A method for integrally forming a composite tank with complex inner wall features

Abstract

The application relates to a complex inner wall feature composite cabin integrated forming method and relates to the field of material forming, and comprises the following steps: processing a rubber forming die and assembling, mixing silicon rubber in proportion, injecting the rubber into the die through a glue injection channel of the die, and standing and solidifying the rubber into a rubber layer; meanwhile, cutting a prepreg sample, laying the prepreg sample on a preforming die to preform a C-shaped groove and a boss; removing part of the rubber forming die, starting to lay the prepreg sample at a skin part of the rubber layer, placing the preformed C-shaped groove and the boss at a predetermined position of the rubber layer after reaching a specified layer number, continuously laying the prepreg sample outside the skin, the C-shaped groove and the boss until reaching a specified thickness, installing a cabin forming die to the removed rubber forming die, and placing the cabin forming die into an oven for temperature rising and solidification; after the mold is cooled, the mold is removed to complete the forming work; and the application has the advantages of improving cabin forming quality, simplifying layer laying, reducing demolding difficulty and processing cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material forming, in particular to a complex inner wall feature composite cabin integrated forming method. BACKGROUND

[0002] At present, the performance requirements of composite cabin products are becoming more and more strict, and it is necessary to reduce weight as much as possible under the premise of meeting the structural strength requirements, and at the same time to meet various functional requirements, so there are high bosses, sealing ring installation grooves (such as C-shaped grooves) and other difficult-to-form features inside the cabin section. Due to the complex design of the cabin body containing such features, there are risks such as inconvenient layering operation, demoulding, irregular feature forming, and internal quality, and in general, the part of the high boss is formed by separately curing and bonding, and the part of the sealing ring installation groove is formed by machining.

[0003] For the machining method of forming the sealing ring installation groove, taking the C-shaped groove as an example. If the "C-shaped" structure is sequentially layered along the y-axis direction according to the quasi-isotropic order, and then machined out of the "C-shaped" structure after curing and forming. Since there are continuous fibers on the two x-axis sides of the "C-shaped" structure, and there are no continuous fibers on the y-axis side, the composite material is only combined by the resin matrix, and since the mechanical properties of the resin matrix and the fibers differ by 3 orders of magnitude, the mechanical strength of the y-axis side cannot meet the requirements, and in the machining process, it is easy to cause delamination and risk of falling along the y-axis, which cannot meet the use requirements.

[0004] If the "C-shaped" structure is sequentially layered along the x-axis direction according to the quasi-isotropic order, and then machined out of the "C-shaped" structure after curing and forming. Since there are continuous fibers on the y-axis side of the "C-shaped" structure, and there are no continuous fibers on the x-axis side, the composite material is only combined by the resin matrix, and since the mechanical properties of the resin matrix and the fibers differ by 3 orders of magnitude, the mechanical strength of the two x-axis sides cannot meet the requirements, and in the machining process, it is easy to cause delamination and risk of falling along the x-axis, which also cannot meet the use requirements.

[0005] Therefore, in view of the above problems, a complex inner wall feature composite cabin integrated forming method is needed. SUMMARY

[0006] (I) Technical problems to be solved

[0007] The technical problem to be solved by the present application is to solve the problem of difficult combination forming of the cabin with complex structure by using multiple forming methods, and poor product quality.

[0008] (II) Technical scheme

[0009] In order to solve the above technical problems, the present application provides a complex inner wall feature composite cabin integrated forming method, comprising the following steps:

[0010] I. According to the structural features of the forming cabin, the cabin is divided into a skin with uniform wall thickness, a C-shaped groove with notches, and a boss with a wall thickness greater than the skin, and pre-compaction molds and forming molds of the three parts of the cabin are processed respectively;

[0011] II. Process the rubber forming mold and assemble it. After mixing the silicone rubber in proportion, the rubber is injected into the mold through the injection channel of the mold and solidified into a rubber layer. At the same time, the prepreg sample is cut and laid on the pre-forming mold to pre-form the C-shaped groove and the boss.

[0012] III. Remove part of the rubber forming mold so that the remaining rubber forming mold and the rubber layer become a combined core mold. Lay the prepreg sample on the skin part of the rubber layer, and after reaching the specified number of layers, place the pre-formed C-shaped groove and its pre-forming mold and the boss at the predetermined position of the rubber layer.

[0013] IV. Continue to lay the prepreg sample outside the skin, C-shaped groove and boss until the specified thickness is reached. Install the cabin forming mold to the position where the rubber forming mold has been removed, and place it in an oven for temperature curing. After the mold cools down, remove the mold to complete the forming work.

[0014] As a further description of the present application, preferably, each mold is wiped with acetone before the forming work.

[0015] As a further description of the present application, preferably, multiple layers of prepreg samples are laid on the boss pre-forming mold, and the boss pre-forming mold is placed on the press to heat and pressurize. After the pressurized mold gap is less than 0.2mm, the press is closed, and the pre-forming of the boss is completed after cooling.

[0016] As a further description of the present application, preferably, multiple layers of prepreg samples are laid on the C-shaped groove pre-forming mold, and then release cloth, non-porous film, air-permeable felt and vacuum bag are laid in sequence outside the prepreg samples. Vacuum bag semi-solid forming is adopted, and the C-shaped groove is pre-formed by placing it in an oven for heating.

[0017] As a further description of the present application, preferably, the C-shaped groove pre-forming mold is a T-shaped pre-compaction mold, and the prepreg sample is laid outside the pre-compaction mold to form a C-shaped structure. The pre-compaction mold is placed together with the pre-formed C-shaped groove at a specified position in the rubber forming mold.

[0018] As a further description of the present application, preferably, when laying the prepreg sample outside the rubber layer, release cloth, non-porous film, air-permeable felt and vacuum bag are laid in sequence outside the prepreg sample, and vacuum is drawn for 30 minutes at room temperature to pre-form the skin part.

[0019] As a further description of the present application, preferably, a sealing rubber strip is attached to the vacuum bag.

[0020] As a further illustration of the present application, preferably, after the skin part is formed, the pre-formed boss or the pre-formed C-shaped groove with a pre-compaction mold is placed outside the partially formed skin and the pre-impregnated sample piece is continuously laid outside the placed boss or C-shaped groove, and after reaching the specified layer group, the pre-formed C-shaped groove or boss with a pre-compaction mold is placed, and finally the pre-impregnated sample piece is continuously laid outside the partially formed skin, C-shaped groove and boss to complete the laying work after the skin is completely formed to the thickness.

[0021] As a further illustration of the present application, preferably, after the skin part is formed, the pre-formed boss or the pre-formed C-shaped groove with a pre-compaction mold is placed outside the partially formed skin and the pre-impregnated sample piece is continuously laid outside the placed boss or C-shaped groove, and after reaching the specified layer group, the pre-formed C-shaped groove or boss with a pre-compaction mold is placed, and finally the pre-impregnated sample piece is continuously laid outside the partially formed skin, C-shaped groove and boss to complete the laying work after the skin is completely formed to the thickness.

[0022] As a further illustration of the present application, preferably, the pre-impregnated sample piece is made of a combination of carbon fiber and epoxy resin or bismaleimide resin.

[0023] (Three) beneficial effects

[0024] The above technical solutions of the present application have the following advantages:

[0025] The present application provides a new forming method for complex structures, which divides the product and designs the mold according to the structure characteristics of the product, designs a pre-compaction tooling for the internal high boss and large thickness area, designs a detachable insert and replaceable groove insert for positions that cannot be demolded such as high boss and C-shaped groove, and realizes integrated forming of complex internal features through uniform pressure of the rubber layer. Compared with the high cost and long cycle of using five-axis machining C-shaped groove today, the present application realizes integrated forming of C-shaped groove type complex features, reduces the machining demand of the features, and has low mold manufacturing difficulty, effectively reducing the machining cost. At the same time, it can also reduce the layering and reduce the thickness of the rubber layer. Moreover, the forming quality is high, the product surface roughness can be controlled to be lower than Ra0.8, thereby reducing the required demolding force, and at the same time, large inverse bevel angles are provided between the mold blocks to reduce friction, directly reducing the difficulty of demolding operation, and solving the problem of demolding of high boss with a thickness of 30mm to 50mm in the cabin body. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a cabin cross-sectional view of the present application;

[0027] Figure 2 is a C-shaped groove pre-forming replacement process diagram of the present application;

[0028] Figure 3 is a final forming mold cross-sectional view of the present application.

[0029] In the diagram: 1. Skin; 2. C-groove; 3. Boss; 4. Rubber layer; 5. Lower mold; 6. Core mold; 61. Inner mold; 62. Outer mold; 7. Pre-compacting mold; 71. Rubber molding insert; 8. Cabin molding female mold; 81. Rubber molding female mold; 9. Cabin molding upper mold; 91. Rubber molding upper mold. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0031] A method for integral molding of a composite material cabin with complex internal wall features includes the following steps:

[0032] Ⅰ. For example Figure 1 As shown, based on the structural characteristics of the molded cabin, the cabin is divided into three parts: a uniformly thick skin 1, a C-shaped groove 2 with slots, and a boss 3 with a wall thickness greater than that of the skin 1. The thickness of the boss 3 should be more than 5 times the thickness of the skin 1. Pre-compacting molds and forming molds for the three parts of the cabin are then machined separately, including a boss pre-forming mold, a universal lower mold 5, a universal core mold 6, a pre-compacting mold 7 for forming the C-shaped groove 2, a cabin forming female mold 8 and a cabin forming upper mold 9 for the final forming of the skin 1, and rubber forming inserts 71, rubber forming female mold 81, and rubber forming upper mold 91 for forming the rubber layer 4.

[0033] The composite material reinforcing fiber system used in the cabin molding includes a carbon fiber system and a resin system. The carbon fiber system selects high-strength medium-modulus carbon fibers, such as T300, T700, T800, T1000, etc., or high-strength high-modulus carbon fibers such as M40J, M55J, etc.; the resin system selects medium-temperature epoxy, high-temperature epoxy, bismaleimide resin, etc.

[0034] II. Clean the pre-compacted boss, pre-compacted mold 7, rubber molding, and cabin molding mold blocks with acetone and assemble them. Figure 2 , Figure 3 The lower mold 5, core mold 6, rubber molding insert 71, rubber molding female mold 81, and rubber molding upper mold 91 constitute a rubber layer molding mold. The core mold 6 includes an inner mold 61 and an outer mold 62, with the inner mold 61 attached to the inner side of the outer mold 62. One side of the inner mold 61 has a groove with the same structure as the boss 3, and the top of the outer mold 62 has a recessed groove for placing the T-shaped rubber molding insert 71.

[0035] The silicone rubber is mixed in proportion and injected into the mold through the injection channel of the mold to form the rubber layer 4. At the same time, the carbon fiber prepreg sample is cut according to the drawing paper using the numerical control cloth cutting machine, and the prepreg sample is laid on the convex pre-compaction mold 7. Then, the release cloth, non-porous film, air-permeable felt and vacuum bag are laid on the surface of the prepreg sample laid on the pre-compaction mold 7 in turn. The vacuum bag is bonded by the sealing rubber strip to ensure air tightness. The vacuum bag is used for semi-solid molding. The mold is placed in an oven, and the temperature is raised to 40℃ for 30min to preform the structure of the C-shaped groove 2. The convex pre-compaction mold is placed on the press, the temperature of the press is raised to 90℃, and the pressure is increased to less than 0.2mm. The mold joint is closed, and the temperature is lowered to below 50℃ to preform the structure of the convex 3. The pre-compacted semi-solid convex 3 composite material sample is demolded and taken out for standby use. The auxiliary material on the surface of the pre-compaction mold 7 is removed, and the preformed C-shaped groove 2 is retained on the pre-compaction mold 7.

[0036] Ⅲ. Combination Figure 2 、 Figure 3 , the rubber molding insert 71, the rubber molding cavity 81 and the rubber molding upper mold 91 are removed, and the lower mold 5, the core mold 6 and the rubber layer 4 become a new combined core mold. The prepreg sample is laid on the skin 1 part of the rubber layer 4. After reaching the specified number of layers, the convex 3 is placed in the predetermined position of the rubber layer 4, and then the prepreg sample is continuously laid on the skin 1 and the convex 3 part to the specified thickness. The release cloth, non-porous film, air-permeable felt and vacuum bag are laid on the surface of the prepreg in turn, and the sealing rubber strip is bonded to ensure air tightness. The vacuum is drawn for 30min at room temperature. After curing, the prepreg is continuously laid to the specified thickness, and then the pre-compaction mold 7 with the preformed C-shaped groove 2 is placed in the position of the original rubber molding insert 71. Alternatively, the pre-compaction mold 7 with the preformed C-shaped groove 2 can be placed first, and then the convex 3 is placed.

[0037] Ⅳ. Continue to lay the prepreg sample outside the skin 1, C-shaped groove 2 and convex 3 until the specified thickness is reached. Combination Figure 2 、 Figure 3 , the cabin molding cavity 8 and the cabin molding upper mold 9 are placed in the positions of the original rubber molding cavity 81 and the rubber molding upper mold 91 respectively, and the oven is used for temperature rise and curing. The oven temperature is set to 220℃, and after the mold temperature rises to 180℃, the oven temperature is adjusted to 180℃, and the oven is kept for 4h, and then the oven is turned off.

[0038] Ⅴ. After the mold temperature is reduced to below 50℃, the oven is opened, the mold is taken out, the mold is turned over, the lower mold 5, the outer mold 62 and the inner mold 61 are taken out in turn, the pre-compaction mold 7 is taken out from the inside of the cabin, and the composite cabin is taken out, and the demolding is completed.

[0039] The product profile obtained according to the above method meets the following requirements:

[0040] Cabin diameter (mm) <300 300-600 600-1000 1000-1500 Outer profile (mm) ±0.3 ±0.5 ±0.8 ±1.0 C-channel diameter (mm) <500 500-700 700-1000 1000-1500 Inner profile (mm) ±0.2 ±0.3 ±0.5 ±0.8

[0041] While using another conventional molding method, the effect produced by the present method is not as good, for example, when molding by a hot press tank:

[0042] Cabin diameter (mm) <300 300-600 600-1000 1000-1500 Outer profile (mm) ±0.5 ±1.0 ±1.5 ±2.0

[0043] It is obvious from the data comparison that the cabin body product of the present method is superior to the cabin body product of the conventional hot press tank molding.

[0044] By using the above newly designed mold and the matching molding method, the thickness of the rubber layer 4 can be reduced under the premise of ensuring that the cabin body structure strength meets the requirements, so that the amount of silicone rubber is reduced by about 50%, thereby reducing the cost of silicone rubber auxiliary materials. At the same time, a large inverted bevel is provided between the mold blocks to reduce friction, and the surface roughness of the product is less than Ra0.8, the required demolding force is small, the difficulty of demolding operation is also reduced, and the problem of demolding of the high boss 30mm to 50mm thick inside the cabin body is solved. Moreover, compared with the high cost and long cycle of using five-axis machining C-shaped groove 2 today, the present application realizes the integrated molding of the complex features of the C-shaped groove 2, reduces the machining demand of the features, and the mold manufacturing difficulty is low, effectively reduces the machining cost, and the product profile degree can be comparable to the molding precision of machining, and there is no risk of "fiber breakage" unique to machining, which achieves multiple goals at once.

[0045] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for integral molding of a composite material cabin with complex internal wall features, characterized in that: Includes the following steps: I. Based on the structural characteristics of the molded cabin, the cabin is divided into three parts: a uniform wall thickness skin (1), a C-shaped groove with a slot (2), and a boss with a wall thickness greater than that of the skin (1). The pre-forming mold and the forming mold of the three parts of the cabin are then processed respectively. II. Process and assemble the rubber molding mold. Mix the silicone rubber in proportion and inject it into the mold through the injection channel of the mold. Let it stand and cure into a rubber layer (4). At the same time, cut the prepreg sample and lay the prepreg sample on the preforming mold to preform the C-shaped groove (2) and the boss (3). III. Remove part of the rubber molding mold so that the remaining rubber molding mold and rubber layer (4) become a combined core mold; start laying prepreg sample at the skin (1) part of the rubber layer (4), and after reaching the specified number of layers, place the pre-formed C-groove (2) and its pre-formed mold and boss (3) into the predetermined position of the rubber layer (4). IV. Continue to lay prepreg samples on the skin (1), C-groove (2) and boss (3) until the specified thickness is reached. Install the cabin molding mold onto the removed rubber molding mold and put it into the oven for heating and curing. After the mold cools down, remove the mold to complete the molding process.

2. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 1, characterized in that: Each mold is wiped with acetone before molding.

3. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 2, characterized in that: Multiple layers of prepreg sample sheets are laid on the preforming mold of boss (3), and the preforming mold of boss (3) is placed in the press to heat and pressurize. After pressing the mold until the mold gap is less than 0.2mm, the press is turned off. After cooling, the mold is demolded to complete the preforming of boss (3).

4. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 3, characterized in that: Multiple layers of prepreg sample were laid on the preforming mold of C-groove (2), and then release cloth, non-porous membrane, breathable felt and vacuum bag were laid on the outside of the prepreg sample in sequence. The vacuum bag was used for semi-curing and the C-groove (2) was heated in an oven to complete the preforming of C-groove (2).

5. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 4, characterized in that: The pre-forming mold of the C-groove (2) is a T-shaped pre-compacting mold (7). The prepreg sample is laid on the outside of the pre-compacting mold (7) to form a C-shaped structure. The pre-compacting mold (7) and the pre-formed C-groove (2) are placed together in the designated position inside the rubber molding mold.

6. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 5, characterized in that: When laying the prepreg sample on the outside of the rubber layer (4), release cloth, non-porous membrane, breathable felt and vacuum bag are laid on the outside of the prepreg sample in sequence, and vacuum is drawn for 30 minutes at room temperature to preform the skin (1) part.

7. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 6, characterized in that: The vacuum bag has a sealing strip attached to it.

8. The method for integral molding of a composite material cabin with complex inner wall features according to claim 7, characterized in that: After the skin (1) is partially formed, a pre-formed boss (3) or a pre-formed C-groove (2) with a pre-compacting mold (7) is first placed in it. Prepreg samples are then laid on the outside of the partially formed skin (1) and the outside of the placed boss (3) or C-groove (2). After reaching the specified layer group, a pre-formed C-groove (2) or boss (3) with a pre-compacting mold (7) is placed in it. Finally, prepreg samples are laid on the outside of the partially formed skin (1), C-groove (2) and boss (3) until the skin (1) is fully formed, and then the laying work is completed.

9. The method for integral molding of a composite material cabin with complex inner wall features according to claim 8, characterized in that: After installing the cabin molding mold, set the oven temperature to exceed the required insulation temperature. Once the mold temperature reaches the insulation temperature, set the oven temperature to the insulation temperature and begin insulation. After insulation, close the oven and wait for the mold to cool down before removing the mold for demolding.

10. The method for integral molding of a composite material cabin with complex inner wall features according to claim 9, characterized in that: The prepreg samples are made of a combination of carbon fiber and epoxy resin or bismaleimide resin.

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