Method of joining first aircraft component to second aircraft component, joint assembly in aircraft and hybrid joint

Abstract

The invention relates to a method of joining a first aircraft component to a second aircraft component, a joint assembly in an aircraft, and a hybrid joint. The joint assembly is located, for example, between the wing skin (5) and the rib foot (3). The joint assembly comprises a plurality of fasteners (7) that mechanically hold the wing skin (5) and the rib foot (3) together. The rib foot (3) comprises a circular fitting surface (11), and a material layer (15) is sandwiched between the fitting surface (11) and the wing skin (5). The material layer (15) has adhesive properties such that the joint is a hybrid joint. The material layer (15) also has structural properties for use as a solid interstice, for example, once the material layer (15) is cured after application, the material layer (15) has structural properties for use as a solid interstice.

Description

Technical Field

[0001] The present disclosure relates to joint assemblies in aircraft structures and methods of joining aircraft components. Background Art

[0002] There are many different ways to join aircraft components together. In some arrangements, the components are mechanically held together, for example, using fasteners. In the context of an aircraft wing, the wing skin may be attached to the rib foot of an aircraft rib, and this may be achieved by mechanically holding the wing skin to the rib foot using fasteners inserted through holes in the wing skin and the rib foot. In such an arrangement, each fastener is typically placed under a preload to ensure a strong connection is achieved. It is important to maintain the correct wing skin profile, so where there is a gap between the rib foot and the wing skin (e.g. due to tolerances between the two components), it may be necessary to provide a shim.

[0003] US8479394 (Airbus Operations Limited) discloses an arrangement in which the wing skin and rib legs are measured before assembly, and shims of varying thickness are manufactured to fit the gap between the two structures. During assembly of the wing, a layer of sealant is applied to the exterior face of each shim, and the wing skin is brought into contact with the sealant / shim. Fasteners are then passed through the wing skin, shims, and rib legs to mechanically attach the wing skin to the rib.

[0004] US Pat. No. 11325691 (The Boeing Company) also discloses a joint between a wing skin and a rib foot. Multiple aligning surfaces are provided on the rib foot. This reduces the total contact area between the rib foot and the wing skin and reduces the need for filler between the surfaces. US Pat. No. 11325691 aims to completely eliminate the need for filler, but if a gap between the aligning surface and the wing skin still exists, it is detected and measured, and a solid filler is then positioned within the gap.

[0005] Both of the above disclosures attempt to improve the efficiency of joining wing skins to rib legs. It is desirable to further improve this process. Alternatively or additionally, it is desirable to provide an improved joint assembly in aircraft structures. Summary of the Invention

[0006] According to a first aspect of the present disclosure, a joint assembly for an aircraft is provided, the joint assembly comprising: a first aircraft component having a plurality of holes therein; a second aircraft component having a plurality of holes therein; and a plurality of fasteners. Each fastener extends through a corresponding hole in the first aircraft component and a corresponding hole in the second aircraft component, and the plurality of fasteners are arranged such that the fasteners mechanically hold the first aircraft component and the second aircraft component together. The first aircraft component comprises a plurality of mateable surfaces arranged at a junction with the second aircraft component, each mateable surface protruding above a non-mateable surface of the first aircraft component, and each mateable surface surrounding a corresponding hole in the first aircraft component. The joint assembly further comprises a material layer directly interposed between the mateable surfaces and the second aircraft component, the material layer having adhesive properties such that the material layer structurally bonds the first aircraft component and the second aircraft component together. The material layer preferably also has structural properties that serve as a filler.

[0007] It has been found that providing a faying surface on the first aircraft component in combination with a layer of material that acts as both an adhesive and a caulk is particularly beneficial. In particular, providing a faying surface can enable the joint to be formed while using only a relatively small amount of material in the layer. This arrangement can also facilitate relatively simple visual indication that the layer of material has been correctly applied between the faying surface and the second component, as the operator can see most or all of the edges of the faying surface.

[0008] Materials with both adhesive properties and structural properties as gap fillers are known. For example, US2019 / 0359815 describes a curable material for simultaneously filling tolerances and for sealing components to be combined in aircraft construction. In various aspects of the present invention, the material in the material layer can be the material disclosed in US2019 / 0359815. The material in the material layer can be cured, and the material has been derived from a curable precursor. The curable precursor (that is, the material before it has been cured) can be a liquid gap filler. The material can be configured to fill the volume generated due to the tolerance between the fitting surface and the second aircraft component, and then solidify to form a solid gap filler. References to "adhesive materials" and the like herein will be understood to refer equally to the same material having structural gap filling properties once cured. The material is also referred to as a "dual-function" material in this article.

[0009] The material layer has structural properties suitable for use as a gap filler. For example, the material layer may have an elastic modulus suitable for use as a gap filler. The material layer may be drillable. The material layer may have a gap filling capability suitable for filling gaps of 3 mm or less, and preferably suitable for filling gaps between 0.2 mm and 2.5 mm.

[0010] It will be understood that reference to a "layer" of material does not necessarily mean that the layer has a uniform thickness. In fact, the layer will typically have varying thicknesses due to tolerances between the mating surface and the second component. A layer of material is located between each mating surface and the second component, and each of these layers does not necessarily need to abut one another.

[0011] The structural bond between the first and second components created by the adhesive properties of the material layers is sufficient to contribute to the strength of the joint assembly. In this case, those skilled in the art will appreciate that the resulting joint assembly (with adhesive and fastener) can be considered a hybrid joint. The adhesive properties of the material are preferably sufficient to ensure that the material acts as a seal (e.g., to prevent moisture from escaping).

[0012] Each mate surface can be substantially circular. The circular surface is preferably centered around the hole around which the mate surface is formed. This arrangement has been found to be particularly beneficial because, if material is injected onto the mate surface through the hole, the mate surface can then substantially match the shape formed by the material layer. Since the material will generally flow radially outward, embodiments of the present invention recognize that the material can be effectively applied to the corresponding circular mate surface. The mate surface can, for example, include chamfers at its outer edges. It has been found that providing chamfers is beneficial in promoting high peel strength between the mate surface and the second aircraft component.

[0013] The hole may have a first diameter, and the accommodating surface may have a second diameter. The second diameter may be between 2 and 4 times the size of the first diameter. The second diameter may be about 3 times the size of the first diameter. This arrangement has been found to be particularly effective.

[0014] The material layer preferably contacts the first aircraft component only on the conforming surface. The material layer preferably does not contact the non-conforming surface of the first aircraft component. This arrangement allows the process to be relatively efficient in terms of time and materials. This arrangement can allow the operator to easily detect (e.g., via a visual indication) that the material has been applied to the conforming surface. This arrangement can also avoid or minimize the need for excessive dispensing of cleaning material.

[0015] The conforming surface may be raised above the non-conforming surface. The conforming surface may be raised above the non-conforming surface by a uniform amount. For example, the conforming surface may be raised above the non-conforming surface by at least 1 mm, preferably at least 2 mm, and preferably between 3 mm and 4 mm. It has been found that a conforming surface raised by 3 mm to 4 mm from the non-conforming surface is particularly beneficial because it tends to prevent water from being trapped between the two surfaces.

[0016] In principle, the joint assembly is suitable for use between many different aircraft components. Embodiments of the present disclosure have been found to be particularly beneficial in the context of a rib / wing skin joint. Thus, in a preferred embodiment, the first aircraft component may be a rib. The rib may include a plurality of rib legs, with a plurality of holes positioned in the rib legs. The second component may be a wing skin.

[0017] It will be understood that the components mentioned herein do not imply a unitary structure. For example, the components themselves may be formed from a plurality of sub-components and may be pre-assembled from a plurality of sub-components.

[0018] According to another aspect of the present invention, a method of joining a first aircraft component to a second aircraft component is provided, wherein the method includes the steps of: bringing the first aircraft component and the second aircraft component into proximity with each other; applying an adhesive material and arranging the first component and the second component so that the adhesive material is located on multiple mating surfaces of the first aircraft component and is directly sandwiched between the mating surfaces and the second aircraft component, wherein the adhesive material is also a curable precursor material and the curable precursor material is applied so that the curable precursor material fills a volume created by tolerances between the mating surfaces and the second aircraft component, and wherein the method includes the steps of curing the curable precursor material so that the curable precursor material forms a solid filler in the volume; drilling a plurality of holes in the first aircraft component and the second aircraft component, each hole comprising a pair of aligned holes in the first component and the second component; and attaching a plurality of fasteners, each fastener extending through a corresponding pair of aligned holes, the fasteners being arranged to mechanically hold the first aircraft component and the second aircraft component together so that the components are simultaneously mechanically held together by the fasteners and adhesively bonded together by the adhesive material.

[0019] In some embodiments, some of the steps described above may be performed in a different order than listed above. For example, the adhesive material may be applied to the first component prior to the step of bringing the first and second components into close proximity. After the adhesive material has been applied, the first and second components may be brought into close proximity, and in doing so, the material may be directly sandwiched between the bonding surface and the second component. This approach may be used, for example, when applying the adhesive material using a "butter and paste" method.

[0020] More preferably, the steps of the above method are performed in the order described. One of the first aircraft component or the second aircraft component, and more preferably the first aircraft component, may include a plurality of guide holes. The guide holes may be holes through which a plurality of holes (for receiving fasteners) are subsequently drilled. The step of applying the adhesive material may include the step of injecting the adhesive material onto the bonding surface through the guide holes in the first aircraft component or the second aircraft component. This arrangement has been found to be particularly beneficial because the adhesive material typically spreads radially and therefore effectively covers the bonding surface.

[0021] According to another aspect of the present invention, a hybrid joint between a wing skin and a rib is provided, the joint comprising: a portion of the wing skin, the portion of the wing skin having a plurality of holes therethrough; and a rib foot of the rib, the rib foot having a plurality of holes therethrough; and a plurality of fasteners mechanically retaining the portion of the wing skin to the rib foot, each fastener extending through a corresponding hole in the rib foot and a corresponding hole in the portion of the wing skin; and wherein the rib foot comprises a plurality of raised pads arranged at a joint with the wing skin, each raised pad surrounding a corresponding hole in the rib foot, and wherein the joint further comprises a cured adhesive directly sandwiched between the pad and the wing skin, the cured adhesive having adhesive properties such that the cured adhesive structurally bonds the pad of the rib foot to the wing skin, and the cured adhesive also having structural properties such that the cured adhesive fills a volume created by tolerances between the pad and the wing skin and acts as a filler.

[0022] Of course, it will be understood that features described with respect to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the present invention may incorporate any of the features described with reference to the apparatus of the present invention, and the apparatus of the present invention may incorporate any of the features described with reference to the method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

[0024] Figure 1 shows a side view of a joint assembly according to a first embodiment of the invention, the joint assembly being formed by a rib leg and a wing skin of an aircraft;

[0025] Figure 2 Shown Figure 1 a plan view of the underside of the rib foot; and

[0026] Figure 3 is a diagram illustrating connecting two aircraft structures to form Figure 1 and Figure 2Flowchart of a method for a joint assembly. DETAILED DESCRIPTION

[0027] According to a first embodiment of the present invention, there is provided Figure 1 The joint assembly shown in FIG. The joint assembly includes a rib 1, and the rib 1 includes a plurality of rib legs 3. For clarity, Figure 1 Only one rib foot 3 is shown in FIG, but it will be appreciated that the rib foot 3 extends around the upper and lower surfaces of the rib 1 in a conventional manner and is arranged to engage with the surrounding wing skin 5 to form a wing box structure.

[0028] The joint assembly also includes a second component in the form of a wing skin 5. The wing skin 5 is mechanically retained to the rib foot 3 via a series of fasteners 7 which extend through corresponding holes 9 in the wing skin 5 and the rib foot 3, respectively (the holes 9 and fasteners 7 are in the Figure 1 is shown in dashed lines and in Figure 2 Only hole 9 is shown).

[0029] exist Figure 1 and Figure 2 In the embodiment of the invention illustrated in FIG, each rib leg 3 includes four spaced apart contact surfaces 11. The contact surfaces 11 are raised approximately 3 mm to 4 mm above the underlying non-contact surface 13 of the rib leg 3. Each contact surface 11 is substantially circular in plan, with the circle centered on the corresponding hole 9 through which the fastener 7 extends. The contact surfaces 11 are substantially flat, but also include a small chamfer 12 around their perimeter. The above arrangement has been found to be particularly beneficial when used in conjunction with a combined adhesive-filler material, as will now be described below:

[0030] Reference Figure 1 The joint assembly includes a material layer 15 sandwiched directly between the cladding surface 11 and the inner surface of the wing skin 5. This material layer 11 has adhesive properties, allowing it to structurally bond and seal the rib leg 3 and the wing skin 5 together. Thus, the joint assembly of the first embodiment is a hybrid joint, with the components held together by both the adhesive bond created by the adhesive material layer 15 and the mechanical connection created by the fastener 7.

[0031] In a first embodiment, the adhesive material is a dual function adhesive-filler material. The material 15 is applied as a curable precursor (see below). Figure 3(described in more detail below). In this viscous form, it is able to flow to fill any volume created by tolerance differences between the wing skin 5 and the rib leg 3 (or more specifically, between the inner surface of the wing skin 5 and the mating surface 11 of the rib leg 3). When subsequently cured, the material 15 then solidifies to form a filler between the wing skin 5 and the rib leg 3. Materials with these properties are described, for example, in US 2019 / 0359815.

[0032] It has been found that providing a circular faying surface 11 on the rib foot 3, in combination with the layer of material 15 that acts as both an adhesive and a caulk, is particularly beneficial. In particular, providing the faying surface 11 enables the joint to be formed while using only a relatively small amount of material 15 in the layer. The raised faying surface 11 and the volume of applied adhesive material 15 result in the material not contacting the non-faying surface 13. Consequently, this arrangement also facilitates relatively simple visual indication that the layer of material 15 has been correctly applied between the faying surface 11 and the wing skin 5, as the operator can see most or all of the edges of each faying surface 11 and will be able to visually check that the surface has been adequately covered (e.g., by checking that the material 15 extends to the edge of the faying surface 11).

[0033] In the first embodiment of the present invention, the accommodating surface 11 is circular and is approximately three times the diameter of the hole 9 through which the fastener 7 is received. This ratio of the diameter of the fastener hole 9 to the diameter of the accommodating surface 11 has been found to be particularly beneficial. The circular nature of the surface is also beneficial because when the adhesive material 15 is applied (see FIG. Figure 3 ), the adhesive material 15 tends to spread radially from the injection point and thus evenly across the bonding surface 11.

[0034] Figure 3 is a diagram illustrating connecting two aircraft structures to form Figure 1 and Figure 2 A flow chart of a method of joint assembly is provided, and reference will now be made to that method.

[0035] The first step 100 of forming the joint assembly is to bring the rib 1 and the wing skin 5 close to each other. In a manner similar to known methods of wing assembly, each aircraft component is held in a jig and the components are carefully brought into the correct position for assembly.

[0036] In the first embodiment of the present invention, the holes 7 are drilled once the wing skin 5 and the rib leg 3 have been bonded by the layer of adhesive material 15. Thus, the fastener holes 7 do not initially exist in the rib leg 3 or the wing skin 5. Instead, the rib leg 3 initially has only pilot holes centered on the locations where the fastener holes 7 will subsequently be drilled (see step 106 below). The first embodiment of the present invention uses these pilot holes in a beneficial manner to ensure efficient and accurate application of the dual-function adhesive-filler material 15. This is performed as the next step 102, in which the dual-function adhesive material 15 is injected through the pilot holes in the rib leg 3. Due to the close proximity of the wing skin 5, the adhesive material will fill the gap between the mating surface 11 and the wing skin 5 and will spread radially outward from the pilot holes and across the mating surface 11. Material 15 is injected through each pilot hole until the operator can visually see the material at the circumferential edge of the corresponding mating surface 11.

[0037] The adhesive material 15 injected through the pilot holes is a curable precursor material and flows to fill any volume created by tolerances between the mate surface 11 and the wing skin 5. In step 104, the injected material is cured, and the material 15 is of the type that, once cured, forms a solid filler in the volume.

[0038] Once the material has solidified to form a solid caulk, the next step 106 is to drill a hole 9 through the wing skin 5, the rib leg 3 and the layer of caulk material 15 sandwiched between the wing skin 5 and the rib leg 3. The hole 9 is centered on the center of each faying surface 11.

[0039] After drilling is complete, a fastener 7 is applied under preload through each hole 9 (step 108), thereby mechanically holding the wing skin to the rib foot.

[0040] Thus, the resulting joint assembly comprises a hybrid joint having both adhesive and mechanical forces that contribute to the strength of the joint.In addition, the joint assembly comprises a shim to ensure the correct shape of the wing skin on the rib foot.

[0041] While the present invention has been described and illustrated with reference to specific embodiments, those skilled in the art will appreciate that the invention lends itself to many different variations not specifically illustrated herein.

[0042] For example, in another embodiment, rather than injecting the adhesive material, the adhesive material is applied using a "butter and paste" method. In this arrangement, the material is applied before the wing skin is brought into position against the rib foot and is subsequently sandwiched between the wing skin and the rib foot as the wing skin is brought into position against the rib foot.

[0043] As another example, joint assemblies having aspects of the present disclosure may be formed between other aircraft components, not necessarily only between a wing skin and a rib foot.

[0044] As another example, the aligning surface 11 need not include chamfers 12. In such an embodiment, external fillets for the material layers may be provided instead. However, such an arrangement is often more time-consuming than assembling an arrangement with internal chamfers on the aligning surface.

[0045] Where reference is made in the foregoing description to wholes or elements that have known, obvious or foreseeable equivalents, such equivalents are incorporated herein as if set forth individually. Reference should be made to the claims to determine the true scope of the invention, which should be interpreted as encompassing any such equivalents. The reader will also understand that wholes or features of the invention that are described as preferred, advantageous, convenient, etc. are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that such optional wholes or features, while potentially beneficial in some embodiments of the invention, may not be desirable in other embodiments and, therefore, may not be present.

Claims

1. A method of joining a first aircraft component to a second aircraft component, wherein: The method comprises the following sequential steps: bringing the first aircraft component and the second aircraft component into proximity with each other; applying an adhesive material and arranging the first component and the second component such that the adhesive material is located on a plurality of cladding surfaces of the first aircraft component and is directly sandwiched between the cladding surfaces and the second aircraft component, wherein the adhesive material is also a curable precursor material, and the curable precursor material is applied such that the curable precursor material fills a volume created by a tolerance between the cladding surface and the second aircraft component, and wherein the method includes the step of curing the curable precursor material such that the curable precursor material forms a solid filler in the volume; drilling a plurality of holes in the first aircraft component and the second aircraft component, each hole comprising a pair of aligned holes in the first component and the second component; and attaching a plurality of fasteners, each fastener extending through a respective pair of aligned apertures, the fasteners being arranged to mechanically hold the first aircraft component and the second aircraft component together, such that the components are simultaneously mechanically held together by the fasteners and adhesively bonded together by the adhesive material, wherein the second aircraft component includes a plurality of pilot holes through which the plurality of holes are subsequently drilled, and wherein the step of applying the adhesive material includes the step of injecting the adhesive material through the pilot holes in the second aircraft component onto the bonding surface, wherein each compliant surface is raised above a non-compliant surface of the first aircraft component, and Each of the bonding surfaces is substantially circular, and when the first aircraft component and the second aircraft component are brought into proximity with each other, each circular surface is centered about a corresponding guide hole through which the adhesive material is injected.

2. The method according to claim 1, wherein The first aircraft component is a rib comprising a plurality of rib legs, the plurality of holes being located in the rib legs of the rib, and wherein the second aircraft component is a wing skin.

3. A joint assembly in an aircraft, the joint assembly comprising: a first aircraft component having a plurality of holes therein; a second aircraft component having a plurality of holes therein; as well as a plurality of fasteners, each fastener extending through a respective hole in the first aircraft component and a respective hole in the second aircraft component, and the plurality of fasteners being arranged such that the fasteners mechanically hold the first aircraft component and the second aircraft component together; and wherein the first aircraft component includes a plurality of compliant surfaces disposed at a junction with the second aircraft component, each compliant surface being raised above a non-compliant surface of the first aircraft component, each compliant surface surrounding a corresponding hole in the first aircraft component, and each compliant surface being substantially circular, the circular surface being centered on the hole surrounded by the compliant surface, wherein the hole has a first diameter and the conforming surface has a second diameter, the second diameter being between 2 and 4 times the size of the first diameter, and wherein the joint assembly further comprises a layer of material sandwiched between the faying surface and the second aircraft component, the layer of material having adhesive properties such that the layer of material structurally bonds the first and second aircraft components together and the layer of material further having structural properties that serve as a filler, wherein a material in the layer of material is cured, the material being derived from a curable precursor configured to fill a volume created by a tolerance between the faying surface and the second aircraft component and subsequently cured to form the solid filler, and The material layer does not contact the non-conforming surface of the first aircraft component.

4. The joint assembly according to claim 3, wherein: The second diameter is about 3 times the size of the first diameter.

5. The joint assembly according to claim 3 or claim 4, wherein: The first aircraft component is a rib comprising a plurality of rib legs, the plurality of holes being located in the rib legs of the rib, and wherein the second aircraft component is a wing skin.

6. A hybrid joint located between a wing skin and a rib, the hybrid joint comprising: a portion of a wing skin, said portion of said wing skin having a plurality of holes therethrough; and a rib foot of the rib, the rib foot having a plurality of holes therethrough; and a plurality of fasteners mechanically retaining the portion of the wing skin to the rib foot, each fastener extending through a respective hole in the rib foot and a respective hole in the portion of the wing skin; and wherein the rib foot comprises a plurality of raised circular pads arranged at a junction with the wing skin, each raised circular pad surrounding a corresponding hole in the rib foot, and wherein the joint further comprises a cured adhesive sandwiched directly between the pad and the wing skin, The cured adhesive has adhesive properties such that the cured adhesive structurally bonds the pad of the rib leg to the wing skin, and the cured adhesive also has structural properties such that the cured adhesive fills a volume created by tolerances between the pad and the wing skin and acts as a shim, and wherein, The cured adhesive does not contact the portion of the rib that is located beneath the raised pad.

Images