Die and method for forming thick-wall composite material part through vacuum bag

Abstract

The invention provides a mold and method for forming a thick-wall composite material part through a vacuum bag, and relates to the technical field of composite material part forming. The mold comprises a cover plate, a frame, a base plate, a vacuum base, a vacuum meter, the vacuum bag and a breathable felt; the vacuum base vacuumizes the space between the vacuum bag and the base plate to form negative pressure, the vacuum meter detects the vacuum degree in the vacuum system, the mold can provide pressure exceeding one atmospheric pressure for the composite material product, and then the mold is made to conduct pressure forming on the composite material product through the vacuum bag. The technical problems that a composite product with the thickness larger than 1.5 mm cannot be formed through an existing vacuum bag technology, the cost of an autoclave forming technology is high, and the production efficiency of the product is low are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite part forming, and particularly relates to a mold and method for forming thick-walled composite parts by using a vacuum bag. Background Art

[0002] Forming by using a vacuum bag is one of the traditional composite forming processes. This process forms a negative pressure inside the vacuum bag to apply a pressure of no more than one atmosphere to the composite part. Its advantages include: simple equipment and low cost. This process only requires auxiliary materials such as a composite forming mold, a vacuum bag, etc., and a vacuum base, and the equipment cost is relatively small; secondly, since it is not restricted by the size of equipment such as an autoclave, the vacuum bag forming can produce composite parts of larger sizes; in addition, compared with the possible uneven pressure distribution at each position during mold clamping in the compression molding process, the vacuum bag process uses air to apply uniform pressure, thus ensuring that each part of the product bears the same pressure; however, this process also has obvious disadvantages: since the vacuum bag can only apply a pressure of no more than one atmosphere, the vacuum bag process cannot form composite parts with a wall thickness exceeding 1.5 mm. This is because as the wall thickness of the composite product increases, the requirement for curing pressure also increases. Usually, products with a wall thickness above 1.5 mm must be pressurized with a pressure exceeding one atmosphere, otherwise the product is prone to internal quality defects such as delamination and dispersion.

[0003] In order to apply a greater and more uniform pressure to the product, traditionally only the expensive autoclave process can be used; the autoclave process uses a closed container and fills inert gas inside the container to apply a pressure exceeding one atmosphere to the product in the vacuum system, and the pressure can often reach several MPa; therefore, the products formed by autoclave have a low porosity and reliable quality; however, due to the use of expensive autoclave equipment, the production cost also increases accordingly. In order to control the production cost, several products that have been produced must be waited to be processed together and cured in one autoclave, which greatly prolongs the production cycle of the product. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, so as to provide a mold and method for forming thick-walled composite parts by using a vacuum bag.

[0005] A mold for forming thick-walled composite parts by using a vacuum bag includes: a mold and a vacuum system. The mold includes a cover plate, a frame, and a base plate that are longitudinally connected in sequence. The vacuum system includes a vacuum base, a vacuum gauge, and a vacuum bag. A breather felt is provided on the cover plate, the vacuum bag is hermetically installed on the base plate, and the vacuum base and the vacuum gauge are arranged on the vacuum bag.

[0006] Furthermore, the mold further includes a stop bar, and the stop bar is arranged at the connection between the cover plate and the frame.

[0007] Furthermore, the mold further includes an internally threaded cylindrical pin, and the frame and the substrate are connected by the internally threaded cylindrical pin.

[0008] Furthermore, the mold further includes a second lifting hole, which is opened on the cover plate.

[0009] Furthermore, the mold further includes a first lifting hole, which is opened on the substrate.

[0010] Furthermore, both the first lifting hole and the second lifting hole are threaded blind holes.

[0011] Furthermore, a first pin hole is opened on the substrate, and a second pin hole corresponding to the first pin hole is opened on the frame. Both the first pin hole and the second pin hole are connected in a mating manner with the internally threaded cylindrical pin.

[0012] Furthermore, the vacuum bag is bonded to the substrate through a sealing strip.

[0013] The present invention further includes a method for forming a thick-walled composite material part by using a vacuum bag. This method is realized based on the mold for forming a thick-walled composite material part by using a vacuum bag described in any one of the above, and the method includes the following steps:

[0014] Step S1, heating the mold;

[0015] Step S2, laying prepregs in layers inside the mold to form a laminate ply;

[0016] Step S3, evacuating the inside of the mold through a vacuum base, heating the mold to 50°C to 60°C, and then disassembling the mold to trim the overflow material;

[0017] Step S4, reassembling the mold, and placing the mold in a curing furnace for curing and forming;

[0018] Step S5, removing the mold to obtain the part.

[0019] Furthermore, the matrix resin of the prepreg is either epoxy resin, or cyanate ester, or bismaleimide resin.

[0020] The technical solution of the present invention has the following advantages:

[0021] In the technical solution provided by the present invention, a pressure is provided to the material by a cover plate, a negative pressure is formed by evacuating the space between the vacuum bag and the substrate by a vacuum base, a vacuum gauge detects the vacuum degree inside the vacuum system, and the mold can provide a pressure exceeding one atmospheric pressure to the composite product, so that the mold presses and forms the composite product through the vacuum bag, which not only overcomes the problem that the composite product with a thickness exceeding 1.5 mm cannot be formed by the vacuum bag process, but also reduces the cost of using the autoclave molding process and improves the production efficiency of the product. Description of the Drawings

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 Schematic diagram of the overall structure of the mold for forming thick-walled composite parts using a vacuum bag according to the present invention;

[0024] Figure 2 Cross-sectional view of the overall structure of the mold for forming thick-walled composite parts using a vacuum bag according to the present invention;

[0025] Figure 3 For the present invention Figure 2 Partial enlarged view of part A;

[0026] Figure 4 Top view of the substrate structure according to the present invention;

[0027] Figure 5 Side view of the substrate structure according to the present invention;

[0028] Figure 6 Top view of the cover plate structure according to the present invention;

[0029] Figure 7 Side view of the cover plate structure according to the present invention;

[0030] Figure 8 Top view of the frame structure according to the present invention;

[0031] Figure 9 Side view of the frame structure according to the present invention;

[0032] Figure 10 Schematic diagram of the bar structure according to the present invention.

[0033] Description of the reference numerals:

[0034] 1 - Cover plate; 2 - Substrate; 3 - Internal threaded cylindrical pin; 4 - Frame; 5 - Vacuum base; 6 - Vacuum gauge; 7 - Vacuum bag; 8 - Breathable felt; 9 - First lifting hole; 10 - First pin hole; 11 - Second lifting hole; 12 - Part disassembly position; 13 - Second pin hole; 14 - Retaining bar. Detailed implementation manners

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0038] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] As Figures 1 to 3 shown, a mold for forming thick-walled composite parts using a vacuum bag includes: a mold and a vacuum system. The mold includes a cover plate 1, a frame 4, and a substrate 2 that are longitudinally connected in sequence. The vacuum system includes a vacuum base 5, a vacuum gauge 6, and a vacuum bag 7. A breathable felt 8 is provided on the cover plate 1. The vacuum bag 7 is hermetically installed on the substrate 2. The vacuum base 5 and the vacuum gauge 6 are provided on the vacuum bag 7. Among them, the vacuum bag 7 is bonded to the substrate 2 through a sealing strip. The main function of the breathable felt 8 is to conduct air and exhaust the air inside the vacuum system, so that the atmosphere forms a positive pressure on the mold.

[0040] The above-mentioned mold for forming thick-walled composite parts using a vacuum bag provides pressure to the material through the cover plate 1, and the vacuum base 5 evacuates the space between the vacuum bag 7 and the substrate 2 to form a negative pressure (the air forms a positive pressure on the substrate 2 and the vacuum bag 7, and the air inside the vacuum bag 7 is negative pressure). The vacuum gauge 6 detects the vacuum degree inside the vacuum system. The mold can provide a pressure exceeding one atmospheric pressure to the composite product, and then the mold presses and forms the composite product through the vacuum bag 7. This not only overcomes the problem that the vacuum bag process cannot form composite products with a thickness exceeding 1.5 mm, but also reduces the cost of using the autoclave molding process and improves the production efficiency of the product.

[0041] As Figure 10 shown, in this embodiment, the mold further includes a stop strip 14, and the stop strip 14 is arranged at the connection of the cover plate 1 and the frame 4; during the pressurization process of the mold, there may be a gap in the height direction between the cover plate 1 and the frame 4, resulting in the breather felt 8 entering the gap. To prevent this phenomenon, a stop strip 14 made of aluminum alloy material is added at the edge connection of the cover plate 1 and the frame 4.

[0042] As Figure 6 and Figure 7 shown, in this embodiment, the mold further includes a second lifting hole 11, and the second lifting hole 11 is opened on the cover plate 1; the area of the cover plate 1 is more than twice the area of the material, so that a pressure above one atmospheric pressure can be provided to the material through the vacuum bag 7. The second lifting hole 11 is a threaded blind hole, and a plurality of second lifting holes 11 are opened at the four corners of the cover plate 1. The setting of the second lifting hole 11 facilitates the lifting and transfer of the mold.

[0043] As Figure 4 、 Figure 8 and Figure 9 shown, in this embodiment, the mold further includes a first lifting hole 9, and the first lifting hole 9 is opened on the substrate 2; a plurality of first lifting holes 9 are opened at the four corners of the substrate 2. The setting of the first lifting hole 9 facilitates the lifting and transfer of the mold. The first lifting hole 9 is a threaded blind hole. In addition, in order to facilitate the demolding operation of the part product, the substrate 2 is composed of four parts spliced together, and four part splitting positions 12 are correspondingly arranged on the substrate 2.

[0044] As Figures 1 to 10 shown, the present invention further includes a method for forming thick-walled composite parts using a vacuum bag. This method is realized based on the mold for forming thick-walled composite parts using a vacuum bag described in any one of the above, and the method includes the following steps:

[0045] Step S1, heating the mold, and heating the mold through an electrothermal blast drying oven;

[0046] Step S2, lay up prepregs in layers inside the mold to form a laminate ply. The matrix resin of the prepreg is either epoxy resin, or cyanate ester, or bismaleimide resin, etc. The reinforcing material of the prepreg is either carbon fiber, or glass fiber, or aramid fiber, etc. The matrix resin and the reinforcing material of the prepreg together constitute a composite material. During the laying process, vacuum pre-compaction is required once every five layers of prepregs are laid.

[0047] Step S3, after the laminate ply is laid up, assemble the mold, make a vacuum system, evacuate the inside of the mold through the vacuum base 5, heat the mold to 50°C - 60°C in a curing furnace, and then disassemble the mold to trim the overflow material.

[0048] Step S4, reassemble the mold and place the mold in a curing furnace for curing and forming.

[0049] Step S5, remove the mold and perform the demolding process to obtain a composite material part with a wall thickness ≥ 1.5 mm.

[0050] As Figures 1 to 10 shown, in this embodiment, the following several test examples were carried out according to the method for forming a thick-walled composite material part using a vacuum bag described above:

[0051] Test Example 1,

[0052] Step A1, set the size of the material to 300 mm × 300 mm × 2 mm, the outer contour size of the cover plate 1 to 425 mm × 425 mm, the vacuum bag 7 can provide a maximum pressure of 0.2 MPa to the material, and heat the mold through an electrothermal blast drying oven.

[0053] Step A2, lay up prepregs in layers inside the mold to form a laminate ply. The single-layer thickness of the prepreg is 0.1 mm, and a total of 20 layers are laid. During the process, vacuum pre-compaction is required every 5 layers of prepregs are laid.

[0054] Step A3, after the laminate ply is laid up, assemble the mold, make a vacuum system, lay a breather felt 8 on the cover plate 1, bond the vacuum bag 7 to the substrate 2 with a sealant strip, install the vacuum base 5 and the vacuum gauge 6 on the vacuum bag 7, evacuate the inside of the mold through the vacuum base 5, heat the mold to 50°C - 60°C in a curing furnace, and then disassemble the mold to trim the overflow material.

[0055] Step A4, reassemble the mold according to Step A3, make a vacuum system, and place the mold in a curing furnace for curing and forming.

[0056] Step A5, remove the mold and perform the demolding process to obtain a composite material part with a wall thickness of 2 mm.

[0057] Test Example 2,

[0058] Step B1: Set the size of the material to 300mm×300mm×4mm, the outer contour size of the cover plate 1 to 520mm×520mm. The vacuum bag 7 can provide a maximum pressure of 0.3MPa to the material, and the mold is heated by an electric thermostatic drying oven.

[0059] Step B2: Lay up prepregs in layers inside the mold to form a laminate layup. The single-layer thickness of the prepreg is 0.1mm, and a total of 40 layers are laid up. During the process, vacuum pre-compaction is required every 5 layers of prepregs laid up.

[0060] Step B3: After the laminate layup is completed, assemble the mold, make a vacuum system. Lay up a breather felt 8 on the cover plate 1. The vacuum bag 7 is bonded to the substrate 2 through a sealant strip. The vacuum base 5 and the vacuum gauge 6 are installed on the vacuum bag 7. Vacuumize the inside of the mold through the vacuum base 5, heat the mold to 50°C - 60°C in a curing furnace, and then disassemble the mold to trim the overflow material.

[0061] Step B4: Reassemble the mold according to Step B3, make a vacuum system, and place the mold in a curing furnace for curing and forming.

[0062] Step B5: Demold the part by removing the mold to obtain a composite material part with a wall thickness of 4mm.

[0063] Test Example 3

[0064] Step C1: Set the size of the material to 300mm×300mm×6mm, the outer contour size of the cover plate 1 to 600mm×600mm. The vacuum bag 7 can provide a maximum pressure of 0.4MPa to the material, and the mold is heated by an electric thermostatic drying oven.

[0065] Step C2: Lay up prepregs in layers inside the mold to form a laminate layup. The single-layer thickness of the prepreg is 0.1mm, and a total of 60 layers are laid up. During the process, vacuum pre-compaction is required every 5 layers of prepregs laid up.

[0066] Step C3: After the laminate layup is completed, assemble the mold, make a vacuum system. Lay up a breather felt 8 on the cover plate 1. The vacuum bag 7 is bonded to the substrate 2 through a sealant strip. The vacuum base 5 and the vacuum gauge 6 are installed on the vacuum bag 7. Vacuumize the inside of the mold through the vacuum base 5, heat the mold to 50°C - 60°C in a curing furnace, and then disassemble the mold to trim the overflow material.

[0067] Step C4: Reassemble the mold according to Step C3, make a vacuum system, and place the mold in a curing furnace for curing and forming.

[0068] Step C5: Demold the mold to perform the demolding process and obtain a composite part with a wall thickness of 6 mm.

[0069] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A mold for forming thick-walled composite parts using a vacuum bag, comprising: A mold and a vacuum system, characterized in that the mold comprises a cover plate (1), a frame (4) and a base plate (2) connected in sequence longitudinally, the vacuum system comprises a vacuum base (5), a vacuum gauge (6) and a vacuum bag (7), an air-permeable felt (8) is arranged on the cover plate (1), the vacuum bag (7) is sealed and mounted on the base plate (2), and the vacuum base (5) and the vacuum gauge (6) are arranged on the vacuum bag (7).

2. A mold for forming thick-walled composite parts using a vacuum bag according to claim 1, characterized in that: The mold further comprises a blocking bar (14), wherein the blocking bar (14) is arranged at the connection between the cover plate (1) and the frame (4).

3. The mold for forming thick-walled composite parts using a vacuum bag according to claim 1, characterized in that: The mould further comprises an internally threaded cylindrical pin (3), and the frame (4) and the base plate (2) are connected via the internally threaded cylindrical pin (3).

4. The mold for forming thick-walled composite parts using a vacuum bag according to claim 1, characterized in that: The mould further comprises a second lifting hole (11), and the second lifting hole (11) is opened on the cover plate (1).

5. The mold for forming thick-walled composite parts using a vacuum bag according to claim 4, characterized in that: The mold further comprises a first hanging hole (9), and the first hanging hole (9) is opened on the base plate (2).

6. The mold for forming thick-walled composite parts using a vacuum bag according to claim 5, characterized in that: The first hoisting hole (9) and the second hoisting hole (11) are both threaded blind holes.

7. The mold for forming thick-walled composite parts using a vacuum bag according to claim 3, characterized in that: The base plate (2) is provided with a first pin hole (10), the frame (4) is provided with a second pin hole (13) corresponding to the first pin hole (10), and both the first pin hole (10) and the second pin hole (13) are matched and connected with the internal thread cylindrical pin (3).

8. The mold for forming thick-walled composite parts using a vacuum bag according to claim 1, characterized in that: The vacuum bag (7) is bonded to the substrate (2) via a sealing tape.

9. A method for forming thick-walled composite parts using a vacuum bag, the method being realized based on the mold for forming thick-walled composite parts using a vacuum bag as claimed in any one of claims 1 to 8, characterized in that: The method comprises the following steps: Step S1, heating the mold; Step S2, laying prepreg in layers inside the mold to form a laminate layer; Step S3, evacuating the inside of the mold through the vacuum base (5), heating the mold to 50° C. to 60° C., and then disassembling the mold to trim the overflow; Step S4, reassembling the mold and placing the mold in a curing furnace for curing and molding; Step S5, removing the mold to obtain the parts.

10. The method for forming thick-walled composite parts using vacuum bags according to claim 9, characterized in that: The matrix resin of the prepreg is either epoxy resin, cyanate ester or bismaleimide resin.

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