Impact-resistant access cover for aircraft wing tank

Abstract

This invention relates to an impact-resistant cap. The impact-resistant cap includes: an impact-resistant protective layer comprising a shell and a honeycomb, wherein the honeycomb is located inside the shell after the impact-resistant cap is assembled onto the fuel tank; an impact-resistant buffer layer located inside the impact-resistant protective layer, comprising a first metal plate and a foam layer located inside the first metal plate; and a leak-proof layer located inside the impact-resistant buffer layer, comprising a second metal plate and a sealing layer on the surface of the second metal plate facing the interior of the fuel tank.

Description

Technical Field

[0001] This invention relates to an impact-resistant cover for a fuel tank on an aircraft wing, which can simultaneously withstand impacts from different types of debris while reducing the weight of the impact-resistant cover and improving aircraft fuel economy. This invention belongs to the field of aircraft structural impact-resistant design. Background Technology

[0002] According to airworthiness regulations, aircraft fuel tank caps must be able to withstand impacts from low-energy engine debris, tire debris, or other possible debris to prevent fuel loss to dangerous levels.

[0003] However, in traditional designs, aircraft fuel tank caps are typically thin-walled structures. This single-layer structure often fails to meet the requirements for resisting low-energy debris impacts and preventing fuel leaks. This can lead to fuel leakage, and in severe cases, the risk of fire and explosion, resulting in incalculable disasters and endangering personnel and property. Therefore, aircraft fuel tanks must maintain structural integrity under impacts such as engine rotor explosions and tire blowouts; any damage from such impacts must not penetrate the fuel tank.

[0004] To eliminate the aforementioned risks, designers often try to resist the impact of debris by increasing the thickness of the fuel tank cap. However, this significantly increases the weight of the fuel tank cap, leading to a substantial increase in fuel consumption, which in turn greatly increases manufacturing and operating costs, severely impacting the aircraft's economics.

[0005] In addition, typical debris includes engine rotor fragments and tire fragments. According to relevant requirements, tire fragments are equal to the tire mass (aircraft weight in V). R At operating speeds of 1%, the debris distribution area is equal to 1.5% of the tire tread, typically corresponding to a size of approximately 0.01m. 2 The impact fragment, weighing approximately 600g, is typically made of rubber. Ignoring potential failure, its failure mode after impacting the cover is generally large-scale plastic deformation of the impacted surface. The engine rotor fragment, a 9.5mm cube weighing 6.68g, is made of steel. Its failure mode after impacting the cover is generally localized penetration. The two types of fragment impacts place significant differences in the structural design requirements for the cover. Summary of the Invention

[0006] The purpose of this invention is to provide an impact-resistant cover for aircraft wing fuel tanks. The impact-resistant cover needs to be structurally designed for the corresponding failure modes of the impact-resistant cover, so as to ensure that the optimized impact-resistant cover can meet the industry standards for impact resistance to rotor debris and tire debris at the same time; and in order to improve the economic efficiency of the aircraft, the impact-resistant cover needs to be lightweight.

[0007] In a first example of the impact-resistant cap, the impact-resistant cap includes: an impact-resistant protective layer comprising a shell and a honeycomb, wherein the honeycomb is located inside the shell after the impact-resistant cap is assembled onto the fuel tank; an impact-resistant buffer layer located inside the impact-resistant protective layer, comprising a first metal plate and a foam layer located inside the first metal plate; and a leak-proof layer located inside the impact-resistant buffer layer, comprising a second metal plate and a sealing layer on the surface of the second metal plate facing the interior of the fuel tank, wherein the impact-resistant protective layer is provided with... The design ensures that when the impact-resistant cover is impacted by tire debris, the shell of the impact-resistant protective layer undergoes overall energy-absorbing deformation and honeycomb-like crushing energy absorption, meeting the requirements for tire debris impact resistance. The impact-resistant buffer layer is designed so that when the impact-resistant cover is impacted by rotor debris, and the rotor debris penetrates the impact-resistant protective layer, the energy is attenuated and continues to impact the impact-resistant buffer layer, continuously consuming the energy of the rotor debris. The impact-resistant protective layer and the impact-resistant buffer layer of the impact-resistant cover are impact-resistant as a whole, ensuring that the energy of the rotor debris is insufficient to rupture the leak-proof layer.

[0008] In the second example of the impact-resistant cover, the first example can be optionally included, wherein the housing is bolted to the wall panel below the wing, and a support nut is provided on the inner side of the second metal plate of the leak-proof layer, the support nut is riveted to the second metal plate by rivets, and bolts are screwed to the support nut.

[0009] In the third example of the impact-resistant cap, one or more of the first and second examples may be optionally included, wherein the housing is pressed to the wall panel by a pressure ring, and the pressure ring and the second metal plate are connected together by bolts to the wall panel and the housing.

[0010] In the fourth example of the impact-resistant cap, one or more of the first to third examples may be included, with the pressure ring connected to the wall panel and the housing via an aluminum alloy woven gasket.

[0011] In the fifth example of the impact-resistant cap, one or more of the first to fourth examples may be included. The shell is in the shape of a double-layered stepped structure. The first step is used to mate with the shape of the pressure ring of the impact-resistant cap, and the second step is used to mate with the wall panel. The mating surface of the second step and the wall panel is provided with a groove, in which a sealing ring is arranged. The honeycomb of the impact-resistant protective layer fills the space inside the first step, and the first metal plate and foam layer of the impact-resistant buffer layer fill the space inside the second step.

[0012] In the sixth example of the impact-resistant cap, one or more of the first to fifth examples may be included, with the inner and outer surfaces of the housing and the honeycomb coated with a polyurea impact-resistant coating.

[0013] In the seventh example of the impact-resistant cap, one or more of the first to sixth examples may be included, wherein the shell is made of titanium alloy or aluminum alloy and the thickness is in the range of 0.4 mm to 2.2 mm, and the honeycomb is made of NOMIX material and the thickness is in the range of 3.2 mm to 7.2 mm.

[0014] In the eighth example of the impact-resistant cap, one or more of the first to seventh examples may be included, wherein the first metal plate is made of aluminum alloy and has a thickness in the range of 0.4 mm to 1.2 mm, and the foam layer is PMI foam and has a thickness in the range of 11.2 mm to 17.4 mm.

[0015] In the ninth example of the impact-resistant cap, one or more of the first to eighth examples may be included, wherein the second metal plate is an aluminum alloy plate and the thickness is in the range of 0.4mm-1.2mm.

[0016] In the tenth example of the impact-resistant cover, one or more of the first to ninth examples may be included, wherein the shell of the impact-resistant protective layer is bonded to the honeycomb, the first metal plate of the impact-resistant buffer layer is bonded to the honeycomb, and the foam layer of the impact-resistant buffer layer is bonded to the second metal plate of the leak-proof layer.

[0017] The impact-resistant cap of the present invention can improve the structural support stiffness in the direction of debris impact, and ensure that the impact load is evenly distributed to each layer of the impact-resistant cap structure in the case of tire debris impact, thereby improving the overall energy absorption capacity of the structure. Internally, it can provide a certain structural stiffness to ensure the oil tank meets the oil pressure requirements, while ensuring the feasibility of manufacturing and performance, and ensuring the sealing and disassembly requirements of the impact-resistant cap.

[0018] Honeycomb structures have low density and high axial stiffness, resulting in strong resistance to bending and compression. This structural design, through a five-layer sandwich design, particularly the honeycomb sandwich design of the protective layer, enhances the overall structural stiffness. This reduces the risk of localized crushing and collapse when the impact-resistant cover is impacted by tire debris. Instead, it allows for greater deformation and overall honeycomb structure to absorb energy through crushing. The impact energy is temporarily absorbed and stored through the overall deformation of the impact-resistant cover's shell, and most of the energy is ultimately dissipated after the tire bounces off, effectively improving the impact-resistant cover's resistance to tire debris impacts.

[0019] Foam materials have low density and similar properties in all directions, providing more effective protection when the impact-resistant cover is locally impacted by rotor debris. If rotor debris penetrates the impact-resistant protective layer (outer shell and honeycomb), its energy has already been attenuated; continued impact on the impact-resistant buffer layer (buffer plate + foam) will continue to consume the debris's energy, ensuring that the debris's energy is insufficient to cause cracks in the inner panel, thus preventing fuel leakage.

[0020] This invention utilizes a sandwich structure composed of metal, honeycomb, and foam structures to simultaneously meet the protection requirements against tire debris impacts (soft, high-energy, but large-area impacts) and rotor debris impacts (hard, low-energy, but concentrated impacts). Attached Figure Description

[0021] To describe embodiments of the above and other features of the present invention, a more detailed description of the invention will be presented with reference to exemplary embodiments of the invention shown in the accompanying drawings. It is to be understood that these drawings depict only exemplary embodiments of the invention and should not be considered as limiting its scope; the invention will be described and explained using the drawings and with the aid of additional features and details. In the drawings:

[0022] Figure 1 This is a cross-sectional side view of an impact-resistant cap according to an embodiment of the present invention;

[0023] Figure 2 This is a partial cross-sectional side view of the impact-resistant cover being mounted on the wing panel according to an embodiment of the present invention;

[0024] Figure 3 This is a partial perspective view of an impact-resistant cap according to an embodiment of the present invention; and

[0025] Figure 4 yes Figure 3 The dashed box outlines a partial sectional side view of the location.

[0026] Figure 1-4 The figures are drawn roughly to scale; however, the dimensions in the accompanying drawings are merely illustrative and not necessarily to scale, but are intended to make the illustration clearer. Other relative dimensions may be used in other embodiments.

[0027] Throughout this and all subsequent content, the same features appearing in different figures are indicated by the same or similar reference numerals.

[0028] List of reference numerals in the attached diagram:

[0029] 1 Impact-resistant cap

[0030] 2. Wall panel

[0031] 11. Shell

[0032] 12 honeycomb

[0033] 21 First Metal Plate

[0034] 22 Foam layer

[0035] 31 Second metal plate

[0036] 41 Pressure Ring

[0037] 51 bolts

[0038] 52. Support plate nut

[0039] 53 Rivets

[0040] 61 Sealing ring

[0041] 62 Phenolic gasket

[0042] 71 Aluminum Alloy Braided Gasket Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0044] The term "outer side" is defined as the side facing the external environment of the fuel tank after the impact-resistant hatch is fitted onto the wing panel.

[0045] The term "inner side" is defined as the side facing inwards from the fuel tank after the impact-resistant hatch is fitted onto the wing panel.

[0046] Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inward,” “outer,” and “outward,” are used to assist in describing the orientation of the invention according to the embodiments illustrated in the figures. The use of directional terms should not be construed as limiting the invention to any particular orientation.

[0047] Figure 1 The diagram schematically shows a cross-sectional side view of the impact-resistant cap 1 of the present invention, viewed from the outside ( Figure 1 (below) to the inside ( Figure 1 The upper part mainly includes an impact-resistant protective layer, an impact-resistant buffer layer, and a leak-proof layer.

[0048] The impact-resistant protective layer can consist of an outer shell 11 and an inner honeycomb 12. After the impact-resistant cover 1 is assembled onto the fuel tank, the honeycomb 12 is located inside the shell 11.

[0049] The inner and outer surfaces of the shell 11 of the impact-resistant protective layer can be coated with an impact-resistant coating such as a polyurea coating. This combination of structure and coating can improve the overall energy absorption capacity of the impact-resistant protective layer during tire debris impact, thereby preventing the shell 11 of the impact-resistant cover 1 from undergoing large-scale plastic deformation, while at the same time reducing the overall thickness of the shell 11 while meeting the requirements for plastic deformation resistance.

[0050] The material of the housing 11 can be titanium alloy or aluminum alloy, and preferably 2024-T351 aluminum alloy.

[0051] The thickness of the shell 11 can be in the range of 0.4mm-2.2mm, preferably in the range of 0.5-2mm, and more preferably 1.5mm.

[0052] The honeycomb 12 can be made of a high-density, high-strength material, which can improve the supporting stiffness of the impact-resistant protective layer in the outward direction of the impact-resistant cover 1 to a certain extent. Simultaneously, it can fully utilize the internal space of the shell 11, allowing structural deformation of the shell 11 within its elastic deformation range, thereby improving the overall energy absorption capacity of the impact-resistant protective layer and meeting the impact resistance requirements of the impact-resistant cover 1 under tire debris impact. In a preferred embodiment, the honeycomb 12 is made of NOMIX material.

[0053] The thickness of the honeycomb 12 can be in the range of 3.2mm-7.2mm, preferably in the range of 4mm-6mm, and more preferably 4.6mm.

[0054] It is understood that the shell 11 and the honeycomb 12 can have any thickness, sufficient to provide the impact-resistant protective layer with resistance to plastic deformation.

[0055] The honeycomb 12 can be bonded to the inside of the housing 11, preferably bonded together by a tank sealant.

[0056] The impact-resistant buffer layer may include a first metal plate 21 and a foam layer 22 located inside the first metal plate 21. The first metal plate 21 and the foam layer 22 may have a thickness sufficient to provide the impact-resistant buffer layer with resistance to plastic deformation.

[0057] The first metal plate 21 can be an aluminum alloy plate, and its thickness can be in the range of 0.4mm-1.2mm, preferably in the range of 0.5mm-1mm.

[0058] The foam layer 22 can be made of closed-cell foam, which will not retain moisture and is used to reduce the weight of the impact-resistant cap body. The foam layer 22 is preferably PMI foam. Among foam materials, under the same density conditions, PMI foam has extremely high compression, tensile, shear modulus, and strength. In addition, its heat distortion temperature reaches 220℃. PMI foam is lightweight and, when filled within the impact-resistant buffer layer, improves the overall structural rigidity of the impact-resistant cap externally and can withstand some of the pressure from the oil on the impact-resistant cap body internally.

[0059] The thickness of the foam layer 22 can be in the range of 11.2mm-17.4mm, preferably in the range of 14mm-14.5mm.

[0060] In the event of rotor fragment impact, due to the small contact area, existing impact-resistant protective layer designs may suffer structural penetration. In this invention, the first metal plate 21 and the foam layer 22 of the impact-resistant buffer layer provide further impact protection against rotor fragments that have penetrated the protective layer, thus completing rotor fragment impact protection. The stop and deformation energy absorption of the combined structure of the first metal plate 21 and the foam layer 22 can further absorb the remaining energy of the rotor fragments after penetrating the impact-resistant protective layer, increasing the rotor fragment impact resistance of the impact-resistant cover 1.

[0061] It is understood that the first metal plate 21 and the foam layer 22 can have any thickness, sufficient to provide further impact protection for the impact-resistant protective layer.

[0062] The foam layer 22 can be bonded to the inside of the first metal plate 21, preferably bonded together by a tank sealant.

[0063] The leak-proof layer may include a second metal plate 31 and a sealing coating on the surface of the second metal plate 31 facing the inside of the fuel tank. The leak-proof layer is mainly used to bear the internal pressure of the fuel, prevent fuel leakage, and meet the sealing requirements after the impact protection layer and the impact buffer layer are damaged by impact.

[0064] The second metal plate 31 can be a thin aluminum alloy plate, and its thickness can be in the range of 0.4mm-1.2mm, preferably in the range of 0.5mm-1mm.

[0065] It is understood that the second metal plate 31 can have any thickness sufficient to provide the sealing required for the leak-proof layer.

[0066] Figure 2 The diagram schematically illustrates a partial cross-sectional side view of the impact-resistant cover 1 of the present invention after it has been assembled onto the wing panel, and... Figure 3 This is a partial perspective view of the impact-resistant port cover according to the present invention after it has been assembled onto the fuel tank. Figure 2 , 3 As shown, the housing 11 of the impact-resistant cover 1 is connected to the wall panel 2 below the wing at the fuel tank via bolts 51. In addition, a support nut 52 is provided on the inner side of the second metal plate 31 of the leak-proof layer along its outer periphery. The support nut 52 can be riveted to the second metal plate 31 via rivets, and the bolts 51 are screwed to the support nut 52.

[0067] Figure 4 yes Figure 3 The dashed box outlines a partial sectional side view of the location. For example... Figure 4 As shown, the second metal plate 31 of the anti-leakage layer is directly riveted to the housing 11 of the anti-impact cover 1 by means of the support plate nut 52 and rivet 53 used to connect the anti-impact cover 1 and the wall panel 2, avoiding the use of special fasteners for connection, thus achieving weight reduction and a reduction in assembly workload.

[0068] Meanwhile, after the impact-resistant cover 1 is connected to the wing panel 2, the bolt 51 can also connect the anti-leakage layer of the impact-resistant cover 1 to the shell 11 of the impact-resistant cover 1, further increasing the reliability of the connection.

[0069] Preferably, the housing 11 is pressed to the wall panel 2 by a pressure ring 41, and the pressure ring 41 and the second metal plate 31 are connected together by bolts 51. Therefore, the impact-resistant cover 1 is clamped to the wall panel 2 by bolts 51, pressure ring 41 and support plate nut 52.

[0070] according to Figure 2 , 3 The shock-resistant cover 1 uses a clamp-on connection and therefore does not participate in wing load transfer. Considering that the primary requirement of the shock-resistant cover 1 is to withstand impact loads, high-strength connections are not required between the shell 11 and honeycomb 12 of the shock-resistant protective layer, the first metal plate 21 of the shock-resistant buffer layer and the honeycomb 12 of the shock-resistant protective layer, and the foam layer 22 of the shock-resistant buffer layer and the second metal plate 31 of the leak-proof layer. Direct bonding with fuel tank sealant is a simple process, lower in cost and higher in assembly efficiency compared to composite material bonding. Furthermore, the fuel tank sealant is self-resistant to fuel oil and also provides leak-proof protection.

[0071] The aluminum alloy braided gasket 71 is used to achieve electrical connection between the impact-resistant cover 1 and the wing panel 2, guiding the current to the wing, thereby enabling the impact-resistant cover 1 to meet lightning protection requirements.

[0072] In a preferred embodiment, the housing 11 can be designed with a double-layered stepped structure. The first step is used to align with the shape of the pressure ring 41 of the impact-resistant cover 1; the second step is used to align with the fuel tank opening of the wing panel 2. A phenolic gasket 62 can be provided on the mating surface of the second step and the panel 2. The phenolic gasket has good wear resistance, transforming metal-to-metal contact into metal-to-non-metal contact, effectively preventing structural wear and protecting structural integrity. Simultaneously, the presence of the phenolic gasket can eliminate structural gaps and avoid potential gap discharge problems.

[0073] The mating surface between the second-layer step and the wall panel 2 can also be provided with a groove, and a sealing ring 61 can be arranged in the groove. The sealing ring 61 between the impact-resistant cover 1 and the wall panel 2 of the wing, as well as the sealing layer of the anti-leakage layer, are used to prevent fuel leakage from the impact-resistant cover 1 under normal working conditions and under impact conditions.

[0074] The honeycomb 12 of the impact-resistant protective layer can fill the space inside the first step, and the first metal plate 21 and closed-cell foam 22 of the impact-resistant buffer layer can fill the space inside the second step.

[0075] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention have been clearly and completely described above in conjunction with the specific embodiments and accompanying drawings.

[0076] Although various embodiments have been described above, it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of them, and are presented by way of example rather than limitation. It will be apparent to those skilled in the art that the disclosed subject matter may be implemented in other specific forms without departing from its spirit and essential characteristics.

[0077] Therefore, the embodiments described above are to be considered exemplary and not restrictive in all respects, and are not intended to limit the invention in any way.

[0078] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. This disclosure also includes various modifications and equivalent variations. In addition, various combinations and methods, further including only one element, one or more or less other combinations and methods, also fall within the scope and concept of this disclosure.

Claims

1. An impact-resistant cap for a fuel tank on an aircraft wing, characterized in that, The impact-resistant cap (1) includes: An impact-resistant protective layer comprising a shell (11) and a honeycomb (12) is provided. After the impact-resistant cap (1) is assembled onto the oil tank, the honeycomb (12) is located inside the shell (11). An impact-resistant buffer layer, located inside the impact-resistant protective layer, comprising a first metal plate (21) and a foam layer (22) located inside the first metal plate (21); and A leak-proof layer is located inside the impact-resistant buffer layer. The leak-proof layer includes a second metal plate (31) and a sealing layer on the surface of the second metal plate (31) facing the interior of the tank. The impact-resistant protective layer is designed such that when the impact-resistant cover is impacted by tire debris, the shell (11) of the impact-resistant protective layer undergoes overall energy-absorbing deformation and the honeycomb (12) generates crushing energy absorption, thus meeting the requirements for resistance to tire debris impact. The impact-resistant buffer layer is designed so that when the impact-resistant cover is impacted by rotor debris, and the rotor debris penetrates the impact-resistant protective layer, the energy is attenuated and continues to impact the impact-resistant buffer layer, continuously consuming the energy of the rotor debris. The impact-resistant protective layer and the impact-resistant buffer layer of the impact-resistant cover are impact-resistant as a whole, ensuring that the energy of the rotor debris is insufficient to rupture the leak-proof layer. The housing (11) is connected to the wall panel (2) under the wing via bolts (51), and A support nut (52) is provided on the inner side of the second metal plate (31) of the anti-seepage layer. The support nut (52) is riveted to the second metal plate (31) by rivets, and the bolt (51) is screwed to the support nut (52) for fastening. The housing (11) is pressed to the wall panel (2) by a pressure ring (41), and the pressure ring (41) and the second metal plate (31) are connected together by bolts (51) to the wall panel (2) and the housing (11). The shell (11) is in the shape of a double-layered step. The first step is used to connect with the shape of the pressure ring (41) of the impact-resistant cover (1). The second step is used to connect with the wall panel (2). The second step and the wall panel (2) have a groove on their mating surface, and a sealing ring (61) is arranged in the groove. Wherein, the honeycomb (12) of the impact-resistant protective layer fills the space inside the first step, and The first metal plate (21) and the foam layer (22) of the impact-resistant buffer layer fill the space inside the second step.

2. The impact-resistant cap according to claim 1, characterized in that, The pressure ring (41) is connected to the wall panel (2) and the housing (11) by an aluminum alloy woven gasket (71).

3. The impact-resistant cap according to claim 1, characterized in that, The inner and outer surfaces of the housing (11) and the honeycomb (12) are coated with a polyurea impact-resistant coating.

4. The impact-resistant cap according to claim 1, characterized in that, The shell (11) is made of titanium alloy or aluminum alloy, and its thickness is in the range of 0.4mm-2.2mm. The honeycomb (12) is made of NOMIX material and has a thickness in the range of 3.2mm-7.2mm.

5. The impact-resistant cap according to claim 1, characterized in that, The first metal plate (21) is made of aluminum alloy and has a thickness in the range of 0.4mm-1.2mm. The foam layer (22) is PMI foam and has a thickness in the range of 11.2 mm to 17.4 mm.

6. The impact-resistant cap according to claim 1, characterized in that, The second metal plate (31) is an aluminum alloy plate with a thickness in the range of 0.4mm-1.2mm.

7. The impact-resistant cap according to claim 1, characterized in that, The shell (11) of the impact-resistant protective layer is bonded to the honeycomb (12), the first metal plate (21) of the impact-resistant buffer layer is bonded to the honeycomb (12), and the foam layer (22) of the impact-resistant buffer layer is bonded to the second metal plate (31) of the leak-proof layer.

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