RTM (Resin Transfer Molding) mold and method for preparing resin composite material by using RTM mold

Abstract

The invention discloses an RTM forming mold and a method for preparing a resin composite material through the RTM forming mold, and belongs to the field of composite material forming. Comprising a lower die and an upper die, the lower die is provided with a die cavity, an O-shaped sealing ring groove is formed in the upward side of the lower die, an O-shaped sealing ring is embedded in the groove, a leading-in interface and a leading-out interface are formed in the upper die, and an O-shaped sealing ring probing groove is formed in the downward side of the upper die. The die is characterized in that an inflation sealing ring groove is formed in the upward side of the lower die and surrounds the outer side of the O-shaped sealing ring groove, an inflation sealing ring is arranged in the inflation sealing ring groove and provided with an inflation and deflation nozzle, and the inflation and deflation nozzle corresponds to an inflation and deflation nozzle containing cavity formed in the upward side of the lower die in a concave mode. An inflatable sealing ring matching groove is formed in the downward side of the upper die; the method comprises the steps of early-stage preparation; laying fibers; injecting liquid epoxy resin; closing the mold; and curing and molding. The method has the advantages that dry spots of the resin composite material are avoided, excellent rigidity and strength are ensured, and the preparation efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material molding, and in particular relates to an RTM molding die, and also relates to a method for preparing a resin composite material by using the RTM molding die. Background Art

[0002] The aforementioned RTM stands for "resin transfer molding," and the resin mentioned above refers to epoxy resin. RTM is a method (also called a "process") for molding epoxy resin-based composite materials using a closed mold. Specifically, an upper mold and a lower mold form a cavity, and a dry fiber layer is placed within the cavity. Because the free height of the dry fiber layer exceeds the height of the cavity—that is, the cavity height is smaller than the free height of the dry fiber layer—the dry fiber layer is under pressure when the upper and lower molds are closed. This not only increases the fiber volume ratio of the finished resin composite, enhancing stiffness and strength, but also prevents defects such as delamination after molding.

[0003] In the prior art, the upper and lower molds are each provided with a C-shaped or semicircular groove with a concave cross-section at corresponding positions on the surfaces of the opposing sides and around each mold. An O-ring is embedded in the semicircular groove of the lower mold, which prevents the liquid epoxy resin from leaking outward during the resin injection and curing process. After the upper and lower molds are joined, bolts are used to secure the upper and lower molds. Liquid epoxy resin is then injected into the mold cavity using pressure. During this stage, the dry fiber layer previously laid in the mold cavity is soaked with the liquid epoxy resin, while excess liquid epoxy resin flows out of the outlet and is recycled. This process is a key step in determining the quality of the finished resin composite material. Once the dry fibers are soaked with the composite material, the entire mold is heated, accelerating the curing speed of the epoxy resin. Ultimately, the liquid epoxy resin forms a solid state through a cross-linking reaction and fuses with the multiple layers of fibers to form a resin composite material, thus obtaining an epoxy resin composite material.

[0004] Resin composites produced by RTM are widely used in the aerospace, automotive, and marine sectors. They have gained significant attention in recent years because they can produce smooth-surfaced parts without the need for prepreg, effectively reducing equipment and process costs. Furthermore, closed-mold molding eliminates the health risks of liquid epoxy resin and significantly reduces environmental pollution.

[0005] During the molding process of a resin composite using the aforementioned mold and process, the quality of the resin composite (also referred to as the "part") after curing and demolding depends on whether the dry fibers are fully impregnated with the liquid epoxy resin. Due to the high viscosity of epoxy resin, its penetration into the dry fiber layer within the cavity of the lower mold (i.e., the mold cavity) is relatively weak, meaning that the liquid epoxy resin flows slowly within the dry fiber layer. If the dry fiber layer is thick, it is easy for localized areas of dry fibers to be unimpregnated by the liquid epoxy resin. This can lead to dry spots after curing, resulting in a defective product and significantly weakening the stiffness and strength of the resin composite. Furthermore, because the mold is opaque, it is difficult to determine whether the dry fiber layer has been fully impregnated with the liquid epoxy resin. Conventional practice is to continue the resin injection process for a period of time, such as 10-30 minutes, after the liquid epoxy resin begins to flow from the outlet. While this approach can reduce the likelihood of dry spots, it also wastes liquid epoxy resin due to blindness and lengthens the injection process, impacting molding efficiency. Summary of the Invention

[0006] The task of the present invention is to provide an RTM molding die that helps to provide ideal equipment conditions for eliminating dry spots and ensures that the prepared resin composite material has excellent stiffness and strength.

[0007] Another task of the present invention is to provide a method for preparing a resin composite material using an RTM molding die, which has simple process steps and no harsh process elements, and can avoid dry spots in the prepared resin composite material and significantly improve the preparation efficiency.

[0008] The task of the present invention is accomplished in this way: an RTM molding mold includes a lower mold and an upper mold that cooperates with the lower mold, the lower mold has a mold cavity, and a connected O-ring sealing groove is formed on the surface of the upper side of the lower mold and around the four sides of the mold cavity, an O-ring is embedded in the O-ring sealing groove, and the upper part of the O-ring protrudes from the O-ring sealing groove, a group of lower mold bolt holes are opened on the lower mold in a spaced state, and a bolt is set on each of the group of lower mold bolt holes, and an introduction interface and a lead-out interface are set on the upper mold and in the area corresponding to the mold cavity, each of which protrudes from the upper surface of the upper mold and communicates with the mold cavity, and upper mold bolts equal in number to the group of lower mold bolt holes are opened at the position of the upper mold corresponding to the bolts. The hole is provided, and the bolt passes through the bolt hole of the upper mold and extends to the top of the upper mold and is equipped with a fixing nut. An O-ring insertion groove is provided on the downward side of the upper mold and at a position corresponding to the O-ring groove for the O-ring to protrude out of the O-ring groove. The characteristic is that an inflatable sealing ring groove is provided on the upward side of the lower mold and at a position surrounding the outside of the O-ring groove, an inflatable sealing ring is provided in the inflatable sealing ring groove, and the inflatable sealing ring has an inflation and deflation nozzle, which corresponds to the inflation and deflation nozzle accommodating cavity recessed on the upward side of the lower mold, and an inflatable sealing ring matching groove for matching with the inflatable sealing ring is provided on the downward side of the upper mold and at a position corresponding to the inflatable sealing ring groove.

[0009] In a specific embodiment of the present invention, the lower mold and the upper mold are made of metal material.

[0010] In another specific embodiment of the present invention, the metal material is steel, aluminum, copper, steel alloy, aluminum alloy or copper alloy.

[0011] In another specific embodiment of the present invention, a spacing distance of 10-20 mm is maintained between the inflatable sealing ring groove and the O-ring groove.

[0012] Another task of the present invention is accomplished by providing a method for preparing a resin composite material using an RTM molding die, comprising the following steps: A) Preliminary preparation: First, an RTM molding mold is prepared. The RTM molding mold includes a lower mold and an upper mold that matches the lower mold. The lower mold has a mold cavity. A connected O-ring sealing groove is formed on the surface of the upper side of the lower mold and around the four sides of the mold cavity. An O-ring is embedded in the O-ring sealing groove, and the upper part of the O-ring protrudes from the O-ring sealing groove. A group of lower mold bolt holes are opened in a spaced state on the lower mold, and a bolt is set on each of the group of lower mold bolt holes. An introduction interface and an extraction interface are set on the upper mold and in the area corresponding to the mold cavity, each of which protrudes from the upper surface of the upper mold and communicates with the mold cavity. Upper mold bolt holes equal in number to the group of lower mold bolt holes are opened at the position of the upper mold corresponding to the bolts, and the bolts extend through the upper mold bolt holes. The mold is extended to the top of the upper mold and is equipped with a fixing nut. An O-ring insertion groove is provided on the downward side of the upper mold and at a position corresponding to the O-ring groove for the O-ring to be inserted into. An inflation seal groove is provided on the upward side of the lower mold and at a position surrounding the outer side of the O-ring groove. An inflation seal groove is provided in the inflation seal groove. The inflation seal has an inflation and deflation nozzle, which corresponds to the inflation and deflation nozzle accommodating cavity concavely arranged on the upward side of the lower mold. An inflation seal matching groove for matching with the inflation seal is provided on the downward side of the upper mold and at a position corresponding to the inflation seal groove. The upper and lower molds are then cleaned, and demolding wax is applied in the mold cavity to obtain a mold. B) laying fibers, laying a dry fiber layer on the mold cavity of the lower mold described in step A) with the upper mold described in step A) removed; after the dry fiber layer is laid, first, the inflation device inflates the inflatable sealing ring through a pipeline connected to the inflation and deflation nozzle, and then the upper mold is returned to a state of cooperation with the lower mold; due to the expansion of the inflatable sealing ring, a non-closed space is formed between the opposite sides of the upper mold and the lower mold, and the sealing ring penetrates into the groove and releases the sealing cooperation with the O-ring; and the inflatable sealing ring cooperates with the inflatable sealing ring, so that the upper mold and the lower mold are in a sealed state with each other by means of the inflatable sealing ring; when the upper mold floats upward relative to the lower mold to the extent of the non-closed space, the fixing nut is rotated to form a sufficient seal between the inflatable sealing ring cooperation groove of the upper mold and the inflatable sealing ring; C) injecting liquid epoxy resin, first, plugging one end of a liquid epoxy resin inlet tube into the inlet interface described in step A), and connecting the other end of the liquid epoxy resin inlet tube to a resin injection mechanism serving as a liquid epoxy resin supply source, and plugging one end of a redundant liquid epoxy resin outlet tube into the outlet interface described in step A), and connecting the other end of the redundant liquid epoxy resin outlet tube to a resin collector, then operating the resin injection mechanism to sequentially inject liquid epoxy resin into the dry fiber layer through the liquid epoxy resin inlet tube and the inlet interface to infiltrate the dry fiber layer, and when the liquid epoxy resin flows out of the outlet interface, stopping the resin injection mechanism, and allowing the liquid epoxy resin flowing out of the outlet interface to enter the resin collector through the redundant liquid epoxy resin outlet tube, thereby obtaining a liquid epoxy resin-impregnated component impregnated with liquid epoxy resin; D) closing the mold, operating the inflation and deflation nozzles described in steps A) and B) to discharge gas from the inflation seal ring, thereby deflation of the inflation seal ring. Under the action of gravity, the upper mold descends to a state of closing the mold with the lower mold. In this closed state, the O-ring described in step A) is inserted into the groove and matched with the O-ring groove. The fixing nut described in step A) is tightened with a tool, so that the upper mold applies pressure to the liquid epoxy resin impregnated part obtained in step C) to increase the fiber volume ratio, thereby obtaining a liquid epoxy resin impregnated part. E) Curing and molding: heating the upper mold and the lower mold to cure the liquid epoxy resin infiltration member obtained in step D). After heating and curing, unscrewing the fixing nut in step D) and removing the upper mold, removing it from the mold cavity, and obtaining a resin composite material.

[0013] In another specific embodiment of the present invention, the cleaning of the upper mold and the lower mold in step A) is performed by using a tool or a detergent, wherein the tool cleaning is performed using a scraper or a shovel; and the detergent cleaning is performed using a solvent-based detergent, wherein the solvent-based detergent is acetone, methyl ethyl ketone, or mesityl oxide.

[0014] In another specific embodiment of the present invention, the release wax in step A) is TR-102 or Stonermold release 8.

[0015] In a further specific embodiment of the present invention, the fibers constituting the dry fiber layer in step B) are carbon fibers having a tensile strength of 3000-7000 MPa, a tensile modulus of 200-600 GPa, a compressive strength of 1000-3000 MPa, an interlaminar shear strength of 50-150 MPa, a flexural strength of 1500-2500 MPa, and a density of 1.5-2.0 g / cm 3 and a porosity of <1-2%.

[0016] In a further specific embodiment of the present invention, the liquid epoxy resin inlet pipe and the redundant liquid epoxy resin outlet pipe in step C) are both transparent PVC pipes.

[0017] The technical effect of the technical solution provided by the present invention is that: since an air-filled sealing ring groove is added to the lower mold of the structural system of the RTM molding mold and an air-filled sealing ring with an inflation and deflation nozzle is arranged in the air-filled sealing ring groove, an air-filled sealing ring matching groove that matches the air-filled sealing ring is correspondingly added to the upper mold, thereby providing favorable conditions for eliminating dry spots for the process of preparing resin composite materials, which is divided into two stages of injection and extrusion; since the preparation process steps are simple and there are no harsh process elements, it can avoid the occurrence of dry spots in the resin composite material, ensure excellent stiffness and strength, and significantly improve the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of the RTM molding die of the present invention; Figure 2 This is a state diagram of the upper mold and the lower mold in the first stage of the process of preparing the resin composite material according to the present invention; Figure 3 This is a state diagram of the upper mold and the lower mold in the second stage of the process of preparing the resin composite material according to the present invention. DETAILED DESCRIPTION

[0019] Example 1: Please see Figures 1 to 3 ,Depend on Figure 1 The RTM molding die structure shown is based on Figure 2 and Figure 3 The method for preparing a resin composite material in two stages of injection and extrusion includes the following steps: A) Preliminary preparation: First, an RTM molding mold is prepared. The RTM molding mold includes a lower mold 1 and an upper mold 2 that cooperates with the lower mold 1. The lower mold 1 has a mold cavity 11. A connected O-ring sealing groove 12 is formed on the surface of the upper side of the lower mold 1 and around the mold cavity 11. An O-ring 121 is embedded in the O-ring sealing groove 12, and the upper part of the O-ring 121 protrudes out of the O-ring sealing groove 12. A group of lower mold bolt holes 13 are opened in a spaced state on the lower mold 1, and each of the group of lower mold bolt holes 13 is provided with a bolt 131. In addition, an inlet interface 21 and an outlet interface 22 are provided in the area corresponding to the mold cavity 11, each of which protrudes from the upper surface of the upper mold 2 and communicates with the mold cavity 11. Upper mold bolt holes 23 equal in number to the group of lower mold bolt holes 13 are opened at the position of the upper mold 2 corresponding to the bolt 131. The bolts 131 extend through the upper mold bolt holes 23 to the top of the upper mold 2 and are equipped with fixing nuts 1311. On the lower side of the upper mold 2 and at the position corresponding to the O-ring groove 12, a hole for the O-ring 121 to protrude from the O-ring groove 12 is opened. The O-ring inserted into the groove 24 is an improvement point of the aforementioned RTM molding mold: an inflatable sealing ring groove 14 is provided on the upper side of the lower mold 1 and at a position surrounding the outer side of the O-ring groove 12. An inflatable sealing ring 141 is provided in the inflatable sealing ring groove 14. The inflatable sealing ring 141 has an inflating and discharging nozzle 1411. The inflating and discharging nozzle 1411 corresponds to the inflating and discharging nozzle accommodating cavity 15 concavely arranged on the upper side of the lower mold 1. A nozzle for inflating and discharging is provided on the lower side of the upper mold 2 and at a position corresponding to the inflatable sealing ring groove 14. The sealing ring 141 cooperates with the inflatable sealing ring matching groove 25, and then the upper mold 2 and the lower mold 1 are cleaned with a scraper, and TR-102 mold release wax is applied (also called "smeared") as a mold release wax in the mold cavity 11 to obtain a mold. In this embodiment, the upper mold 2 and the lower mold 1 are made of steel, such as stainless steel or mold steel. The inflatable sealing ring groove 14 and the O-ring groove 12 are kept at a distance of 10 mm. The O-ring 121 is a rubber ring, and the inflatable sealing ring 141 is a hollow cavity, that is, a rubber ring with an air cavity. Figure 1 As shown, since the upper die 2 and the lower die 1 are rectangular, the aforementioned set of bolts 131 has four, which are respectively distributed at the four corners of the lower die 1; B) Laying the fiber, laying a dry fiber layer on the mold cavity 11 of the lower mold 1 described in step A) in the state where the upper mold 2 described in step A) is removed, and after the dry fiber layer is laid, the inflation device first inflates the inflation seal ring 141 through the pipeline connected to the inflation and discharge nozzle 1411, and then returns the upper mold 2 to the state of matching with the lower mold 1, and due to the inflation of the inflation seal ring 141, a non-closed space 4 is formed between the opposite sides of the upper mold 2 and the lower mold 1, and the O-ring penetrates into the groove 24 to release the sealing cooperation with the O-ring 121, and the inflation seal ring cooperates with the inflation seal ring groove 25 to release the sealing cooperation with the inflation seal ring The upper mold 2 and the lower mold 1 are in a sealed state with each other by means of the inflatable sealing ring 141. When the upper mold 2 floats upward relative to the lower mold 1 to the extent of the non-closed space 4, the fixing nut 1311 is rotated to make the inflatable sealing ring matching groove 25 of the upper mold 2 and the inflatable sealing ring 141 form a sufficient seal. The fiber of the dry fiber layer described in this step is carbon fiber, and the tensile strength of the carbon fiber is 3000MPa, the tensile modulus is -600GPa, the compressive strength is 1000MPa, the interlayer shear strength is 50MPa, the bending strength is 2500MPa, and the density is 2g / cm 3 and a porosity of <1%.

[0020] C) Injecting liquid epoxy resin, first, one end of a liquid epoxy resin inlet tube 5 is plugged into the inlet interface 21 described in step A), and the other end of the liquid epoxy resin inlet tube 5 is connected to a resin injection mechanism serving as a liquid epoxy resin supply source, and one end of a redundant liquid epoxy resin outlet tube 6 is plugged into the outlet interface 22 described in step A), and the other end of the redundant liquid epoxy resin outlet tube 6 is connected to a resin collector, then the resin injection mechanism is put into operation, and the liquid epoxy resin is sequentially introduced into the dry fiber layer through the liquid epoxy resin inlet tube 5 and the inlet interface 21 to infiltrate the dry fiber layer, and when the liquid epoxy resin flows out from the outlet interface 22, the resin injection mechanism is stopped, and the liquid epoxy resin flowing out from the outlet interface 22 enters the resin collector through the redundant liquid epoxy resin outlet tube 6, to obtain the following Figure 2 The liquid epoxy resin impregnated part 3 after being impregnated with liquid epoxy resin in the mold cavity 11 is shown as the injection part after the liquid epoxy resin is injected. The liquid epoxy resin inlet pipe 5 and the redundant liquid epoxy resin outlet pipe 6 described in this step are both transparent PVC. It can be seen that this step is the first stage in the preparation process, which is the injection stage. The state of the upper mold 2 and the lower mold 1 can be determined by the following formula: Figure 2 As shown; D) Mold closing: by operating the inflation and deflation nozzle 1411 described in steps A) and B), the gas in the inflation seal ring 141 is discharged to deflate the inflation seal ring 141. Under the action of gravity, the upper mold 2 descends to a mold closing state with the lower mold 1. In this mold closing state, the O-ring described in step A) is inserted into the groove 24 and matched with the O-ring groove 12, and the fixing nut 1311 described in step A) is tightened with a tool, so that the upper mold 2 applies pressure to the liquid epoxy resin impregnated part 3 obtained in step C) to increase the fiber volume ratio, thereby obtaining a liquid epoxy resin impregnated part 7. It can be seen that this step is the second stage in the preparation process, and the second stage is the extrusion stage. The state of the upper mold 2 and the lower mold 1 can be determined by Figure 3 As shown; E) Curing and forming: The upper mold 2 and the lower mold 1 are heated to cure the liquid epoxy resin-impregnated member 7 obtained in step D). After heating and curing, the fixing nut 1311 described in step D) is unscrewed, the upper mold 2 is removed, and the member is removed from the mold cavity 11 to obtain a resin composite material. Due to the wide variety of epoxy resins, epoxy resins with different physical and chemical properties have different curing temperatures and curing times. However, since the curing temperatures and curing times for different liquid epoxy resins are well known in the art, they will not cause confusion to those skilled in the art. For example, the curing temperature of low-temperature curing epoxy resins ranges from room temperature to 80°C, and the curing time is 24 hours at room temperature or 1-4 hours at 60°C. Another example is the curing temperature of medium-temperature curing epoxy resins, which ranges from 80-120°C and 30-180 minutes. Another example is the curing temperature of high-temperature curing epoxy resins, which ranges from 120-200°C (or even higher), and 15-60 minutes. Therefore, the applicant does not need to specifically limit the curing temperature and time in this embodiment.

[0021] Example 2: In step A), the materials of the upper mold 2 and lower mold 1 are changed to aluminum alloy, acetone is used for cleaning, Stoner Mold Release 8 is used instead of mold release wax, and the distance between the inflatable seal ring groove 14 and the aforementioned O-ring seal groove 12 is changed to 20 mm. In step B), the carbon fiber strength is changed to 7000 MPa, the tensile modulus is changed to 200 GPa, the compressive strength is changed to 1500 MPa, the interlaminar shear strength is changed to 100 MPa, the flexural strength is changed to 1500 MPa, and the density is changed to 1.5 g / cm 3 The porosity was changed to <2%. The rest was the same as described in Example 1.

[0022] Example 3: In step A), only the materials of the upper mold 2 and lower mold 1 are changed to copper alloy, the cleaning agent is changed to methyl ethyl ketone, the mold release wax is changed to Stoner Mold Release 8, and the distance between the inflatable seal ring groove 14 and the aforementioned O-ring seal groove 12 is changed to 15 mm. In step B), the carbon fiber strength is changed to 4500 MPa, the tensile modulus is changed to 350 GPa, the compressive strength is changed to 3000 MPa, the interlaminar shear strength is changed to 75 MPa, the flexural strength is changed to 2200 MPa, and the density is changed to 2 g / cm 3 The porosity is changed to <1.5%. The rest is the same as described in Example 1.

[0023] Example 4: In step A), only the materials of the upper mold 2 and lower mold 1 are changed to steel alloy, the cleaning agent is changed to mesityl oxide, the mold release wax is changed to Stoner Mold Release 8, and the distance between the inflation seal groove 14 and the aforementioned O-ring seal groove 12 is changed to 12 mm. In step B), the carbon fiber strength is changed to 6000 MPa, the tensile modulus is changed to 450 GPa, the compressive strength is changed to 2000 MPa, the interlaminar shear strength is changed to 135 MPa, the flexural strength is changed to 1800 MPa, and the density is changed to 1.8 g / cm 3 The porosity was changed to <1.2%. The rest was the same as described in Example 1.

[0024] The beneficial effects of Examples 1 to 4 of the present invention are reflected in reducing the likelihood of dry spots and shortening working hours to improve production efficiency. During the injection phase, because the fibers are not over-extended, their permeability is higher than in conventional processes, allowing the liquid epoxy resin to fully infiltrate their microstructures. Consequently, the likelihood of dry spots is reduced compared to conventional processes. Furthermore, during the subsequent extrusion phase, due to the reduced volume of the mold cavity (i.e., mold cavity 11), excess liquid epoxy resin is squeezed (i.e., blocked) by the O-ring 121 and flows toward the fiber layup, ultimately exiting through the outlet, similarly reducing the likelihood of dry spots.

[0025] The shortened process time and improved production efficiency achieved by the present invention's preparation method are also attributed to the improved fiber permeability during the injection phase. In conventional processes, the fiber layup is already squeezed, resulting in lower permeability. Consequently, the liquid epoxy resin flows slowly through the fibers, requiring a longer time to pass through the fibers and exit the outlet. This also increases the likelihood of dry spots forming within the fibers, indicating insufficient resin saturation. To reduce the likelihood of dry spots, after the liquid has exited the mold, the injection time is typically extended by 10 to 30 minutes to ensure adequate fiber saturation. When using the mold structure of the present invention, during the first injection phase, the fibers are not over-extruded and have higher permeability. Therefore, under the same environmental and part dimensions, the liquid epoxy resin is more easily absorbed into the fiber structure, and the time it takes to exit the outlet is also shortened. Any excess liquid epoxy resin that flows out of the outlet is extruded during the second, extrusion phase. Due to the smaller mold cavity, the epoxy resin is forced through the fibers and toward the outlet, further reducing the likelihood of dry spots. Therefore, after extrusion, mold heating and curing can begin immediately without further injection. This will undoubtedly not only reduce the amount of epoxy resin used, reduce the waste of raw materials, and take less time to complete the same operation, but also improve the production efficiency of resin composite materials.

Claims

1. An RTM molding die, comprising a lower die (1) and an upper die (2) matched with the lower die (1), the lower die (1) having a die cavity (11), a connected O-ring groove (12) formed on the surface of the upper side of the lower die (1) and surrounding the die cavity (11), an O-ring (121) embedded in the O-ring groove (12), and the upper part of the O-ring (121) protrudes out of the O-ring groove (12), a group of lower die bolt holes (13) are opened in a spaced state on the lower die (1), each of the group of lower die bolt holes (13) is provided with a bolt (131), and a bolt (131) is provided on the upper die (2) and in the area corresponding to the die cavity (11). There is an introduction interface (21) and an outlet interface (22) each extending out of the upper surface of the upper die (2) and communicating with the die cavity (11); upper die bolt holes (23) equal in number to the group of lower die bolt holes (13) are provided at positions of the upper die (2) corresponding to the bolts (131); the bolts (131) extend through the upper die bolt holes (23) to the top of the upper die (2) and are provided with fixing nuts (1311); an O-ring insertion groove (24) for the O-ring (121) extending out of the O-ring groove (12) is provided on the downward side of the upper die (2) and at a position corresponding to the O-ring groove (12), wherein the O-ring insertion groove (24) is provided, wherein the O-ring (121) extending out of the O-ring groove (12) is inserted into the O-ring insertion groove. The invention is characterized in that: An inflatable sealing ring groove (14) is provided on the upward side of the lower mold (1) and at a position surrounding the outer side of the O-ring groove (12). An inflatable sealing ring (141) is provided in the inflatable sealing ring groove (14). The inflatable sealing ring (141) has an inflating and discharging nozzle (1411). The inflating and discharging nozzle (1411) corresponds to the inflating and discharging nozzle accommodating cavity (15) recessed on the upward side of the lower mold (1). An inflatable sealing ring matching groove (25) for matching with the inflatable sealing ring (141) is provided on the downward side of the upper mold (2) and at a position corresponding to the inflatable sealing ring groove (14).

2. The RTM molding die according to claim 1, characterized in that: The lower mold (1) and the upper mold (2) are made of metal material.

3. The RTM molding die according to claim 2, characterized in that: The metal material is steel, aluminum, copper, steel alloy, aluminum alloy or copper alloy.

4. The RTM molding die according to claim 1, wherein: A spacing distance of 10-20 mm is maintained between the inflatable sealing ring groove (14) and the O-type sealing ring groove (12).

5. A method for preparing a resin composite material using the RTM molding die according to claim 1, characterized in that: The following steps are involved: A) Preliminary preparation: first, an RTM molding mold as claimed in claim 1 is prepared, cleaned, and mold release wax is coated in the mold cavity (11) to obtain a mold; B) laying fibers, laying a dry fiber layer on the mold cavity (11) of the lower mold (1) in step A) while removing the upper mold (2) in step A), after the dry fiber layer is laid, the inflation device first inflates the inflation seal ring (141) through the pipeline connected to the inflation and deflation nozzle (1411), and then returns the upper mold (2) to the state of matching with the lower mold (1), and due to the expansion of the inflation seal ring (141), a non-closed space (4) is formed between the opposite sides of the upper mold (2) and the lower mold (1), and the O-type seal The ring probe groove (24) releases the sealing fit with the O-ring (121), and the upper mold (2) and the lower mold (1) are in a sealed state with each other by the sealing fit of the inflatable sealing ring fitting groove (25) and the inflatable sealing ring (141). When the upper mold (2) floats upward relative to the lower mold (1) to the extent of the non-closed space (4), the fixing nut (1311) is rotated to form a sufficient seal between the inflatable sealing ring fitting groove (25) of the upper mold (2) and the inflatable sealing ring (141); C) injecting liquid epoxy resin, firstly, one end of a liquid epoxy resin introduction tube (5) is plugged into the introduction interface (21) described in step A), and the other end of the liquid epoxy resin introduction tube (5) is connected to the resin injection mechanism as the liquid epoxy resin supply source, and one end of a redundant liquid epoxy resin outlet tube (6) is plugged into the outlet interface (22) described in step A), and the other end of the redundant liquid epoxy resin outlet tube (6) is connected to the resin collector, and then the resin is injected into the liquid epoxy resin tube. The injection mechanism enters a working state, and the liquid epoxy resin is sequentially introduced into the dry fiber layer through the liquid epoxy resin introduction pipe (5) and the introduction interface (21) to infiltrate the dry fiber layer. When the liquid epoxy resin flows out from the outlet interface (22), the resin injection mechanism stops working, and the liquid epoxy resin flowing out from the outlet interface (22) enters the resin collector through the redundant liquid epoxy resin outlet pipe (6), thereby obtaining a liquid epoxy resin infiltrated part (3) infiltrated with the liquid epoxy resin. D) closing the mold, by operating the inflation and deflation nozzles (1411) described in steps A) and B), the gas in the inflation seal ring (141) is discharged to deflate the inflation seal ring (141), and under the action of gravity, the upper mold (2) descends to a state of closing the mold with the lower mold (1), in which the O-ring probing groove (24) described in step A) is matched with the O-ring groove (12), and the fixing nut (1311) described in step A) is tightened with a tool, so that the upper mold (2) applies pressure to the liquid epoxy resin impregnated part (3) obtained in step C) to increase the fiber volume ratio, thereby obtaining a liquid epoxy resin impregnated part (7); E) Curing and molding, heating the upper mold (2) and the lower mold (1) to cure the liquid epoxy resin infiltration member (7) obtained in step D), and after heating and curing, unscrewing the fixing nut (1311) described in step D) and evacuating the upper mold (2), taking it out from the mold cavity (11), and obtaining a resin composite material.

6. The method for preparing a resin composite material using an RTM molding die according to claim 5, characterized in that: The cleaning of the upper mold (2) and the lower mold (1) in step A) is performed by using a tool or a cleaning agent. The tool cleaning is performed by using a scraper or a shovel. The cleaning agent cleaning is performed by using a solvent-based cleaning agent. The solvent-based cleaning agent is acetone, methyl ethyl ketone or isopropyl alcohol.

7. The method for preparing a resin composite material using an RTM molding die according to claim 5, wherein: The release wax in step A) is TR-102 or Stoner mold release 8.

8. The method for preparing a resin composite material using an RTM molding die according to claim 5, wherein: The fibers constituting the dry fiber layer in step B) are carbon fibers having a tensile strength of 3000-7000 MPa, a tensile modulus of 200-600 GPa, a compressive strength of 1000-3000 MPa, an interlaminar shear strength of 50-150 MPa, a flexural strength of 1500-2500 MPa, and a density of 1.5-2.0 g / cm 3 and a porosity of <1-2%.

9. The method for preparing a resin composite material using an RTM molding die according to claim 5, wherein: The liquid epoxy resin inlet pipe (5) and the redundant liquid epoxy resin outlet pipe (6) described in step C) are both transparent PVC pipes.

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