Low pressure pre-evacuation transverse shrinkage pre-setting method for hat-stiffened wall panel tubular vacuum bag

Abstract

The application belongs to the field of aviation composite structure production, and particularly relates to a low-pressure pre-extraction transverse shrinkage preset method for a hat-shaped stiffened wall plate tubular vacuum bag, air in the tubular vacuum bag is extracted through a vacuum nozzle connected to a vacuum device until transverse shrinkage occurs; the tubular vacuum bag after transverse shrinkage is placed in a hat-shaped stringer cap cavity, the position of the tubular vacuum bag is controlled by adjusting the air extraction pressure, and the vacuum pressure value in the tubular vacuum bag is collected in real time; the vacuum pressure value in the tubular vacuum bag is analyzed to determine the sealing performance of the tubular vacuum bag. The tubular vacuum bag in the shrinkage state is pre-placed in the stringer cap cavity, which can effectively reduce the inclusion problem in the forming process caused by poor adaptability of the tubular vacuum bag and the hat-shaped stringer cavity; a sealed vacuum device is made of different material combinations, and the air in the tubular vacuum bag is extracted to transverse shrinkage through the device, which can detect the integrity of the tubular vacuum bag in advance.

Description

Technical Field

[0001] This application belongs to the field of aerospace composite material structural component production, and specifically relates to a low-pressure pre-extraction and transverse shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag. Background Technology

[0002] Composite materials possess many excellent properties, including high specific strength and modulus, fatigue resistance, corrosion resistance, and good overall formability. Their panel structures are increasingly widely used in modern aircraft structures. Today's passenger aircraft fuselage composite panels typically employ a cap-shaped Ω-string structure and skin, assembled through a "dry stringer + wet skin" co-bonding process. During molding, a tubular vacuum bag is needed to ensure uniform pressure on the skin within the stringer cap cavity during the panel curing stage, achieving sufficient strength and surface quality. Figure 1 As shown;

[0003] During the use of tubular vacuum bags, due to placement deviations or manufacturing errors of the cap-shaped stringer, the shape of the cap cavity may not be perfectly matched with the size of the tubular vacuum bag. This can cause the bottom corner of the tubular vacuum bag to get stuck between the stringer and the skin, and after curing, it may be stuck together by the adhesive film and unable to detach. In addition, minor damage to the tubular vacuum bag itself is difficult to identify with the naked eye before use. Using a tubular vacuum bag with minor damage can compromise the vacuum seal during the overall molding of the wall panel during the autoclave curing process, resulting in a drop in the curing pressure of the wall panel and making it impossible to guarantee the molding quality.

[0004] Therefore, how to prevent the tubular vacuum bag from getting trapped and leaking air during the wall panel forming process is a problem that needs to be solved. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a low-pressure pre-extraction and transverse shrinkage pre-setting method for tubular vacuum bags in cap-shaped reinforced wall panels, thereby resolving the common problems of inclusion and leakage of tubular vacuum bags during the wall panel forming process in the prior art.

[0006] The technical solution of this application is: a low-pressure pre-extraction and transverse shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag, comprising:

[0007] A vacuum sealing device is made using breathable felt, vacuum bag film, and a first vacuum sealing strip; the vacuum sealing device is then used to cover the end of the tubular vacuum bag.

[0008] Air is extracted from the tubular vacuum bag by connecting a vacuum nozzle to a vacuum device until lateral contraction occurs.

[0009] The laterally contracted tubular vacuum bag is placed inside the cap-shaped stringer cavity. The position of the tubular vacuum bag is controlled by adjusting the pumping pressure, and the vacuum pressure value inside the tubular vacuum bag is collected in real time.

[0010] The vacuum pressure inside the tubular vacuum bag was analyzed to determine its sealing performance.

[0011] Preferably, the specific method for manufacturing the vacuum sealing device is as follows:

[0012] First, place a layer of vacuum bag film, and then stick the first vacuum sealing strip around the vacuum bag film. The first vacuum sealing strip should be more than 20mm away from the edge of the vacuum bag film.

[0013] Then, a layer of breathable felt is placed on the vacuum bag film, and finally the vacuum bag film is folded in half and sealed to cover the breathable felt, forming a structure with three sides sealed and one side open.

[0014] Preferably, a vacuum nozzle base is placed on the breathable felt; and an insulating liner is retained on the first vacuum sealing strip.

[0015] Preferably, an opening is provided on the vacuum sealing device, and a portion of the breathable felt structure is extracted from the opening of the vacuum sealing device and inserted into the tubular vacuum bag.

[0016] Preferably, before extracting air from the tubular vacuum bag, the end of the tubular vacuum bag is fully opened, and a semi-circular hard plastic ring is placed inside. The tubular vacuum bag is then opened into a semi-circular structure. Pressure-sensitive adhesive tape with a width greater than 50mm is pasted on the outer surface of the end of the tubular vacuum bag. After pasting, the end of the tubular vacuum bag is returned to its original shape. Finally, a second vacuum sealing strip with a width of 6-8mm and a length of 40-60mm is pasted on each side of the end of the tubular vacuum bag at the waist position.

[0017] Preferably, the vacuum sealing device is used to cover the end of the tubular vacuum bag. First, the portion of the breathable felt pulled out from the opening is inserted into the cavity of the tubular vacuum bag. Then, the opening reserved by the sealing vacuum device is used to cover the end of the tubular vacuum bag again. The end of the tubular vacuum bag is then fully opened by hand so that the end cross-section is trapezoidal. The first vacuum sealing strip at the opening is pasted onto the pressure-sensitive tape, and at the same time, it is pasted onto the second vacuum sealing strip on the pressure-sensitive tape. The second vacuum sealing strip is pressed firmly to make it in a sealed state.

[0018] Preferably, before using a vacuum sealing device to cover the end of the tubular vacuum bag, a clamp is used to seal the end of the tubular vacuum bag.

[0019] Preferably, after the vacuum nozzle is connected to the vacuum equipment, the vacuum equipment is turned on to pump air and the vacuum pressure is adjusted to -0.05MPa~-0.06MPa; when the vacuum pressure value fluctuation is within the set value range, the vacuum pressure value is determined to be stable; when the vacuum pressure value is stable for at least 3 minutes, the sealing performance of the tubular vacuum bag is determined to be good, and the tubular vacuum bag, which is kept in a contracted state, is placed in the cap-shaped stringer cavity in advance.

[0020] The low-pressure pre-extraction and transverse shrinkage pre-setting method for cap-shaped reinforced wall panel tubular vacuum bags of this application has the following advantages:

[0021] By using the "low-pressure pre-extraction lateral shrinkage" step, the soft tubular vacuum bag undergoes lateral shrinkage and slight length reduction before entering the cap cavity, forming a "pre-set state" with a size smaller than its theoretical installation space.

[0022] In traditional methods, vacuum bags are full, and their bottom corners are easily squeezed into sharp-angled gaps when placed. After pre-shrinking, the overall outline of the bag becomes smaller, and there is no longer enough space for the bottom corners to be rolled in, thus avoiding the "mixing" phenomenon that occurs when the bag is permanently bonded by the adhesive film after curing.

[0023] It significantly reduces the scrap rate of parts caused by vacuum bag contamination, reduces subsequent manual cleaning work and the potential risk of damage to expensive composite material structures, and greatly improves the first-pass yield of production.

[0024] The tubular vacuum bag in its contracted state is pre-placed inside the stringer cap cavity, which can effectively reduce the problem of inclusions during the molding process caused by poor compatibility between the tubular vacuum bag and the stringer cap cavity. By combining different materials to make a sealing vacuum device, and by using this device to extract air from the tubular vacuum bag until it contracts laterally, its integrity can be pre-tested. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of co-bonding of composite material panels for fuselage in the background art;

[0026] Figure 2 A schematic diagram of the sealing vacuum device for this application is provided.

[0027] Figure 3 This is a schematic diagram of the end of the tubular vacuum bag in this application;

[0028] Figure 4 ① is an isometric view of the end of the tubular vacuum bag covered by the sealing vacuum device of this application; Figure 4 ② is the corresponding cross-sectional view;

[0029] Figure 5 ① is an isometric view of the structure pre-installed in the cap-shaped stringer cavity of the tubular vacuum bag in the contracted state after pre-evacuation of the tubular vacuum bag in this application; Figure 5 ② is the corresponding cross-sectional view.

[0030] 1. Vacuum bag film; 2. First vacuum sealing strip; 3. Breathable felt; 4. Vacuum nozzle base; 5. Tubular vacuum bag end; 6. Pressure-sensitive adhesive tape; 7. Second vacuum sealing strip; 8. Semi-circular hard plastic ring; 9. Skin; 10. Hat-shaped stringer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0032] The first aspect of this application provides a low-pressure pre-extraction and lateral shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag, comprising the following steps:

[0033] Step S100: A vacuum sealing device is made using a breathable felt 3, a vacuum bag film 1, and a first vacuum sealing strip 2; the vacuum sealing device is then used to cover the end of the tubular vacuum bag.

[0034] Preferably, the specific method for manufacturing the vacuum sealing device is as follows:

[0035] First, place a layer of vacuum bag film 1, and then stick the first vacuum sealing strip 2 around the vacuum bag film 1. The first vacuum sealing strip 2 is more than 20mm away from the edge of the vacuum bag film 1.

[0036] Then, a breathable felt 3 is placed on the vacuum bag film 1, and finally the vacuum bag film 1 is folded in half and sealed so that it covers the breathable felt 3, forming a structure with three sides sealed and one side open.

[0037] A vacuum nozzle base 4 is placed on the breathable felt 3 to ensure that a vacuum device can be used to connect the vacuum nozzle for evacuation after sealing is completed.

[0038] The first vacuum sealing strip 2 retains an insulating liner to isolate the breathable felt 3 from the sealing strip, preventing the first vacuum sealing strip 2 at the opening of the vacuum device from being contaminated by the breathable felt 3.

[0039] The vacuum bag film 1 has a size of 400mm×500mm; the breathable felt 3 has a size of 80mm×500mm.

[0040] During sealing, retain the release liner paper from the first vacuum sealing strip 2 at the opening position to isolate it from the breathable felt 3 and prevent contamination of the strip. Finally, pull the breathable felt 3 out of the opening position for more than 50mm, in the following shape: Figure 2 As shown.

[0041] Before evacuating the air from the tubular vacuum bag, fully open the end 5 of the tubular vacuum bag and insert a semi-circular hard plastic ring inside. Spring the tubular vacuum bag into a semi-circular structure. Attach a pressure-sensitive adhesive tape 6 with a width greater than 50mm to the outer surface of the end 5 of the tubular vacuum bag. After attaching, allow the end 5 of the tubular vacuum bag to return to its original shape. Finally, attach a second vacuum sealing strip 7, 6-8mm wide and 40-60mm long, to the waist of both sides of the end 5 of the tubular vacuum bag and above the pressure-sensitive adhesive tape 6. Figure 3 As shown.

[0042] Preferably, the vacuum sealing device covers the end of the tubular vacuum bag. First, the portion of the breathable felt 3 pulled out from the opening is inserted into the cavity of the tubular vacuum bag. Then, the opening reserved by the sealing vacuum device is used to cover the end 5 of the tubular vacuum bag. The end 5 of the tubular vacuum bag is then fully opened by hand, making the end cross-section trapezoidal. The first vacuum sealing strip 2 at the opening is then attached to the pressure-sensitive tape 6, and simultaneously attached to the second vacuum sealing strip 7 on the pressure-sensitive tape 6. The sealing strips are then pressed firmly to achieve a sealed state. Figure 4 As shown in ① and ②.

[0043] In step S200, air is extracted from the tubular vacuum bag by connecting a vacuum device through a vacuum nozzle until lateral contraction occurs.

[0044] Seal the uncovered end of the tubular vacuum bag using a clamp. Connect a vacuum nozzle to a vacuum device and turn on the device to evacuate air. Adjust the vacuum pressure to -0.05MPa to -0.06MPa. As air is extracted, the tubular vacuum bag 5 will gradually shrink laterally. Simultaneously, the integrity of the tubular vacuum bag can be pre-checked based on the change in vacuum pressure. (The shape is as follows...) Figure 5 As shown in ① and ②.

[0045] In step S300, the laterally contracted tubular vacuum bag is placed inside the inner cavity of the cap-shaped stringer 10. The position of the tubular vacuum bag is controlled by adjusting the pumping pressure, and the vacuum pressure value inside the tubular vacuum bag is collected in real time. The vacuum pressure value inside the tubular vacuum bag is analyzed to determine the sealing performance of the tubular vacuum bag.

[0046] After the vacuum pressure stabilizes at -0.05MPa to -0.06MPa for at least 1 minute, the tubular vacuum bag, which is in a contracted state, is pre-placed inside the cavity of the cap-shaped stringer 10. At this time, the position of the contracted tubular vacuum bag can be adjusted within the cap cavity. Maintaining this state, the cap-shaped stringer 10 is flipped and placed on the skin 9 for stringer bonding and positioning, as shown in the figure. Figure 5 As shown.

[0047] In summary, this application has the following advantages:

[0048] By using the "low-pressure pre-extraction lateral shrinkage" step, the soft tubular vacuum bag undergoes lateral shrinkage and slight length reduction before entering the cap cavity, forming a "pre-set state" with a size smaller than its theoretical installation space.

[0049] In traditional methods, vacuum bags are full, and their bottom corners are easily squeezed into sharp-angled gaps when placed. After pre-shrinking, the overall outline of the bag becomes smaller, and there is no longer enough space for the bottom corners to be rolled in, thus avoiding the "mixing" phenomenon that occurs when the bag is permanently bonded by the adhesive film after curing.

[0050] It significantly reduces the scrap rate of parts caused by vacuum bag contamination, reduces subsequent manual cleaning work and the potential risk of damage to expensive composite material structures, and greatly improves the first-pass yield of production.

[0051] The shrunken vacuum bag acts like a smaller "glove," allowing it to be guided more easily and smoothly into the cap cavity of the cap-shaped stringer, fundamentally eliminating the risk of it being "stretched open" and squeezed into the gap between the stringer and the skin due to size mismatch.

[0052] The tubular vacuum bag in its contracted state is pre-placed inside the stringer cap cavity, which can effectively reduce the problem of inclusions during the molding process caused by poor compatibility between the tubular vacuum bag and the stringer cap cavity. By combining different materials to make a sealing vacuum device, and by using this device to extract air from the tubular vacuum bag until it contracts laterally, its integrity can be pre-tested.

[0053] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for pre-extraction and lateral shrinkage pre-setting of a cap-shaped reinforced tubular vacuum bag, characterized in that, include: A vacuum sealing device is made using a breathable felt (3), a vacuum bag film (1), and a first vacuum sealing strip (2); the vacuum sealing device is then used to cover the end of the tubular vacuum bag. Air is extracted from the tubular vacuum bag by connecting a vacuum nozzle to a vacuum device until lateral contraction occurs. The laterally contracted tubular vacuum bag is placed inside the cap cavity of the cap-shaped stringer (10), and the position of the tubular vacuum bag is controlled by adjusting the pumping pressure. The vacuum pressure value inside the tubular vacuum bag is collected in real time. The vacuum pressure inside the tubular vacuum bag was analyzed to determine its sealing performance. The specific method for making a vacuum sealing device is as follows: First, place a layer of vacuum bag film (1), and then stick the first vacuum sealing strip (2) around the vacuum bag film (1). The distance between the first vacuum sealing strip (2) and the edge of the vacuum bag film (1) is >20mm. Then, a layer of breathable felt (3) is placed on the vacuum bag film (1), and finally the vacuum bag film (1) is folded in half and sealed so that it covers the breathable felt (3), forming a structure with three sides sealed and one side open. An opening is made in the vacuum sealing device, and part of the structure of the breathable felt (3) is pulled out from the opening of the vacuum sealing device and inserted into the tubular vacuum bag. Before extracting air from the tubular vacuum bag, fully open the end (5) of the tubular vacuum bag and insert a semi-circular hard plastic ring (8) inside. Blow the tubular vacuum bag open into a semi-circular structure. Stick a pressure-sensitive tape (6) with a width > 50mm on the outer surface of the end (5) of the tubular vacuum bag. After sticking, restore the end (5) of the tubular vacuum bag to its original shape. Finally, stick a second vacuum sealing strip (7) with a width of 6~8mm and a length of 40~60mm on each of the two sides of the end (5) of the tubular vacuum bag. Cover the end of the tubular vacuum bag with the vacuum sealing device. First, insert the part of the breathable felt (3) that was pulled out at the opening into the cavity of the tubular vacuum bag. Then, cover the end of the tubular vacuum bag (5) with the opening reserved by the sealing vacuum device. Use your hand to fully open the end of the tubular vacuum bag (5) so that the end cross section is trapezoidal. Use the first vacuum sealing strip (2) at the opening to stick on the pressure-sensitive tape (6) and at the same time stick on the pressure-sensitive tape (6) on the end of the tubular vacuum bag (5). Press the second vacuum sealing strip (7) firmly to make it in a sealed state.

2. The low-pressure pre-extraction and transverse shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag as described in claim 1, characterized in that, A vacuum nozzle base (4) is placed on the breathable felt (3); an isolation liner is retained on the first vacuum sealing strip (2); the size of the vacuum bag film (1) is 400mm×500mm; the size of the breathable felt (3) is 80mm×500mm.

3. The low-pressure pre-extraction and transverse shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag as described in claim 1, characterized in that, Before using a vacuum sealing device to cover the end (5) of the tubular vacuum bag, use a clamp to seal the end of the tubular vacuum bag.

4. The low-pressure pre-extraction and transverse shrinkage pre-setting method for a cap-shaped reinforced wall panel tubular vacuum bag as described in claim 1, characterized in that, After connecting the vacuum nozzle to the vacuum equipment, turn on the vacuum equipment to pump air and adjust the vacuum pressure to -0.05MPa~-0.06Mpa; when the vacuum pressure value fluctuation is within the set value range, it is determined that the vacuum pressure value is stable. When the vacuum pressure value is stable for at least 3 minutes, it is determined that the sealing performance of the tubular vacuum bag is good. The tubular vacuum bag, which is kept in a contracted state, is placed in the cavity of the cap-shaped stringer (10).

Images