An RTM mold and method for molding a braided composite material ducted fan blade

Abstract

This application provides an RTM mold and a method for forming braided composite ducted fan blades, belonging to the field of composite material molding technology. It includes an upper mold, a lower mold, a left mold, and a right mold. The upper mold is located directly above the lower mold. The left and right molds are installed opposite each other between the upper and lower molds through insertion openings. The inner surfaces of the upper and lower molds, the left and right molds cooperate to form a cavity to accommodate the braided composite material preform. The RTM mold provided in this application enables efficient, high-precision, and low-defect forming of complex irregular-shaped composite materials.

Description

Technical Field

[0001] This application relates to an RTM mold and a method for forming woven composite ducted fan blades, belonging to the field of composite material molding technology. Background Technology

[0002] Three-dimensional braided composite materials possess excellent properties such as lightweight and high strength, good structural designability, and ease of molding complex components. They are widely used in aerospace, transportation, and military energy fields, for example, in rocket throat liners, propeller blades, engine nozzles, missile nose cones, and carbon fiber vehicle frames. In contrast, two-dimensional braiding technology offers advantages such as low material loss and high automation, enabling the one-time molding of complex components and making it ideal for molding various curved surfaces and irregularly shaped structural parts.

[0003] While two-dimensional braiding technology offers numerous advantages, the composite molding of complex, irregularly shaped preforms after braiding is a crucial step in determining the final composite material product. To ensure the accuracy of the dimensions of complex, irregularly shaped structures, common composite molding processes include compression molding and resin transfer molding (RTM). However, compression molding is suitable for composite molding of preforms made from prepregs, while RTM is more suitable for composite molding of complex, irregularly shaped preforms made from dry fiber braiding. Nevertheless, both of these molding methods cannot avoid problems such as resin leakage and insufficient resin, which are significant shortcomings in current composite molding processes. Summary of the Invention

[0004] In view of this, this application firstly provides an RTM mold that can realize efficient, high-precision, and low-defect molding of complex irregular-shaped composite materials.

[0005] Specifically, this application is implemented through the following scheme:

[0006] An RTM mold includes an upper mold, a lower mold, a left mold, and a right mold.

[0007] The upper mold is located directly above the lower mold.

[0008] The upper mold includes a back side, an end side wall, and an inner side. The back side is provided with a locking bolt hole, and at least three sets of locking bolt holes are provided. The locking bolt holes are through holes and are distributed on the back side of the upper mold. There are two end side walls, and the side of the two end side walls facing the lower mold is a parting surface. A non-through hole positioning hole is provided on the parting surface. A sprue connection hole is provided on one of the end side walls. An upper groove is provided on the inner side near the end side wall. The sprue connection hole is a through hole. A sprue hole is provided on the inner side corresponding to the sprue connection hole. An L-shaped channel is formed from the sprue connection hole to the sprue hole.

[0009] The lower mold includes a back side, an end side wall, and an inner side. There are two end side walls, and the side of the two end side walls facing the upper mold is a parting surface. The parting surface is provided with a second locking thread hole and a second positioning hole. Both the second locking thread hole and the second positioning hole are not through holes. The glue outlet connection hole is provided on one of the end side walls and is not at the same end as the glue inlet connection hole. The inner side is provided with a lower groove away from the end side wall. The glue outlet connection hole is a through hole. The inner side corresponding to the glue outlet connection hole is provided with a glue outlet hole. A straight channel is formed from the glue outlet connection hole to the glue outlet hole.

[0010] The upper and lower slots are correspondingly arranged to form an insert. The left and right molds are installed between the upper and lower slots through the insert. The inner side of the upper mold, the inner side of the lower mold, the left mold, and the right mold cooperate to form a cavity to accommodate the woven composite material preform.

[0011] Furthermore, as a preferred option:

[0012] The upper mold pin hole is provided on the back side corresponding to the upper slot, and the lower mold pin hole is provided on the back side corresponding to the lower slot. The upper mold pin hole and the lower mold pin hole are provided in a corresponding manner and are both through holes, used to fix the upper mold, lower mold, left mold and right mold.

[0013] The locking bolt holes are provided in six groups of two, which are distributed at the two ends and the middle of the back side of the upper mold.

[0014] The back side of the upper mold is provided with several mold opening ejector screw thread holes, which are through holes.

[0015] The upper mold is provided with an upper mold handle on the end side wall.

[0016] A lower mold handle is provided on the end side wall of the lower mold.

[0017] The lower mold, left mold, and right mold are provided with sealing grooves at positions corresponding to the edge of the cavity, and the sealing grooves are filled with rubber rings.

[0018] The RTM mold proposed in this invention can directly produce composite material products without post-processing steps such as grinding and polishing, which greatly reduces production costs while ensuring the quality of composite materials. The design of structures such as locking bolt holes, glue inlet connection holes, positioning holes, and glue inlet holes can ensure that the final composite material will not have major defects such as insufficient glue or glue leakage.

[0019] The upper mold, lower mold, left mold, and right mold, which have the above-mentioned characteristics, form a mold assembly, and switch valves are respectively provided on both sides of the mold assembly. Therefore, the applicant's second objective is to provide a method for using the above-mentioned RTM mold to form composite material ducted fan blades, the steps of which are as follows:

[0020] Step 1: Check that the glue inlet and outlet are clear. After sealing the edges of the cavity, evenly apply release wax or release agent to the inner surface of the cavity.

[0021] Step two: Select the resin type according to the requirements of the woven composite ducted fan blades, ensuring that the viscosity of the selected resin does not exceed 600 mPa·s. First, tighten the left and right molds with the woven composite preform, then lock the upper and lower molds together. Connect the glue inlet and outlet connection holes to the external air compressor and vacuum pump, respectively.

[0022] Step 3: Open the valve connecting the vacuum pump and the mold assembly to check the overall airtightness of the mold. After reaching negative one atmosphere, turn on the air compressor and adjust the pressure value to no higher than 0.5 MPa. Open the valve connecting the air compressor and the mold assembly. When resin appears in the air pipe connected to the vacuum tank and there are no air bubbles, close both valves. Remove the vacuum tank and high-pressure tank, and place the entire mold in the oven. Set the oven's temperature program according to the resin curing process. Molding begins.

[0023] Step 4: After the mold has cooled down, remove the locking bolts, open the mold in reverse order of assembly, perform a preliminary inspection, remove excess resin, and obtain the molded woven composite material ducted fan blades.

[0024] The molding process proposed in conjunction with the RTM mold with the above features can achieve efficient, high-precision, and low-defect molding of complex irregular-shaped composite materials. In particular, the segmented RTM mold will help to assemble complex irregular-shaped preforms, reducing the extrusion, wrinkling, and damage of surface fibers during the assembly process.

[0025] Preferred,

[0026] In step one, the release wax or release agent is applied by smearing or spraying.

[0027] In step two:

[0028] A high-pressure tank is installed between the glue inlet connection hole and the air compressor. The resin tank after mixing and degassing is placed inside the high-pressure tank. The high-pressure tank and the glue inlet connection hole are connected by a high-pressure resistant air pipe.

[0029] A vacuum tank is installed between the glue outlet connection hole and the vacuum pump. The resin collection tank is placed in the vacuum tank to prevent the extracted resin from flowing into the vacuum pump. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is an assembly diagram of the RTM mold and ducted fan blades in this application;

[0032] Figure 2 This is a schematic diagram of the back side structure of the mold on the RTM in this application;

[0033] Figure 3 This is a schematic diagram of the inner side structure of the mold on the RTM in this application;

[0034] Figure 4 This is a schematic diagram showing the relative positional relationship between the glue inlet connection hole and the glue inlet hole in this application;

[0035] Figure 5 This is a schematic diagram of the inner side structure of the RTM lower mold in this application;

[0036] Figure 6 This is a schematic diagram of the back side structure of the RTM lower mold in this application;

[0037] Figure 7 This is a schematic diagram of the mold structure on the left side of the RTM in this application;

[0038] Figure 8 This is a schematic diagram of the mold structure on the right side of the RTM in this application;

[0039] Figure 9 Schematic diagram of adhesive injection into the ducted fan blades made of woven composite materials;

[0040] Figure 10 Schematic diagram of the forming process for woven composite material ducted fan blades;

[0041] Figure 11 This is a schematic diagram of the processing flow of this application.

[0042] Numbered in the diagram: 1. Upper mold; 11. Mold locking bolt hole one; 12. Mold opening ejector screw threaded hole; 13. Upper mold pin hole; 14. Upper mold handle; 15. Inlet connection hole; 16. Positioning hole one; 17. Inlet hole; 18. Upper slot; 1a. Back side; 1b. End side wall; 1c. Parting surface; 1d. Inner side; 1e. Cavity top; 2. Lower mold; 21. Mold locking threaded hole two; 22. Positioning hole two; 23. Lower mold pin hole; 24. Lower mold handle; 25. 1. Glue outlet hole; 26. Glue outlet connection hole; 27. Lower mold sealing ring groove; 28. Lower slot; 3. Left mold; 31. Pin hole one; 32. Sealing ring groove one; 4. Right mold; 41. Pin hole two; 42. Sealing ring groove two; 5. Mold assembly; 51. Switch valve; 52. Pressure-resistant air pipe; 6. Air compressor; 61. Resin tank; 62. High-pressure tank; 7. Vacuum pump; 71. Resin collection tank; 72. Vacuum tank; 8. Oven; A. Braided composite material preform. Detailed Implementation

[0043] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0044] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be located directly or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to that other component. The terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or position based on the orientation or position shown in the accompanying drawings, and are only for ease of description and should not be construed as limiting the present technical solution.

[0045] Example 1

[0046] This embodiment describes an RTM mold, combined with... Figure 1 It includes an upper mold 1, a lower mold 2, a left mold 3, and a right mold 4, with the upper mold 1 located directly above the lower mold 2.

[0047] Combination Figures 2 to 4The upper mold 1 includes a back side 1a, an end side wall 1b, a parting surface 1c, an inner side 1d, and a cavity top 1e. The back side 1a is provided with a locking bolt hole 11, which is a through hole. There are three sets of six locking bolt holes 11, distributed at the two ends and the middle of the back side 1a of the upper mold. There are two end side walls 1b. The side of the two end side walls 1b facing the lower mold 2 is the parting surface 1c. The non-through hole positioning hole 16 is provided on the parting surface 1c. The inlet connection hole 15 is provided on one of the end side walls. The inner side 1d is provided with an upper groove 18 near the end side wall. The inlet connection hole 15 is a through hole. The inner side corresponding to the inlet connection hole 15 is provided with an inlet hole 17. The inlet connection hole 15 and the inlet hole 17 form an L-shaped channel.

[0048] Combination Figure 5 , Figure 6 The lower mold 2 also includes a back side, an end side wall, and an inner side. There are two end side walls, and the two end side walls facing the upper mold 1 are parting surfaces. The parting surfaces are provided with a locking thread hole 21 and a positioning hole 22. Neither the locking thread hole 21 nor the positioning hole 22 is a through hole. The outlet connection hole 26 is provided on one of the end side walls. The outlet connection hole 26 is a through hole and is not at the same end as the inlet connection hole 15. The inner side is provided with a lower groove 28 at a position away from the end side wall. The inner side corresponding to the outlet connection hole 26 is provided with an outlet hole 27. A straight channel is formed from the outlet connection hole 26 to the outlet hole 27.

[0049] The upper slot 18 and the lower slot 28 are correspondingly set to form an insert. The left mold 3 and the right mold 4 are installed between the upper slot 1 and the lower slot 2 through the insert. The inner side of the upper mold 1 is provided with a cavity top 1e, and the inner side of the lower mold 2 is provided with a cavity bottom. The cavity top 1e and the cavity bottom are correspondingly set, and together with the left mold 3 and the right mold 4, they form a cavity to accommodate the woven composite material preform A.

[0050] In the above scheme:

[0051] An upper mold pin hole 13 is provided on the back side corresponding to the upper slot 18, and a lower mold pin hole 23 is provided on the back side corresponding to the lower slot 28. The upper mold pin hole 13 and the lower mold pin hole 23 are correspondingly provided and are both through holes. Figure 7 , Figure 8 The left mold and the right mold, which correspond to the upper mold pin hole 13 and the lower mold pin hole 23, are respectively provided with pin hole 1 31 and pin hole 2 41. Pins and other connecting parts are installed in the upper mold pin hole 13, the lower mold pin hole 23, pin hole 1 31 and pin hole 2 41 to complete the fixation of the upper mold 1, the lower mold 2, the left mold 3 and the right mold 4.

[0052] Four ejector screw threaded holes 12 are provided on the back side of the upper mold 1. The ejector screw threaded holes 12 are through holes.

[0053] For ease of installation, an upper mold handle 14 can be provided on the end side wall 1b of the upper mold 1; and a lower mold handle 24 can be provided on the end side wall of the lower mold 2. The upper mold handle 14 and the lower mold handle 24 can be provided separately or simultaneously.

[0054] Combination Figure 5 , Figure 7 , Figure 8 A lower mold sealing ring groove 27 is provided at the position corresponding to the edge of the cavity in the lower mold 2. A sealing ring groove 32 and a sealing groove 42 are respectively provided at the positions corresponding to the edge of the cavity in the left mold and the right mold. The lower mold sealing ring groove 27, sealing ring groove 32 and sealing groove 42 are filled with rubber rings for sealing resin.

[0055] The RTM mold proposed in this invention can directly produce composite material products without post-processing steps such as grinding and polishing, which greatly reduces production costs while ensuring the quality of composite materials. The design of structures such as locking bolt holes, glue inlet connection holes, positioning holes, and glue inlet holes can ensure that the final composite material will not have major defects such as insufficient glue or glue leakage.

[0056] The upper mold 1, lower mold 2, left mold 3, and right mold 4, when combined to form a mold assembly 5, allow for the molding of woven composite material ducted fan blades. Figure 11 The specific steps are as follows:

[0057] Step 1: Check if the glue inlet hole 17 and glue outlet hole 25 are unobstructed. After installing the sealing strips on each segment of the mold to complete the sealing treatment of the cavity edges, evenly cover the inner surface of the cavity with release wax or release agent by smearing or spraying.

[0058] Step 2: Select the resin type according to whether the woven composite ducted fan blades have requirements such as high temperature resistance, toughening and wear resistance. Ensure that the viscosity of the selected resin does not exceed 600 mPa·s. First, tighten the left mold 3 and the right mold 4 with the woven composite preform A, and then lock the upper mold 1 and the lower mold 2 to complete the assembly of the mold body 5.

[0059] Step 3, combined Figure 9 Connect the inlet port 15 and the outlet port 26 as follows: Figure 10 The external air compressor 6 and vacuum pump 7 are connected as shown:

[0060] A high-pressure tank 62 is provided between the glue inlet connection hole 15 and the air compressor 6. The resin tank 61 after mixing and degassing is placed in the high-pressure tank 62. The high-pressure tank 62 and the glue inlet connection hole 15 are connected by a high-pressure resistant air pipe 52.

[0061] A vacuum tank 72 is provided between the glue outlet connection hole 26 and the vacuum pump 7. The resin collection tank 71 is placed in the vacuum tank 72 to prevent the extracted resin from flowing into the vacuum pump 7.

[0062] Step 4: Open the switch valve 52 connecting the vacuum pump 7 and the mold assembly 5. Check the airtightness of the mold assembly 5. After reaching negative one atmosphere, turn on the air compressor 6 and adjust it to a suitable pressure value, generally not higher than 0.5 MPa. Open the switch valve connecting the air compressor 6 and the mold assembly 5. When resin appears in the air pipe connected to the vacuum tank 72 and there are no air bubbles, close both switch valves 52. After removing the vacuum tank 72 and the high-pressure tank 62, combine... Figure 10 Place the overall mold 5 in the oven 8, set the oven's temperature program according to the resin curing process, and mold.

[0063] Step 5: After the mold has cooled completely, remove the locking bolts and open the mold in reverse order of assembly. Use the set screws to open the upper mold. Perform a preliminary inspection and classification on the obtained composite material products. Clean the excess resin from the disassembled RTM mold pieces to obtain the molded woven composite ducted fan blades. Begin the preparation of the next part.

[0064] The molding process proposed in conjunction with the RTM mold with the above features can achieve efficient, high-precision, and low-defect molding of complex irregular-shaped composite materials. In particular, the segmented RTM mold will help to assemble complex irregular-shaped preforms, reducing the extrusion, wrinkling, and damage of surface fibers during the assembly process.

[0065] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. An RTM mold, characterized in that: It includes an upper mold, a lower mold, a left mold, and a right mold. The upper mold is located directly above the lower mold. The upper mold includes a back side, an end sidewall, and an inner side. The back side is provided with a locking bolt hole, and there are at least three sets of locking bolt holes. The locking bolt holes are through holes and are distributed on the back side of the upper mold. There are two end sidewalls, and the side of the two end sidewalls facing the lower mold is a parting surface. A non-through hole positioning hole is provided on the parting surface. The inlet connection hole is provided on one of the end sidewalls. An upper groove is provided on the inner side near the end sidewall. The inlet connection hole is a through hole. An inlet hole is provided on the inner side corresponding to the inlet connection hole. An L-shaped channel is formed from the inlet connection hole to the inlet hole. The lower mold includes two back sides, two end sidewalls, and two inner sides. There are two end sidewalls, and the two end sidewalls are parting surfaces facing the upper mold. The parting surfaces are provided with two locking thread holes and two positioning holes, neither of which are through holes. The glue outlet connection hole is provided on one of the end sidewalls and is not at the same end as the glue inlet connection hole. The inner side is provided with a lower groove away from the end sidewall. The glue outlet connection hole is a through hole. The inner side is provided with a glue outlet hole at the location corresponding to the glue outlet connection hole. A straight channel is formed from the glue outlet connection hole to the glue outlet hole. The upper and lower slots are correspondingly set to form an insert opening. The left mold and the right mold are installed opposite each other between the upper and lower slots through the insert opening. The inner side one, inner side two, left mold and right mold cooperate to form a cavity to accommodate the woven composite material preform. The upper mold pin hole is provided on the back side corresponding to the upper slot, and the lower mold pin hole is provided on the back side corresponding to the lower slot. The upper mold pin hole and the lower mold pin hole are provided in a corresponding manner and are both through holes. The left mold and the right mold corresponding to the upper mold pin hole and the lower mold pin hole are respectively provided with pin hole one and pin hole two. The pin connector is inserted into the upper mold pin hole, the lower mold pin hole, pin hole one, and pin hole two to complete the fixation of the upper mold, the lower mold, the left mold, and the right mold.

2. The RTM mold according to claim 1, characterized in that: The locking bolt holes are provided in six parts, with two holes per group, distributed at the two ends and the middle of the back side of the upper mold.

3. The RTM mold according to claim 1, characterized in that: The back side of the upper mold is provided with several mold opening ejector screw thread holes, which are through holes.

4. The RTM mold according to claim 1, characterized in that: The upper mold is provided with an upper mold handle on the end side wall.

5. An RTM mold according to claim 1, characterized in that: A lower mold handle is provided on the end side wall of the lower mold.

6. An RTM mold according to any one of claims 1 to 5, characterized in that: The lower mold, left mold, and right mold are provided with sealing grooves at positions corresponding to the edge of the cavity, and the sealing grooves are filled with rubber rings.

7. A method for forming composite material ducted fan blades using the RTM mold of claim 1, characterized in that, The steps are as follows: The upper mold, lower mold, left mold, and right mold form a complete mold assembly, with switch valves installed on both sides of the mold assembly. Step 1: Check that the glue inlet and outlet are clear. After sealing the edges of the cavity, evenly apply release wax or release agent to the inner surface of the cavity. Step two: Select the resin type according to the requirements of the woven composite ducted fan blades, ensuring that the viscosity of the selected resin does not exceed 600 mPa·s. First, tighten the left and right molds with the woven composite preform, then lock the upper and lower molds together. Connect the glue inlet and outlet connection holes to the external air compressor and vacuum pump, respectively. A high-pressure tank is installed between the glue inlet connection hole and the air compressor. The resin tank after mixing and degassing is placed inside the high-pressure tank. The high-pressure tank is connected to the glue inlet connection hole via a high-pressure resistant air pipe. A vacuum tank is provided between the glue outlet connection hole and the vacuum pump. The resin collection tank is placed in the vacuum tank to prevent the extracted resin from flowing into the vacuum pump. Step 3: Open the valve connecting the vacuum pump and the mold assembly to check the overall airtightness of the mold. After reaching negative one atmosphere, turn on the air compressor and adjust the pressure value to no higher than 0.5 MPa. Open the valve connecting the air compressor and the mold assembly. When resin appears in the air pipe connected to the vacuum tank and there are no air bubbles, close both valves. Remove the vacuum tank and high-pressure tank, and place the entire mold in the oven. Set the oven's temperature program according to the resin curing process. Molding begins. Step 4: After the mold has cooled down, remove the locking bolts, open the mold in reverse order of assembly, perform a preliminary inspection, remove excess resin, and obtain the molded woven composite material ducted fan blades.

8. A method for using an RTM mold to weave composite ducted fan blades according to claim 7, characterized in that: In step one, the release wax or release agent is applied by smearing or spraying.

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