Integrated forming method for composite cabin with complex inner wall characteristics

Abstract

The invention relates to an integrated molding method for a composite cabin with complex inner wall characteristics, which relates to the field of material molding, and comprises the following steps: processing and assembling a rubber molding mold, mixing silicone rubber according to a ratio, injecting the rubber into the mold through a rubber injection channel of the mold, and standing and curing to form a rubber layer; meanwhile, cutting a prepreg sample piece, and laying the prepreg sample piece on a preforming mold to preform a C-shaped groove and a boss; part of the rubber forming mold is removed, prepreg sample pieces start to be laid on the skin portion of the rubber layer, and after the specified number of layers is reached, preformed C-shaped grooves and bosses are placed in the preset positions of the rubber layer; a prepreg sample piece is continuously laid outside the skin, the C-shaped groove and the boss until the specified thickness is reached, and the cabin forming mold is installed at the position of the removed rubber forming mold and put into a drying oven to be heated and cured; the method has the beneficial effects that the cabin forming quality is improved, layering is easy and convenient, and the demolding difficulty and the machining cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of material forming, and in particular to an integrated forming method for a composite material cabin with complex inner wall features. Background Art

[0002] At present, the performance requirements for composite cabin products are becoming more and more stringent. It is necessary to reduce weight as much as possible while meeting the structural strength requirements, and at the same time meet various functional requirements. Therefore, there will be high bosses and sealing ring installation grooves (such as C-shaped grooves) inside the cabin section, which are difficult to form. Due to the complex design of cabin molds with such features, there are also risks such as inconvenient layering operations, inability to demold, irregular feature molding, and low internal quality. Usually, the high boss part is formed by curing and bonding separately, and the sealing ring installation groove part is formed by machining.

[0003] For the mechanical processing method to form the sealing ring installation groove, take the C-type groove as an example. If the "C-type" structure is first layered in a quasi-isotropic order along the y-axis direction, and then machined out after solidification and forming, the "C-type" structure will be formed. Since there are continuous fibers on the two x-axis sides of the "C-type" structure, but no continuous fibers on the y-axis side, the composite material is only combined with the resin matrix. Since the mechanical properties of the resin matrix and the fiber differ by 3 orders of magnitude, the mechanical strength of the y-axis side cannot meet the requirements, and it is easy to cause delamination and the risk of falling off along the y-axis during the machining process, which cannot meet the use requirements.

[0004] If the "C-type" structure is first layered in a quasi-isotropic order along the x-axis direction, and then machined after solidification, the "C-type" structure will be formed. Since there are continuous fibers on the y-axis side of the "C-type" structure, but no continuous fibers on the x-axis side, the composite material is only combined with the resin matrix. Since the mechanical properties of the resin matrix and the fiber differ by 3 orders of magnitude, the mechanical strength of the two x-axis sides cannot meet the requirements, and it is easy to cause delamination and the risk of falling off along the x-axis during the machining process, and it cannot meet the use requirements.

[0005] Therefore, in view of the above shortcomings, it is necessary to provide an integrated molding method for a composite cabin with complex inner wall features. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] The technical problem to be solved by the present invention is to solve the problem that it is difficult to form a cabin with a complex structure by combining multiple forming methods, resulting in poor product quality.

[0008] (II) Technical solution

[0009] In order to solve the above technical problems, the present invention provides a method for integrated molding of a composite cabin with complex inner wall features, comprising the following steps:

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

[0011] Ⅱ. Process the rubber molding mold and assemble it, mix the silicone rubber in proportion, inject the rubber into the mold through the injection channel of the mold, and let it stand and solidify into a rubber layer; at the same time, cut the prepreg sample, and lay the prepreg sample on the preforming mold to preform the C-shaped groove and boss;

[0012] Ⅲ. Remove part of the rubber molding mold so that the remaining rubber molding mold and the rubber layer become a combined core mold; start to lay the prepreg sample on the skin part of the rubber layer, and after reaching the specified number of layers, place the preformed C-shaped groove and its preformed mold and boss into the predetermined position of the rubber layer;

[0013] IV. Continue to lay prepreg samples on the skin, C-groove and boss until the specified thickness is reached, install the cabin molding mold to the removed rubber molding mold, and put it into the oven for heating and curing; after the mold is cooled, remove the mold to complete the molding work.

[0014] As a further illustration of the present invention, preferably, each mold is wiped with acetone before molding.

[0015] As a further illustration of the present invention, preferably, multiple layers of prepreg samples are laid on the boss preforming mold, and the boss preforming mold is placed on a press to heat and pressurize it. The press is closed after the mold is pressurized until the mold gap is less than 0.2 mm, and the mold is removed after cooling to complete the preforming of the boss.

[0016] As a further illustration of the present invention, preferably, a plurality of layers of prepreg samples are laid on the C-groove preforming mold, and then a release cloth, a non-porous film, a breathable felt and a vacuum bag are laid in sequence outside the prepreg sample, and the vacuum bag is semi-cured and placed in an oven for heating to complete the preforming of the C-groove.

[0017] As a further illustration of the present invention, preferably, the C-groove preforming mold is a T-shaped pre-compacting mold, and the prepreg sample is laid outside the pre-compacting mold to form a C-shaped structure; the pre-compacting mold and the preformed C-groove are placed together in a designated position in the rubber molding mold.

[0018] As a further illustration of the present invention, preferably, when the prepreg sample is laid outside the rubber layer, a release cloth, a non-porous film, a breathable felt and a vacuum bag are laid out in sequence outside the prepreg sample, and vacuum is drawn at room temperature for 30 minutes to preform the skin part.

[0019] As a further illustration of the present invention, preferably, a sealing strip is bonded to the vacuum bag.

[0020] As a further explanation of the present invention, preferably, after the skin is partially formed, a preformed boss or a preformed C-groove with a pre-compacting mold is first placed, and the prepreg sample is continued to be laid outside the partially formed skin and outside the placed boss or C-groove. After reaching the specified layer group, the preformed C-groove or boss with a pre-compacting mold is placed again, and finally, the prepreg sample is continued to be laid outside the partially formed skin, C-groove and boss to the thickness of the fully formed skin to complete the laying work.

[0021] As a further explanation of the present invention, preferably, after the cabin forming mold is installed, the oven temperature is set to exceed the required insulation temperature. After the mold temperature reaches the insulation temperature, the oven temperature is set to the insulation temperature to start insulation. After insulation, the oven is turned off, and the mold is taken out for demolding after the mold is cooled down.

[0022] As a further illustration of the present invention, preferably, the prepreg sample sheet adopts a combination material of carbon fiber and epoxy resin or bismaleimide resin.

[0023] (III) Beneficial effects

[0024] The above technical solution of the present invention has the following advantages:

[0025] The present invention provides a new method for forming a complex structure. The product parting and mold design are carried out according to the product structure characteristics. Pre-compacting tooling is designed for the internal high boss and large thickness area. Removable inserts and replaceable groove inserts are designed for the high boss, C-shaped groove and other positions that cannot be demolded. Then, the rubber layer is uniformly pressurized to achieve integrated molding of complex internal features. Compared with the high cost and long cycle of five-axis machining of C-shaped grooves, the present invention realizes the integrated molding of complex features of C-shaped groove type, reduces the machining requirements of the feature, and the mold manufacturing difficulty is low, effectively reducing the machining cost. At the same time, it can also reduce the thickness of the rubber layer by laying and thinning. Moreover, the molding quality is high, and the surface roughness of the product can be controlled to be lower than Ra0.8, thereby reducing the required demolding force. At the same time, large chamfer angles are set between the mold blocks to reduce friction, directly reduce the difficulty of demolding operation, and solve the problem that the high boss 30mm to 50mm thick inside the cabin cannot be demolded. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2 This is a diagram of the C-groove preforming replacement process of the present invention;

[0028] Figure 3 It is a cross-sectional view of the final molding die of the present invention.

[0029] In the figure: 1. skin; 2. C-shaped 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 DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] A method for integrally forming a composite cabin with complex inner wall features, comprising the following steps:

[0032] Ⅰ. If Figure 1 As shown, according to the structural characteristics of the formed cabin, the cabin is divided into three parts: a skin 1 with uniform wall thickness, a C-shaped groove 2 with notches, and a boss 3 with a wall thickness greater than the skin 1, wherein the thickness of the boss 3 should be more than 5 times the thickness of the skin 1. The pre-compacting molds and forming molds of the three parts of the cabin are processed 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 a rubber forming insert 71, a rubber forming female mold 81 and a rubber forming upper mold 91 for forming the rubber layer 4.

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

[0034] Ⅱ. Clean the boss pre-compacting mold, pre-compacting mold 7, rubber molding, and cabin molding molds with acetone and assemble them. Figure 2 , Figure 3 , wherein the lower mold 5, the core mold 6, the rubber molding insert 71, the rubber molding female mold 81 and the 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, and the inner mold 61 is attached to the inner side of the outer mold 62. A groove with the same structure as the boss 3 is opened on one side of the inner mold 61, and a sinking groove is opened on the top of the outer mold 62 for placing the T-shaped rubber molding insert 71.

[0035] After the silicone rubber is mixed in proportion, the rubber is injected into the mold through the injection channel of the mold and allowed to stand and solidify into a rubber layer 4. At the same time, a CNC cloth cutting machine is used to cut the carbon fiber prepreg sample according to the blanking drawing, and the prepreg sample is laid on the boss pre-compacting and pre-compacting mold 7. Subsequently, the release cloth, non-porous membrane, breathable felt and vacuum bag are laid in sequence on the prepreg surface already covered by the pre-compacting mold 7. The vacuum bag is bonded by sealing strips to ensure air tightness. The vacuum bag is semi-cured and molded by vacuum bag pressing. It is placed in an oven and heated to 40°C for 30 minutes to preform the structure of the C-shaped groove 2. The boss pre-compacting mold is placed on the press, the press is heated to 90°C, and the press is pressurized until the mold joint seam is less than 0.2mm. The press is closed and the temperature is lowered to below 50°C to preform the structure of the boss 3. The pre-pressed and semi-cured boss 3 composite material sample is demolded and taken out for use. The auxiliary material on the surface of the pre-compacting mold 7 is removed, and the preformed C-shaped groove 2 remains on the pre-compacting mold 7 .

[0036] III. Combination Figure 2 , Figure 3 , remove the rubber molding insert 71, the rubber molding female mold 81 and the rubber molding upper mold 91, then the lower mold 5, the core mold 6 and the rubber layer 4 become a new combined core mold. Start laying the prepreg sample on the skin 1 of the rubber layer 4. After reaching the specified number of layers, first place the boss 3 in the predetermined position of the rubber layer 4, and then continue to lay the prepreg sample on the skin 1 and the boss 3 to the specified thickness. Lay the release cloth, non-porous membrane, breathable felt and vacuum bag on the surface of the prepreg in turn, and ensure air tightness by bonding with sealing strips, and evacuate at room temperature for 30 minutes. After curing, continue to lay the prepreg, and after reaching the specified thickness, put the pre-compacted mold 7 with the pre-formed C-shaped groove 2 into the position of the original rubber molding insert 71. Alternatively, the pre-compacted mold 7 with the pre-formed C-shaped groove 2 can be placed first, and then the boss 3 can be placed later.

[0037] IV. Continue to lay prepreg samples on the skin 1, C-shaped groove 2 and boss 3 until the specified thickness is reached. Figure 2 , Figure 3 , place the cabin molding female mold 8 and the cabin molding upper mold 9 on the positions of the original rubber molding female mold 81 and the rubber molding upper mold 91 respectively, put them into the oven for heating and curing, set the oven temperature to 220℃, adjust the oven temperature to 180℃ after the mold temperature rises to 180℃, keep warm for 4 hours, and close the oven.

[0038] V. After the mold temperature drops below 50°C, open the oven, take out the mold and flip it over, remove the lower mold 5, outer mold 62, inner mold 61 in sequence, take out the pre-compacted mold 7 from the inside of the cabin, take out the composite cabin, and complete demoulding.

[0039] The product profile obtained according to the above method satisfies:

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

[0041] The effect of this method is not as good as that of other conventional molding methods, such as when molding by hot-pressing tank:

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

[0043] The data comparison clearly shows that the cabin products formed by this method are superior to those formed by conventional autoclaves.

[0044] Through the above-mentioned newly designed mold and the matching molding method, the thickness of the rubber layer 4 can be reduced while ensuring that the structural strength of the cabin meets the requirements, so that the amount of silicone rubber used is reduced by about 50%, thereby reducing the cost of silicone rubber auxiliary materials. At the same time, large chamfer angles are set between the mold blocks to reduce friction, and the surface roughness of the product is lower than Ra0.8, the required demoulding force is small, and the difficulty of demoulding operation is also reduced, solving the problem that the high boss 30mm to 50mm thickness inside the cabin cannot be demoulded. Moreover, compared with the high cost and long cycle of the current five-axis machining of the C-groove 2, the solution of the present invention realizes the integrated molding of the complex features of the C-groove 2, reduces the machining requirements of the feature, and the mold manufacturing difficulty is low, effectively reducing the machining cost, and the product contour degree can be comparable to the machining molding accuracy, and there will be no risk of "fiber breakage" unique to machining, achieving multiple goals at one stroke.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for integrated molding of a composite cabin with complex inner wall features, characterized in that: The following steps are involved: Ⅰ. According to the structural characteristics of the formed cabin, the cabin is divided into three parts: a skin (1) with uniform wall thickness, a C-shaped groove (2) with notches, and a boss (3) with a wall thickness greater than the skin (1), and preforming molds and forming molds are processed for the three parts of the cabin respectively; Ⅱ. Processing and assembling the rubber molding mold, mixing the silicone rubber in proportion, injecting the rubber into the mold through the injection channel of the mold and allowing it to stand and cure to form a rubber layer (4); at the same time, cutting the prepreg sample, laying the prepreg sample on the preforming mold to preform the C-shaped groove (2) and the boss (3); III. removing part of the rubber molding mold so that the remaining rubber molding mold and the rubber layer (4) become a combined core mold; starting to lay prepreg samples on the skin (1) of the rubber layer (4), after reaching the specified number of layers, placing the preformed C-shaped groove (2) and its preformed mold and boss (3) into the predetermined position of the rubber layer (4); IV. Continue to lay prepreg samples on the skin (1), C-shaped groove (2) and boss (3) until the specified thickness is reached, install the cabin molding mold to the removed rubber molding mold, and put it into an oven for heating and curing; after the mold is cooled, remove the mold to complete the molding work.

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 work.

3. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 2, characterized in that: A plurality of prepreg samples are laid on the boss (3) preforming mold, and the boss (3) preforming mold is placed on a press to increase the temperature and pressurize the mold. The press is closed after the mold gap is less than 0.2 mm, and the mold is removed after cooling to complete the preforming of the 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: A plurality of prepreg samples are laid on the C-shaped groove (2) preforming mold, and then a release cloth, a non-porous film, a breathable felt and a vacuum bag are laid in sequence outside the prepreg sample, and the vacuum bag is semi-cured and formed, and then placed in an oven for heating to complete the preforming of the C-shaped 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 C-shaped groove (2) preforming mold is a T-shaped pre-compacting mold (7), and the prepreg sample is spread outside the pre-compacting mold (7) to form a C-shaped structure; the pre-compacting mold (7) and the pre-formed C-shaped groove (2) are placed together at a designated position in 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 the prepreg sample is laid outside the rubber layer (4), a release cloth, a non-porous film, a breathable felt and a vacuum bag are laid out in sequence outside the prepreg sample, and vacuum is drawn at room temperature for 30 minutes 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: A sealing strip is bonded to the vacuum bag.

8. The method for integrated 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 preformed boss (3) or a preformed C-shaped groove (2) with a pre-compacting mold (7) is first placed, and the prepreg sample is continued to be laid outside the partially formed skin (1) and the outer side of the placed boss (3) or C-shaped groove (2). After reaching the specified layer group, the preformed C-shaped groove (2) or boss (3) with a pre-compacting mold (7) is placed again, and finally the prepreg sample is continued to be laid outside the partially formed skin (1), C-shaped groove (2) and boss (3) to the thickness of the fully formed skin (1) to complete the laying work.

9. The method for integrated molding of a composite material cabin with complex inner wall features according to claim 8, characterized in that: After installing the cabin forming mold, set the oven temperature to exceed the required insulation temperature. After the mold temperature reaches the insulation temperature, set the oven temperature to the insulation temperature to start insulation. After insulation, turn off the oven, and take out the mold for demoulding after the mold cools down.

10. The method for integrated 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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