A carbon fiber front hood trim forming die and forming method

Abstract

The application discloses a carbon fiber front machine cover decoration piece forming die and a forming method, and relates to the technical field of carbon fiber forming die and forming method. The forming base is sequentially provided with two independent sealing cavities from inside to outside; the two independent sealing cavities are respectively an independent part forming vacuum cavity and a buffer pressure stabilizing vacuum cavity; the differential pressure linkage control mechanism matches the rheological characteristics of carbon fiber prepreg resin, and independently controls vacuumizing, pressure maintaining and pressure releasing of the part forming vacuum cavity and the buffer pressure stabilizing vacuum cavity according to forming process stages, so as to adapt to the forming process of differential pressure exhaust, temperature control compaction and segmented curing. The whole forming die and process can be completely adapted to conventional ordinary oven equipment, and the dependence on high-end autoclave equipment is abandoned. Meanwhile, through structural innovation and process fine control, the short board of poor quality and low yield of traditional oven forming process is solved, and high-precision and low-defect forming effect under low-cost production conditions is realized.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber hood trim molding technology, and specifically relates to a carbon fiber hood trim molding mold and molding method. Background Technology

[0002] Carbon fiber composites are widely used in the automotive lightweighting field due to their excellent specific strength, specific stiffness, and lightweight properties. The carbon fiber hood is a core exterior trim component of a vehicle, and it has extremely stringent technical requirements for surface quality, overall contour accuracy, and control of internal pore defects, directly determining the overall appearance quality and structural performance of the vehicle.

[0003] Currently, the mainstream molding method for high-performance carbon fiber components in the industry is autoclave molding. This process can effectively remove gases and volatiles from the prepreg through a high-temperature, high-pressure, and sealed molding environment, suppressing the formation of porosity in the product and resulting in excellent product quality. However, the purchase, operation, maintenance, and energy costs of autoclave equipment are extremely high, the molding production threshold is high, and the mass production economy is poor, making it unsuitable for the large-scale, low-cost production needs of small and medium-sized enterprises.

[0004] To reduce production costs, the industry generally adopts a conventional vacuum bag molding process combined with an oven. This process has low equipment investment and wide applicability, but it has significant technical drawbacks. The traditional molding mode only uses a fixed single negative pressure molding logic, which cannot combine the rheological characteristics of carbon fiber prepreg resin for staged process control. It uses a single pressure parameter in different molding stages such as low-temperature degassing, melt flow, and high-temperature curing, resulting in poor molding matching.

[0005] However, for large-sized, complex-curved carbon fiber components such as the front hood, a single constant vacuum pressure cannot completely remove deep-seated air and resin volatiles during the effective window of resin melting and gelation. This can easily lead to defects such as high porosity, interlayer voids, and surface ripples and depressions. At the same time, conventional molding processes lack precise temperature control linkage, pressure stabilization and replenishment, gradient pressure release, and stress relief methods. As a result, finished products are prone to warping, cracking, and uneven strength, making it difficult to meet the high-precision and high-consistency mass production requirements of high-end automotive exterior parts. Summary of the Invention

[0006] The purpose of this invention is to provide a molding die and molding method for carbon fiber hood trim, which breaks through the technical bottleneck of traditional structure and single pressure molding, and can realize low porosity, high precision and high stability molding of carbon fiber hood under ordinary oven equipment conditions.

[0007] To solve the above-mentioned technical problems, the present invention provides a carbon fiber hood trim molding die, including a molding base, a sealing cover, a double-cavity sealing molding structure and a differential pressure linkage control mechanism.

[0008] The molding base is an integral molding structure with two independent sealed cavities arranged sequentially from the inside to the outside. The two independent sealed cavities are an independent part molding vacuum cavity and a buffer pressure stabilizing vacuum cavity, respectively. The differential pressure linkage control mechanism matches the rheological characteristics of the carbon fiber prepreg resin and independently controls the vacuuming, pressure holding, and pressure release of the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity according to the molding process stage, so as to adapt to the molding process of differential pressure exhaust, temperature control compaction, and segmented curing.

[0009] Preferably, the molding cavity surface of the molding base is covered with a first vacuum bag, which encloses and forms a part molding vacuum cavity covered with a prepreg layer.

[0010] Preferably, the outer surface of the sealing cover is covered with a second vacuum bag, forming a buffered and pressure-stabilized vacuum chamber.

[0011] Preferably, the differential pressure linkage control mechanism is also electrically connected to a temperature monitoring component to collect the temperature of the prepreg in the molding cavity in real time, and adaptively match the differential pressure parameters and pressure relief timing of the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity according to the resin melting and flow temperature range.

[0012] The present invention also provides a method for molding carbon fiber hood trim, comprising the following steps:

[0013] S1. Mold constant temperature preheating: Preheat the entire molding mold to 40±5℃, keep the temperature uniform and stable, and complete the molding pretreatment.

[0014] S2, Laying up and sealing the parts: Laying carbon fiber prepreg in the molding cavity of the molding base, laying the first vacuum bag and sealing it to form a closed vacuum cavity for molding the parts.

[0015] S3. Cover snapping and pressure stabilization sealing: Align and snap the sealing cover with the molding base, lay a second vacuum bag on the outer surface of the sealing cover and seal it to form an independent buffer pressure stabilization vacuum chamber.

[0016] S4. Constant temperature differential pressure exhaust: The vacuum chamber for part forming and the buffer pressure stabilizing vacuum chamber are evacuated simultaneously through the differential pressure linkage control mechanism. The vacuum degree of the part forming vacuum chamber is controlled to be -0.85 ~ -0.90 bar, and the vacuum degree of the buffer pressure stabilizing vacuum chamber is higher than that of the part forming vacuum chamber. The pressure is stabilized for 15~20 minutes to completely remove the gas trapped inside the carbon fiber prepreg by using the stable pressure difference.

[0017] S5. Temperature threshold precision compaction: The whole mold is sent into the oven to heat up, and the temperature of the prepreg is monitored in real time. When the temperature reaches the optimal flow temperature of the resin at 90℃±3℃, the pressure of the buffer and pressure stabilizing vacuum chamber is released, and only the negative pressure of the part forming vacuum chamber is retained to compact the prepreg. The temperature is kept constant and the pressure is maintained for 10 minutes to complete the resin impregnation molding.

[0018] S6. Segmented high-temperature curing: Continuously heat up to 150℃ and keep at a constant temperature for 30 minutes to allow the prepreg resin to fully cross-link and cure, thus completing the part shaping.

[0019] S7. Low-temperature demolding and part removal: After curing, the oven temperature is reduced according to the process. When the mold temperature drops below 60℃, the sealing cover is removed and the carbon fiber front hood trim is taken out.

[0020] Preferably, before the layup operation in step S2, a prepreg pretreatment step is also included: the carbon fiber prepreg is placed in a room temperature environment and allowed to stand for 20-30 minutes to warm up, removing condensation on the surface of the prepreg. At the same time, the prepreg is rolled and flattened as a whole to remove the initial air inside the material, and the prepreg is cut into oriented pieces according to the stress zones of the hood trim to ensure that the layup texture and stress direction match the product structure.

[0021] Preferably, in step S2, a layered staggered layup process is adopted, with adjacent layers of carbon fiber prepreg laid alternately at 45° / 0°. After each layer is laid, a single manual pre-compaction is performed, and the layers are staggered and overlapped with an overlap width controlled at 8~12mm. This avoids molding defects caused by concentrated gaps in the overall splicing and improves the overall structural strength and integrity of the product.

[0022] Preferably, during the differential pressure exhaust stabilization process in step S4, the vacuum level of the dual chambers is monitored in real time. If pressure decay occurs, pressure is replenished in real time through dual independent vacuum pumping components, maintaining the chamber pressure difference fluctuation within ±0.02 bar throughout the process, ensuring stable and unfluctuated pressure during the exhaust process.

[0023] Preferably, step S7 adopts a segmented gradient cooling process. After curing, the product is cooled to 90°C at a rate of 3~5°C / min, kept at a constant temperature for 10 minutes to eliminate internal stress, and then cooled to below 60°C for demolding to avoid product warping, cracking and deformation caused by rapid cooling.

[0024] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0025] 1. This invention differs from conventional fixed pressure molding schemes by setting up an adaptively adjustable differential pressure linkage control mechanism and equipping it with a temperature monitoring component, which can collect the temperature of the prepreg in the molding cavity in real time and accurately capture the optimal melting and flow window of the resin.

[0026] 2. This invention utilizes a dual-chamber independent pressure control system to achieve segmented control logic for gradual venting under constant temperature differential pressure in the early stage and precise pressure release and compaction during the resin melting stage. This completely solves the problems of incomplete venting and uneven resin impregnation in traditional single negative pressure molding. The dual-chamber pressure difference can be dynamically calibrated and real-time pressure replenishment and stabilization can be implemented throughout the process, keeping molding pressure fluctuations within a minimal range. This maximizes the removal of deep gases and volatiles from the prepreg, significantly reducing product porosity and substantially improving the internal density and structural uniformity of carbon fiber products.

[0027] 3. This invention features a fully customized molding process tailored to the structural characteristics of carbon fiber hoods, encompassing exclusive steps such as prepreg reheating and leveling, directional cutting, 45° / 0° staggered layering, manual pre-compaction, and gradient cooling stress relief. The staggered layering combined with precise compaction effectively enhances interlayer bonding strength and avoids structural defects caused by concentrated gaps. The segmented gradient cooling process gradually releases internal molding stress, preventing warping, cracking, and deformation caused by rapid cooling. Throughout the process, stable pressure control ensures uniform stress distribution during the molding of large-size curved hood surfaces, effectively optimizing surface flatness and contour accuracy. The finished product's appearance quality and structural strength are significantly superior to products manufactured using traditional methods.

[0028] 4. The entire molding mold and process of this invention are fully adaptable to conventional oven equipment, eliminating reliance on high-end autoclaves and greatly reducing equipment investment, production energy consumption, and maintenance costs. Simultaneously, through structural innovation and refined process control, it overcomes the shortcomings of traditional oven molding processes, such as poor quality and low yield, achieving high-precision, low-defect molding results under low-cost production conditions. Attached Figure Description

[0029] Figure 1 A schematic diagram of the overall structure of the carbon fiber hood trim molding die provided by the present invention;

[0030] Figure 2 A schematic diagram of the internal structure of the carbon fiber hood trim molding die provided by the present invention;

[0031] Figure 3 A cross-sectional view of the carbon fiber hood trim molding die provided by the present invention;

[0032] Figure 4 This is a schematic diagram of a carbon fiber hood trim piece formed using the method provided in this invention.

[0033] The meanings of the markings in the attached diagram are as follows:

[0034] In the figure: 1. Molding base; 2. Sealing cover; 3. First vacuum bag; 4. Second vacuum bag; 100. Prepreg layer. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this invention, it should be noted that, 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example

[0039] This invention provides a molding die for a carbon fiber hood trim piece. Please refer to [link / reference]. Figure 1-3 It includes a molding base 1, a sealing cover 2, a dual-cavity sealing molding structure, and a differential pressure linkage control mechanism. The molding base 1 is an integral molding structure with two independent sealing cavities arranged sequentially from the inside to the outside. The two independent sealing cavities are an independent part molding vacuum cavity and a buffer pressure stabilizing vacuum cavity, respectively. The differential pressure linkage control mechanism matches the rheological characteristics of the carbon fiber prepreg resin and independently controls the vacuuming, pressure holding, and pressure release of the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity according to the molding process stage, so as to adapt to the molding process of differential pressure exhaust, temperature control compaction, and segmented curing.

[0040] In this embodiment, the molding cavity surface of the molding base 1 is covered with a first vacuum bag 3, which encloses and forms a part molding vacuum cavity covering the prepreg layer 100; the outer surface of the sealing cover 2 is covered with a second vacuum bag 4, which encloses and forms a buffer pressure stabilizing vacuum cavity.

[0041] Specifically, the differential pressure linkage control mechanism is also electrically connected to a temperature monitoring component to collect the temperature of the prepreg in the molding cavity in real time, and adaptively match the differential pressure parameters and pressure relief timing of the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity according to the resin melting and flow temperature range.

[0042] This invention differs from conventional fixed-pressure molding schemes by setting up an adaptively adjustable differential pressure linkage control mechanism and equipping it with a temperature monitoring component, which can collect the temperature of the prepreg in the molding cavity in real time and accurately capture the optimal melting and flow window of the resin.

[0043] The present invention also provides a method for molding a carbon fiber hood trim, which includes the following steps:

[0044] S1. Mold constant temperature preheating: Preheat the entire molding mold to 40±5℃, keep the temperature uniform and stable, and complete the molding pretreatment.

[0045] S2, Laying up and sealing the parts: Carbon fiber prepreg is laid in the molding cavity of the molding base 1, the first vacuum bag 3 is laid and sealed to form a closed vacuum cavity for molding the parts.

[0046] S3. Cover snapping and pressure stabilization sealing: Align and snap the sealing cover 2 with the molding base 1, lay the second vacuum bag 4 on the outer surface of the sealing cover 2 and seal it to form an independent buffer pressure stabilization vacuum chamber.

[0047] S4. Constant temperature differential pressure exhaust: The vacuum chamber for part forming and the buffer pressure stabilizing vacuum chamber are evacuated simultaneously through the differential pressure linkage control mechanism. The vacuum degree of the part forming vacuum chamber is controlled to be -0.85 ~ -0.90 bar, and the vacuum degree of the buffer pressure stabilizing vacuum chamber is higher than that of the part forming vacuum chamber. The pressure is stabilized for 15~20 minutes to completely remove the gas trapped inside the carbon fiber prepreg by using the stable pressure difference.

[0048] S5. Temperature threshold precision compaction: The whole mold is sent into the oven to heat up, and the temperature of the prepreg is monitored in real time. When the temperature reaches the optimal flow temperature of the resin at 90℃±3℃, the pressure of the buffer and pressure stabilizing vacuum chamber is released, and only the negative pressure of the part forming vacuum chamber is retained to compact the prepreg. The temperature is kept constant and the pressure is maintained for 10 minutes to complete the resin impregnation molding.

[0049] S6. Segmented high-temperature curing: Continuously heat up to 150℃ and keep at a constant temperature for 30 minutes to allow the prepreg resin to fully cross-link and cure, thus completing the part shaping.

[0050] S7. Low-temperature demolding and part removal: After curing, the oven temperature is reduced according to the program. When the mold temperature drops below 60℃, remove the sealing cover 2 and take out the carbon fiber front hood trim 100. Figure 4 As shown.

[0051] Specifically, before the layup operation in step S2, a prepreg pretreatment step is also included: the carbon fiber prepreg is placed in a room temperature environment and allowed to stand for 20-30 minutes to warm up, removing condensation on the surface of the prepreg. At the same time, the prepreg is rolled and flattened as a whole to remove the initial air inside the material. The prepreg is also cut into directional pieces according to the stress zones of the hood trim to ensure that the layup texture and stress direction match the product structure.

[0052] Furthermore, in step S2, a layered staggered layup process is adopted. The adjacent two layers of carbon fiber prepreg are laid alternately at 45° / 0°. After each layer is laid, a single manual pre-compaction is performed. The layers are staggered and overlapped, with the overlap width controlled at 8~12mm. This avoids molding defects caused by concentrated gaps in the overall splicing and improves the overall structural strength and integrity of the product.

[0053] This invention features a customized full-process molding technology specifically designed to suit the structural characteristics of carbon fiber hoods. It encompasses exclusive steps such as prepreg reheating and leveling, directional cutting, 45° / 0° staggered layering, manual pre-compaction, and gradient cooling stress relief. The staggered layering combined with precise compaction effectively enhances interlayer bonding strength and avoids structural defects caused by concentrated gaps. The segmented gradient cooling process gradually releases internal molding stress, preventing warping, cracking, and deformation caused by rapid cooling. Throughout the process, stable pressure control ensures uniform stress distribution during the molding of large-size curved hood surfaces, effectively optimizing surface flatness and contour accuracy. The finished product's appearance quality and structural strength are significantly superior to products manufactured using traditional methods.

[0054] Specifically, during the differential pressure exhaust stabilization process in step S4, the vacuum level of the dual chambers is monitored in real time. If pressure decay occurs, pressure is replenished in real time through dual independent vacuum pumping components. Throughout the process, the pressure difference fluctuation of the chambers is maintained at no more than ±0.02 bar, ensuring that the pressure is stable and without fluctuation during the exhaust process.

[0055] Specifically, step S7 adopts a segmented gradient cooling process. After curing, the product is cooled to 90°C at a rate of 3~5°C / min, kept at a constant temperature for 10 minutes to eliminate internal stress, and then cooled to below 60°C for demolding to avoid product warping, cracking and deformation caused by rapid cooling.

[0056] This invention utilizes a dual-chamber independent pressure control system to achieve segmented control logic for gradual venting under constant temperature differential pressure in the early stage and precise pressure release and compaction during the resin melting stage. This completely solves the problems of incomplete venting and uneven resin impregnation in traditional single negative pressure molding. The dual-chamber pressure difference can be dynamically calibrated and real-time pressure replenishment and stabilization can be implemented throughout the process, keeping molding pressure fluctuations within a minimal range. This maximizes the removal of deep gases and volatiles from the prepreg, significantly reducing product porosity and substantially improving the internal density and structural uniformity of carbon fiber products.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A molding die for a carbon fiber hood trim piece, characterized in that, Includes a molding base (1), a sealing cover (2), a double-cavity sealing molding structure, and a differential pressure linkage control mechanism; The molding base (1) is an integral molding structure with two independent sealed cavities arranged sequentially from the inside to the outside. The two independent sealed cavities are an independent part molding vacuum cavity and a buffer pressure stabilizing vacuum cavity, respectively. The differential pressure linkage control mechanism matches the rheological characteristics of carbon fiber prepreg resin and independently controls the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity for vacuuming, pressure holding and pressure release according to the molding process stage, so as to adapt to the molding process of differential pressure exhaust, temperature control compaction and segmented curing.

2. The carbon fiber hood trim molding die according to claim 1, characterized in that, The molding cavity surface of the molding base (1) is covered with a first vacuum bag (3), which encloses and forms a part molding vacuum cavity covered with a prepreg layer (100).

3. The carbon fiber hood trim molding die according to claim 1, characterized in that, The outer surface of the sealing cover (2) is covered with a second vacuum bag (4), which encloses and forms a buffer pressure-stabilizing vacuum cavity.

4. The carbon fiber hood trim molding die according to claim 1, characterized in that, The differential pressure linkage control mechanism is also electrically connected to a temperature monitoring component, which collects the temperature of the prepreg in the molding cavity in real time, and adaptively matches the differential pressure parameters and pressure relief timing of the part molding vacuum cavity and the buffer pressure stabilizing vacuum cavity according to the resin melting and flow temperature range.

5. A method for molding a carbon fiber hood trim piece, characterized in that, Includes the following steps: S1. Mold constant temperature preheating: Preheat the entire molding mold to 40±5℃, keep the temperature uniform and stable, and complete the molding pretreatment. S2, Laying and sealing of parts: Carbon fiber prepreg is laid in the molding cavity of the molding base (1), the first vacuum bag (3) is laid and sealed to form a closed part molding vacuum cavity. S3, Cover snapping and pressure stabilization sealing: Align and snap the sealing cover (2) with the molding base (1), lay a second vacuum bag (4) on the outer surface of the sealing cover (2) and seal it to form an independent buffer pressure stabilization vacuum chamber; S4. Constant temperature differential pressure exhaust: The vacuum chamber for part forming and the buffer pressure stabilizing vacuum chamber are evacuated simultaneously through the differential pressure linkage control mechanism. The vacuum degree of the part forming vacuum chamber is controlled to be -0.85 ~ -0.90 bar, and the vacuum degree of the buffer pressure stabilizing vacuum chamber is higher than that of the part forming vacuum chamber. The pressure is stabilized for 15~20 minutes to completely remove the gas trapped inside the carbon fiber prepreg by using the stable pressure difference. S5. Temperature threshold precision compaction: The whole mold is sent into the oven to heat up, and the temperature of the prepreg is monitored in real time. When the temperature reaches the optimal flow temperature of the resin at 90℃±3℃, the pressure of the buffer and pressure stabilizing vacuum chamber is released, and only the negative pressure of the part forming vacuum chamber is retained to compact the prepreg. The temperature is kept constant and the pressure is maintained for 10 minutes to complete the resin impregnation molding. S6. Segmented high-temperature curing: Continuously heat up to 150℃ and keep at a constant temperature for 30 minutes to allow the prepreg resin to fully cross-link and cure, thus completing the part shaping. S7. Low-temperature demolding and removal of parts: After curing, the oven temperature is reduced by the process. When the mold temperature drops below 60°C, the sealing cover (2) is removed and the carbon fiber front hood trim (100) is taken out.

6. The method for molding a carbon fiber hood trim according to claim 5, characterized in that, Before the layup operation in step S2, a prepreg pretreatment step is also included: the carbon fiber prepreg is placed in a room temperature environment and allowed to stand for 20-30 minutes to warm up, removing condensation on the surface of the prepreg. At the same time, the prepreg is rolled and flattened as a whole to remove the initial air inside the material. The prepreg is also cut into oriented pieces according to the stress zones of the hood trim to ensure that the layup texture and stress direction match the product structure.

7. The method for molding a carbon fiber hood trim piece according to claim 5, characterized in that, In step S2, a layered staggered layup process is adopted. The adjacent two layers of carbon fiber prepreg are laid alternately at 45° / 0°. After each layer is laid, a single manual pre-compaction is performed. The layers are staggered and overlapped, with the overlap width controlled at 8~12mm. This avoids molding defects caused by concentrated gaps in the overall splicing and improves the overall structural strength and integrity of the product.

8. The method for molding a carbon fiber hood trim according to claim 5, characterized in that, In step S4, during the differential pressure exhaust and stabilization process, the vacuum level of the dual chambers is monitored in real time. If pressure decay occurs, pressure is replenished in real time through dual independent vacuum pumping components. Throughout the process, the pressure difference fluctuation of the chambers is maintained at no more than ±0.02 bar, ensuring that the pressure is stable and without fluctuation during the exhaust process.

9. The method for molding a carbon fiber hood trim piece according to claim 5, characterized in that, Step S7 adopts a segmented gradient cooling process. After curing, the product is cooled to 90°C at a rate of 3~5°C / min, kept at a constant temperature for 10 minutes to eliminate internal stress, and then cooled to below 60°C for demolding to avoid product warping, cracking and deformation caused by rapid cooling.

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