fiber composite materials in this embodiment of the invention. The components are: 1. Upper mold, 2. Sealing frame, 3. Diaphragm-prepreg assembly, 4. Lower mold, 5. Heating system, 6. Prepreg, 7. Non-porous diaphragm, 8. Porous diaphragm, 9. High-pressure gas chamber, 10. Vacuum assembly, 11. Pressurization assembly, 12. Electric heating assembly, 13. Gas depressurization and recovery device, and 14. Vacuum chamber. Detailed Implementation

[0017] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0018] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0020] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] Please see Figures 1-5 As shown, Figure 1 This is a schematic flowchart of the hot gas pressure-diaphragm co-molding method for resin-based fiber composite materials in an embodiment of the present invention. The embodiment of the present invention provides a hot gas pressure-diaphragm co-molding method for resin-based fiber composite materials, comprising: Step S1: Cut the prepreg 6 of the resin-based fiber composite material according to the shape of the mold; Specifically, the cutting operation uses a multi-axis CNC cutting machine, and images are acquired in real time during the operation. The cutting path is corrected based on the vision system to improve the cutting accuracy. It is understood that the resin-based fiber composite material uses thermoplastic or thermosetting resins. Preferably, the thermoplastic resin includes polyetheretherketone, polyamide, polyethylene or polyphenylene sulfide, etc., and the thermosetting resin includes epoxy resin, phenolic resin or polyester resin, etc. The fiber includes carbon fiber, glass fiber, basalt fiber or aramid fiber, etc. Those skilled in the art can select the corresponding material according to the specific scenario. This invention does not limit the selection, and all of them are within the protection scope of this invention.

[0022] Step S2: The prepreg 6 is multi-layered, with a non-porous diaphragm 7 laid on the upper surface of the prepreg and a porous diaphragm 8 laid on the lower surface of the prepreg to obtain the diaphragm-prepreg assembly 3. Specifically, both the non-porous diaphragm 7 and the porous diaphragm 8 are made of polytetrafluoroethylene heat-resistant film material.

[0023] The upper surface is covered with a non-porous diaphragm 7 to isolate the high-pressure gas chamber 9 in the upper part of the mold from the vacuum chamber 14 in the lower part; the lower surface is covered with a porous diaphragm 8 to facilitate vacuum treatment of the components and prevent resin from flowing into the vacuum pipe.

[0024] Please see Figure 2 As shown, it is a plan view of the resin-based fiber composite material hot air pressure-diaphragm co-molding device in an embodiment of the present invention; This invention also provides a hot air pressure-diaphragm co-molding apparatus for realizing a hot air pressure-diaphragm co-molding method for resin-based fiber composite materials, comprising: 1 is the upper mold, 2 is the sealing frame, 3 is the diaphragm-prepreg assembly, 4 is the lower mold, 5 is the heating system, 6 is the prepreg, 7 is the non-porous diaphragm, 8 is the porous diaphragm, 9 is the high-pressure gas chamber, 10 is the vacuum assembly, 11 is the pressurization assembly, 12 is the electric heating assembly, 13 is the gas depressurization and recovery device, and 14 is the vacuum chamber.

[0025] Please see Figure 3 As shown, it is a plan view of the diaphragm-prepreg assembly of the resin-based fiber composite hot air pressure-diaphragm co-molding device in an embodiment of the present invention. The diaphragm-prepreg assembly 3 includes a non-porous diaphragm 7 and a porous diaphragm 8. The non-porous diaphragm 7 is disposed on the upper surface of the cut prepreg 6, and the porous diaphragm 8 is disposed on the lower surface of the cut prepreg 6 to form the diaphragm-prepreg assembly 3. The upper mold 1 is located above the diaphragm-prepreg assembly. It has several oil channels inside that are connected to the heating system 5. Its hollow interior is a high-pressure gas chamber 9. Its top is connected to the electric heating assembly 12 and the gas pressure reduction and recovery device 13 through a gas pipe. One end of the gas pipe is connected to the high-pressure gas chamber 9. The lower mold 4 is located below the diaphragm-prepreg assembly. It has several oil channels inside that connect to the heating system 5. The bottom of the mold is equipped with a vacuum assembly 10 that is connected to the vacuum chamber 14 through a vacuum channel. A sealing assembly, disposed between the upper mold and the lower mold, for sealing the diaphragm-prepreg assembly 3, includes two sealing frames 2 disposed at the corresponding edges of the upper and lower surfaces of the diaphragm-prepreg assembly 3; Heating system 5, which is connected to upper mold 1 and lower mold 4, heats heat transfer oil by means of a mold temperature controller, so that the heat transfer oil flows through the hot runner of upper mold 1 and lower mold 4 to heat the diaphragm-prepreg assembly 3; The vacuum assembly 10 includes a vacuum pump and a vacuum pipe, wherein the vacuum pump is connected to the vacuum chamber 14 in the lower mold 4 through the vacuum pipe; The pressurization component 11 is connected to the electric heating component 12 and supplies high-pressure gas to the electric heating component 12 through a gas pipeline; The electric heating component 12 is connected to the high-pressure gas chamber 9 and the pressurizing component 11. It receives gas from the pressurizing component 11 through a gas pipeline, heats it inside, and delivers it to the high-pressure gas chamber 9. The gas pressure reduction and recovery device 13 includes a gas storage tank and a pressure reducing valve. The gas storage tank is located above the upper mold 1 and is connected to the high-pressure gas chamber 9 and the electric heating component 12 through a gas pipeline. The pressure reducing valve is installed outside the gas storage tank.

[0026] Step S3: Place the diaphragm-prepreg assembly 3 on the molding area of ​​the upper surface of the lower mold 4 and fix it. Close the upper mold 1 and the lower mold 4. The molding areas of the upper mold 1 and the lower mold 4 are provided with silicone sealing frames 2 to seal the upper and lower cavities formed by the mold cavity and the surface of the diaphragm-prepreg assembly 3 in a planar manner. Step S4: Start the heating system 5 to preheat the diaphragm-prepreg assembly 3 inside the mold, and at the same time, introduce pressurized gas into the electric heating assembly 12 for heating; Please see Figure 2 and Figure 3 As shown, specifically, oil channels are provided in the molds (upper mold 1 and lower mold 4), and the heat transfer oil is heated by a mold temperature controller to preheat the diaphragm-prepreg assembly inside the mold. Among them, the heat transfer oil preferably uses special silicone oil, which can be used stably for a long time between -40℃ and 400℃, so that the heating system can accurately control the temperature below 400℃; In this embodiment, the pressurizing gas is an inert gas, preferably nitrogen, with an adjustable pressure range of 0–70 MPa; the heating method is electric heating, wherein the heating temperature is the same as the preheating temperature; the preheating temperature is greater than the melting temperature of the prepreg and less than the thermal degradation temperature of the prepreg.

[0027] Specifically, in step S4, the target heating temperature for heating the pressurized gas is determined based on the target viscosity, wherein the target viscosity is 1.2 times the viscosity of the prepreg at the first temperature, and the first temperature is the thermal degradation temperature of the prepreg.

[0028] Specifically, the thermal degradation temperature of the prepreg is obtained as the first temperature. The viscosity of the prepreg is measured multiple times at the first temperature. The target viscosity is set to 1.2 times the viscosity of the prepreg at the first temperature. After multiple tests, the average heating temperature when the viscosity of the prepreg is 1.2 times the viscosity at the first temperature is obtained, and this is recorded as the target heating temperature, so that the prepreg has sufficient ductility before stretching.

[0029] Specifically, for thermosetting resin-based fiber composites, the preheating temperature is lower than the resin gel temperature of the prepreg, and for thermoplastic resin-based fiber composites, the preheating temperature is higher than the resin melting temperature of the prepreg.

[0030] Step S5: Vacuuming is performed on the vacuum cavity 14 formed by the lower mold 4 and the lower surface of the diaphragm-prepreg assembly 3, while the heated pressurized gas is introduced into the high-pressure gas cavity 9 formed by the upper mold 1 and the upper surface of the diaphragm-prepreg assembly 3. In one specific embodiment, the vacuum degree of the lower vacuum chamber of the mold is first evacuated to ≤50mbar, and then the pressure in the high-pressure gas chamber is increased to the target hot pressing pressure at a rate of 0.15MPa / s, while the vacuum degree of the lower mold forming chamber is evacuated to ≤5mbar. Specifically, the target hot-pressing pressure is determined based on the service performance of the prepreg; In one specific embodiment, the service performance equivalent is determined based on the shrinkage rate and adhesiveness of the prepreg 6, and the target hot-pressing pressure is determined based on the service performance equivalent.

[0031] The formula for calculating the service performance equivalent is as follows:

[0032] in, For service performance equivalent, Dimensionless, S is shrinkage rate, A is tensile strength (MPa). For standard tensile strength, and This coefficient is determined based on material properties and experience, and can be quantified through standardized tests of viscosity retention time (h) and gel time (h). Its value ranges from 0 to 1. Preferably, in this embodiment, It is 40 MPa. It is 0.6. It is 0.5; The formula for calculating the target hot-pressing pressure is:

[0033] Where P is the target hot-pressing pressure. For service performance equivalent, The standard hot-pressing pressure is used, and k is an empirically determined coefficient ranging from 1.0 to 1.3. It is related to the target porosity. When the target porosity requirement for the finished component is more stringent, the value of k can be a larger value within the range. Preferably, in this embodiment, The value is 60 MPa, and k is 1.1. Specifically, the core principle of using shrinkage rate and tensile strength to set the target pressure is to actively intervene and compensate for the internal changes of the material during the curing process through external pressure, thereby obtaining a finished product with qualified performance and controllable internal stress. By combining multiple parameters, the system can accurately output the required hot pressing pressure. Among them, the prepreg has a large shrinkage rate, which requires higher hot pressing pressure to compensate for the volume shrinkage, so that the finished product size is close to the mold size. The lower the tensile strength, the lower the upper limit of the internal stress it can withstand. The internal stress generated by the hot pressing pressure is far lower than the tensile strength of the material, to prevent damage.

[0034] Step S6: Under the combined effect of high pressure-vacuum loading and high temperature environment, the diaphragm-prepreg assembly 3 deforms and adheres to the molding surface of the lower mold, and is subjected to gradient temperature and pressure curing for a specified time according to the resin characteristics. For step S7, please refer to [link / reference]. Figure 4 As shown, after the specified time is reached, the input of the pressurized gas is turned off, the electric heating component 12 is turned off and the gas depressurization and recovery device is turned on to recover the pressurized gas in the high-pressure gas chamber. After the mold is cooled down, the mold is opened and the part is taken out to obtain the hot gas pressure-diaphragm co-molded component. The gas pressure reduction and recovery device 13 includes a gas storage tank connected to the high-pressure gas chamber. A pressure reducing valve is installed on the outside of the gas storage tank. After the specified time is reached, the input of the pressurized gas is shut off, the electric heating component is turned off, and the valve of the pressure reducing valve of the gas pressure reduction and recovery device is opened to reduce the pressure of the high-pressure gas chamber and recover the pressurized gas in the high-pressure gas chamber at the same time.

[0035] It is understood that the specified time is the time required for gradient temperature and pressure holding curing.

[0036] In one specific embodiment, the cooling method is gradient cooling, which reduces the temperature to three gradients: 80% of the curing temperature, 50% of the curing temperature, and room temperature. Each gradient is held for 5 minutes to suppress defects such as deformation, cracking, and springback of the part.

[0037] Step S8 involves cutting the hot air pressure-diaphragm co-molded component to remove excess material edges and burrs, obtaining the finished component. This is prior art and will not be described in detail here. Example

[0038] Step S1: Use a multi-axis CNC cutting machine to cut the prepreg of carbon fiber epoxy resin composite material into circles with a diameter of 200mm. Step S2: Move the prepreg to the laying station and lay multiple layers according to the [90 / 45 / 0 / 45 / 90] layup design; after laying, lay a non-porous membrane with a diameter of 250mm on the upper surface of the prepreg and a porous membrane with a diameter of 250mm on the lower surface to form a double membrane forming method. The membrane material is polytetrafluoroethylene with a thickness of 0.2mm. The diameter of the porous membrane is 0.1mm, the opening area accounts for 40%, and the holes are arranged in a hexagonal array. Step S3: Place the diaphragm-prepreg assembly in the lower mold and fix it so that it is located in the molding area. After the mold is closed, seal it with a sealing frame. The sealing frame is a silicone ring with an inner diameter of 220mm, an outer diameter of 221mm, and a thickness of 10mm. Step S4: Start the heating system to preheat the diaphragm-prepreg assembly inside the mold at a temperature of 30°C. At the same time, pressurized gas is introduced into the electric heating assembly for heating at a temperature of 30°C. Step S5: The lower mold is evacuated using a high-power vacuum pump and mold circuit to a vacuum level of ≤50mbar. Hot pressurized gas is then introduced into the high-pressure gas chamber and increased to 1MPa at a rate of 0.15MPa / s. Step S6: Under the combined effect of continuous loading of hot pressurized gas and high temperature environment, the diaphragm-prepreg assembly deforms and fits into the mold. Then, the mold temperature is heated to 100℃ and 150℃ respectively and pressure is maintained for 2 hours for curing. Step S7: Turn off the pressurized gas and electric heating components and turn on the gas depressurization and recovery device to recover the gas in the high-pressure gas chamber. Perform three gradient coolings on the mold at 120°C, 80°C and room temperature and open the mold to remove the part. After demolding, the hot gas pressure-diaphragm co-molded component is obtained. Step S8 involves precisely cutting the hot air pressure-diaphragm co-molded component, removing excess material edges and burrs, and obtaining the finished component.

[0039] In this embodiment, epoxy resin E51 is selected. Example

[0040] Step S1: Use a multi-axis CNC cutting machine to cut the prepreg of carbon fiber polyether ether ketone composite material into circles with a diameter of 200 mm. Step S2: Move the prepreg to the laying station and lay multiple layers according to the [90 / 45 / 0 / 45 / 90] layup design; after laying, lay a non-porous membrane with a diameter of 250mm on the upper surface of the prepreg and a porous membrane with a diameter of 250mm on the lower surface to form a double membrane forming method. The membrane material is polytetrafluoroethylene with a thickness of 0.2mm. The diameter of the porous membrane is 0.1mm, the opening area accounts for 40%, and the holes are arranged in a hexagonal array. Step S3: Place the diaphragm-prepreg assembly in the lower mold and fix it so that it is located in the molding area. After the mold is closed, seal it with a sealing frame. The sealing frame is a silicone ring with an inner diameter of 220mm, an outer diameter of 221mm, and a thickness of 10mm. Step S4: Start the heating system to preheat the diaphragm-prepreg assembly inside the mold to a temperature of 340°C. At the same time, pressurized gas is introduced into the electric heating assembly for heating to a temperature of 340°C. Step S5: The lower mold is evacuated using a high-power vacuum pump and mold circuit to a vacuum level of ≤50mbar. Hot pressurized gas is then introduced into the high-pressure gas chamber and increased to 2.5MPa at a rate of 0.15MPa / s. Step S6: Under the combined effect of continuous loading of hot pressurized gas and high temperature environment, the diaphragm-prepreg assembly 3 deforms and fits into the mold. Then the mold temperature is cooled to 140℃ and pressure is maintained for 10 minutes for curing. Step S7: Turn off the pressurized gas and electric heating components and turn on the gas depressurization and recovery device to recover the gas in the high-pressure gas chamber. Perform three gradient coolings on the mold at 110°C, 60°C and room temperature and open the mold to remove the part. After demolding, the hot gas pressure-diaphragm co-molded component is obtained. Step S8 involves precisely cutting the hot air pressure-diaphragm co-molded component, removing excess material edges and burrs, and obtaining the finished component.

[0041] The performance of the finished components from Examples 1 and 2 was tested, and the results are shown in the table below: Table 1 Performance test results of Example 1 and Example 2

[0042] As can be seen from Table 1, the product material obtained by using the present invention has significantly reduced internal porosity and has a dense and uniform structure, ensuring the complete transfer of mechanical properties and long-term stability. It can realize the manufacturing of composite material components with the same performance as the autoclave process, and the cost and energy consumption are greatly reduced and it is easy to automate.

[0043] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials, characterized in that, include: Step S1: Cut the prepreg of the resin-based fiber composite material according to the shape of the mold; Step S2: The prepreg is laid in multiple layers. A non-porous diaphragm is laid on the upper surface of the prepreg, and a porous diaphragm is laid on the lower surface of the prepreg to obtain a diaphragm-prepreg assembly. Step S3: Place the diaphragm-prepreg assembly on the molding area of ​​the upper surface of the lower mold and fix it. Close the upper mold and the lower mold. The molding areas of the upper mold and the lower mold are provided with silicone sealing frames to seal the upper and lower cavities formed by the mold cavity and the surface of the diaphragm-prepreg assembly in a planar manner. Step S4: Start the heating system to preheat the diaphragm-prepreg assembly inside the mold, and at the same time, introduce pressurized gas into the electric heating assembly for heating; Step S5: Vacuum the vacuum cavity formed by the lower mold and the lower surface of the diaphragm-prepreg assembly, and at the same time introduce the heated pressurized gas into the high-pressure gas cavity formed by the upper mold and the upper surface of the diaphragm-prepreg assembly. Step S6: Under the combined effect of high pressure-vacuum loading and high temperature environment, the diaphragm-prepreg assembly deforms and adheres to the molding surface of the lower mold cavity, and gradient temperature and pressure are maintained for a specified time according to the resin characteristics for curing. Step S7: After the specified time is reached, the input of the pressurized gas is turned off, the electric heating component is turned off and the gas depressurization and recovery device is turned on to recover the pressurized gas in the high-pressure gas chamber. After the mold is cooled down, the mold is opened and the part is taken out to obtain the hot gas pressure-diaphragm co-molded component. Step S8: Cut the hot air pressure-diaphragm co-molding component to remove excess material edges and burrs, and obtain the finished component.

2. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1, characterized in that, The resin-based fiber composite material uses thermoplastic resin or thermosetting resin.

3. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1, characterized in that, In step S2, both the non-porous membrane and the porous membrane are made of polytetrafluoroethylene heat-resistant film material.

4. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1, characterized in that, In step S4, Oil channels are provided on the mold, and the heat transfer oil is heated by a mold temperature controller to preheat the diaphragm-prepreg assembly inside the mold; The pressurized gas is heated electrically, and the target heating temperature of the pressurized gas is the same as the preheating temperature.

5. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1 or 4, characterized in that, In step S4, the pressurizing gas is an inert gas with a pressure adjustment range of 0–70 MPa. The target heating temperature for heating the pressurized gas is determined based on the target viscosity, wherein the target viscosity is 1.2 times the viscosity of the resin at the first temperature, and the first temperature is the thermal degradation temperature of the prepreg.

6. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 4, characterized in that, Step S5 further includes: First, the vacuum degree of the lower mold vacuum chamber is evacuated to ≤50mbar, and then the pressure in the high-pressure gas chamber is increased to the target hot-pressing pressure at a rate of 0.15MPa / s, while the vacuum degree of the vacuum chamber is evacuated to ≤5mbar. The target hot-pressing pressure is determined based on the service performance of the prepreg.

7. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 6, characterized in that, In step S5, the service performance equivalent is determined based on the shrinkage rate and adhesion of the prepreg, and the target hot-pressing pressure is determined based on the service performance equivalent.

8. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1, characterized in that, In step S7, the gas pressure reduction and recovery device includes a gas storage tank connected to the high-pressure gas chamber. A pressure reducing valve is installed on the outside of the gas storage tank. After the specified time is reached, the input of the pressurized gas is shut off, the electric heating component is turned off, and the valve of the pressure reducing valve of the gas pressure reduction and recovery device is opened to reduce the pressure of the high-pressure gas chamber and recover the pressurized gas in the high-pressure gas chamber at the same time.

9. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 8, characterized in that, In step S7, the cooling method is gradient cooling, which lowers the temperature to three gradients: 80% of the curing temperature, 50% of the curing temperature, and room temperature. Each gradient is held for 5 minutes to suppress defects in the part.

10. The method for hot gas pressure-diaphragm co-molding of resin-based fiber composite materials according to claim 1, characterized in that, In step S4, For thermosetting resin-based fiber composites, the preheating temperature is lower than the resin gel temperature of the prepreg; For thermoplastic resin-based fiber composites, the preheating temperature is greater than the resin melting temperature of the prepreg.

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