Composite material pressurized prepreg molding die and molding method

Abstract

This invention provides a pressure-intensified prepreg molding die and molding method for composite materials. The die includes a lower die and an upper die; when the upper die is placed on the lower die and closed, a closed mold cavity is formed; prepreg is laid layer by layer on the first cavity to form a prepreg stack; the prepreg stack is cured inside the mold cavity under the action of the closing force and the die temperature to form a composite material; a pressure-intensifying hole is located inside the lower die; its top is connected to the mold cavity and located within the process allowance area of ​​the prepreg stack; a pressure-intensifying device is filled with pressure-transmitting fluid, and its bottom is connected to the bottom of the pressure-intensifying hole through a pressure-transmitting pipeline; the molding method is completed using a molding die. This application controls the resin pressure in the prepreg stack through the pressure-intensifying device, effectively controlling porosity defects in the molding of composite material products.

Description

Technical Field

[0001] This invention pertains to composite material molding processes, specifically relating to a composite material pressure-intensified prepreg molding die and molding method. Background Technology

[0002] Prepreg compression molding is a traditional technology widely used in the industry. In this process, prepreg is cut into appropriate shapes, and multiple layers are laid on a mold according to the layup design. A press forces the upper and lower molds to close, and the prepreg is continuously compacted under the clamping force. Simultaneously, the resin cures under the influence of temperature and time, completing the composite material molding. Because prepreg is a resin-impregnated fiber fabric or unidirectional tape, air is easily trapped during the layup process. For mass production, to improve efficiency and shorten mold heating time, a hot-mold, cold-material process is usually adopted. Therefore, when the prepreg stack is placed on the mold, the mold temperature causes the resin on the upper and lower surfaces of the prepreg to melt first, reaching a viscous flow state. The molten resin flows under the clamping force and fills the gaps between the upper and lower surface layers, forming a relatively dense resin film. This, to some extent, seals the channels for air trapped inside the prepreg stack to escape, leading to porosity defects inside the molded composite product.

[0003] To reduce porosity defects, a vacuum function is typically added to the mold. However, the upper and lower molds are only in the closed state, and vacuuming can only be performed after the mold cavity is sealed. Simultaneously, it's crucial to prevent the viscous resin on the prepreg laminate surface from flowing towards the vacuum source under vacuum, thus blocking the vacuum lines. Therefore, the effective vacuuming time is very short. For large-sized, thick, and complex composite material products, vacuuming is ineffective in removing trapped air, making it difficult to effectively control porosity defects. For resin systems that generate small molecules during curing, the molding process cannot achieve full vacuuming like autoclave, OOA, and VARI processes. Therefore, adding a vacuum function to the mold cannot reduce porosity defects in such composite materials. Furthermore, the small molecules generated during curing aggregate on the mold surface, resulting in an uneven surface, low dimensional accuracy, and poor appearance quality after molding.

[0004] In compression molding, due to the limitations of the mold design, the clamping force of the press cannot be effectively and completely applied to the prepreg stack. A portion of the clamping force is borne by the mold, with the prepreg stack only bearing a portion. Therefore, even if the press clamping force is set, the inability to ensure the consistency of the prepreg stack dimensions during engineering will lead to uncontrollable pressure on the prepreg stack, and consequently, uncontrollable resin pressure within the prepreg stack, resulting in difficulty in controlling porosity defects. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a composite material pressure-intensified prepreg molding die and molding method.

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] In a first aspect, a composite material pressurized prepreg molding die includes: a lower die having a first cavity at its top; an upper die having a second cavity at its bottom; when the upper die is placed on the lower die and closed in place, the first cavity and the second cavity are joined to form a closed mold cavity; a prepreg being laid layer by layer on the first cavity to form a prepreg stack; the prepreg stack being cured inside the mold cavity under the action of the closing force and the mold temperature to form a composite material; a pressurizing hole located inside the lower die; its top communicating with the mold cavity and located within the process allowance area of ​​the prepreg stack; and a pressurizing device containing a pressure-transmitting fluid, the bottom of which is connected to the bottom of the pressurizing hole via a pressure-transmitting pipeline.

[0008] According to the technical solution provided in the embodiments of this application, the distance between the top of the pressure-boosting hole and the product cutting line is 30mm; the distance between the top of the pressure-boosting hole and the edge of the prepreg stack to be cut is 10mm to 30mm.

[0009] According to the technical solution provided in the embodiments of this application, the diameter of the end of the pressure-boosting hole that communicates with the mold cavity is 0.5mm to 2mm.

[0010] According to the technical solution provided in the embodiments of this application, the liquid level of the pressure transmitting fluid inside the pressurizing device is not higher than the horizontal position at the end of the pressurizing orifice cavity, and the difference between the two liquid levels is 0mm to 5mm.

[0011] According to the technical solution provided in the embodiments of this application, the pressure transmitting fluid adopts a single-component resin compatible with the prepreg resin system, and the viscosity of the pressure transmitting fluid (6) is less than 400 mPa.s.

[0012] According to the technical solution provided in the embodiments of this application, the number of pressure boosting holes is one or more, and they are evenly distributed in the process allowance area; the pressure boosting device is one or more.

[0013] According to the technical solution provided in the embodiments of this application, the pressurization device is turned on 20s to 30s before the prepreg resin system gels; the pressurization device is turned off 20s to 30s after the prepreg resin system gels.

[0014] According to the technical solution provided in the embodiments of this application, for resin systems that do not produce small molecules during the curing process, the pressure value set by the pressurizing device is 0.6MPa to 0.8MPa; for resin systems that produce small molecules during the curing process, the pressure value set by the pressurizing device is 1.2MPa to 1.6MPa.

[0015] According to the technical solution provided in the embodiments of this application, heating oil channels are evenly distributed inside the upper mold and the lower mold, and the heating oil channels are connected to the mold temperature controller.

[0016] According to the technical solution provided in the embodiments of this application, the pressure transmission pipeline is connected to the pressure transmission pipeline through a sealing joint, and the bottom of the pressurization device is connected to the pressure transmission pipeline through a sealing joint.

[0017] Secondly, a method for compression molding of composite prepreg, using the molding die described above, includes the following steps:

[0018] Install the mold, control the pressure boosting device and the amount of pressure transmitting fluid, and ensure that the liquid level of the pressure transmitting fluid in the pressure boosting device is not higher than the horizontal position at the end of the pressure boosting orifice mold cavity, with a liquid level difference of 0mm to 5mm.

[0019] Cut the prepreg, and the dimensions of the cut prepreg include the process allowance area;

[0020] The cut multi-layer prepreg is laid on the lower mold, and the process allowance area of ​​the prepreg layer covers the pressure hole.

[0021] When the upper and lower molds are closed, the prepreg stacks are compacted under the action of the closing force; the resin melts under the action of the mold temperature and reaches a viscous flow state. The resin wets the fibers inside the prepreg and fills the gaps between the layers, within the layers, and between the stacks and the mold cavity. It is also injected into the pressure injection hole until the upper and lower molds are closed in place.

[0022] Set the pressure boosting value of the pressurizing device and turn on the pressurizing device 20s to 30s before the prepreg resin system gels;

[0023] Turn off the pressurization device 20-30 seconds after the prepreg resin system has gelled.

[0024] Prepreg laminates are cured inside the mold cavity under the action of clamping force and mold temperature to form a composite material.

[0025] The present invention has the following beneficial effects:

[0026] Because this application incorporates a pressure-boosting hole in the mold, one end of which connects to the mold cavity and the other end to a pressure-boosting device, which contains a pressure-transmitting fluid, the pressure is effectively transmitted to the interior of the prepreg stack during the prepreg molding process. Compared to existing technologies where the clamping force of the press cannot effectively and completely act on the prepreg stack, this increases the resin pressure, ensuring that the pressure acts entirely on the resin inside the prepreg stack, effectively controlling porosity defects. Simultaneously, the pressure-boosting device achieves quantitative control of the resin pressure inside the prepreg stack, ensuring consistency of process parameters and thus product quality. For prepreg resin systems that generate small molecules during curing, this not only effectively controls porosity defects but also ensures product surface smoothness, dimensional accuracy, and appearance quality.

[0027] Using the molding method described in this invention, the pressure-transmitting fluid efficiently and rapidly transfers the pressure from the pressurizing device to the prepreg resin system. The resin pressure rises sharply, compressing air bubbles and trapped air within the prepreg laminate resin, significantly reducing or eliminating the volume of the bubbles. As the resin gels and cures, the composite material is molded, effectively controlling the porosity of the composite material. Similarly, for resin systems that generate small molecules during the curing process, sufficient resin pressure can effectively compress and break down these small molecules, effectively controlling pore defects while ensuring product surface smoothness, dimensional accuracy, and appearance quality. Attached Figure Description

[0028] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 This is a cross-sectional schematic diagram of the molding die structure described in this application.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Lower mold; 2. Upper mold; 3. Prepreg stack; 4. Pressure boosting hole; 5. Pressure boosting device; 6. Pressure transmitting fluid; 7. Pressure transmitting device; 8. Sealing joint; 9. Heating oil passage. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," "counterclockwise," "front end," "rear end," and "side," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the disclosed product is in use. They are only for the convenience of describing this disclosure 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 this disclosure. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of this disclosure, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," "join," and "dock" 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 disclosure based on the specific circumstances.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] A composite material pressurized prepreg molding die includes: a lower mold 1 with a first cavity at its top; an upper mold 2 with a second cavity at its bottom; when the upper mold 2 is placed on the lower mold 1 and closed in place, the first cavity and the second cavity are joined to form a closed mold cavity; prepreg is laid layer by layer on the first cavity to form a prepreg stack 3; the prepreg stack 3 is cured inside the mold cavity under the action of the closing force and the mold temperature to form a composite material; a pressurizing hole 4 located inside the lower mold 1; its top is connected to the mold cavity and located within the process allowance area of ​​the prepreg stack 3; and a pressurizing device 5 containing a pressure transmitting fluid 6, the bottom of which is connected to the bottom of the pressurizing hole 4 through a pressure transmitting pipe 7.

[0040] Among them, such as Figure 1 As shown, the upper mold 2 and lower mold 1 are closed in place, and the first cavity and the second cavity are joined to form a closed mold cavity. It can be understood that the prepreg is cut into the appropriate shape, and multiple layers of prepreg are laid on the lower mold 1 according to the layup design requirements. The dimensions of the prepreg include process allowances. After laying, the edges of the entire prepreg stack 3 contact the edges of the mold cavity. The thickness of the prepreg stack 3 is slightly greater than the depth of the mold cavity, and it is in a relatively loose initial state. The prepreg stack 3 covers the pressure inlet 4.

[0041] It is understood that the top of the pressure-boosting hole 4 is connected to the mold cavity, and the top of the pressure-boosting hole 4 will gradually come into contact with the prepreg stack (3) during the molding process.

[0042] The process allowance area is the area formed by the excess prepreg stack (3) to be cut from the final composite material product formed by the prepreg stack (3) and the product cutting line.

[0043] The lower mold 1 is equipped with a pressure-increasing hole 4, which is located within the process allowance area of ​​the composite material product. It should be noted that the area of ​​the prepreg laminate 3 is larger than that of the composite material product. The product cutting line of the composite material product is located inside the edge of the prepreg laminate 3, so that the final composite material product can be cut according to the product cutting line. Here, it can be understood that if the composite material product requires holes, the interior of the holes also constitutes a process allowance. Since there are at least two product cutting lines, one outer and one inner, the prepreg laminate 3 to be cut is located both outside the outer product cutting line and inside the inner product cutting line.

[0044] The process allowance area set in the pressure boosting hole 4 helps to prevent the pressure transmission fluid 6 from entering the effective area of ​​the product and affecting the product performance.

[0045] Since the pressurizing device 5 is connected to the pressurizing hole 4 through the pressure transmission pipeline 7, the pressurizing device 5, the pressure transmission pipeline 7 and the pressurizing hole 4 contain pressure transmission fluid 6.

[0046] The booster device 5 can use pneumatic, hydraulic or mechanical methods to boost pressure and achieve effective pressure control.

[0047] The pressurizing device 5 facilitates quantitative pressure control. The pressure-transmitting fluid 6 efficiently transmits the pressure of the pressurizing device 5 to the interior of the prepreg stack 3 in the prepreg molding process. By controlling and increasing the resin pressure, the air bubbles inside the resin of the prepreg stack 3 are compressed, causing the volume of the air bubbles to be significantly reduced or eliminated, thereby effectively controlling pore defects.

[0048] Because this application incorporates a pressure-boosting hole 4 on the mold, with one end connected to the mold cavity and the other end connected to a pressure-boosting device 5, and a pressure-transmitting fluid 6 inside the pressure-boosting device 5, pressure is effectively transmitted to the interior of the prepreg stack 3 in the prepreg molding process. Compared to the prior art where the clamping force of the press cannot effectively and completely act on the prepreg stack 3, this application increases the resin pressure, ensuring that the pressure acts entirely on the resin inside the prepreg stack 3, effectively controlling porosity defects. Simultaneously, the pressure-boosting device 5 achieves quantitative control of the resin pressure inside the prepreg stack 3, ensuring the consistency of process parameters and thus the consistency of product quality. For prepreg resin systems that generate small molecules during curing, this application not only effectively controls porosity defects but also ensures product surface smoothness, dimensional accuracy, and appearance quality. Vacuum molding processes are difficult to operate and prone to incomplete removal of trapped air; this application uses liquid pressure transmission, which is more efficient.

[0049] In one embodiment of this application, the distance between the top of the pressure-boosting hole 4 and the product cutting line is 30mm; the distance between the top of the pressure-boosting hole 4 and the edge of the prepreg stack 3 to be cut is 10mm to 30mm.

[0050] Specifically, the allowance is set so that the distance beyond the product cutting line is the process allowance. Process verification shows that when the distance between the top of the pressure inlet 4 and the product cutting line is greater than 30mm, the pressure transmitting fluid 6 will not penetrate into the effective area of ​​the product. Generally, 30mm is chosen. If the distance is too small, the pressure transmitting fluid 6 may penetrate into the product; if the distance is too large, the process allowance will be too large, increasing raw material costs.

[0051] The distance between the top of the pressure boosting hole 4 and the edge of the prepreg stack 3 to be cut is 10mm to 30mm, generally 30mm is selected. Smaller is also acceptable, but it cannot be as small as 0, which would result in the inability to transmit liquid pressure or poor pressure transmission effect. It is necessary to ensure that the pressure transmitting liquid 6 only fills the edge part. If it is greater than 30mm, the raw material cost will increase.

[0052] In summary, the distance between the product cutting line and the edge of the prepreg stack 3 should be greater than 60mm. The diameter of the hole in the product to be cut should be at least 60mm.

[0053] In one embodiment of this application, the diameter of the end of the pressure-boosting hole 4 that contacts the prepreg laminate 3 is 0.5 mm to 2 mm.

[0054] Specifically, since this application uses liquid pressure transmission, the pressure transmission efficiency is high. Because the pressure boosting device 5 can set and control the pressure value, the pressure of the pressure boosting hole 4 is fixed. If the diameter of the mold cavity end of the pressure boosting hole 4 is too large, too much pressure transmission fluid 6 will enter the stack, causing the product to become uncontrollable. On the other hand, the smaller the diameter of the mold cavity end of the pressure boosting hole 4, the smaller the flow rate can be at the same pressure, and the smaller the total amount of pressure transmission fluid 6 entering the stack, which makes it easier to control the product performance.

[0055] The diameter of the other end of the pressure boosting hole 4 is not required, which is convenient for installing sealing joints 8 and other rough management. If the diameter of this end is small, it will cause unnecessary trouble for the installation.

[0056] In one embodiment of this application, the liquid level of the pressure-transmitting fluid 6 inside the pressure boosting device 5 is not higher than the horizontal position at the end of the mold cavity of the pressure boosting hole 4, and the difference between the two liquid levels is 0mm to 5mm.

[0057] Specifically, the position of the pressurizing device 5 and the amount of pressure-transmitting fluid 6 are controlled so that the level of the pressure-transmitting fluid 6 inside the pressurizing device 5 is not higher than the horizontal position of the mold cavity end of the pressurizing hole 4. Ideally, the two fluid levels should be level, but considering process requirements, an error of 1mm to 5mm is sufficient and also convenient to control without overly restricting actual operation. Even if they are not completely level, the surface tension of the fluid will prevent leakage; however, the fluid level difference should not be too high, and should be controlled within 5mm, because if the fluid level difference is too high, the pressure-transmitting fluid 6 will seep in without external force.

[0058] In one embodiment of this application, the pressure transmitting fluid 6 is a single-component resin compatible with the prepreg resin system, and the viscosity of the pressure transmitting fluid 6 is less than 400 mPa·s.

[0059] Specifically, the pressure-transmitting fluid 6 uses a single-component resin compatible with the prepreg resin system, i.e., a resin without a curing agent. For example, if the prepreg resin system is an epoxy resin system, then the pressure-transmitting fluid 6 is also made of epoxy resin and does not contain a curing agent. It is liquid at room temperature and its viscosity during use is less than 400 mPa·s. Depending on the different prepreg resin systems, the pressure-transmitting fluid 6 can be epoxy resin, phenolic resin, vinyl ester resin, etc.

[0060] Generally, after a small amount of pressure-transmitting fluid 6 enters the prepreg stack 3 and mixes with the prepreg resin system, the curing agent in the prepreg resin system can promote its curing because the pressure-transmitting fluid 6 is a single-component resin compatible with the prepreg resin system, which facilitates mold cleaning and subsequent product processing.

[0061] The viscosity of the pressure-transmitting fluid 6 is less than 400 mPa·s. Because the orifice diameter at the top of the pressure-boosting orifice is fixed, if the viscosity of the pressure-transmitting fluid is too high, it will affect its fluidity, resulting in a poor pressure transmission effect.

[0062] In one embodiment of this application, the number of the pressure boosting holes 4 is one or more, and they are evenly distributed in the process allowance area; the number of the pressure boosting devices 5 is one or more.

[0063] Specifically, if the volume of the composite material product is too large, it is recommended to evenly distribute several pressure-boosting holes 4 in the product process allowance area of ​​the lower mold 1. These holes can be controlled using one or more pressure-boosting devices 5. This is to prevent excessive flow of the pressure-transmitting fluid 6 into the prepreg laminate 3 through a single pressure-boosting hole 4, which could exceed the cutting line of the final composite material product, affecting the curing degree of the final composite material product and thus impacting product quality.

[0064] In one embodiment of this application, the pressurizing device 5 is turned on 20s to 30s before the prepreg resin system gels; the pressurizing device 5 is turned off 20s to 30s after the prepreg resin system gels.

[0065] Specifically, the pressurization device 5 is activated 20 to 30 seconds before the prepreg resin system gels. At this time, the resin in the prepreg stack 3 has become a flowable liquid, and the liquid pressure transmission instantly reaches the preset pressure, controlling and limiting the expansion of air bubbles and entrained air. At the same time, the amount of pressure-transmitting liquid 6 entering the stack is very small, ensuring product performance.

[0066] If the pressurizing device 5 is activated too early, excessive pressure-transmitting fluid 6 may enter the prepreg stack 3, exceeding the cutting line of the final composite product and affecting the curing degree of the final composite product. If the pressurizing device 5 is activated too late, the prepreg resin system in the pressurizing hole 4 cannot effectively flow back into the prepreg stack 3, and the cured resin system will block the pressurizing hole 4. If the pressurizing device 5 is activated after the prepreg resin system has gelled, the resin will cure and be unable to transmit liquid pressure, failing to achieve the expected pressurization effect, ultimately leading to uncontrollable pore defects.

[0067] Specifically, the shut-off time of the pressurizing device 5 is controlled to be 20-30 seconds after the prepreg resin system has gelled. At this time, the resin has already solidified and molded, and continuous pressurization will not be effective and will only increase costs.

[0068] In one embodiment of this application, for resin systems that do not produce small molecules during the curing process, the pressure value set by the pressurizing device 5 is 0.6MPa to 0.8MPa; for resin systems that produce small molecules during the curing process, the pressure value set by the pressurizing device 5 is 1.2MPa to 1.6MPa.

[0069] Specifically, the pressure values ​​set for different resin systems are process-verified values, and the molding effect is best within the specified range.

[0070] The pressurization device 5 is controlled by hydraulic, pneumatic or mechanical means. Based on the principle of liquid pressure transmission, it realizes the quantitative control of the resin pressure inside the prepreg stack 3 during the prepreg molding process, ensuring the consistency of process parameters.

[0071] In one embodiment of this application, heating oil channels 9 are evenly distributed inside the upper mold 2 and the lower mold 1, and the heating oil channels 9 are connected to a mold temperature controller.

[0072] Specifically, the mold temperature is controlled by a mold temperature controller to ensure the mold temperature and temperature uniformity, so as to meet the process requirements of composite material molding.

[0073] In one embodiment of this application, the pressure transmission line 7 is connected to the pressure transmission line 7 via a sealing joint 8, and the bottom of the pressurization device 5 is connected to the pressure transmission line 7 via a sealing joint 8.

[0074] Specifically, the sealing joint 8 ensures airtightness during the pressure transmission process, effectively transmits pressure, and thus effectively controls pore defects.

[0075] Example 2

[0076] A method for compression molding of composite prepreg, using the molding die described above, includes the following steps:

[0077] Install the mold, control the amount of pressure boosting device 5 and pressure transmitting fluid 6, so that the liquid level of pressure transmitting fluid 6 in pressure boosting device 5 is not higher than the horizontal position of the mold cavity end of pressure boosting hole 4, and the difference between the two liquid levels is controlled between 0mm and 5mm.

[0078] Cut the prepreg, and the dimensions of the cut prepreg include the process allowance area;

[0079] The cut multi-layer prepreg is laid on the lower mold 1, and the process allowance area of ​​the prepreg stack 3 covers the pressure hole 4.

[0080] When the upper mold 2 and the lower mold 1 are closed, the prepreg stack 3 is compacted under the action of the closing force; the resin melts under the action of the mold temperature and reaches the viscous flow state. The resin wets the fibers inside the prepreg and fills the gaps between the layers, within the layers, and between the stack and the mold cavity of the prepreg stack 3, and injects into the pressure hole 4 until the upper mold 2 and the lower mold 1 are closed in place.

[0081] Set the pressure value of the pressurizing device 5, and turn on the pressurizing device 5 20s to 30s before the prepreg resin system gels;

[0082] 20-30 seconds after the prepreg resin system gels, turn off the pressurization device 5.

[0083] The prepreg laminate 3 is cured inside the mold cavity under the action of clamping force and mold temperature to form a composite material.

[0084] Specifically, in actual operation, the mold is assembled according to the mold scheme described above and installed on the press equipment. The heating oil channels 9 of the upper mold 2 and the lower mold 1 are connected to the mold temperature controller. The pressure boosting device 5, the pressure transmission pipeline 7 and the pressure boosting hole 4 are filled with pressure transmission fluid 6. The position of the pressure boosting device 5 and the amount of pressure transmission fluid 6 are controlled so that the liquid level of the pressure transmission fluid 6 inside the pressure boosting device 5 is not higher than the horizontal position of the mold cavity end of the pressure boosting hole 4, and the difference between the two liquid levels is controlled between 0mm and 5mm.

[0085] The prepreg is cut into the appropriate shape, and multiple layers of prepreg are laid on the lower mold 1 according to the layup design requirements. The dimensions of the prepreg include process allowances. After laying, the edges of the entire prepreg stack 3 contact the edges of the mold cavity, and the thickness of the prepreg stack 3 is slightly greater than the depth of the mold cavity, in a relatively fluffy initial state. The prepreg stack 3 covers the pressure inlet 4.

[0086] During the mold closing process of the upper mold 2 and the lower mold 1, the initially relatively loose prepreg laminate 3 gradually becomes denser under the action of the mold closing force. The resin of the prepreg laminate 3 gradually melts under the action of the mold temperature, reaching a viscous flow state. The molten resin flows under the action of the mold closing force, further wetting the fibers inside the prepreg and filling the gaps between the layers, within the layers, and between the laminate and the mold cavity of the prepreg laminate 3. At the same time, some resin enters the pressure inlet 4 until the upper mold 2 and the lower mold 1 are closed in place, forming a closed mold cavity.

[0087] Before the prepreg resin system gels, a pressure boosting value is set. Upon activating the pressure boosting device 5, the pressure of the pressure-transmitting fluid 6 in the device exceeds the resin pressure inside the prepreg stack 3. The pressure-transmitting fluid 6 inside the pressure boosting hole 4 pushes the resin initially entering the hole back into the prepreg stack 3. Based on the principle of liquid pressure transmission, the pressure-transmitting fluid 6 efficiently and rapidly transmits the pressure from the pressure boosting device 5 to the prepreg resin system, causing a sharp increase in resin pressure. This compresses air bubbles and trapped air within the prepreg stack 3, significantly reducing or eliminating the volume of the bubbles. As the resin gels and cures, the composite material is formed, effectively controlling its porosity. Similarly, for resin systems that generate small molecules during the curing process, sufficient resin pressure effectively compresses and breaks down these small molecules, effectively controlling pore defects while ensuring product surface smoothness, dimensional accuracy, and appearance quality.

[0088] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A composite material pressurized prepreg molding die, characterized in that, include: The lower mold (1) has a first cavity at its top; The upper mold (2) has a second cavity at its bottom; when the upper mold (2) is placed on the lower mold (1) and the mold is closed in place, the first cavity and the second cavity are joined together to form a closed mold cavity; Prepreg is laid layer by layer on the first cavity to form a prepreg stack (3); the prepreg stack (3) is cured inside the cavity under the action of clamping force and mold temperature to form a composite material; The pressure boosting hole (4) is located inside the lower mold (1); its top is connected to the mold cavity and is located in the process allowance area of ​​the prepreg stack (3); The pressure boosting device (5) contains a pressure transmitting fluid (6) and its bottom is connected to the bottom of the pressure boosting hole (4) through a pressure transmitting pipe (7). The pressure boosting device (5) is used to quantitatively control the pressure. The pressure transmitting fluid (6) transmits the pressure of the pressure boosting device (5) to the interior of the prepreg stack (3). By controlling and increasing the resin pressure, the air bubbles inside the prepreg stack (3) are compressed. The pressure transmitting fluid (6) is a single-component resin compatible with the prepreg resin system. The number of pressure boosting holes (4) is one or more, and they are evenly distributed in the process allowance area. The pressure boosting device (5) is one or more. Heating oil channels (9) are evenly distributed inside the upper mold (2) and the lower mold (1). The heating oil channels (9) are connected to the mold temperature controller.

2. The composite material pressurized prepreg molding die according to claim 1, characterized in that, The distance between the top of the pressure-boosting hole (4) and the product cutting line is 30mm; the distance between the top of the pressure-boosting hole (4) and the edge of the prepreg stack (3) to be cut is 10mm~30mm.

3. The composite material pressurized prepreg molding die according to claim 1, characterized in that, The diameter of the end of the pressure-boosting hole (4) that connects to the mold cavity is 0.5 mm to 2 mm.

4. The composite material pressurized prepreg molding die according to claim 1, characterized in that, The liquid level of the pressure-transmitting fluid (6) inside the pressure boosting device (5) is not higher than the horizontal position of the mold cavity end of the pressure boosting hole (4), and the difference between the two liquid levels is 0mm ~ 5mm.

5. A composite material pressurized prepreg molding die according to claim 1, characterized in that, The viscosity of the pressure-transmitting fluid (6) is less than 400 mPa·s.

6. The composite material pressurized prepreg molding die according to claim 1, characterized in that, The pressurizing device (5) is turned on 20-30 seconds before the prepreg resin system gels; the pressurizing device (5) is turned off 20-30 seconds after the prepreg resin system gels.

7. A composite material pressurized prepreg molding die according to claim 1, characterized in that, For resin systems that do not produce small molecules during the curing process, the pressure setting of the pressurizing device (5) is 0.6 MPa ~ 0.8 MPa; For resin systems that produce small molecules during the curing process, the pressure setting of the pressurizing device (5) is 1.2 MPa to 1.6 MPa.

8. A method for compression molding of composite prepreg, characterized in that, The molding process, performed using any one of claims 1 to 7, includes the following steps: Install the mold, control the amount of pressure boosting device (5) and pressure transmission fluid (6) so that the liquid level of pressure transmission fluid (6) of pressure boosting device (5) is not higher than the horizontal position of the mold cavity end of pressure boosting hole (4) and the difference between the two liquid levels is 0mm ~ 5mm; Cut the prepreg, and the dimensions of the cut prepreg include the process allowance area; The cut multi-layer prepreg is laid on the lower mold (1), and the process allowance area of ​​the prepreg stack (3) covers the pressure hole (4). The upper mold (2) and the lower mold (1) are closed, and the prepreg stack (3) is compacted under the action of the closing force; the resin melts under the action of the mold temperature and reaches the viscous flow state. The resin wets the fibers inside the prepreg and fills the gaps between the layers, inside the layers and between the stack and the mold cavity of the prepreg stack (3), and injects into the pressure hole (4) until the upper mold (2) and the lower mold (1) are closed in place; Set the pressure value of the pressurizing device (5) and turn on the pressurizing device (5) 20s~30s before the prepreg resin system gels. 20-30 seconds after the prepreg resin system gels, turn off the pressurization device (5). The prepreg laminate (3) is cured inside the mold cavity under the action of clamping force and mold temperature to form a composite material.

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