Method for eliminating internal pores of composite material product in mold pressing process and composite material product

Abstract

The invention discloses a method for eliminating internal pores of a composite material product in a mold pressing process and the composite material product, and belongs to the field of composite material forming. The method for eliminating the internal pores of the composite material product in the mold pressing process aims at solving the problems that the internal pore elimination cost is high and the effect is poor when an existing composite material is subjected to mold pressing forming, and comprises the steps that first-time exhausting is conducted after a premix is preformed; carrying out vacuumizing operation on the vacuumizing mold with the premix preform; the premix prefabricated body is separated from the vacuumizing mold, the premix prefabricated body is put into a compression molding mold to be subjected to compression molding, and in the compression molding process, only the pressure of the molding mold is removed for at least one time; and a die cavity of the vacuumizing die is consistent with a die cavity of the compression molding die. The internal pores of the composite material product can be greatly reduced through two-time exhausting, the overall quality and performance of the final product are improved, operation is easy, the operation requirement for professionals is not high, and cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material molding, and more specifically relates to a method for eliminating internal pores of a composite material product during a molding process and the composite material product. Background Art

[0002] Chopped fiber premix integrally molded composite materials are composite materials that are manufactured by using equipment to cut continuous fibers (carbon fiber, glass fiber, quartz fiber, etc.) into chopped fibers of a certain length, impregnating the fibers with resin to form a premix, and then performing integral compression molding. This type of composite material product is easy to produce and has excellent performance. It has been widely used in aerospace, automotive, shipbuilding, electronics, construction and other fields. This type of composite material premix has good wettability, high production efficiency, high repeatability and low production cost. It is suitable for mass production of products. The fiber length of the premix can be designed, and the product performance can be improved by changing the fiber length. In addition, the stiffness and mechanical properties of this type of product are much higher than those of other types of composite materials. However, during the overall compression molding, a fully enclosed metal mold is used, and the mold cannot be designed with vent holes. If vent holes are designed on the mold, a large amount of resin will be lost during the molding process, resulting in the product resin content being too low and the fiber being exposed, causing the product to be scrapped. However, if the venting is not performed in time, after the molding is completed, the composite resin has been solidified, and the unexhausted air, water vapor and other small gas molecules will remain inside the product and form pores. The pores will form stress concentration areas inside the product, which will greatly reduce the service life of the product and may cause immeasurable losses.

[0003] Corresponding improvements have also been made to the above problems, such as Chinese patent application number CN201210242500.7, published on November 7, 2012, which discloses a composite material vacuum-assisted compression molding system, including an open molding mold, the mold including an upper mold and a lower mold, the lower mold is sealed and connected to a vacuum bag pressing system; the outer side of the mold is connected to a compression heating system. The present invention also discloses a method for vacuum-assisted compression molding of composite material products: first prepare an open molding mold, and place the prepreg on the lower mold, lay the isolation film, the demoulding cloth, and the breathable felt in sequence, seal and connect the vacuum bag film, so that the formed vacuum bag pressing cavity is connected to the vacuum pump; the upper mold and the lower mold are connected to the compression heating system; under the condition of maintaining the vacuum bag pressure, the upper mold and the lower mold are molded together, the prepreg is molded and pressurized by the compression heating system, and the upper and lower molds are heated at the same time, and the curing treatment is carried out after reaching the curing temperature, and the composite material product is formed after the curing reaction is completed. The shortcomings of this patent are: high cost and low molding efficiency.

[0004] Another example is Chinese patent application number CN201510870273.6, which was published on February 24, 2016. The patent discloses a fiber-reinforced thermoplastic resin-based composite laminate molding method and molding device, which belongs to the field of fiber-reinforced composite material technology and is designed to solve the problem of high porosity of existing fiber-reinforced thermoplastic resin-based composite laminates. The fiber-reinforced thermoplastic resin-based composite laminate molding method disclosed in the present invention uses an ultrasonic component to ultrasonically treat the fibers and thermoplastic resin in the mold. Ultrasonic vibration can promote the flow of resin fluid, thereby increasing the discharge rate of gas inside the melt and reducing the porosity of the laminate parts; at the same time, applying ultrasonic vibration is conducive to the uniform distribution of fibers and avoids mutual squeezing of fibers caused by pressure; in addition, it can also reduce molding pressure, shorten preparation time, and reduce residual stress of laminate parts. The shortcomings of this patent are: the use of ultrasonic components has high maintenance costs and the control of ultrasonic waves also tests the level of operators, and the applicability is not wide. Summary of the invention

[0005] 1. Problems to be solved

[0006] Aiming at the problem that the cost of eliminating internal pores in existing composite material compression molding is high and the effect is poor, the present invention provides a method for eliminating internal pores of composite material products during compression molding and a composite material product. The present invention greatly reduces the internal pores of the composite material product by exhausting twice, improves the overall quality and performance of the final product, is simple to operate, does not require high professional operation requirements, and is low in cost.

[0007] 2. Technical solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] A method for eliminating internal pores of a composite material product during a molding process comprises the following steps:

[0010] S1: First exhaust of the premix preform: placing the premix preform into a vacuum mold, and performing a vacuum operation on the vacuum mold with the premix preform to complete the first exhaust of the premix preform;

[0011] S2: Second degassing of the premix preform: the premix preform is separated from the vacuum mold, and the premix preform that has been degassing for the first time is placed in a compression molding mold to be compression molded into a composite material product; and during the compression molding process, there is at least one operation of only relieving the pressure of the molding mold to complete the second degassing of the premix preform;

[0012] Wherein: the mold cavity in the vacuum mold is consistent with the mold cavity in the compression molding mold.

[0013] By adopting the above technical scheme, the premix preform is firstly exhausted. Since there is a large amount of air, water vapor and other small gas molecules inside the premix obtained by impregnating the fiber with resin, the gas inside the premix preform is greatly reduced after the first exhaust, so that the gas inside the premix preform is prevented from forming internal pores during the molding process, thereby providing a good foundation for the subsequent molding process.

[0014] Secondly, during the molding process, the molding die is only subjected to the molding exhaust operation by releasing the pressure. When the premix preform is being molded, after the external pressure is released, the pressure inside the molding die drops rapidly, and pores are formed between the molding die and the premix preform, which is conducive to the discharge of gas, completing the second exhaust, further reducing the gas content in the premix preform and the bubbles generated during the molding process, thereby ensuring that the final composite product has fewer internal pores, improving the product performance, and extending the product life;

[0015] Finally, different molds are used for the first exhaust and the second exhaust, so that vacuuming and compression molding do not interfere with each other and will not affect the product quality of the final composite product; and they can be carried out simultaneously, thereby speeding up production efficiency;

[0016] The whole method greatly reduces the internal pores of the composite material product through two exhausts, improves the overall quality and performance of the final product, and is simple to operate, has low requirements on the operation of professionals, and is low in cost.

[0017] Furthermore, the vacuum operation in step S1 is specifically as follows: preforming the premix on a vacuum mold to obtain a premix preform, covering the vacuum mold with the premix preform with a vacuum bag film, and installing a vacuum air nozzle on the vacuum bag film, and the vacuum air nozzle is connected to a vacuum pump to achieve vacuum treatment of the vacuum mold with the premix preform.

[0018] By adopting the above technical scheme, the premix is ​​first preformed using a vacuum mold to obtain a premix preform, and then the outer surface of the premix preform is pressurized by using the pressure difference between the vacuum pressure and the atmospheric pressure, so that the air, water vapor and other small gas molecules in the premix preform can be discharged smoothly; and the strong suction force provided by the vacuum pump can quickly reduce the air pressure in the vacuum mold, so that the gas molecules in the premix preform itself and between the premix preform and the vacuum mold can be quickly extracted, thereby shortening the exhaust time and improving the exhaust efficiency.

[0019] Furthermore, the vacuuming operation further includes sequentially covering the surface of the premix preform with an isolating breathable film and a breathable felt, wherein the isolating breathable film is disposed between the premix preform and the breathable felt. The isolating breathable film is a perforated isolating film.

[0020] By adopting the above technical scheme, the breathable felt is isolated by an isolating breathable membrane to prevent impurities on the breathable felt from contaminating the product premix preform; the breathable felt absorbs water vapor and conducts air, which is beneficial to the discharge of air, water vapor and other small gas molecules in the premix preform, further enhancing the exhaust effect.

[0021] Furthermore, the number of the vacuum air nozzles is several and they are evenly distributed on the vacuum bag film; at the same time, the vacuum degree is maintained at ≤-0.095MPa during the vacuum operation to ensure that a sufficient pressure difference is formed between the atmospheric pressure and the pressure inside the vacuum bag, thereby promoting the full discharge of small gas molecules in the premix preform in the vacuum bag.

[0022] Furthermore, in the step S2, during the compression molding process, when the resin in the premix preform is in a molten state, the compression molding die is only subjected to a pressure-releasing operation, and then pressure is applied to the compression molding die again to complete the compression molding of the premix preform.

[0023] By adopting the above technical scheme, when the resin in the premix preform is in a molten state, the resin in the compression molding mold is reacting violently. At this time, the temperature of the resin system is greater than 100°C, and the violently reacting resin will carry out a large amount of water vapor and other small gas molecules. By removing the external pressure from the compression molding mold, the internal pressure of the compression molding mold drops rapidly, and pores are formed between the compression molding mold and the premix preform. The small gas molecules volatilized by the violently reacting resin can be fully released from the pores. The small gas molecules in the premix preform can be carried out during the release process, thereby ensuring that the internal pores of the composite material product finally prepared are small, thereby improving the product quality.

[0024] Furthermore, the pressure-releasing operation specifically includes: removing the pressure applied from the outside to the compression molding die, and keeping the upper male die and the lower female die in the compression molding die in contact, while maintaining the pressure-releasing time at 30s to 60s.

[0025] With the above technical solution, since the pressure is released when the resin reacts most violently, the pressure release time should not be too long, otherwise the best time for pressing in the molding process will be missed, resulting in product scrapping. In addition, too long exhaust time will lead to incomplete subsequent curing of the resin, thus affecting the final quality. The pressure release time should not be too short, otherwise the gas may not be fully discharged, affecting the final quality.

[0026] Furthermore, after the compression molding die is relieved of pressure, pressure is applied to the compression molding die again, and the applied pressure is the maximum pressure required for molding the composite material product; and the pressure is applied when the resin is still in a molten state.

[0027] By adopting the above technical scheme, maximum pressure is applied when the resin is in a molten state, so that the resin can be completely filled into every corner of the compression molding mold, thereby eliminating defects such as bubbles and gaps, and improving the density and uniformity of the product; and accelerating the flow and filling process of the resin, shortening the production cycle, and improving production efficiency; at the same time, the resin is evenly distributed in the compression molding mold, reducing the wear and damage of the compression molding mold caused by uneven force, thereby extending the service life of the compression molding mold.

[0028] Furthermore, when the pressure is released, a gap of 0.1 mm to 0.2 mm is formed between the film surface in the upper male mold in the compression molding mold and the premix preform in the mold cavity of the compression molding mold; and the maximum pressure required for molding the composite product is applied to the compression molding mold again after the resin is in a molten state for 5 minutes to 10 minutes.

[0029] By adopting the above technical scheme, when the molding process reaches the resin melting state (i.e., the resin gel temperature), the resin reaction in the mold cavity of the compression molding mold is most intense; this is not only the best time to apply the maximum pressure for compression molding, but also the best time for the resin to release the internal gas of the system, and the resin melting state will last for 5min to 10min; before the resin melting state ends, the compression molding pressure is only removed from the compression molding mold for 30s to 60s, so that a 0.1mm to 0.2mm gap is formed between the upper positive mold surface and the premix preform in the mold cavity, and the pores can promote the full discharge of gas in the resin system and improve the internal quality of the composite material after the product is compression molded.

[0030] A composite material product is prepared by using any of the above-mentioned methods for eliminating internal pores in a composite material product during a molding process.

[0031] The composite material product prepared by this method has greatly reduced internal pores, and the overall quality and performance of the final product are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The left and right cross-sectional schematic diagrams of the product obtained in Comparative Example 1;

[0033] Figure 2 The left and right cross-sectional schematic diagrams of the product obtained in Comparative Example 2;

[0034] Figure 3 The left and right cross-sectional schematic diagrams of the product prepared in this application. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments and drawings.

[0036] A method for eliminating internal pores of a composite material product during a molding process comprises the following steps:

[0037] S1: First exhaust of the premix preform: placing the premix preform into a vacuum mold, and performing a vacuum operation on the vacuum mold with the premix preform to complete the first exhaust of the premix preform;

[0038] S2: Second degassing of the premix preform: the premix preform is separated from the vacuum mold, and the premix preform that has been degassing for the first time is placed in a compression molding mold to be compression molded into a composite material product; and during the compression molding process, there is at least one operation of only relieving the pressure of the molding mold to complete the second degassing of the premix preform;

[0039] Wherein: the mold cavity in the vacuum mold is consistent with the mold cavity in the compression molding mold.

[0040] Specifically, in this embodiment, the vacuuming operation of the premix preform and the compression molding operation are creatively performed independently, and the exhaust is performed separately, thereby greatly reducing the internal porosity of the composite product and improving the overall quality and performance of the final product. The operation is simple, does not require high operating requirements from professionals, and is low in cost.

[0041] And at least one molding exhaust operation is performed during the molding process. The molding exhaust method is to only relieve the pressure on the molding die, that is, to keep the molding die in the same state during the molding process, and only relieve the external pressure on the molding die. When the premix preform is molded, after the external pressure is relieved, the pressure inside the molding die drops rapidly, and pores are formed between the molding die and the premix preform, which is conducive to the discharge of gas, completing the second exhaust, further reducing the gas content in the premix preform and the bubbles generated during the molding process, thereby ensuring that the final composite product has fewer internal pores, improving product performance, and extending product service life. This molding exhaust method is easy to operate, does not require additional parts to be added to the molding die to achieve exhaust operations, saves costs and does not cause other interference, and ensures the quality of composite products.

[0042] It is worth mentioning that currently, the method for reducing the porosity of premix preforms during the compression molding process is usually to use an integrated mold, that is, vacuuming and compression molding are performed in one mold to achieve the effect of reducing the internal porosity of the final product. The inventor has tried this before, but found that this method has the following disadvantages during use:

[0043] The integrated mold uses a press, mold, and vacuum pump as one. After preforming (preforming refers to the operation of pre-laying the resin-impregnated fiber into a shape similar to the final product), the vacuum system is directly made on the product mold, and only one product can be pre-evacuated at a time. In addition, since the vacuum system has high requirements for sealing, the production of the vacuum system will consume a certain amount of working time, and for large parts, the vacuuming process generally needs to be maintained for more than 12 hours to achieve a good pre-evacuation effect. The production of the vacuum system and pre-evacuation occupy equipment such as presses and vacuum pumps, resulting in idle equipment resources and low compression molding efficiency;

[0044] The integrated mold uses a press, mold, product preform, vacuum system, etc. as the whole pressing, and the vacuum system consumes auxiliary materials such as vacuum bag film, isolation film, demoulding cloth, breathable felt, etc. During molding, the auxiliary materials used by the vacuum system remain in the molding system. Under the thousand-ton pressing pressure, all types of auxiliary materials will be crushed. The molding heating and pressing process is the process of resin from viscosity-melting-solidification. After the auxiliary materials are crushed, they will be brought into the product along with the molten state of the resin, causing impurities to be mixed in the product. When the product is working, internal defects will form in the mixed area, resulting in a decrease in product quality;

[0045] The integrated vacuum system in the integrated mold is made on the mold, and the vacuum bag will form an accumulation on the mold with a special-shaped surface, resulting in a very poor covering effect, resulting in poor product molding quality. Therefore, the integrated vacuum-assisted compression molding can only use the "semi-covering" form to make the vacuum system, that is, the vacuum bag is not placed on the lower mold surface of the mold. Therefore, the integrated vacuum-assisted compression molding is only suitable for thin plate products;

[0046] In the integrated mold, it is necessary to design an exhaust system on the compression molding mold, and integrate the press, vacuum pump, etc. into one. This will lead to difficulty in mold design, high manufacturing costs, and difficulty in mold maintenance and repair. In addition, the integrated vacuum system requires higher strength and better temperature resistance of vacuum auxiliary materials, which increases the price of auxiliary materials. Therefore, the integrated mold will result in high production costs.

[0047] On the other hand, in the present invention, since the compression molding mold and the vacuum molding mold are operated independently, the vacuum molding mold can be vacuumed after the pre-molding is completed, and the premix preform can be transferred into the compression molding mold for compression molding after the vacuuming is completed; during compression molding, the vacuum molding mold can be used to pre-evacuate the premix preform, which can avoid equipment idleness and improve compression efficiency; and vacuuming and compression molding do not interfere with each other, and will not affect the product quality of the final composite material product; at the same time, there is no need to consider the limitations of compression molding when performing the vacuuming operation, and the vacuum molding mold can be designed according to the product, which can meet the pre-molding and vacuuming of thin plates, special-shaped products, rotating bodies and the like, and can meet the pre-evacuation requirements of thick products, and has a wide range of applications; only one additional vacuum molding mold is required, and the mold is only used for vacuuming, so the mold design and manufacturing costs are low, the mold maintenance is simple, the vacuum system and the compression molding system are independent, and the requirements for vacuum auxiliary materials are low, so the vacuum cost can be reduced.

[0048] Furthermore, the vacuuming operation in step S1 is specifically as follows: using the premix to perform preforming on the vacuuming mold to obtain a premix preform, covering the vacuuming mold with the premix preform with a vacuum bag film, and installing a vacuum air nozzle on the vacuum bag film, and the vacuum air nozzle is connected to a vacuum pump to achieve vacuuming of the vacuuming mold with the premix preform. Because the mold cavity of the vacuuming mold is consistent with the mold cavity of the compression molding mold, the premix can be preformed to obtain the premix preform.

[0049] Specifically, in the present embodiment, a vacuum mold with a premix preform is covered on its surface by a vacuum bag film to form a pressure cavity, which is connected to a vacuum pump through a vacuum air nozzle; the outer surface of the premix preform is pressurized by utilizing the pressure difference between the vacuum pressure and the atmospheric pressure, so that the air, water vapor and other small gas molecules in the premix preform can be smoothly discharged; and the strong suction force provided by the vacuum pump can quickly reduce the air pressure in the vacuum mold, so that the gas molecules in the premix preform itself and between the premix preform and the vacuum mold can be quickly extracted, thereby shortening the exhaust time and improving the exhaust efficiency.

[0050] Furthermore, the vacuuming operation also includes sequentially covering the surface of the premix preform with an isolating breathable film and a breathable felt, wherein the isolating breathable film is disposed between the premix preform and the breathable felt.

[0051] The breathable membrane isolates the breathable felt to prevent impurities on the breathable felt from contaminating the premix preform of the product; the breathable felt absorbs and guides gas, which is beneficial to the discharge of air, water vapor and other small gas molecules in the premix preform, further enhancing the exhaust effect.

[0052] Furthermore, the number of the vacuum air nozzles is several and they are evenly distributed on the vacuum bag film; at the same time, the vacuum degree is maintained at ≤-0.095MPa during the vacuum operation to ensure that a sufficient pressure difference with the atmospheric pressure is formed, so that the small gas molecules in the premix preform are fully extracted.

[0053] Furthermore, in the step S2, during the compression molding process, when the resin contained in the premix preform in the compression molding mold is in a molten state (i.e., the molding system is heated to the resin gel temperature), the compression molding mold is only subjected to a pressure relief operation, and then pressure is applied to the compression molding mold again to complete the compression molding of the premix preform.

[0054] It is worth mentioning here that, because the premix is ​​formed by impregnating the fiber with resin, the compression molding process is to gradually apply pressure to the product while the compression molding mold and the premix preform are heated. The resin in the premix preform is reacting violently in a molten state. At this time, the temperature of the resin system is greater than 100°C. The violently reacting resin will carry out a large amount of water vapor and other small gas molecules; when the resin is in a molten state, the compression molding mold is only pressure-relieved, and the internal pressure of the compression molding mold is rapidly reduced. Pores are formed between the compression molding mold and the premix preform, and the small gas molecules volatilized by the violently reacting resin can be fully released from the pores. The small gas molecules in the premix can be carried out during the release process, thereby ensuring that the final composite product has fewer internal pores and the product quality is improved.

[0055] The traditional molding process is to continuously pressurize and gradually apply pressing pressure to the product. When the temperature of the heating system rises to the resin gel temperature, the resin has completely softened and is close to a fluid state due to the existence of pressure. At this time, the internal reinforcement system (referring to the fiber) of the product has become dense, and a resin-rich layer will form on the surface of the product, and the resin layer is also reacting violently. Because of the pressure, the molding system is close to a sealed state, and the air, water vapor and other small gas molecules carried out by the violent reaction and volatilization of the resin in the mold cannot be discharged. Therefore, the small gas molecules that are not discharged will affect the product quality.

[0056] Furthermore, the pressure-releasing operation specifically includes: removing the pressure applied by the outside to the compression molding die, and keeping the upper male mold and the lower female mold in the compression molding die in contact, while the pressure-releasing time is maintained at 30s to 60s. Specifically, the pressure applied by the outside refers to the pressure applied by the press to the compression molding die, that is, removing the pressure applied by the press to the compression molding die, and keeping the upper male mold and the lower female mold in the compression molding die in contact, and the pressure-releasing time is maintained at 30s to 60s. In a pressure-free state, a gap of 0.1mm to 0.2mm will be formed between the upper and lower molds, and the gap will provide a channel for the release of gas in the closed mold cavity.

[0057] Specifically, in this embodiment, only the pressure relief operation is to remove the external pressure on the compression molding die, so that the compression molding die is in a state of no force and the compression molding die maintains the state of contact between the upper male mold and the lower female mold, that is, the upper male mold is not raised, so as to avoid the problem of product scrapping caused by the collapse of the premix preform in the compression molding die. Because the resin molten state will last for 10 to 20 minutes, the time for pressure relief should not be too long or too short. Too long will directly lead to the extension of the time of the entire compression molding process, thereby reducing production efficiency and increasing production costs. In addition, too long exhaust time will cause the resin to be incompletely cured in the subsequent period, thus affecting the final quality; too short pressure relief should not be too short, because too short may cause the gas to be unable to be fully discharged, affecting the final quality.

[0058] Furthermore, after the pressure on the molding die is released, pressure is applied to the molding die again, and the applied pressure is the maximum pressure required for molding the composite material product; and the pressure is applied for a time when the resin is still in a molten state.

[0059] Applying maximum pressure when the resin is in a molten state allows the resin to completely fill every corner of the molding mold, thereby eliminating defects such as bubbles and gaps, and improving the density and uniformity of the product; and accelerating the flow and filling process of the resin, shortening the production cycle, and improving production efficiency; at the same time, the resin is evenly distributed in the molding mold, reducing the wear and damage of the molding mold due to uneven force, thereby extending the service life of the molding mold.

[0060] Furthermore, when the pressure is released, a gap of 0.1mm to 0.2mm is formed between the film surface of the upper male mold in the compression molding mold and the premix preform in the mold cavity of the compression molding mold; and the maximum pressure required for molding the composite product is applied to the compression molding mold again after the resin is in a molten state for 5min to 10min. The compression molding process is to gradually heat up the premix preform and gradually apply molding pressure to the product molding mold. For example, the gel temperature of a certain type of epoxy resin is 130℃. When the temperature rises to 130℃ during the compression process, the epoxy resin enters a molten state (the temperature of the resin system in the molten state is the resin gel temperature. The gel temperatures of various types of resins are different, so the timing of the resin entering the molten state is also different. For details, please refer to the resin gel temperature) and is reacting violently. Therefore, at the beginning of entering this temperature, the compression molding system can be depressurized and vented. After reacting at this temperature for 5min to 10min, all molding pressure needs to be applied to the molding mold to ensure that the resin fully fills the mold cavity and ensures the quality of product molding.

[0061] A composite material product is prepared by the method for eliminating internal pores of a composite material product during molding as described in any one of the above. The composite material product prepared by the method has greatly reduced internal pores, and the overall quality and performance of the final product are greatly improved.

[0062] In order to better highlight the effect of this application, the following examples are given:

[0063] Example 1

[0064] A composite material product, wherein the premix is ​​prepared during the compression molding process using the method for eliminating internal pores in the composite material product during the compression molding process described in the present application, namely, first placing the premix preform into a vacuum mold, and performing a vacuum operation on the vacuum mold with the premix preform to complete the first exhaust of the premix preform; the premix preform is separated from the vacuum mold, and the premix preform that has undergone the first exhaust is placed into a molding mold to compression mold the composite material product; and during the compression molding process, there is at least one operation of only relieving the pressure on the molding mold to complete the second exhaust of the premix preform. The left and right sections of the obtained product are as follows Figure 3 shown.

[0065] Comparative Example 1

[0066] A composite material product, wherein the premix preform is prepared in a molding process using an existing integrated molding mold (i.e., the vacuuming operation and the molding operation are in the same mold), and the left and right sections of the product are as follows Figure 1 shown.

[0067] Comparative Example 2

[0068] A composite material product, wherein the premix preform is first placed in a vacuum mold during the compression molding process, the vacuum mold with the premix preform is vacuumed to complete the first exhaust of the premix preform material, and then placed in a molding mold for compression molding in a conventional manner without exhausting the preform material. The left and right sections of the product are as follows Figure 2 shown.

[0069] By comparison Figure 1 , Figure 2 and Figure 3 It can be seen that the products produced by traditional compression molding have large and scattered internal pores and poor product quality; the products that are molded by evacuating the premix preform before compression molding have large and concentrated internal pores and average internal quality because they have been pre-evacuated once before compression molding; the products that are molded by evacuating the premix preform before venting the product during the compression molding stage have small and fewer internal pores and better internal quality.

[0070] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A method for eliminating internal pores in a composite material product during a molding process, characterized in that: The steps include: S1: First exhaust of the premix preform: placing the premix preform into a vacuum mold, and performing a vacuum operation on the vacuum mold with the premix preform to complete the first exhaust of the premix preform; S2: Second degassing of the premix preform: the premix preform is separated from the vacuum mold, and the premix preform that has been degassing for the first time is placed in a compression molding mold to be compression molded into a composite material product; and during the compression molding process, there is at least one operation of only relieving the pressure of the molding mold to complete the second degassing of the premix preform; Wherein: the mold cavity in the vacuum mold is consistent with the mold cavity in the compression molding mold.

2. A method for eliminating internal pores in a composite material product during a molding process according to claim 1, characterized in that: The vacuuming operation in step S1 is specifically as follows: using the premix to perform preforming on a vacuuming mold to obtain a premix preform, covering the vacuuming mold with the premix preform with a vacuum bag film, and installing a vacuum air nozzle on the vacuum bag film, and the vacuum air nozzle is connected to a vacuum pump to achieve vacuuming of the vacuuming mold with the premix preform.

3. A method for eliminating internal pores in a composite material product during a molding process according to claim 2, characterized in that: The vacuuming operation also includes sequentially covering the surface of the premix preform with an isolating breathable film and a breathable felt, wherein the isolating film is arranged between the premix preform and the breathable felt.

4. The method for eliminating internal pores of a composite material product during molding according to claim 2, characterized in that: The number of the vacuum air nozzles is several and they are evenly distributed on the vacuum bag film; meanwhile, the vacuum degree is maintained at ≤-0.095MPa during the vacuum operation.

5. The method for eliminating internal pores of a composite material product during molding according to claim 1, characterized in that: In the step S2, during the compression molding process, when the resin in the premix preform is in a molten state, the compression molding die is subjected to a pressure-releasing operation, and then pressure is applied to the compression molding die again to complete the compression molding of the premix preform.

6. The method for eliminating internal pores of a composite material product during molding according to claim 5, characterized in that: The pressure-releasing operation specifically includes: removing the pressure applied by the outside to the compression molding die, and keeping the upper male die and the lower female die in the compression molding die in contact, while the pressure-releasing time is kept at 30s to 60s.

7. A method for eliminating internal pores in a composite material product during a molding process according to claim 6, characterized in that: After the compression molding die is relieved of pressure, pressure is applied to the compression molding die again. The applied pressure is the maximum pressure required for molding the composite material product. The pressure is applied while the resin is still in a molten state.

8. The method for eliminating internal pores of a composite material product during molding according to claim 5, characterized in that: When the pressure is released, a gap of 0.1 mm to 0.2 mm is formed between the film surface of the upper male mold in the compression molding mold and the premix preform in the mold cavity of the compression molding mold; and the maximum pressure required for molding the composite product is applied to the compression molding mold again after the resin is in a molten state for 5 minutes to 10 minutes.

9. A composite material product, characterized in that: The composite material is prepared by the method for eliminating internal pores of a composite material product during a molding process as described in any one of claims 1 to 8.

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