An aircraft ventral fin of a foam sandwich construction and a method of forming the same

Abstract

The application discloses an aircraft belly fin with a foamed sandwich structure and a forming method thereof, the longitudinal section of the belly fin is an acute-angle triangular structure with a gradually reduced size, the belly fin comprises a belly fin front section and a belly fin rear section which are spliced together, the matching surface of the belly fin front section and the aircraft fuselage adopts a profile design, the matching surfaces of the belly fin front section, the belly fin rear section and the aircraft fuselage are respectively provided with threaded holes for fixation, the belly fin front section and the belly fin rear section are respectively and alternately filled with foamed filling blocks and nylon filling blocks, and the upper end surface of the belly fin front section is fixedly connected with the aircraft fuselage through a fixing assembly. The application realizes lightweight design, can effectively reduce the overall weight of the aircraft and improve flight efficiency.

Description

Technical Field

[0001] This invention belongs to the field of aircraft technology and relates to an aircraft ventral fin with a foam sandwich structure and its molding method. Background Technology

[0002] With the continuous development of aerospace technology, the requirements for aircraft performance are increasing. As a crucial component of aircraft, the ventral fin plays a key role in improving flight stability and controlling flight attitude. Traditional ventral fin materials suffer from problems such as high weight, insufficient strength, poor corrosion resistance, difficulty in processing, and unsuitability for mass production, thus hindering the improvement of aircraft performance and mass production. Therefore, developing a new lightweight, high-strength, and corrosion-resistant ventral fin material is of great significance. The purpose of this invention is to provide a foam-sandwich structure ventral fin for aircraft to solve the problems existing in the prior art, ensuring both strength and rigidity while meeting weight requirements, and better adapting to mass production. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an aircraft ventral fin with a foam sandwich structure that solves the above-mentioned problems, such as large weight, insufficient strength, poor corrosion resistance, difficulty in processing, and unsuitability for mass production of traditional ventral fins.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A foam sandwich structure for an aircraft ventral fin, the longitudinal section of which is an acute-angled triangle with a gradually decreasing shape, the ventral fin includes a front section and a rear section of the ventral fin spliced ​​together, the mating surface of the front section of the ventral fin with the aircraft fuselage adopts a conformal design, threaded holes for fixing are respectively provided on the mating surfaces of the front section and the rear section of the ventral fin with the fuselage, the front section and the rear section of the ventral fin are alternately filled with foam filling blocks and nylon filling blocks, respectively, and the upper end face of the front section of the ventral fin is fixedly connected to the aircraft fuselage through a fixing component.

[0006] Furthermore, a stepped mating structure is provided between the anterior and posterior segments of the pelvic fin. A groove is opened in the middle of the end face of the anterior segment of the pelvic fin, which is spliced ​​with the posterior segment of the pelvic fin. An integral protrusion is provided in the middle of the end face of the posterior segment of the pelvic fin, which is spliced ​​with the anterior segment of the pelvic fin. The protrusion and the groove are mated together.

[0007] Furthermore, a connecting shaft for connecting to the aircraft fuselage is pre-embedded in the foam filling block at the front of the ventral fin. The upper end of the connecting shaft passes through the front of the ventral fin and then through the aircraft fuselage, where it is fixedly connected to the aircraft fuselage using a fixing component.

[0008] Furthermore, the fixing assembly includes a thin nut, a clamping block, and a washer. After the clamping block is fitted onto the upper end of the connecting shaft that passes through the aircraft fuselage, a washer is placed on top of it. The thin nut is threaded into the upper end of the connecting shaft. The thin nut sequentially clamps the washer and the clamping block so that the clamping block presses against the aircraft fuselage.

[0009] Furthermore, the clamping block is a cylindrical structure with a through hole in the middle, the clamping block has an annular cavity, the clamping block is a thin-walled structure with an opening at the top, and the gasket covers the upper end face of the clamping block.

[0010] Furthermore, the inner wall of the outer ring of the clamping block is provided with several reinforcing columns, and the top of the reinforcing column is provided with a cylindrical protrusion protruding from the reinforcing column. The lower end face of the shim at the cylindrical protrusion is provided with a threaded countersunk hole that mates with the adjusting screw. The adjusting screw is assembled onto the shim from the lower end of the shim.

[0011] Furthermore, the outer diameter of the gasket is larger than that of the clamping block, the upper end of the connecting shaft has a stepped structure with a smaller end outer diameter, the inner hole of the gasket is larger than the outer diameter of the external thread at the upper end of the connecting shaft, and the inner hole of the gasket is smaller than the outer diameter of the lower part of the external thread section of the connecting shaft.

[0012] Furthermore, the foam filler blocks are made of PMI foam material, and the nylon filler blocks are made of nylon 1010 material.

[0013] Furthermore, the threaded holes connecting the front and rear sections of the ventral fin to the aircraft fuselage are respectively opened at the positions where the nylon filler blocks are located, and the threaded holes are respectively fitted with pins and threaded sleeves.

[0014] A method for forming a foam sandwich structure for an aircraft ventral fin, wherein the front section of the ventral fin includes a front section skin, and the front section skin is alternately filled with foam filler blocks and nylon filler blocks. The connecting shaft, the front section skin of the ventral fin, the foam filler blocks and the nylon filler blocks are formed into one piece by a co-curing method, and the pin and screw sleeve is a post-installed structure.

[0015] The posterior section of the pelvic fin includes a posterior fin skin, which is alternately filled with foam filler blocks and nylon filler blocks. The posterior fin skin, foam filler blocks, and nylon filler blocks are molded into one piece by a co-curing method, and the pin and screw sleeve is a post-installed structure.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention creates a lightweight design that can effectively reduce the overall weight of the aircraft and improve flight efficiency.

[0018] This invention creates a high-strength property that can enhance the structural strength and stability of aircraft;

[0019] The invention provides excellent corrosion resistance, making it suitable for various harsh flight environments;

[0020] The manufacturing process created by this invention is simple, low-cost, and easy to mass-produce. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the anterior segment of the pelvic fin with the anterior skin removed, according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the structure of the posterior segment of the pelvic fin after removing the posterior segment skin, according to an embodiment of the present invention.

[0025] Figure 4 This is a longitudinal sectional view of the anterior segment of the pelvic fin in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the connecting shaft according to an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the structure of the clamping block according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Anterior section of pelvic fin; 11. Groove; 12. Anterior section of pelvic fin skin; 2. Posterior section of pelvic fin; 21. Protrusion; 3. Fixing component; 31. Thin nut; 32. Washer; 33. Clamping block; 331. Reinforcing post; 332. Cylindrical protrusion; 34. Adjusting screw; 4. Connecting shaft; 5. Pin threaded sleeve; a. Foam filling block; b. Nylon filling block. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] like Figures 1 to 6 As shown, a foam-sandwich structure for an aircraft ventral fin includes a spliced ​​front section 1 and a rear section 2. The entire ventral fin is approximately 4 meters long, 300 mm high, and 110 mm wide, weighing 15-25 kg. The surface where it mates with the aircraft fuselage is designed to conform to the shape of the fuselage. The longitudinal cross-section of the ventral fin is a gradually decreasing acute-angled triangle structure, which can effectively reduce air resistance, increase the directional stability of the aircraft, and also offset some of the torque exerted on the aircraft fuselage by the lateral force of the vertical tail.

[0035] The front section 1 and rear section 2 of the pelvic fin are provided with a stepped mating structure. A groove 11, 5-20mm deep, is formed in the middle of the end face of the front section 1, which is spliced ​​with the rear section 2. An integral protrusion 21, 5-20mm high, is provided in the middle of the end face of the rear section 2, which is spliced ​​with the front section 1. The protrusion 21 mates with the groove 11, serving both a positioning function and effectively preventing the rear section 2 from falling off. The end face of the front section 1 that mates with the yaw rudder is an arc surface. Threaded holes are provided on the mating surfaces of the front section 1 and rear section 2 with the fuselage to further secure the foam-laminated aircraft pelvic fin. The upper end face of the front section 1 is fixedly connected to the aircraft fuselage via a fixing component 3.

[0036] The ventral fin front section 1 includes a ventral fin front skin 12, which is made of carbon fiber composite material, combining the properties of carbon fiber with a cost reduction, thus making it suitable for mass production. The ventral fin front skin 12 is alternately filled with foam filler blocks a and nylon filler blocks b. Foam filler blocks a are made of PMI foam material, which reduces the weight of the entire ventral fin while meeting strength requirements. Nylon filler blocks b are made of nylon 1010 material, which strengthens the ventral fin while also reducing weight. To ensure connection strength, a connecting shaft 4 for connection to the fuselage is pre-embedded in foam filler block a. The connecting shaft 4 is made of high-strength aluminum alloy, and the portion of the connecting shaft 4 embedded in the foam area is designed with an inverted conical structure to improve strength. The upper end of the connecting shaft 4 extends out of the ventral fin front section 1 and passes through the aircraft fuselage, where it is fixed by a fixing component 3. The threaded hole connecting the ventral fin front section 1 to the aircraft fuselage is located at the position of the nylon filler block b. To ensure connection strength, a pin-and-threaded sleeve 5 is inserted into the threaded hole. The connecting shaft 4, the front skin of the ventral fin 12, the foam filling block a and the nylon filling block b are molded into one piece by co-curing. The pin and screw sleeve 5 is a post-installed structure.

[0037] The fixing component 3 includes a thin nut 31, a clamping block 33, and a washer 32. After the clamping block 33 is fitted onto the upper end of the connecting shaft 4 that passes through the aircraft fuselage, the washer 32 is placed on top. The thin nut 31 is threaded into the upper end of the connecting shaft 4. The thin nut 31 locks the clamping block 33, so that the clamping block 33 presses against the aircraft fuselage to fix the front section of the ventral fin 1 and the aircraft fuselage.

[0038] The clamping block 33 is a cylindrical structure with a through hole in the middle. In order to reduce the weight of the clamping block 33, the clamping block 33 has an annular cavity. The clamping block 33 is a thin-walled structure with an opening at the top. The gasket 32 ​​covers the upper surface of the clamping block 33.

[0039] The inner wall of the outer ring of the clamping block 33 is provided with a number of evenly distributed reinforcing posts 331, preferably four. The top of each reinforcing post 331 has a cylindrical protrusion 332 protruding from it. The lower end face of the washer 32 at the cylindrical protrusion 332 has a threaded countersunk hole that mates with the adjusting screw 34. The adjusting screw 34 is fitted onto the washer 32 from its lower end. The outer diameter of the washer 32 is larger than that of the clamping block 33. The upper end of the connecting shaft 4 has a stepped structure with a smaller outer diameter at the end. The inner hole of the washer 32 is larger than the outer diameter of the external thread at the upper end of the connecting shaft 4, and smaller than the outer diameter of the lower part of the external thread section of the connecting shaft 4, allowing the washer 32 to press against the clamping block 33.

[0040] If the gap between the clamping block 33 and the front section 1 of the ventral fin is not appropriate, it can be adjusted by rotating the adjusting screw 34 to achieve a reasonable gap. The mounting holes of the four cylindrical protrusions 332 and the adjusting screw 34 are fitted with a clearance fit, with a gap of 0.2-0.8mm. The end face of the adjusting screw 34 is in face-to-face contact with the cylindrical protrusions 332. In other words, after clamping, the end face of the cylindrical protrusions 332 is the force-bearing surface.

[0041] The thin nut 31 is made of stainless steel. The clamping block 33 is made of high-strength aluminum alloy and can withstand large clamping forces. The washer 32 and the adjusting screw 34 are made of stainless steel.

[0042] The rear section 2 of the pelvic fin includes a rear fin skin 22, a foam filler block a, and a nylon filler block b. The rear fin skin 22, like the front fin section 1, is made of carbon fiber composite material. The foam filler block a uses PMI foam material, and the nylon filler block b uses nylon 1010 material. The entire rear fin section 2 is a typical foam sandwich structure. To improve overall strength, a nylon filler block b is inserted at every other foam block. To ensure connection strength, the threaded holes connecting the rear fin section 2 to the aircraft fuselage are located at the positions of the nylon filler blocks b. To ensure thread strength, the threaded holes are fitted with pin inserts 5. The rear fin skin 22, foam filler block a, and nylon filler block b are molded as a single unit using a co-curing method. The pin inserts 5 are a post-installed structure.

[0043] The anterior ventral fin skin 12 and posterior ventral fin skin 22 are respectively manufactured using prepreg layup and autoclave curing. To ensure product uniformity, foam filler block a and nylon filler block b are used as male molds, eliminating the need for new molds. During layup, a layer of adhesive film is first laid on the surface of foam filler block a and nylon filler block b. This fills the small pores on the surface of foam filler block a and enhances the interface between foam filler block a and the prepreg. Then, according to design requirements, prepreg is laid on the surface of foam filler block a and nylon filler block b. After the layup is completed and the vacuum auxiliary material is wrapped, the product is placed in an autoclave for pressurization and temperature curing.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A foam-laminated ventral fin for an aircraft, characterized in that: The longitudinal section of the pelvic fin is an acute-angled triangle with a gradually decreasing shape. The pelvic fin includes a front section (1) and a rear section (2) of the pelvic fin, which are spliced ​​together. The mating surface between the front section (1) of the pelvic fin and the aircraft fuselage adopts a conformal design. The mating surfaces between the front section (1) of the pelvic fin and the rear section (2) of the pelvic fin and the aircraft fuselage are respectively provided with threaded holes for fixing. The front section (1) of the pelvic fin and the rear section (2) of the pelvic fin are alternately filled with foam filling blocks (a) and nylon filling blocks (b). The upper end of the front section (1) of the pelvic fin is fixedly connected to the aircraft fuselage through a fixing component (3).

2. The aircraft ventral fin with a foam sandwich structure according to claim 1, characterized in that: A stepped mating structure is provided between the anterior segment (1) and the posterior segment (2) of the pelvic fin. A groove (11) is opened on the middle part of the end face of the anterior segment (1) which is spliced ​​with the posterior segment (2) of the pelvic fin. A protrusion (21) integral with it is provided on the middle part of the end face of the posterior segment (2) which is spliced ​​with the anterior segment (1). The protrusion (21) and the groove (11) are mated together.

3. The aircraft ventral fin with a foam sandwich structure according to claim 1, characterized in that: The foam filling block (a) of the front section (1) of the ventral fin has a pre-embedded connecting shaft (4) for connecting with the aircraft fuselage. The upper end of the connecting shaft (4) passes through the front section (1) of the ventral fin and then through the aircraft fuselage and is fixedly connected to the aircraft fuselage by a fixing component (3).

4. The aircraft ventral fin with a foam sandwich structure according to claim 3, characterized in that: The fixing component (3) includes a thin nut (31), a clamping block (33) and a washer (32). After the clamping block (33) is fitted onto the upper end of the connecting shaft (4) that passes through the aircraft fuselage, the washer (32) is placed on top of it. The thin nut (31) is threaded into the upper end of the connecting shaft (4). The thin nut (31) presses the washer (32) and the clamping block (33) in sequence, so that the clamping block (33) presses the aircraft fuselage.

5. The aircraft ventral fin with a foam sandwich structure according to claim 4, characterized in that: The clamping block (33) is a cylindrical structure with a through hole in the middle. The clamping block (33) has an annular cavity. The clamping block (33) is a thin-walled structure with an opening at the top. The gasket (32) covers the upper surface of the clamping block (33).

6. The aircraft ventral fin with a foam sandwich structure according to claim 5, characterized in that: The inner wall of the outer ring of the clamping block (33) is provided with several reinforcing columns (331). The top of the reinforcing column (331) is provided with a cylindrical protrusion (332) protruding from the reinforcing column (331). The lower end face of the gasket (32) at the cylindrical protrusion (332) is provided with a threaded countersunk hole that matches the adjusting screw (34). The adjusting screw (34) is assembled onto the gasket (32) from the lower end of the gasket (32).

7. The aircraft ventral fin with a foam sandwich structure according to claim 4, characterized in that: The outer diameter of the gasket (32) is larger than that of the clamping block (33). The upper end of the connecting shaft (4) is a stepped structure with a smaller end outer diameter. The inner hole of the gasket (32) is larger than the outer diameter of the external thread at the upper end of the connecting shaft (4). The inner hole of the gasket (32) is smaller than the outer diameter of the lower part of the external thread section of the connecting shaft (4).

8. The aircraft ventral fin with a foam sandwich structure according to claim 1, characterized in that: The foam filler block (a) is made of PMI foam material, and the nylon filler block (b) is made of nylon 1010 material.

9. The aircraft ventral fin with a foam sandwich structure according to claim 1, characterized in that: The threaded holes connecting the front section (1) and rear section (2) of the ventral fin to the aircraft fuselage are respectively opened at the position where the nylon filler block (b) is located, and the threaded holes are respectively fitted with pin sleeves (5).

10. A method for molding an aircraft ventral fin with a foam sandwich structure according to any one of claims 1 to 9, characterized in that: The anterior segment of the pelvic fin (1) includes an anterior segment skin (12), which is alternately filled with foam filling blocks (a) and nylon filling blocks (b). The connecting shaft (4), the anterior segment skin (12), the foam filling blocks (a) and the nylon filling blocks (b) are molded into one piece by co-curing. The pin and threaded sleeve (5) is a post-installed structure. The posterior segment of the pelvic fin (2) includes a posterior segment skin (22), which is alternately filled with foam filling blocks (a) and nylon filling blocks (b). The posterior segment skin (22), foam filling blocks (a) and nylon filling blocks (b) are molded into one piece by co-curing. The pin sleeve (5) is a post-installed structure.

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