Mold for forming polygonal composite tube based on autoclave forming and method of manufacture

Abstract

This invention belongs to the field of composite material manufacturing technology, and provides a composite material polygonal tube forming mold and manufacturing method based on autoclave molding. The method includes: S1, laying carbon fiber prepreg on the forming surface of the core mold; S2, installing several outer mold flat plates on the outer surface of the prepreg, and fixing the outer mold flat plates to the core mold using positioning connectors, and placing an outer mold radius block between two outer mold flat plates; S3, encapsulating the core mold, outer mold flat plates, and outer mold radius block to form a vacuum-sealed bag; S4, sending the encapsulated mold to an autoclave for curing; S5, after curing, removing the core mold, outer mold flat plates, and outer mold radius block to obtain the composite material polygonal tube. This invention solves the problems of fiber continuity disruption and poor radius porosity while ensuring the dimensional accuracy of the inner and outer surfaces.

Description

Technical Field

[0001] This invention belongs to the field of composite material manufacturing technology, and particularly relates to a composite material polygon tube forming mold and manufacturing method based on autoclave forming. Background Technology

[0002] Composite material tubular parts have a wide range of applications, and their lightweight and high-strength characteristics make them particularly suitable for the aerospace field. Traditional composite material tubing typically employs molding processes to ensure dimensional accuracy of the inner and outer surfaces. Due to the inherent properties of composite materials, the thickness of the prepreg before curing is greater than its thickness after curing. This characteristic leads to a thicker prefabricated part after installation. Furthermore, in traditional tubular parts with upper and lower molded structures, the molded surface is prone to fabric trapping during curing, disrupting the continuity of the outermost fibers. Additionally, the overall mold structure cannot provide adequate pressure to the part at the radius (R-corners), resulting in poor porosity and even bridging. Summary of the Invention

[0003] The purpose of this invention is to provide a composite material polygon tube forming mold and manufacturing method based on autoclave molding, so as to solve the above-mentioned problems and achieve the goal of solving the problems of fiber continuity disruption and poor R-angle porosity while ensuring the dimensional accuracy of the inner and outer surfaces.

[0004] To achieve the above objectives, the present invention provides the following solution: a composite material polygonal tube molding mold based on autoclave molding, wherein the molding mold is sealed and then sent to an autoclave for curing, the mold comprising:

[0005] The core mold has a prism structure, and all sides of the core mold are forming surfaces;

[0006] The outer mold assembly includes several outer mold flat plates and several outer mold R-corner blocks. The several outer mold flat plates are respectively arranged corresponding to each forming surface of the core mold, and a positioning connector is provided between the outer mold flat plates and the core mold. The outer mold R-corner blocks are arranged between two adjacent outer mold flat plates, and the outer mold R-corner blocks are adapted to the edges of the outer mold flat plates.

[0007] Preferably, the two ends of several forming surfaces of the core mold are respectively provided with annular core mold allowance lines and core mold product lines, the core mold allowance lines are located outside the core mold product lines, and the positioning connectors are located outside the core mold allowance lines.

[0008] Preferably, the positioning connector includes two sets of core mold positioning holes and two sets of core mold bolt holes formed on the core mold forming surface. The two core mold positioning holes and the two core mold bolt holes are respectively located at both ends of the core mold forming surface, and positioning pins are fixedly connected in the core mold positioning holes.

[0009] It also includes two sets of outer mold positioning holes and two sets of outer mold connecting holes formed on the outer mold flat plate. The two outer mold positioning holes and the two outer mold connecting holes are respectively located at both ends of the outer mold flat plate. The outer mold positioning holes are correspondingly provided with the positioning pins. The outer mold connecting holes are detachably connected to the core mold bolt holes by bolts.

[0010] Preferably, the two ends of the core mold are provided with core mold through holes along the axis of the core mold.

[0011] A method for manufacturing composite polygonal tubes based on autoclave molding includes the following steps:

[0012] S1. Lay carbon fiber prepreg on the molding surface of the core mold;

[0013] S2. Install several outer mold flat plates on the outer surface of the prepreg after it has been laid, and use positioning connectors to fix the several outer mold flat plates to the core mold, and place an outer mold R-corner block between the two outer mold flat plates;

[0014] S3. Encapsulate the core mold, outer mold flat plate, and outer mold R-corner block to form a vacuum-sealed bag;

[0015] S4. After sealing, the mold is sent to an autoclave for curing;

[0016] S5. After curing, remove the core mold, outer mold flat plate and outer mold R-corner block to obtain the composite material polygonal tube.

[0017] Preferably, the two ends of several molding surfaces of the core mold are respectively provided with annular core mold allowance lines and core mold product lines. The core mold allowance lines are located outside the core mold product lines. The positioning connectors are located outside the core mold allowance lines. In step S1, the carbon fiber prepreg laid should extend beyond the core mold allowance lines on both sides and be edged with unvulcanized rubber.

[0018] The installation process requires multiple vacuuming and pre-pressurization processes before installation.

[0019] Preferably, in step S2, after placing the outer mold R-corner block, the outer mold R-corner block is fixed with high-temperature resistant tape.

[0020] Preferably, in step S3, after the core mold is assembled with several outer mold flat plates and outer mold R-corner blocks, the outer layer is sequentially covered with an isolation film, a breathable felt and a vacuum bag to encapsulate the core mold, outer mold flat plates and outer mold R-corner blocks;

[0021] Auxiliary materials need to be placed on the outer side of the outer mold flat plate, the outer mold R-corner block, and the inner side of the core mold to form a vacuum-sealed bag.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] 1. This invention proposes a composite polygon tube molding die and manufacturing method based on autoclave molding. After laying prepreg on the surface of the core mold, each molding surface and R-corner is segmented along the R-corner edge by the outer mold assembly. During the autoclave curing stage, uniform, synchronous and stable pressure is applied to the parts by synchronously pressing and moving each outer module into the shaft, thereby producing a composite polygon tube with accurate product dimensions, continuous fibers and low porosity.

[0024] 2. Due to the inherent properties of composite materials, the thickness of the prepreg before curing is greater than that after curing. This characteristic leads to a thicker prefabricated part after installation. Compared to traditional pipe parts with upper and lower molded structures, where fabric is easily trapped at the molded surface during curing, resulting in the disruption of the outermost fiber continuity and reduced part performance, this invention divides the outer mold into blocks along the R-corner edge. Each planar area and R-corner area of ​​the polygonal tube will have a separate outer module. The pre-assembly process before curing will evenly distribute the impact of the thicker part, preventing the disruption of fiber continuity caused by fabric trapping.

[0025] 3. Compared with the auxiliary materials on the outer surface of parts in traditional autoclave processes, although they can provide uniform, continuous and stable pressure for the parts, the outer surface of the parts is not smooth and the size and appearance do not meet the requirements of tubular products. Based on this, the present invention adds an outer mold assembly to the outer surface of the parts. The smooth surface of the outer mold assembly contacts the parts, so that the internal quality of each area can reach the aerospace quality level requirements while meeting the dimensional accuracy of the parts. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the core mold of the present invention;

[0028] Figure 2 This is a schematic diagram of the mold assembly of the core mold, outer mold flat plate, and outer mold R-corner block of the present invention;

[0029] Figure 3 The polygonal composite material tube after demolding according to an embodiment of the present invention;

[0030] Among them, 1. Core mold; 2. Core mold allowance line; 3. Core mold product line; 4. Core mold positioning hole; 5. Core mold bolt hole; 6. Outer mold flat plate; 7. Outer mold R-corner block; 8. Core mold through hole; 9. Outer mold positioning hole; 10. Outer mold connection hole. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1:

[0034] Reference Figures 1-3 This invention provides a composite material polygonal tube molding die based on autoclave molding. After the molding die is encapsulated, it is sent to an autoclave for curing. The die includes:

[0035] Core mold 1 has a prism structure, and all sides of core mold 1 are molding surfaces;

[0036] The outer mold assembly includes several outer mold flat plates 6 and several outer mold R-corner blocks 7. The several outer mold flat plates 6 are respectively arranged corresponding to each forming surface of the core mold 1, and a positioning connector is provided between the outer mold flat plates 6 and the core mold 1. The outer mold R-corner blocks 7 are arranged between two adjacent outer mold flat plates 6, and the outer mold R-corner blocks 7 are adapted to the edge of the outer mold flat plates 6.

[0037] The core mold 1 is a metal male mold, whose main function is to facilitate the laying of carbon fiber unidirectional prepreg and to define the structure of the composite polygonal tube through its own geometry. Several outer mold flat plates 6 and several outer mold R-corner blocks 7 can form a metal composite mold block, whose main function is to apply uniform, synchronous, and stable pressure to the part during the curing stage. Overall, this invention divides each forming surface and R-corner into blocks along the R-corner edge of the outer mold. During the curing stage, the outer modules can be used to synchronously press and move inward to apply uniform, synchronous, and stable pressure to the part, thereby producing a composite polygonal tube with accurate product dimensions, continuous fibers, low porosity, and high internal quality in each area. At the same time, the block treatment of the outer mold can also evenly distribute the impact of the part's thickness before curing, and will not cause the fiber continuity to be damaged due to fabric trapping.

[0038] Further optimization of the scheme: the structure of the core mold 1 and the outer mold assembly can be customized according to the required structure of the composite polygonal tube, so that the composite polygonal tube can be a tube with a constant cross section or a tube with a non-constant cross section, and the number of sides and geometric dimensions of the part can be adjusted according to different load conditions.

[0039] In a further optimized design, annular core mold allowance lines 2 and core mold product lines 3 are respectively provided at both ends of several molding surfaces of the core mold 1. The core mold allowance lines 2 are located outside the core mold product lines 3, and the positioning connectors are located outside the core mold allowance lines 2.

[0040] like Figure 1 As shown, the main function of the mandrel allowance line 2 is to provide a boundary reference for the laying of carbon fiber unidirectional prepreg and to ensure that the demolded part has sufficient machining allowance after curing.

[0041] The scheme is further optimized. The positioning connector includes two sets of core mold positioning holes 4 and two sets of core mold bolt holes 5 opened on the forming surface of the core mold 1. The two core mold positioning holes 4 and the two core mold bolt holes 5 are located at both ends of the forming surface of the core mold 1, and positioning pins are fixedly connected in the core mold positioning holes 4.

[0042] It also includes two sets of outer mold positioning holes 9 and two sets of outer mold connecting holes 10 opened on the outer mold flat plate 6. The two outer mold positioning holes 9 and the two outer mold connecting holes 10 are located at both ends of the outer mold flat plate 6, respectively. The outer mold positioning holes 9 are correspondingly set with the positioning pins, and the outer mold connecting holes 10 are detachably connected to the core mold bolt holes 5 by bolts.

[0043] like Figure 2 As shown, bolts are used to connect the outer mold connecting hole 10 and the core mold bolt hole 5 via threads, which can prevent the outer mold flat plate 6 from falling off. The locating pin is slidably connected to the outer mold locating hole 9, which can provide positioning for the installation of the outer mold flat plate 6, and also provide a limit to the movement direction of the outer mold flat plate 6 in the axial direction during the curing stage, so as to accurately apply pressure to the part.

[0044] To further optimize the design, through holes 8 are provided at both ends of the core mold 1 along its axis.

[0045] like Figure 2 As shown, the main function of the through hole 8 in the core mold is to facilitate air circulation during the curing stage. That is, the through hole 8 in the core mold allows the air in the autoclave to contact the various parts of the core mold 1 more quickly, especially the part near the middle of the core mold 1, which can improve the heat transfer efficiency.

[0046] Example 2:

[0047] A method for manufacturing composite polygonal tubes based on autoclave molding includes the following steps:

[0048] S1. Lay carbon fiber prepreg on the molding surface of core mold 1;

[0049] S2. Install several outer mold flat plates 6 on the outer surface of the prepreg after it has been laid, and use positioning connectors to fix the several outer mold flat plates 6 to the core mold 1, and place an outer mold R-corner block 7 between the two outer mold flat plates 6.

[0050] In step S2, after inserting the outer mold flat plate 6 into the positioning pin, use bolts to pass through the outer mold connecting hole 10 and connect it to the core mold bolt hole 5 to prevent the outer mold flat plate 6 from falling off.

[0051] S3. Encapsulate the core mold 1, the outer mold flat plate 6, and the outer mold R-corner block 7 to form a vacuum-sealed bag;

[0052] S4. After sealing, the mold is sent to an autoclave for curing;

[0053] S5. After curing, remove the core mold 1, outer mold flat plate 6 and outer mold R corner block 7 to obtain the composite material polygonal tube.

[0054] To further optimize the scheme, the two ends of several molding surfaces of the core mold 1 are respectively provided with annular core mold allowance lines 2 and core mold product lines 3. The core mold allowance lines 2 are located outside the core mold product lines 3. The positioning connectors are set outside the core mold allowance lines 2. In step S1, the carbon fiber prepreg laid should extend beyond the core mold allowance lines 2 on both sides and use unvulcanized rubber baffles.

[0055] The installation process requires multiple vacuuming and pre-pressurization processes before installation.

[0056] To further optimize the solution, in step S2, after placing the outer mold R-corner block 7, use high-temperature resistant tape to fix the outer mold R-corner block 7.

[0057] Further optimize the scheme. In step S3, after the core mold 1 is molded with several outer mold flat plates 6 and outer mold R-corner blocks 7, the outer layer is covered with an isolation film, a breathable felt and a vacuum bag in sequence to encapsulate the core mold 1, outer mold flat plates 6 and outer mold R-corner blocks 7.

[0058] Auxiliary materials need to be placed on the outer side of the outer mold flat plate 6 and the outer mold R corner block 7, as well as the inner side of the core mold 1, to form a vacuum-sealed bag.

[0059] The specific implementation steps for a particular product in this embodiment are as follows:

[0060] Step S1: Lay carbon fiber prepreg on the molding surface of the mandrel 1. The prepreg should be laid beyond the mandrel allowance line 2, and uncured rubber should be used to baffle the edges of the part. During the laying process, vacuum pre-compression is performed every two layers. The vacuum degree should be maintained above 0.08 MPa for more than 15 minutes. Every six layers, pre-compression is performed by heating in a can, with a pressure of 0.6 MPa and a temperature of 60-70°C for more than 15 minutes.

[0061] Step S2, as follows Figure 2First, install each outer mold flat plate 6 on the outer surface of the core mold 1 after the prepreg has been laid, and use bolts to connect the outer mold connecting hole 10 and the core mold bolt hole 5 to prevent the outer mold flat plate 6 from falling off; after all the outer mold flat plates 6 are installed, place each outer mold R corner block 7 between two adjacent outer mold flat plates 6, and use high temperature resistant tape to fix the outer mold R corner block 7 to prevent it from falling off.

[0062] Step S3: Seal the mold after mold closing in the manner of mold → release film → breathable felt → vacuum bag. Auxiliary materials need to be placed on the outer side of the outer mold assembly and the inner side of the core mold 1 to form a vacuum-sealed bag. After sealing, perform a leakage check. First, evacuate the parts to a vacuum level of not less than 0.092 MPa. Connect the parts to the vacuum system for at least 15 minutes. Then turn off the vacuum system. Within 5 minutes, the vacuum gauge reading should not drop by more than 0.002 MPa.

[0063] Step S4: The encapsulated mold is sent to an autoclave for curing. Initial pressure is applied (0.6~0.7) MPa, and the temperature is raised to 80±5℃ and held for 30±5 min. Then the temperature is raised to 120±5℃ and held for 120±30 min. Finally, the temperature is lowered to below 60℃ to release the pressure and remove the mold from the autoclave. Vacuum is applied throughout the curing process.

[0064] During the curing process, the pressure comes from the compressed gas inside the autoclave. As the temperature rises and the material softens, it provides stable and continuous pressure to the part, which facilitates the discharge of gas and thus produces a part of excellent quality. Because the outer mold structure is segmented along the R-corner line, each plate and R-corner area can effectively transmit the pressure of the autoclave, thereby ensuring the internal quality of the part.

[0065] Step S5: After curing, remove the auxiliary materials and outer mold components, and remove the part from the core mold 1 along the length direction with the help of the demolding ring and demolding equipment.

[0066] Next, the excess parts are cut and removed according to the position of the core mold product line 3 reserved in core mold 1 to obtain the composite material polygonal tube, such as... Figure 3 .

[0067] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0068] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A composite material polygonal tube forming mold based on autoclave forming, characterized in that, After being packaged, the molding mold is sent to an autoclave for curing. The mold includes: The core mold (1) is a prism structure, and all sides of the core mold (1) are forming surfaces; The outer mold assembly includes several outer mold flat plates (6) and several outer mold corner blocks (7). The several outer mold flat plates (6) are respectively arranged corresponding to each forming surface of the core mold (1), and a positioning connector is provided between the outer mold flat plates (6) and the core mold (1). The outer mold corner blocks (7) are arranged between two adjacent outer mold flat plates (6), and the outer mold corner blocks (7) are adapted to the edge of the outer mold flat plates (6). The positioning connector includes two sets of core mold positioning holes (4) and two sets of core mold bolt holes (5) formed on the core mold (1). The two core mold positioning holes (4) and the two core mold bolt holes (5) are respectively located at both ends of the core mold (1) forming surface. A positioning pin is fixedly connected in the core mold positioning hole (4). It also includes two sets of outer mold positioning holes (9) and two sets of outer mold connecting holes (10) opened on the outer mold flat plate (6). The two outer mold positioning holes (9) and the two outer mold connecting holes (10) are respectively located at both ends of the outer mold flat plate (6). The outer mold positioning holes (9) are correspondingly set with the positioning pins. The outer mold connecting holes (10) are detachably connected to the core mold bolt holes (5) by bolts.

2. The composite polygonal tube forming mold based on autoclave forming according to claim 1, characterized in that: The core mold (1) has an annular core mold allowance line (2) and a core mold product line (3) at both ends of several molding surfaces. The core mold allowance line (2) is located outside the core mold product line (3), and the positioning connector is located outside the core mold allowance line (2).

3. The composite material polygonal tube forming mold based on autoclave forming according to claim 1, characterized in that: The two ends of the core mold (1) are provided with core mold through holes (8) along the axis of the core mold (1).

4. A method for manufacturing composite polygonal tubes based on autoclave molding, wherein the composite polygonal tube molding die based on autoclave molding as described in claim 1 is characterized in that, Includes the following steps: S1. Apply carbon fiber prepreg to the molding surface of the core mold (1); S2. Install several outer mold flat plates (6) on the outer surface of the prepreg after it has been laid, and use positioning connectors to fix the several outer mold flat plates (6) to the core mold (1), and place an outer mold R-corner block (7) between the two outer mold flat plates (6). S3. The core mold (1), the outer mold flat plate (6) and the outer mold R corner block (7) are sealed to form a vacuum sealed bag; S4. After sealing, the mold is sent to an autoclave for curing; S5. After curing, remove the core mold (1), outer mold flat plate (6) and outer mold R corner block (7) to obtain the composite material polygonal tube.

5. The method for manufacturing composite polygonal tubes based on autoclave molding according to claim 4, characterized in that: The two ends of several molding surfaces of the core mold (1) are respectively provided with annular core mold allowance lines (2) and core mold product lines (3). The core mold allowance lines (2) are located outside the core mold product lines (3). The positioning connectors are located outside the core mold allowance lines (2). In step S1, the carbon fiber prepreg laid should extend beyond the core mold allowance lines (2) on both sides and use unvulcanized rubber baffles. The installation process requires multiple vacuuming and pre-pressurization processes before installation.

6. The method for manufacturing composite polygonal tubes based on autoclave molding according to claim 4, characterized in that: In step S2, after placing the outer mold R-corner block (7), the outer mold R-corner block (7) is fixed with high-temperature resistant tape.

7. The method for manufacturing composite polygonal tubes based on autoclave molding according to claim 4, characterized in that: In step S3, after the core mold (1) is molded with several outer mold flat plates (6) and outer mold R-corner blocks (7), the outer layer is covered with an isolation film, a breathable felt and a vacuum bag in sequence to encapsulate the core mold (1), the outer mold flat plates (6) and the outer mold R-corner blocks (7); Auxiliary materials need to be placed on the outer side of the outer mold flat plate (6), the outer mold R corner block (7), and the inner side of the core mold (1) to form a vacuum sealed bag.

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