A cap type rib co-curing molding structure and method suitable for large size fuel tank

Abstract

The application relates to a cap-shaped rib co-curing forming structure and method suitable for large-size oil tanks, and relates to the forming field, wherein a gas bag with flowing gas is arranged in the inside of the cap-shaped rib to form a convex part and a hollow part of the cap-shaped rib, an AIRPAD pressure equalizing plate is used to form an arc surface part of the cap-shaped rib, and a support tool made of a composite material with a thermal expansion coefficient of 0 is used to co-cure the cap-shaped rib and the oil tank, so that the forming quality of the internal narrow and super-long hyperboloid structure of the longitudinal super-long cap-shaped rib is ensured.

Description

Technical Field

[0001] This invention relates to the field of molding technology, and in particular to a cap-shaped rib co-curing molding structure and method suitable for large-size fuel tanks. Background Technology

[0002] Co-curing technology for large-sized, complex composite fuel tanks has long been a goal in the development of integral fuel tanks for aircraft. Sealing large fuel tanks is a major challenge in fuel tank manufacturing, directly impacting their economic cost and service life. Integral fuel tanks offer significant advantages in both sealing performance and service life. The fuselage barrel section of the fuel tank structure and the cap-shaped ribs are both ultra-long components, presenting considerable technical difficulties in integral co-curing molding.

[0003] Because the cap-shaped rib has a hyperbolic structure, traditional molds are made of high-strength metal materials. This makes it impossible to ensure balanced pressure during the molding of ultra-long cap-shaped rib cavities with hyperbolic variations, resulting in internal quality defects and preventing the overall co-curing and molding of the oil tank and cap-shaped rib.

[0004] Therefore, to address the above shortcomings, there is a need to provide a cap-shaped rib co-curing molding structure and method suitable for large-size fuel tanks. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by this invention is to address the issue that traditional molds cannot ensure uniform pressure on ultra-long cap-shaped ribs, resulting in a high probability that the quality of the cap-shaped ribs after molding will not meet the standards.

[0007] (II) Technical Solution

[0008] To solve the above-mentioned technical problems, the present invention provides a cap-shaped rib co-curing molding structure suitable for large-size fuel tanks, including an airbag with flowing gas inside for forming the protruding part and hollow part of the cap-shaped rib, an AIRPAD pressure equalizing plate for forming the arc part of the cap-shaped rib, and a support fixture made of composite material with a thermal expansion coefficient of 0 to co-cur the cap-shaped rib and the fuel tank.

[0009] As a further explanation of the present invention, preferably, the cap-shaped rib has a length of 3m and a hyperbolic structure with a cross-section of 30mm×50mm.

[0010] As a further explanation of the present invention, preferably, a skin is laid between the pressure equalizing plate and the curved surface.

[0011] This invention also provides a method for co-curing and molding cap-shaped ribs suitable for large-size fuel tanks, comprising the following steps:

[0012] Ⅰ. Use supporting fixtures to position and reinforce the fuselage structural components on the fuel tank, and reserve cap-shaped rib grooves on the structural components;

[0013] II. Lay the cap-shaped rib prepreg on the outer surface of the airbag to form a cap-shaped rib structure that fits the airbag. Then place it in the groove, vacuum and pre-compact it so that the prepreg completely fits the airbag surface, forming a protrusion.

[0014] Ⅲ. Lay the skin over the curved surface of the cap-shaped rib to be formed, position the pressure equalizing plate and cover it on the product surface, and then start pressing the pressure equalizing plate to form the curved surface;

[0015] IV. The oil tank is sent into the autoclave for heating to achieve co-curing. Then, the pressure equalizing plate and skin are removed, the gas in the airbag is extracted, and the airbag is removed to complete the co-curing molding.

[0016] As a further explanation of the present invention, preferably, the pressure equalizing plate and the oil tank are sealed with a vacuum bag, and the pressure equalizing plate pressurizes the skin and the curved surface by drawing a vacuum.

[0017] As a further explanation of the present invention, preferably, the maximum temperature inside the autoclave is 180°C.

[0018] (III) Beneficial Effects

[0019] The above-described technical solution of the present invention has the following advantages:

[0020] This invention solves the problem of uneven molding pressure leading to substandard internal quality by using a composite material with a thermal expansion coefficient close to 0 as a supporting tool, combined with the use of an open airbag and an AIRPAD pressure equalizing plate. This solves the process problem of the inability to co-cur the cap-shaped ribs and the barrel section structure. Attached Figure Description

[0021] Figure 1 This is a front view of the barrel-shaped fuel tank of the present invention;

[0022] Figure 2 This is a front view of the open-type airbag of the present invention;

[0023] Figure 3 This is a front view of the pressure equalizing plate of the present invention;

[0024] Figure 4 This is a front view of the support fixture of the present invention;

[0025] Figure 5 This is a front view of the molded cap-shaped rib of the present invention.

[0026] In the diagram: 1. Airbag; 11. Air inlet; 2. Pressure equalizing plate; 3. Cap-shaped rib; 31. Protrusion; 32. Curved surface; 33. Hollow part; 4. Support fixture; 5. Oil tank. Detailed Implementation

[0027] 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.

[0028] A cap-shaped rib co-curing molding structure suitable for large-size fuel tanks includes an airbag 1 with flowing gas inside, a pressure equalizing plate 2 using AIRPAD, and a support fixture 4 using a composite material with a thermal expansion coefficient close to 0, to co-cur the cap-shaped rib 3 and the fuel tank 5.

[0029] Combination Figure 1 , Figure 5 The cap-shaped rib 3 is a slender hyperbolic structure with a total length of 3m and a cross-section of only 30mm×50mm. It is an ultra-long irregular structural component, consisting of a protrusion 31 and an arc-shaped part 32. The protrusion 31 has a hollow part 33 in the middle, and the outer surface of the oil tank 5 has a groove. The arc-shaped part 32 is embedded in the groove and fixedly connected to the oil tank 5.

[0030] like Figure 2 As shown, the airbag 1 uses an open-type airbag as the inner expansion core mold for the protrusion 31 of the cap-shaped rib 3 to form the protrusion 31 and the hollow part 33. Air ports 11 are provided at both ends along the length of the airbag 1, allowing flowing gas to be blown into the airbag 1 during molding. This ensures that the internal and external molding air pressures of the cap-shaped rib 3 are both the same as the pressure inside the can, effectively solving the problem of unstable rubber expansion leading to uneven molding pressure in the cap-shaped rib 3, thus affecting the internal molding quality of the cap-shaped rib 3.

[0031] like Figure 3 As shown, the equalizing plate 2 is made of AIRPAD rubber through a mold. AIRPAD is a non-silicone rubber that is not only resistant to high temperatures but also does not cause silicone contamination. By using the equalizing plate 2 to replace the traditional vacuum bag pressing method, the AIRPAD equalizing plate is molded, and its shape accuracy is better suited to the product than a vacuum bag. This allows for effective control of the product's shape accuracy. Therefore, even though the cap-shaped rib 3 uses a male mold, the overall shape still meets the design requirements.

[0032] like Figure 4As shown, the support fixture 4 is made of a composite material with a thermal expansion coefficient close to 0. It is connected to the oil tank 5 in the middle and surrounded by structural components, which are connected to the pressure equalization plate 2, etc. This solves the problem of insufficient product strength, which causes product deformation, and also solves the problem of the mismatch between the thermal expansion coefficients of traditional metal fixtures and composite materials, which leads to deformation and damage of the already formed product components in the length direction.

[0033] This invention also provides a method for co-curing and molding cap-shaped ribs suitable for large-size fuel tanks, comprising the following steps:

[0034] I. The fuselage structural components on the fuel tank 1 are positioned and reinforced using the support fixture 4, and a groove for the cap-shaped rib 3 is reserved on the structural components.

[0035] II. The cap-shaped rib 3 prepreg is laid on the outer surface of the airbag 1 to form a cap-shaped rib 3 structure that fits the airbag 1. Then it is placed in the groove, vacuumed and pre-compacted so that the prepreg is completely attached to the surface of the airbag 1, at which point the protrusion 31 is formed.

[0036] Ⅲ. Lay the skin over the arc surface 32 of the cap-shaped rib 3 to be formed, position the pressure equalizing plate 2 and cover it on the product surface, seal the pressure equalizing plate 2 and oil tank 5 with a vacuum bag, and use vacuum to press the skin and arc surface 32 by the pressure equalizing plate 2 to form the arc surface 32.

[0037] IV. The oil tank 5 is sent into the autoclave for heating. The maximum temperature inside the autoclave is 180°C to achieve co-curing. Then, the pressure equalizing plate 2 and the skin are removed, and the gas inside the airbag 1 is extracted to complete the co-curing molding.

[0038] By utilizing the above method, the process problem of uneven pressure preventing the co-curing of the cap-shaped rib 3 and the fuel tank 5 is solved by using the internally flowing gas bladder 1. By laying a skin between the equalizing plate 2 and the pre-formed arc-shaped surface 32, the pressure becomes more uniform, and the surface finish of the formed arc-shaped surface 32 is higher, with a contour accuracy of approximately 0.2. Simultaneously, with the support fixture made of composite materials, the temperature inside the autoclave can reach 180℃, compared to the traditional method which can only reach a maximum of 160℃ with a long molding time and a pass rate of only about 85%. The co-curing molding effect of this invention better meets design standards, achieving a product pass rate of 99.79% after co-curing molding. It has good application value and can effectively promote the development and application of co-curing molding of large-size composite fuel tanks in the aerospace field.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-curing and molding cap-shaped ribs suitable for large-size fuel tanks, characterized in that: The cap-shaped rib (3) used for molding is a hyperbolic structure with a length of 3m and a cross-section of 30mm×50mm. The cap-shaped rib (3) consists of a protruding part (31) and an arc-shaped part (32). The protruding part (31) has a hollow part (33) in the middle. The outer surface of the oil tank (5) has a groove, and the cap-shaped rib (3) is embedded in the groove. Includes the following steps, I. Use composite material with low thermal expansion coefficient to support tooling (4) to position and strengthen the fuselage structural parts on the oil tank (5), and reserve a groove for cap-shaped rib (3) on the structural parts; II. An open-type airbag (1) with flowing gas inside is used as the inner expansion core mold for the protrusion (31) in the cap-shaped rib (3); the prepreg of the cap-shaped rib (3) is laid on the outer surface of the airbag (1) to form a cap-shaped rib (3) structure that fits the airbag (1), and then placed in the groove, vacuumed and pre-compacted so that the prepreg is completely attached to the surface of the airbag (1), at which time the protrusion (31) and the hollow part (33) are formed. Ⅲ. Lay the skin on the curved surface (32) of the cap-shaped rib (3), and after positioning the pressure equalizing plate (2) using AIRPAD, cover the skin surface outside the curved surface (32). Then start pressing the pressure equalizing plate (2) to make the curved surface (32) form and the contour reaches 0.

2. IV. The oil tank (5) is sent into the autoclave for heating to achieve co-curing. The maximum temperature in the autoclave is 180°C. Then, the pressure equalizing plate (2) and the skin are removed, and the gas in the airbag (1) is extracted to complete the co-curing molding.

2. The method for co-curing and molding cap-shaped ribs suitable for large-size fuel tanks according to claim 1, characterized in that: The pressure equalizing plate (2) and the oil tank (5) are sealed with a vacuum bag, and the pressure equalizing plate (2) pressurizes the skin and the curved surface (32) by vacuuming.

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