Panel-insert assembly and method

A panel-insert assembly including a panel having a core and a skin layer positioned over the core, wherein the skin layer defines an opening therein, and an insert positioned below the skin layer, wherein the insert is aligned with the opening.

FIELD

This application relates to sandwich panels and, more particularly, to sandwich panels having an insert, such as a threaded insert, connected thereto.

BACKGROUND

Sandwich panels are typically formed from a core sandwiched between two face sheets. The core may be relatively thick, yet lightweight, as compared to the face sheets. The face sheets may be relative thin, yet stiff. Therefore, sandwich panels typically possess relatively high strength and stiffness at relatively low weight. As such, sandwich panels are used in various applications, including aerospace applications, automotive applications, residential and commercial building applications and the like.

For example, sandwich panels are used in the construction of aircraft, such as commercial aircraft. Specifically, sandwich panels are used as the flooring, walls and bulkheads that define the passenger cabin of an aircraft. Therefore, such sandwich panels often are connected to the airframe of the aircraft such that loads applied to the sandwich panels are transferred to the airframe.

Connecting a sandwich panel to an airframe is typically effected with mechanical fasteners, such as bolts, that engage threaded inserts connected to the sandwich panel. The threaded inserts are typically potted (with an adhesive) into appropriately sized holes formed in the sandwich panel. The adhesives commonly used require long cure times, add undesired weight, and offer only limited pull strength protection since the load is transferred to the panel only through the adhesive. Also, care must be taken such that the threaded inserts are not placed too high in the holes, which may result in a gap being formed, or placed too low in the holes, which may result in unintentional pullout during tightening of the mechanical fastener.

Accordingly, those skilled in the art continue with research and development efforts in the field of sandwich panels.

SUMMARY

In one embodiment, the disclosed panel-insert assembly may include a panel having a core and a skin layer positioned over the core, wherein the skin layer defines an opening therein, and an insert positioned below the skin layer, wherein the insert is aligned with the opening.

In another embodiment, the disclosed panel-insert assembly may include a sandwich panel and an insert. The sandwich panel may include a core having a first major side and a second major side opposed from the first major side, a first skin layer positioned over the first major side, wherein the first skin layer defines an opening, and wherein the opening is elongated along an opening axis, and a second skin layer positioned over the second major side. The insert may be positioned below the skin layer, wherein the insert defines a threaded bore, and wherein the threaded bore is aligned with the opening.

In another embodiment, disclosed is a method for connecting an insert to a panel, the panel including a core and a skin layer, the method including (1) forming an opening in the skin layer; (2) inserting the insert through the opening such that the insert is positioned below the skin layer; and (3) rotating the insert relative to the opening.

Other embodiments of the disclosed panel-insert assembly and method will become apparent from the following detailed description, the accompanying drawings and the appended claims.

DETAILED DESCRIPTION

Referring toFIGS. 1-3, one embodiment of the disclosed panel-insert assembly, generally designated10, may include a sandwich panel12and an insert14. The insert14may be inserted through an opening16in the sandwich panel12in a manner that provides 360 degrees of contact between the insert14and the sandwich panel12, thereby providing a strong connection therebetween.

As best shown inFIG. 2, the sandwich panel12may include a layered structure13that includes a core18, a first skin layer20and a second skin layer22. The insert14may be positioned below the first skin layer20, thereby providing better load transfer between the insert14and the sandwich panel12(as opposed to a potted insert).

While the layered structure13of the sandwich panel12is shown with three layers18,20,22, additional layers, such as additional core layers, additional skin layers and/or additional other layers, may be included without departing from the scope of the present disclosure. The second skin layer22may be optional and, therefore, may be omitted from the layered structure13of the sandwich panel12without departing from the scope of the present disclosure.

The core18of the sandwich panel12may include a first major side24and an opposed second major side26. The first skin layer20may be connected (e.g., adhered, welded, braised, mechanically fastened etc.) to the first major side24of the core18and the second skin layer22may be connected (e.g., adhered, welded, braised, mechanically fastened etc.) to the second major side of the core18, thereby sandwiching the core18between the first skin layer20and the second skin layer22.

The cross-sectional thickness T1of the core18of the sandwich panel12may be relatively thick, as compared to the cross-sectional thicknesses T2, T3of the first skin layer20and the second skin layer22(e.g., T1>T2and T1>T3). For example, the cross-sectional thickness T1of the core18may be two or more times greater (e.g., five times greater) than the cross-sectional thickness T2of the first skin layer20. However, the core18may have a relatively lower density (basis weight divided by cross-sectional thickness), as compared to the densities of the first skin layer20and the second skin layer22.

Structurally, the core18of the sandwich panel12may be solid. However, lower densities may be achieved using a non-solid structure. As one specific, non-limiting example, the core18may be (or may include) a foam. As another specific, non-limiting example, the core18may be fluted or may include fluting. As yet another specific, non-limiting example, the core18may be (or may include) a honeycomb structure.

Compositionally, the core18may be formed from the same, similar or different materials than the first20and second22skin layers. However, the core may typically be a structure with less density than the skin layers20,22. As one specific, non-limiting example, the core18may be formed from a polymer (e.g., expanded polystyrene). As another specific, non-limiting example, the core18may be a honeycomb structure formed from a composite, such as a carbon fiber-reinforced composite or a fiberglass composite. As yet another specific, non-limiting example, the core18may be a honeycomb structure formed from a ceramic or metal, such as titanium, steel, aluminum or an aluminum alloy.

The first skin layer20, which may be single ply or multi-ply, may be any material capable of being layered over and connected to the core18. As one specific, non-limiting example, the first skin layer20may be a polymer, such as a polymer film, sheet or mesh. As another specific, non-limiting example, the first skin layer20may be a composite, such as a carbon fiber-reinforced composite or a fiberglass composite. As another specific, non-limiting example, the first skin layer20may be a ceramic. As yet another specific, non-limiting example, the first skin layer20may be a metal film, sheet or mesh.

The second skin layer22, which may be single ply or multi-ply, may be formed from the same, similar or different material than the first skin layer20. As one specific, non-limiting example, the second skin layer22may be a polymer, such as a polymer film, sheet or mesh. As another specific, non-limiting example, the second skin layer22may be a composite, such as a carbon fiber-reinforced composite or a fiberglass composite. As yet another specific, non-limiting example, the second skin layer22may be a metal film, sheet or mesh.

InFIG. 1, only a portion of a sandwich panel12is shown. Those skilled in the art will appreciate that the overall size and shape of the sandwich panel12may depend on the end application. For example, the sandwich panel12may be used to construct the passenger cabin of an aircraft and, therefore, may be sized and shaped accordingly. Additionally, while the sandwich panel12is shown inFIGS. 1-3as being a substantially planar structure, non-planar sandwich panels12(e.g., curved sandwich panels12) are also contemplated.

Still referring toFIGS. 1-3, the opening16in the sandwich panel12may be formed in the first skin layer20. The opening16may extend through the cross-sectional thickness T2of the first skin layer20. Therefore, the opening16may provide access to the core18positioned below the first skin layer20. As is described in greater detail herein, the opening16may facilitate connecting the insert14to the sandwich panel12by insertion of the insert14below the first skin layer20by way of the opening16.

The opening16in the first skin layer20of the sandwich panel12may have a maximum length L and a maximum width W that allow the insert14to pass therethrough. The width W of the opening16may be dictated by the cross-sectional thickness T4(FIG. 5) of the insert14. The length L of the opening16may extend along an opening axis O, and may be greater than the width W (e.g., the opening16may be elongated), and the length L may be dictated by the major and minor dimensions D1, D2of the insert14.

As best shown inFIGS. 1 and 3, the opening16in the first skin layer20of the sandwich panel12may be obround in plan view. However, openings16of various shapes may be used without departing from the scope of the present disclosure. For example, while not shown in the drawings, the opening16may be rectangular, trapezoidal, irregular or the like.

The opening16in the first skin layer20of the sandwich panel12may be formed using various techniques. As one non-limiting example, the opening16may be formed by cutting out, such as with a blade, a portion of the first skin layer20. As another non-limiting example, the opening16may be formed by machining, such as with a router, a portion of the first skin layer20.

Referring toFIGS. 4 and 5, the insert14may include a body30having an engagement surface32and an outer periphery34. As best shown inFIG. 5, the engagement surface32of the body30of the insert14may be substantially planar, thereby allowing the engagement surface32to flushly abut the first skin layer20when the insert14is inserted into the sandwich panel12below the first skin layer20, as shown inFIGS. 1-3. However, those skilled in the art will appreciate that the engagement surface32of the body30of the insert14may be shaped/contoured (e.g., curved) to closely correspond with the shape/contour of the first skin layer20below which the insert14is positioned.

Referring toFIG. 4, the body30of the insert14may include a major dimension D1extending along a major axis M1and a minor dimension D2extending along a minor axis M2, wherein the major dimension D1is greater than the minor dimension D2. For example, the major dimension D1may be about 1.1 to about 3 times greater than the minor dimension D2, such as about 1.5 to about 2 times greater than the minor dimension D2. Furthermore, the major dimension D1may be greater than the length L of the opening16in the first skin layer20, as shown inFIG. 3, while the minor dimension D2may be substantially equal to or less than the length L of the opening16in the first skin layer20.

In one particular implementation, the major axis M1may be perpendicular to the minor axis M2, as shown in the drawings with an ellipse-shaped (in plan view) insert14. However, it is also contemplated that the major axis M1may be transverse to, but not perpendicular to, the minor axis M2.

While an ellipse-shaped insert14is shown in the drawings, those skilled in the art will appreciate that inserts14of various shapes may provide the disclosed major and minor dimensions D1, D2, and may be used without departing from the scope of the present disclosure. As one alternative example, the insert14may be a non-elliptical oval. As another alternative example, the insert14may be rectilinear (e.g., a rectangle). As yet another alternative example, the insert14may have an irregular and/or non-symmetric shape.

The body30of the insert14may define a bore36therein. The bore36may be sized and shaped to receive and engage a mechanical fastener, such as a screw, a bolt, a rivet or the like. In one particular implementation, the bore36of the insert14may be threaded to receive and engage a threaded fastener (e.g., a screw or a bolt).

Optionally, the portion of the body30surrounding the bore36may have a greater cross-sectional thickness T4than the rest of the body30to provide the bore36with greater depth. For example, the body30of the insert14may have a flanged or T-shaped profile, as shown inFIG. 5. At this point, those skilled in the art will appreciate that providing the insert14with a deeper threaded bore36may facilitate a stronger connection between the insert14and a threaded mechanical fastener.

The insert14may be formed from various materials or combination of materials. As one general, non-limiting example, the insert14may be formed from metal, such as steel. As another general, non-limiting example, the insert14may be formed from a polymer, such as polyethylene terephthalate. As another general, non-limiting example, the insert14may be formed from a combination of materials, such as a polymer body having a metallic threaded insert (defining the bore36) connected thereto. For example, the metallic threaded insert may be press-fit into the polymer body. As yet another general, non-limiting example, the insert14may be formed from a combination of materials, such as a ceramic body having a metallic threaded insert (defining the bore36) connected thereto. For example, the metallic threaded insert may be press-fit into the ceramic body. As one specific, non-limiting example, the insert14may be a steel, such as a stainless steel, nut plate.

As shown inFIGS. 1-3, the insert14may be connected to the sandwich panel12by inserting the insert14through the opening16in the first skin layer20such that the insert14is positioned below the first skin layer20(e.g., between the first skin layer20and the core18). Once below the first skin layer20, the insert14may be oriented such that the entire outer periphery34of the insert14is positioned vertically below (relative to the vertical axis V of the insert14shown inFIG. 2) the first skin layer20and radially outside (relative to vertical axis V of the insert14) of the opening16in the first skin layer20, thereby providing 360 degrees of contact between the engagement surface32of the insert14and the underside21of the first skin layer20of the sandwich panel12.

Also disclosed is a method for connecting an insert to a sandwich panel. One embodiment of the disclosed method is shown inFIG. 6and is generally designated100. The method100is described below with references toFIGS. 7-10. Additional steps may be included in the disclosed method100without departing from the scope of the present disclosure.

At Block102, the method100may begin with the step of forming an opening16in the skin layer20of the sandwich panel12, as shown inFIG. 7. The opening16may extend through the skin layer20(down to the core18), and may have a length L and a width W. The opening16may be formed by cutting, machining or the like the skin layer20of the sandwich panel12.

At Block104, the insert14may be inserted through the opening16in the skin layer20of the sandwich panel12, as shown inFIGS. 8 and 9. To facilitate insertion of the insert14, the insert14may be arranged such that the minor dimension D2of the insert14is aligned with the length L (FIG. 7) of the opening16, thereby allowing the smaller, minor dimension D2of the insert14to pass through the opening16.

The insert14may be inserted such that it is positioned below the skin layer20of the sandwich panel12. In one optional variation, a portion of the skin layer20may be delaminated from the core18to facilitate receiving the insert14below the skin layer20(e.g., between the skin layer20and the core18). In another optional variation, a portion of the core18may be removed (e.g., cut out) to form a void sized and shaped to accommodate the insert14.

At Block106, the insert14(particularly the threaded bore36of the insert) may be aligned with the opening16in the skin layer20of the sandwich panel12, as shown inFIG. 10. For example, the insert14may define a bore36, such as a threaded bore36, and the bore36of the insert14may be vertically aligned (see vertical axis V inFIG. 2) with the opening16in the skin layer20of the sandwich panel12.

At Block108, the insert14may be rotated relative to the opening16, as shown by arrow R inFIG. 10. The rotation may be made about the vertical axis V (seeFIG. 2) such that the major dimension D1(seeFIG. 4) of the insert14is aligned with the length L (seeFIG. 3) of the opening16, thereby providing 360 degrees of contact between the engagement surface32(FIG. 4) of the insert14and the underside21(FIG. 2) of the skin layer20of the sandwich panel12. As one example, when the major axis M1is substantially perpendicular to the minor axis M2, the rotating step (Block108) may involve rotating the insert14ninety degrees about the vertical axis V. As another example, the rotating step may require rotating the insert14less than ninety degrees (or more than ninety degrees), such as when the insert14is nonsymmetrical.

Thus, in the final, rotated configuration, the major axis M1(FIG. 4) of the insert14may be aligned with (e.g., substantially parallel with) the opening axis O (FIG. 3) of the opening16in the sandwich panel12, as shown inFIG. 1.

Examples of the disclosure may be described in the context of an aircraft manufacturing and service method200, as shown inFIG. 11, and an aircraft202, as shown inFIG. 12. During pre-production, the aircraft manufacturing and service method200may include specification and design204of the aircraft202and material procurement206. During production, component/subassembly manufacturing208and system integration210of the aircraft202takes place. Thereafter, the aircraft202may go through certification and delivery212in order to be placed in service214. While in service by a customer, the aircraft202is scheduled for routine maintenance and service216, which may also include modification, reconfiguration, refurbishment and the like.

As shown inFIG. 12, the aircraft202produced by example method200may include an airframe218with a plurality of systems220and an interior222. Examples of the plurality of systems220may include one or more of a propulsion system224, an electrical system226, a hydraulic system228, and an environmental system230. Any number of other systems may be included.

The disclosed panel-insert assembly10and method100may be employed during any one or more of the stages of the aircraft manufacturing and service method200. For example, components or subassemblies corresponding to component/subassembly manufacturing208, system integration210, and or maintenance and service216may be fabricated or manufactured using the disclosed panel-insert assembly10and method100. Also, one or more apparatus examples, method examples, or a combination thereof may be utilized during component/subassembly manufacturing208and/or system integration210, for example, by substantially expediting assembly of or reducing the cost of an aircraft202, such as the airframe218and/or the interior222. Similarly, one or more of system examples, method examples, or a combination thereof may be utilized while the aircraft202is in service, for example and without limitation, to maintenance and service216.

The disclosed system and method are described in the context of an aircraft; however, one of ordinary skill in the art will readily recognize that the disclosed service system may be utilized for a variety of different components for a variety of different types of vehicles. For example, implementations of the embodiments described herein may be implemented in any type of vehicle including, e.g., helicopters, passenger ships, automobiles and the like.

Although various embodiments of the disclosed panel-insert assembly and method have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.