An integrated molding process for composite material shells customized according to functional and performance requirements

Abstract

This invention provides an integrated molding process for composite material shells based on customized functional and performance requirements, belonging to the field of composite material molding technology. The process includes: S1, dividing the shell into regions based on overall mechanical load-bearing capacity requirements and special functional needs; S2, selecting suitable composite materials based on the specific requirements of different regions; S3, spraying a release agent after preheating the molding mold; S4, laying prepreg and functional particles in the order of "continuous fiber prepreg - functional material - discontinuous fiber prepreg," and then placing the molding mold in a vacuum bag and evacuating it; S5, finally molding the shell using a hot-pressing process based on material properties. This invention, through the ingenious combination of main materials and local functional materials, and the flexible integrated molding manufacturing method, maximizes the utilization of material properties, further improves lightweighting, and enables integrated structural / functional manufacturing according to requirements. It offers advantages such as low cost, high production efficiency, and customization.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, and in particular relates to an integrated molding process for composite material shells that are customized according to functional and performance requirements. Background Technology

[0002] Shell-type components are common in aerospace, rail transportation, and automotive industries, requiring load-bearing and enclosure capabilities. During service, they must not only withstand loads but also fulfill functions such as fire resistance, vibration damping, and electromagnetic shielding. Using lightweight, high-strength composite materials to manufacture shell-type components not only reduces structural weight and improves load-bearing capacity but also allows for customized manufacturing using multi-material molding and hot-pressing processes to meet specific load-bearing requirements and functional needs of specific parts, thus satisfying localized reinforcement and functional requirements. Traditional shell manufacturing is performance-driven and involves segmented production processes. It first forms the main structure and then applies specific coatings to achieve functions such as fire resistance, heat insulation, electromagnetic shielding, vibration reduction, and noise reduction, thus integrating the structure and function of composite shell-type components. However, this method increases the number of processes and production costs. Taking the battery cover of new energy vehicles as an example, this patented technology enables integrated manufacturing of the load-bearing substrate and functional layers, improving manufacturing efficiency and meeting the special functional requirements of new energy battery covers, such as electromagnetic shielding and fire resistance. Its innovative design gives it broad application prospects in fields such as new energy batteries.

[0003] With the rapid development of battery technology, performance and functional requirements for battery modules have been raised, including load-bearing stability, impact resistance, fire resistance, and electromagnetic shielding. Among these, the battery cover, as a crucial component of the battery module, plays a key role in battery performance, safety, and lifespan. Current manufacturing technologies typically require spraying fire-retardant and electromagnetic shielding materials after the cover is formed, involving numerous and complex processes, resulting in slow manufacturing efficiency and high production costs.

[0004] Chinese patent CN 109353031A discloses a method for manufacturing a battery case cover. The battery case cover prepared by this method uses continuous fiber-reinforced thermosetting resin prepreg and SMC sheet as the main materials, and is manufactured through vacuum compaction and mold curing. However, although SMC sheet can adapt to the molding requirements of complex structures, its overall mechanical load-bearing capacity is poor due to the discontinuous fiber nature of the main material. Furthermore, the casing requires subsequent coating with specific materials to achieve fire-retardant, flame-retardant, and electromagnetic shielding functions, which increases manufacturing steps, reduces production efficiency, and raises production costs. Chinese patent CN 110982177A discloses a flame-retardant and thermally conductive nanocomposite material and its preparation method and application. The battery case cover can achieve a flame-retardant effect by adding flame-retardant and thermally conductive materials throughout the casing. However, in actual use, only the surface of the cover is required to have fire-retardant functionality. This manufacturing method results in functional redundancy and waste, further increasing production costs.

[0005] Therefore, a method for designing and manufacturing functional shells is needed that allows for the division of functional areas based on the specific usage requirements of different regions of the shell, the selection of appropriate functional materials, and the integral molding of multiple materials. This invention is primarily applied to the production and manufacturing of functional shell structures. By filling functional materials into structural materials and using an integral molding process to manufacture composite material shell parts, it not only avoids post-processing steps and improves manufacturing efficiency but also achieves integrated structural / functional manufacturing, reducing production costs. This technology has significant advantages in industries such as new energy batteries and the design and manufacturing of functional shell structures. Summary of the Invention

[0006] This invention provides an integrated molding process for composite material shells customized according to functional and performance requirements. It is a method for preparing functional shells with defined regions. The main body region uses continuous fiber prepregs such as unidirectional continuous fiber reinforced thermosetting prepregs and continuous fiber reinforced thermosetting woven prepregs to meet the basic functions of load-bearing, covering, and impact resistance. Based on the load distribution under service conditions, local reinforcement regions are defined, and the same material as the main body region is selected as the reinforcing material. The thickness of these regions is increased by applying additional layers. For regions with complex structural molding requirements, various discontinuous fiber prepregs such as chopped glass fiber, carbon fiber sheet molding compound, and chopped carbon fiber prepregs are used to form complex shell structures, improving surface quality and aesthetics. For regions with specific functional requirements such as flame retardancy, wave absorption, conductivity, and vibration damping, specific functional particles or films are selected to meet the region's needs for fire resistance, electromagnetic shielding, vibration reduction, and noise reduction.

[0007] The technical solution adopted in this invention is as follows:

[0008] A process for integral molding of composite material shells based on functional and performance customization requirements, the process comprising the following steps:

[0009] S1. Based on the overall mechanical load-bearing performance requirements and special functional needs of the shell, the shell is divided into regions according to the service load and working conditions. The regions include the main body region, the local load-bearing reinforcement region, the complex forming region, and the special functional region.

[0010] S2. Select suitable composite materials based on the specific requirements of different areas; specifically: for the main body area, use continuous fiber prepreg to meet the basic functions of shell load-bearing, covering, and impact resistance; for local load-bearing reinforcement areas, use continuous fiber prepreg as a reinforcing layup; for complex molding areas, use discontinuous fiber prepreg to adapt to the molding requirements of complex structures; for special functional areas, use functional particles to meet functional requirements. Among these, the resin in continuous fiber prepreg and discontinuous fiber prepreg is the same.

[0011] S3. Determine the preheating temperature of the molding die based on the resin softening temperature in the prepreg. Spray the release agent after the molding die is preheated. Cut out the corresponding prepreg according to the shape of the molding die, the area it is divided into, and the functional requirements of the area.

[0012] S4. Following the sequence of "continuous fiber prepreg - functional material - non-continuous fiber prepreg", lay the prepreg flat onto the molding die. After evenly sprinkling the functional particles onto the molding die, place the molding die into a vacuum bag and vacuum it to ensure tight adhesion between the materials. When laying the prepreg, ensure it adheres closely to the molding die with minimal wrinkles.

[0013] S5. Using an autoclave or molding machine, the shell is finally formed using a hot pressing molding process based on material properties. The hot pressing molding process based on material properties is divided into five stages according to the relationship between the resin's viscosity-temperature curve and shear stress-shear rate curve: preheating and pre-pressing, heat preservation, heating, hot pressing and heat preservation, and cooling. Specifically, the preheating and pre-pressing stage involves continuous preheating and pre-pressing at 160℃ and 0.5MPa for 120 minutes to allow the resin to fully... The components are impregnated; during the heat preservation stage, the resin is kept at 240℃ and 0.5MPa for 120 minutes to cure at a relatively low reaction rate; during the heating stage, the reaction temperature is increased to 371℃ at a rate of 7℃ / min and maintained at 2.5MPa for 45 minutes to accelerate the curing speed; during the hot pressing and heat preservation stage, a total pressure of 2.5MPa is applied and the resin is kept at 371℃ for 350 minutes until the hot pressing is completed, allowing the resin to fully cure; during the cooling stage, the resin is allowed to cool naturally or be forced to room temperature while maintaining the total pressure, and then the molding mold is opened to remove the product.

[0014] Furthermore, the continuous fiber prepreg includes unidirectional continuous fiber reinforced thermosetting prepreg and continuous fiber reinforced thermosetting woven prepreg.

[0015] Furthermore, the continuous fiber prepreg uses one or more of glass fiber, carbon fiber, basalt fiber, and aramid fiber, with a fiber mass content of 40% to 75%.

[0016] Furthermore, the resin used in the continuous fiber prepreg and the discontinuous fiber prepreg is one of epoxy resin, cyanate ester resin, bismaleimide resin, benzoxazine resin, phenolic resin, epoxy vinyl resin, and unsaturated polyester resin.

[0017] Furthermore, the discontinuous fiber prepreg is one or more of chopped glass fiber prepreg, carbon fiber sheet molding compound prepreg, and chopped carbon fiber prepreg; preferably, the discontinuous fiber prepreg includes chopped glass fiber prepreg with a resin volume fraction of 33%, chopped carbon fiber prepreg with a resin volume fraction of 40%, and carbon fiber sheet molding compound with a resin volume fraction of 45%.

[0018] Furthermore, the functional particles include, but are not limited to, flame retardants with flame-retardant function, metal particles or micropowders with electromagnetic shielding function, and non-metallic particles or micropowders with electromagnetic shielding function.

[0019] Furthermore, the flame retardant with flame retardant function includes halogenated flame retardants and halogen-free flame retardants. The halogenated flame retardant is a compound flame retardant composed of one or more of decabromodiphenyl ethane, bromotriazine, and tetrabromobisphenol A and antimony trioxide. The halogen-free flame retardant is one or more of melamine polyphosphate, piperazine pyrophosphate, and aluminum diethylphosphite.

[0020] Furthermore, the metal particles or powders with electromagnetic shielding function are one or more of iron, nickel, copper, aluminum, and steel; the non-metallic particles or powders with electromagnetic shielding function are one or more of graphene, ferrite ceramics, and carbon fiber.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention achieves customized production based on the specific functions and performance requirements of the shell by dividing the shell into functional areas, selecting appropriate functional materials, and integrating multiple material systems into a single molding process. By introducing different materials during the shell molding process, the performance of different areas of the shell can be customized to give the shell functions such as load-bearing stability, fire resistance, electromagnetic shielding, and vibration and noise reduction. This flexibility allows manufacturers to produce functional shell structures with superior performance and better suited to specific application scenarios, based on market demand and customer customization requirements.

[0023] 2. This invention also has advantages in improving production efficiency and reducing production costs. Through advanced molding and hot pressing processes, multiple materials are laid out collaboratively. A staged, time-based temperature and pressure control system based on material properties, along with an integrated hot pressing molding process, ensures full adhesion between the materials inside the shell, avoiding defects such as internal pores that affect the shell's load-bearing capacity. This process simplifies the original multi-step production to a single step, enabling a highly automated production process and improving efficiency. Simultaneously, through rational material utilization and optimized molding processes, production costs are reduced, making customized production more economically feasible.

[0024] 3. In terms of manufacturing process, the present invention lays out and evenly sprinkles the prepreg and functional materials in the molding mold in the order of "continuous fiber prepreg - functional material - non-continuous fiber prepreg" according to performance and functional requirements. Vacuuming is carried out by vacuum bags to ensure tight adhesion between materials. Then, a hot pressing molding process based on material characteristics is used to coordinate and control temperature and pressure in stages to ensure that the prepreg and functional materials are fully combined during the molding process, and to ensure that the prepreg is fully impregnated and cured as a whole during the molding process.

[0025] In summary, the shell preparation method provided by this invention, through the ingenious combination of main materials and local functional materials, and the flexible area-divided integrated molding manufacturing method, can maximize the utilization of material properties, further improve the lightweight level, and can also realize the integrated manufacturing of structure and function according to needs, with advantages such as low cost, high production efficiency, and customization. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the top cover of a new energy battery pack.

[0027] Figure 2 This is a schematic diagram of the upper cover mold structure.

[0028] Figure 3 This is a process flow diagram.

[0029] Figure 1 In the middle, there are 1 local load-bearing reinforcement areas; 2 complex forming areas; 3 electromagnetic shielding areas; and 4 fire-resistant and flame-retardant areas. Detailed Implementation

[0030] The following describes the specific implementation of the present invention using the top cover of a new energy battery pack as an example. The structure of the top cover of the new energy battery pack is as follows: Figure 1 As shown.

[0031] The battery pack cover is a crucial component of the battery assembly. During operation, it must protect the internal battery components from impacts and environmental contamination such as dust and oil. This requires the cover to have basic load-bearing and protective functions. Specifically: to improve the load-bearing capacity of the front end of the cover, it needs local reinforcement; to accommodate the spatial structure of the battery cell electrical connectors in the middle of the battery pack, while preventing battery cell combustion and providing the driver with escape time, the middle area of ​​the cover needs to have complex spatial shaping capabilities and fire-retardant functions; to protect the battery management system located at the end of the battery pack from electromagnetic interference that could prevent it from malfunctioning, the end of the cover needs to provide a certain level of electromagnetic shielding.

[0032] The integrated molding process of the composite material shell is as follows: Figure 3 As shown, the specific steps include the following:

[0033] S1. Based on the overall mechanical load-bearing performance requirements and special functional needs of the new energy battery pack cover, the new energy battery pack cover is divided into areas according to the service load and operating conditions, including the main area, local load-bearing reinforcement area 1, complex molding area 2, electromagnetic shielding area 3, and fire-retardant area 4. Figure 1 As shown.

[0034] S2. Based on the specific requirements of different areas, select suitable composite materials; specifically: for the main body area, use epoxy resin unidirectional continuous fiber reinforced thermosetting prepreg; for the local load-bearing reinforcement area 1, select epoxy resin unidirectional continuous fiber reinforced thermosetting prepreg as the reinforcing layup; for the complex molding area 2, select epoxy resin chopped carbon fiber prepreg to meet the requirements of complex structure molding; for the fire-retardant area 4, select melamine polyphosphate halogen-free flame retardant to meet its fire-retardant requirements; for the electromagnetic shielding area 3, select aluminum powder particles to meet its electromagnetic shielding requirements.

[0035] S3. Preheat the molding die to the epoxy resin softening temperature and spray with a release agent; the molding die is a cavity-type die, such as... Figure 2 As shown, the front recess is the local load-bearing reinforcement area 1, the middle is the fire-retardant area 4, the central "rice" shaped area is the complex molding area 2, and the end recess is the electromagnetic shielding area 3. Based on the shape and spatial structure of the molding die, a cutting pattern is designed, and CNC cutting equipment is used to cut the carbon fiber prepreg along the designed edges according to the predetermined cutting pattern.

[0036] S4. Lay and evenly distribute the prepregs in the molding die in the following order: continuous fiber prepreg - functional material - discontinuous fiber prepreg. Specifically, first, lay the epoxy resin unidirectional continuous fiber reinforced thermosetting prepreg evenly in the molding die as the matrix material to fulfill its load-bearing and covering function; then, lay the epoxy resin unidirectional continuous fiber reinforced thermosetting prepreg evenly in the local load-bearing reinforcement area 1; next, evenly distribute the melamine polyphosphate halogen-free flame retardant in the fire-retardant area 4 of the molding die; evenly distribute the metal particles in the electromagnetic shielding area 3 of the molding die; finally, evenly distribute the epoxy resin chopped carbon fiber prepreg in the complex molding area 2 of the molding die. When laying the prepregs, ensure they fit as closely as possible to the die with minimal wrinkles. Place the molding die in a vacuum bag and vacuum it to ensure tight adhesion between the materials.

[0037] S5. Using an autoclave, a hot-press molding process based on material properties is employed to form the top cover of the new energy battery pack. The process flow is divided into stages and temperature / pressing and curing time parameters for each stage, based on the relationship between the resin's viscosity-temperature curve and shear stress-shear rate curve. The process flow is divided into five stages: preheating and pre-pressing, heat preservation, heating, hot-pressing and heat preservation, and cooling. Specifically, in the preheating and pre-pressing stage, preheating and pre-pressing are carried out at 160℃ and 0.5MPa for 120 minutes to fully impregnate all components with resin. In the heat preservation stage, heat preservation is carried out at 240℃ and 0.5MPa for 120 minutes to cure the resin at a relatively low reaction rate. In the heating stage, the reaction temperature is increased to 371℃ at a rate of 7℃ / min and maintained at 2.5MPa for 45 minutes to accelerate the curing speed. In the hot-pressing and heat preservation stage, a total pressure of 2.5MPa is applied at 371℃ for 350 minutes until the hot-pressing is completed, allowing the resin to fully cure. In the cooling stage, while maintaining total pressure, the resin is allowed to cool naturally or be forced to room temperature, and then the molding mold is opened to remove the product.

[0038] The preheating and pre-pressing stage aims to fully impregnate each component with resin, eliminating molding defects such as pores and air gaps between components, and preventing shell cracking due to stress concentration during subsequent processes and service. The heat preservation stage aims to cure the resin at a lower reaction rate. During the heat preservation process, the resin flow must be closely monitored. Once the flowing resin has become gelled, full pressure should be applied quickly. The heating stage aims to increase the reaction temperature to accelerate the curing rate. The heating rate should not be too fast to avoid temperature differences between the mold edge and the middle carbon fiber prepreg, which could cause the curing reaction to become too concentrated, resulting in delamination between material layers. The hot pressing and heat preservation stage, from the application of full pressure to the end of the entire hot pressing process, aims to allow the resin to fully cure and form the entire composite material shell. The cooling stage, while maintaining pressure, uses natural cooling or forced cooling to room temperature. Too short a cooling time may cause the shell to warp or crack, while too long a cooling time not only does not help the quality of the shell but also reduces production efficiency.

[0039] The resulting new energy battery pack cover has good overall load-bearing and protective performance, no molding defects in its complex spatial structure, and fire-retardant and electromagnetic shielding functions. This invention can realize the integrated manufacturing of the load-bearing substrate and functional layers, improve manufacturing efficiency, and meet the special functional requirements of new energy battery covers for electromagnetic shielding, fire resistance and flame retardancy. Its innovative design makes it have broad application prospects in the field of new energy batteries.

Claims

1. A one-piece molding process for composite material shells customized according to functional and performance requirements, characterized in that, The integrated molding process for the composite material shell includes the following steps: S1. Based on the overall mechanical load-bearing performance requirements and special functional needs of the shell, the shell is divided into regions according to the service load and working conditions. The regions include the main body region, the local load-bearing reinforcement region, the complex forming region, and the special functional region. S2. Select suitable composite materials based on the specific requirements of different areas; specifically: use continuous fiber prepreg for the main body area; use continuous fiber prepreg for local load-bearing reinforcement areas; use discontinuous fiber prepreg for complex molding areas; use functional particles for special functional areas; among them, the resin in continuous fiber prepreg and discontinuous fiber prepreg is the same. S3. Determine the preheating temperature of the molding die based on the resin softening temperature in the prepreg. Spray the release agent after the molding die is preheated. Cut out the corresponding prepreg according to the shape of the molding die, the area it is divided into, and the functional requirements of the area. S4. In the order of "continuous fiber prepreg - functional material - non-continuous fiber prepreg", lay the prepreg flat on the molding die, and then evenly sprinkle the functional particles on the molding die. Place the molding die in a vacuum bag and vacuum it. S5. The shell is finally formed by using a hot pressing molding process based on material properties. The hot pressing molding process based on material properties is divided into process flow stages and temperature and curing time parameters for each stage according to the relationship between the resin's "viscosity-temperature curve" and "shear stress-shear rate curve".

2. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 1, characterized in that, In S2, the continuous fiber prepreg includes unidirectional continuous fiber reinforced thermosetting prepreg and continuous fiber reinforced thermosetting woven prepreg.

3. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 2, characterized in that, The continuous fiber prepreg uses one or more of glass fiber, carbon fiber, basalt fiber, and aramid fiber, with a fiber mass content of 40% to 75%.

4. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 1, characterized in that, In S2, the discontinuous fiber prepreg is one or more of chopped glass fiber prepreg, carbon fiber sheet molding compound prepreg, and chopped carbon fiber prepreg.

5. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 2 or 4, characterized in that, The resin used in both the continuous fiber prepreg and the discontinuous fiber prepreg is one of epoxy resin, cyanate ester resin, bismaleimide resin, benzoxazine resin, phenolic resin, epoxy vinyl resin, and unsaturated polyester resin.

6. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 1, characterized in that, In S2, the functional particles include flame retardants with flame retardant function, metal particles or micropowders with electromagnetic shielding function, and non-metallic particles or micropowders with electromagnetic shielding function.

7. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 6, characterized in that, The flame retardant with flame retardant function is selected from a compound flame retardant composed of one or more of decabromodiphenyl ethane, bromotriazine and tetrabromobisphenol A and antimony trioxide, or a halogen-free flame retardant composed of one or more of melamine polyphosphate, piperazine pyrophosphate and aluminum diethylphosphite.

8. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 6, characterized in that, The metal particles or powders with electromagnetic shielding function are one or more of iron, nickel, copper, and aluminum.

9. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 6, characterized in that, The non-metallic particles or powders with electromagnetic shielding function are one or more of graphene, ferrite ceramics, and carbon fiber.

10. The integrated molding process for composite material shells customized according to functional and performance requirements as described in claim 1, characterized in that, In S5, the hot pressing process based on material properties includes five stages: preheating and pre-pressing, heat preservation, heating, hot pressing and heat preservation, and cooling. Specifically: the preheating and pre-pressing stage is carried out at 160°C and 0.5MPa for 120 minutes; the heat preservation stage is carried out at 240°C and 0.5MPa for 120 minutes; and the heating stage increases the reaction temperature to 371°C at a rate of 7°C / min and is carried out at 2.5MPa for 45 minutes. During the hot pressing and heat preservation stage, a total pressure of 2.5 MPa is applied and maintained at 371°C for 350 minutes until the hot pressing is completed. During the cooling stage, the product is naturally or forcibly cooled to room temperature while maintaining the total pressure, and then the molding mold is opened to remove the product.

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