Hot-pressing vacuum-assisted and segmented pressurizing and heating curing forming method and product thereof

Abstract

The invention discloses a hot-pressing vacuum-assisted and segmented pressurizing and heating curing forming method and a product thereof, and belongs to the technical field of materials and processing, the forming method comprises the following steps: S1, preparing a prepreg, and laying the prepreg according to a preset laying mode to obtain a laying blank; s2, auxiliary materials are laid on the surface of the laying green body, wherein the auxiliary materials at least comprise vacuum bags; s3, the mold is closed, the interior of the vacuum bag is vacuumized, and the laying layer green body is in a vacuum state; under the condition that the interior of the vacuum bag is kept vacuum, external air pressure is applied to the laying layer green body; meanwhile, heating and curing are conducted on the laying layer green body; and S4, after curing is completed, demolding is conducted, and the composite material product is obtained through aftertreatment. The hot-pressing vacuum auxiliary forming method disclosed by the invention can effectively solve the problems that an existing composite material forming process is difficult to consider both high quality and high efficiency, and is high in cost and high in energy consumption.

Description

Technical Field

[0001] This invention relates to the field of materials and processing technology, specifically to a hot-pressing vacuum-assisted and segmented pressure and heating curing molding method and its products. Background Technology

[0002] Composite materials, such as carbon fiber reinforced composites and glass fiber reinforced composites, are widely used in aerospace, rail transportation, automotive lightweighting, and energy storage equipment due to their excellent properties such as high specific strength, high specific modulus, corrosion resistance, and fatigue resistance. The molding process of composite materials directly determines the final quality, production efficiency, and production cost of the finished product.

[0003] Currently, there are two main types of typical molding processes in the industrial production of composite material products.

[0004] One type is the traditional compression molding process, whose process flow is: prepreg cutting, material laying, mold closing, heat curing, demolding, dimensional machining, and surface treatment. Although this process is simple and requires relatively low equipment investment, it has the following obvious drawbacks. First, during the mold closing and pressurization process, interlayer gas is difficult to completely escape, which can easily lead to defects such as delamination or porosity inside the product. Second, due to the high porosity, the surface quality of the product is poor, often requiring multiple filler and grinding processes before proceeding to the next step, increasing subsequent labor costs. In addition, once delamination or separation occurs, the product is directly scrapped and cannot be repaired.

[0005] Another type is autoclave molding, which is one of the mainstream processes for preparing high-performance composite material components. Its process flow is as follows: prepreg cutting, material laying, release fabric laying, air-wicking foam laying, sealing the mold with sealing strips and vacuum bags, vacuuming and conducting vacuum testing, sending the mold into the autoclave, simultaneously vacuuming the mold inside the autoclave and pressurizing and heating it with air in the autoclave to cure the mold, demolding, dimensional processing, and surface finishing. This process can produce products with stable quality, excellent mechanical properties, and low porosity, but it still has significant drawbacks in practical applications. 1. The production cycle is long, making it unsuitable for mass production. The entire curing process requires sending the mold into a large autoclave for heating and cooling, which is slow, resulting in a long molding cycle for a single product and making it difficult to meet the needs of mass production.

[0006] 2. Numerous auxiliary consumables that are not reusable. The process uses a large amount of auxiliary materials such as vacuum bags, air-guiding cotton, release cloth, and sealing strips, most of which are for single use. This not only increases material costs but also generates a large amount of industrial waste.

[0007] 3. Extremely high energy consumption. Autoclaves require heating and pressurizing the entire tank space, have a large heat capacity, and low energy utilization efficiency. According to statistics, energy consumption accounts for 20%-25% of the total cost of autoclave processes.

[0008] 4. High equipment investment and limited size adaptability. Autoclave equipment itself is expensive, and the size of the products is limited by the tank volume. For products with complex corner structures or large irregular shapes, it is difficult to ensure the uniformity of temperature and pressure.

[0009] To address the aforementioned issues, existing research has made some process improvements. For example, some studies have proposed a new process combining autoclave and vacuum-assisted molding, aiming to combine the advantages of both processes; other studies have explored the effect of preforming pressure on the fiber volume fraction of vacuum-assisted molded composite materials, highlighting the importance of optimizing pressure parameters. While these studies have made breakthroughs in specific areas, most remain at the laboratory stage, or still struggle to achieve a balance between high quality, high efficiency, and low cost in industrial applications.

[0010] Therefore, how to provide a new composite material molding method that can achieve or approach the high quality level of autoclave technology, significantly shorten the production cycle, reduce energy consumption and material costs, and meet the molding requirements of complex structural products has become an urgent technical problem to be solved in this field. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method and its products, aiming to solve the problems of existing composite material molding processes that are difficult to balance high quality and high efficiency, and suffer from high cost and high energy consumption. To achieve the above objectives, this invention provides the following technical solution: A hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method includes the following steps: S1, Prepare prepreg by laying the prepreg in a preset layup manner to obtain a layup preform; S2, lay auxiliary materials on the surface of the plywood, the auxiliary materials including at least a vacuum bag; S3, close the mold and evacuate the inside of the vacuum bag to put the layup preform in a vacuum state; while maintaining the vacuum inside the vacuum bag, apply external air pressure to the layup preform; at the same time, heat and solidify the layup preform. S4. After curing, the product is demolded and then post-processed to obtain the composite material product.

[0012] Furthermore, in step S3, the external air pressure is applied in a segmented pressurization manner.

[0013] Furthermore, the segmented pressurization method includes at least three stages: the first stage applies a pressure of 2 to 3.5 kg / cm² and a treatment time of 5 to 15 minutes; the second stage applies a pressure of 3.5 to 6 kg / cm² and a treatment time of 6 to 15 minutes; and the third stage applies a pressure of 6 to 12 kg / cm² and a treatment time of 8 to 15 minutes.

[0014] Furthermore, in step S3, the heating and curing process employs a segmented heating method.

[0015] Furthermore, the segmented heating method includes at least three stages: the first stage heating temperature is 50-65℃ and the processing time is 5-15 minutes; the second stage heating temperature is 65-85℃ and the processing time is 6-15 minutes; the third stage heating temperature is 120-145℃ and the processing time is 8-15 minutes.

[0016] Furthermore, in step S3, the vacuum level of the vacuum pump is ≤10. -3 torr.

[0017] Furthermore, in step S2, the auxiliary materials also include release fabric and air-guiding cotton, and the release fabric, air-guiding cotton and vacuum bag are laid out in sequence.

[0018] Furthermore, the prepreg is one or more of carbon fiber prepreg, glass fiber prepreg, or aramid fiber prepreg.

[0019] Furthermore, the post-processing includes dimensional machining and surface finishing.

[0020] A composite material product is prepared by the above-mentioned hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method; the composite material product is a battery pack, battery casing or battery housing device.

[0021] The beneficial effects of this invention are: 1. This invention provides a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method, which combines vacuum bag-assisted vacuuming with hot press pressurization, and after mold closing, vacuuming the interior of the plywood to ≤10℃. -3 The high vacuum of the Torr system effectively eliminates interlayer gas, removing the root cause of porosity. Simultaneously, the segmented pressurization and heating methods ensure that the resin fully impregnates the fibers during curing, avoiding defects such as dry spots and delamination. Using the method of this invention, composite material products with quality comparable to those produced by expensive autoclave processes can be prepared, meeting the application requirements for high-quality composite material products.

[0022] 2. This invention uses a hot press for direct conductive heating, eliminating the need for heating and cooling the entire tank space as in autoclave processes. This results in faster heating and cooling rates and a significantly shorter curing cycle. Compared to autoclave molding technology, the production time of this invention is less than 25%, significantly improving production efficiency and meeting the requirements of large-scale production.

[0023] 3. This invention eliminates the need for expensive autoclave equipment; a conventional hot press can be used, resulting in low equipment investment costs. Furthermore, the heating process only requires heating the mold and the product, resulting in a small heat capacity and high energy efficiency, reducing energy consumption by over 75% compared to autoclave processes. In addition, while the vacuum bag is disposable, all auxiliary consumables such as release fabric, air-guiding foam, and vacuum bags can be reused up to 25 times, significantly reducing material costs.

[0024] 4. This invention employs vacuum-assisted and segmented pressurization and heating. After vacuuming, the vacuum bag adheres tightly to the surface of the product, allowing external pressure to be evenly transmitted to all parts of the product, including complex areas such as edges, corners, and curved surfaces. Therefore, this invention is particularly suitable for molding composite material products with complex geometries or high dimensional accuracy requirements, solving the problems of defects easily occurring in edge and corner areas in traditional processes and the limitations of autoclave processes due to the size of the autoclave. Attached Figure Description

[0025] Figure 1 A process flow diagram of a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method provided by the present invention; Figure 2 A schematic diagram of a mold for a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method provided by the present invention.

[0026] Figure 3 This refers to a finished bag or luggage product prepared by a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method.

[0027] The attached diagram is labeled as follows: 1. Prepreg; 2. Lower mold; 3. Upper mold; 4. Air guide cotton; 5. Vacuum bag; 6. Vacuum interface; 7. Sealing strip; 8. High-pressure air compressor. Detailed Implementation

[0028] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. Those skilled in the art should understand that the present invention can be implemented even without certain specific details. In some other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the spirit of the present invention.

[0029] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," "x-direction," "y-direction," and "z-direction" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0030] Example 1 See attached Figure 1-3 This embodiment provides a hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method, which can be used to prepare carbon fiber reinforced composite battery cases, such as... Figure 1 As shown, the specific steps are as follows: S1, Prepare prepreg 1, lay up prepreg 1 according to the preset layup method to obtain layup blank.

[0031] Carbon fiber prepreg 1 can be used as the molding raw material. For example, the carbon fiber is T700 grade, the resin system is epoxy resin, and the resin content is 38wt%. According to the preset size of the battery case, the prepreg 1 is cut into the required shape and size using a cutting device. At the same time, UD unidirectional tape prepreg 1 in the ±45° direction is cut for later use.

[0032] Then, after cleaning the surface of the lower mold 2, apply a release agent and lay up multiple layers of prepreg 1 in the clean mold cavity. On the basis of the main layup, four additional layers of UD unidirectional tape prepreg 1 in the ±45° direction can be laid up at the four corners of the product to ensure that the corners have higher structural strength. After the layup is completed, the layup blank is obtained.

[0033] S2, lay auxiliary materials on the surface of the plywood, including at least vacuum bags 5.

[0034] The auxiliary materials, including release fabric, air-guiding cotton 4, and vacuum bag 5, are laid out sequentially on the surface of the plywood. The specific laying order is as follows: First, lay a layer of release fabric on the surface of the plywood. The release fabric can be made of polytetrafluoroethylene. Ensure that the release fabric completely covers the plywood without any omissions or wrinkles. Then, lay the air-guiding cotton 4 on the surface of the release fabric. The air-guiding cotton 4 can be made of glass fiber. The laying range of the air-guiding cotton 4 is consistent with that of the release fabric. Finally, cover the surface of the air-guiding cotton 4 with a vacuum bag 5. The vacuum bag 5 can be made of nylon. The edges of the vacuum bag 5 can be completely sealed to the edge of the mold with sealing strips 7 to ensure a tight seal. At the same time, a vacuum interface 6 is reserved on the vacuum bag 5 for subsequent vacuuming operations.

[0035] S3, close the mold and evacuate the inside of the vacuum bag 5 to put the plywood in a vacuum state; while maintaining the vacuum inside the vacuum bag 5, apply external air pressure to the plywood; at the same time, heat and solidify the plywood.

[0036] Specifically, the lower mold 2, with the auxiliary materials laid out, is fed into a conventional hot press to close with the upper mold 3. For example, a YH-500 hot press can be used. During the mold closing process, the closing speed and pressure are controlled to avoid displacement of the plywood or damage to the auxiliary materials due to excessive closing speed. After mold closing, a vacuum pump is connected through the vacuum interface 6 to evacuate the inside of the vacuum bag 5. The vacuum level is ≤10. -3 torr.

[0037] Under vacuum conditions, a high-pressure air compressor 8 is used to apply external air pressure to the ply sheet through a segmented pressurization method. The specific segment parameters are as follows: The first stage: apply a pressure of 2 to 3.5 kg / cm² and process for 5 to 15 minutes to initially compact the ply blank and remove the small amount of gas remaining on the ply surface; The second stage involves applying a pressure of 3.5–6 kg / cm² and a treatment time of 6–15 minutes to further compact the layers and promote initial resin flow. The third stage involves applying a pressure of 6–12 kg / cm² and processing for 8–15 minutes to ensure that the resin fully impregnates the carbon fibers and reduces porosity and dry spot defects.

[0038] The pressurization and heating / curing processes are carried out simultaneously. The heating / curing process adopts a segmented heating method, in which the mold and the plywood are directly heated by the heating plate of the hot press. The specific segmented parameters are as follows: The first stage: the heating temperature is 50-65℃ and the processing time is 5-15 minutes. It is used to preheat the preform and make the resin soften slowly. The second stage involves heating at 65–85°C for 6–15 minutes to promote initial cross-linking of the resin and reduce resin loss. The third stage involves heating at 120–145°C for 8–15 minutes to achieve complete resin curing and ensure the mechanical properties of the product.

[0039] During the heat curing process, vacuum level, pressure, and temperature are monitored in real time to ensure that all parameters remain stable within the preset range. If a decrease in vacuum level, pressure fluctuation, or temperature deviation occurs, the parameters of the vacuum pump and hot press are adjusted promptly. During the curing process, the resin fully impregnates the fibers under the synergistic effect of vacuum negative pressure and external positive pressure, and interlayer gas is completely expelled.

[0040] S4, after curing, is demolded and then post-processed to obtain composite material products.

[0041] After heat curing, stop heating and pressurizing, maintain a vacuum state until the mold temperature drops below 50℃, turn off the vacuum pump, turn on the hot press, remove the mold, and perform demolding. Use a special demolding tool during demolding to avoid scratching the product surface. Remove the vacuum bag 5, air-guiding cotton 4, and release cloth from the surface. All three are intact and can be used again. After post-processing steps such as dimensional machining and polishing, the final carbon fiber composite battery case is obtained.

[0042] The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method provided by this invention produces products with porosity and tensile strength comparable to those of traditional autoclave processes, achieving high-quality requirements. The molding cycle is less than 25% of that of traditional autoclave processes, energy consumption is less than 25% of that of autoclave processes, consumables can be reused, and equipment investment is significantly reduced. Compared with traditional molding processes, the porosity of the products is significantly reduced, and the mechanical properties are significantly improved, demonstrating outstanding comprehensive advantages.

[0043] In the above embodiments, the type, layup method, and size of the prepreg 1, the specific specifications of the auxiliary materials, and the parameters of segmented pressurization and segmented heating can all be adjusted according to the actual product requirements. As long as they conform to the scope defined in the invention, the technical effects of the invention can be achieved. For example, the prepreg 1 can be aramid fiber prepreg 1, or any combination of multiple prepregs 1; the number of stages and the parameter values ​​of each stage can be adjusted within the parameter range defined in the invention according to the curing characteristics of the resin system; the material and specifications of the auxiliary materials can be replaced according to the surface quality requirements and cost requirements of the product, as long as the functions of vacuum sealing, gas conduction, and release can be achieved.

[0044] In addition to the battery packs, battery casings, and battery housings mentioned in the above embodiments, the composite material products prepared by this invention can also be used in other composite material components in aerospace, rail transportation, and automotive lightweighting, achieving high quality, high efficiency, and low cost.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A method for hot-pressing vacuum-assisted and segmented pressurization and heating curing molding, characterized in that, Includes the following steps: S1, Prepare prepreg by laying the prepreg in a preset layup manner to obtain a layup preform; S2, lay auxiliary materials on the surface of the plywood, the auxiliary materials including at least a vacuum bag; S3, close the mold and evacuate the inside of the vacuum bag to put the layup preform in a vacuum state; while maintaining the vacuum inside the vacuum bag, apply external air pressure to the layup preform; at the same time, heat and solidify the layup preform. S4. After curing, the product is demolded and then post-processed to obtain the composite material product.

2. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, In step S3, the external air pressure is applied in a segmented pressurization manner.

3. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 2, characterized in that, The segmented pressurization method includes at least three stages: the first stage applies a pressure of 2 to 3.5 kg / cm² and a treatment time of 5 to 15 minutes; the second stage applies a pressure of 3.5 to 6 kg / cm² and a treatment time of 6 to 15 minutes; and the third stage applies a pressure of 6 to 12 kg / cm² and a treatment time of 8 to 15 minutes.

4. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, In step S3, the heating and curing process is carried out using a segmented heating method.

5. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 4, characterized in that, The segmented heating method includes at least three stages: the first stage heating temperature is 50-65℃ and the processing time is 5-15 minutes; the second stage heating temperature is 65-85℃ and the processing time is 6-15 minutes; the third stage heating temperature is 120-145℃ and the processing time is 8-15 minutes.

6. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, In step S3, the vacuum level of the vacuum pump is ≤10. -3 torr.

7. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, In step S2, the auxiliary materials also include release fabric and air-guiding cotton, and the release fabric, air-guiding cotton and vacuum bag are laid out in sequence.

8. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, The prepreg is one or a combination of carbon fiber prepreg, glass fiber prepreg, or aramid fiber prepreg.

9. The hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to claim 1, characterized in that, The post-processing includes dimensional machining and surface finishing.

10. A composite material product, characterized in that, The composite material is prepared by the hot-pressing vacuum-assisted and segmented pressurization and heating curing molding method according to any one of claims 1 to 9; the composite material product is a battery box, battery casing or battery housing device.

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