Patent Description:
An aircraft may include a plurality of acoustic panels for attenuating noise generated by, for example, its engines and windage. Various types and configurations of acoustic panels are known in the art. While these known acoustic panels have various advantages, there is still room in the art for improvement.

<CIT> relates to a sandwich element for the sound-insulating interior lining of a transport means.

<CIT> relates to a baffle, and specifically a kind of broadband sound insulation cellular board.

<CIT> relates to a shell structure of a fuselage.

<CIT> relates to an internal arrangement of the walls of the fuselage delimiting the passenger cabin of an aircraft and, more particularly, to a luxury internal arrangement of the cabin.

<CIT> relates generally to gas turbine engines, and, more specifically, to noise attenuating acoustic liners therein.

<CIT> relates to the attenuation of sound waves, and more particularly, to methods of manufacturing septum caps.

According to an aspect of the present invention, a wall structure is provided as claimed in claim <NUM>.

Various embodiments of the invention are claimed in the dependent claims.

<FIG> is a partial, perspective sectional illustration of a fuselage <NUM> for an aircraft <NUM> such as, but not limited to, an airplane. This fuselage <NUM> is configured with a (e.g., tubular) fuselage wall structure <NUM>, which wall structure <NUM> forms an exterior (e.g., outermost) tubular wall of the aircraft <NUM>. The wall structure <NUM> includes an exterior fuselage skin <NUM> and one or more acoustic panels 28A-E (generally referred to as "<NUM>").

The exterior fuselage skin <NUM> extends circumferentially about (e.g., partially or completely around) and longitudinally along a longitudinal centerline <NUM> of the fuselage <NUM>. The exterior fuselage skin <NUM> is configured to form an exterior (e.g., outermost, radial outer) surface <NUM> of the fuselage <NUM>, which surface <NUM> is an exterior aerodynamic flow surface of the aircraft <NUM>. The exterior fuselage skin <NUM> extends radially outward, relative to the centerline <NUM>, from an interior (e.g., radial inner) surface <NUM> of the exterior fuselage skin <NUM> to the exterior surface <NUM> of the exterior fuselage skin <NUM>. The exterior fuselage skin <NUM> of <FIG> is configured as a single layer skin / sheet; e.g., a single panel of material (e.g., sheet metal) extends between and forms the exterior and the interior surfaces <NUM> and <NUM>. However, in other embodiments, the exterior fuselage skin <NUM> may be configured as a multi-layer skin; e.g., a laminated multi-ply skin. The present disclosure therefore is not limited to any particular exterior fuselage skin configurations nor materials.

The acoustic panels <NUM> are arranged with the exterior fuselage skin <NUM> and within an interior of the fuselage <NUM>. For example, each of the acoustic panels 28A-D is connected (e.g., mechanically fastened and/or otherwise attached) to the exterior fuselage skin <NUM>, at its interior surface <NUM>, through one or more mounts <NUM> (not all visible in <FIG>). Each of these mounts <NUM> is a vibration-isolating mount. Each mount <NUM>, for example, may be constructed from elastomeric (e.g., rubber) material. The mounts <NUM> are thereby configured to dampen and/or limit / prevent transmission of vibrations between the exterior fuselage skin <NUM> and the acoustic panels <NUM>. The mounts <NUM> are also configured to provide an air gap <NUM> (e.g., an air plenum) between the exterior fuselage skin <NUM> and the acoustic panels <NUM>; see also <FIG>. This air gap <NUM> increases sound attenuation performance by providing an additional resonance chamber between the exterior fuselage skin <NUM> and the acoustic panels <NUM>. Of course, one or more of the acoustic panels <NUM> (e.g., the acoustic panels 28E) may also or alternatively be connected to the exterior fuselage skin <NUM> through other intermediate elements; e.g., a floor structure <NUM> and/or a shelf / trim structure <NUM>. The present disclosure therefore is not limited to any particular technique for mounting the acoustic panels <NUM> to the exterior fuselage skin <NUM>.

Referring to <FIG> and <FIG>, each of the acoustic panels <NUM> includes a perforated first (e.g., radial outer) skin <NUM>, a perforated second (e.g., radial inner) skin <NUM> and a core structure <NUM>. Briefly, the core structure <NUM> is disposed and extends radially between the first skin <NUM> and the second skin <NUM>. The core structure <NUM> is also connected to the first skin <NUM> and the second skin <NUM> as described below in further detail.

The first skin <NUM> of <FIG> and <FIG> may be configured as a relatively thin sheet or layer of material that extends longitudinally and circumferentially about the centerline <NUM> (see <FIG>). This first skin <NUM> has a radial thickness that extends vertically between opposing outer and inner side surfaces. The first skin <NUM> includes a plurality of first perforations <NUM> (see <FIG>); e.g., apertures such as through-holes. Each of these first perforations <NUM> extends generally radially completely through the first skin <NUM> between its side surfaces.

The second skin <NUM> of <FIG> and <FIG> may be configured as a relatively thin sheet or layer of material that extends longitudinally and circumferentially about the centerline <NUM> (see <FIG>). This second skin <NUM> has a radial thickness that extends vertically between opposing outer and inner side surfaces. The second skin <NUM> includes a plurality of second perforations <NUM>; e.g., apertures such as through-holes. Each of these second perforations <NUM> extends generally radially completely through the second skin <NUM> between its side surfaces.

The core structure <NUM> is configured to form one or more first cavities <NUM> and one or more second cavities <NUM> between the first skin <NUM> and the second skin <NUM>. The core structure <NUM> of <FIG> and <FIG>, for example, includes a first cellular core <NUM>, a second cellular core <NUM> and a fluid impervious (e.g., solid, unperforated, non-porous) septum <NUM>.

The first cellular core <NUM> is configured to form the one or more first cavities <NUM>. For example, the first cellular core <NUM> may be configured as a honeycomb core. The first cellular core <NUM> of <FIG> includes a plurality of corrugated sidewalls <NUM>. These sidewalls <NUM> are arranged in a side-by-side array and connected to one another such that each adjacent pair of sidewalls <NUM> forms an array of the first cavities <NUM> therebetween. Each of these first cavities <NUM> extends radially through the first cellular core <NUM> to and between the first skin <NUM> and the septum <NUM>. Each first cavity <NUM> may thereby be fluidly coupled with one or more of the first perforations <NUM> in the first skin <NUM>. Referring to <FIG>, each first cavity <NUM> may have a polygonal (e.g., hexagonal) cross-sectional geometry when viewed in a plane parallel to one or more of the elements <NUM> and <NUM>. The present disclosure, however, is not limited to any particular first cellular core configurations.

The second cellular core <NUM> (e.g., see <FIG>) is configured to form the one or more second cavities <NUM> (e.g., see <FIG>). For example, the second cellular core <NUM> may be configured as a honeycomb core. The second cellular core <NUM> of <FIG> includes a plurality of corrugated sidewalls <NUM>. These sidewalls <NUM> are arranged in a side-by-side array and connected to one another such that each adjacent pair of sidewalls <NUM> forms an array of the second cavities <NUM> therebetween. Each of these second cavities <NUM> extends radially through the second cellular core <NUM> to and between the second skin <NUM> and the septum <NUM> (e.g., see <FIG>). Each second cavity <NUM> may thereby be fluidly coupled with one or more of the second perforations <NUM> in the second skin <NUM>. Referring to <FIG>, each second cavity <NUM> may have a polygonal (e.g., hexagonal) cross-sectional geometry when viewed in a plane parallel to one or more of the elements <NUM> and <NUM>. The present disclosure, however, is not limited to any particular second cellular core configurations.

The septum <NUM> of <FIG> and <FIG> may be configured as a relatively thin sheet or layer of (e.g., continuous and uninterrupted) material that extends longitudinally and circumferentially about the centerline <NUM>. This septum <NUM> is arranged radially between and connected to the first cellular core <NUM> and the second cellular core <NUM>. The septum <NUM>, for example, may be fused, adhered, welded, brazed and/or otherwise bonded to the first cellular core <NUM> and/or the second cellular core <NUM>. The septum <NUM> may also or alternatively be mechanically fastened to the first cellular core <NUM> and/or the second cellular core <NUM>. Alternatively, the septum <NUM> may be formed integral with the first cellular core <NUM> and/or the second cellular core <NUM> as a monolithic body using, for example, additive manufacturing. Each of the first and the second cellular cores <NUM> and <NUM> may be similarly respectively connected to (e.g., bonded, fastened and/or integral with) the first and the second skins <NUM> and <NUM>. The present disclosure, however, is not limited to any particular acoustic panel manufacturing methods.

By arranging the septum <NUM> between the first and the second cellular cores <NUM> and <NUM>, the septum <NUM> is radially between and defines respective ends of the first and the second cavities <NUM> and <NUM>. In addition, the septum <NUM> fluidly isolates each of the first cavities <NUM> from the second cavities <NUM> and, similarly, fluidly isolates each of the second cavities <NUM> from the first cavities <NUM>. Thus, each of the cavities <NUM>, <NUM> may form a discrete resonance chamber for sound suppression. Each cavity <NUM>, <NUM> may also be tailored to attenuate different acoustic tones.

Referring to <FIG>, during operation, each acoustic panel <NUM> is operable to attenuate sound (e.g., noise) from two different directions; thus, the acoustic panel <NUM> may be termed a two-way acoustic panel. The first cellular core <NUM> and the first cavities <NUM> are operable to attenuate sound generated and/or propagating outside of the fuselage <NUM> (see <FIG>). At the same time, the second cellular core <NUM> and the second cavities <NUM> are operable to attenuate sound generated and/or propagating inside the fuselage <NUM>; e.g., within an aircraft cabin <NUM> of <FIG>. The acoustic panels <NUM> may thereby be operable to significantly reduce sound hear by passengers within the fuselage <NUM>.

The components <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of the acoustic panel <NUM> may be constructed from various materials and in various configurations. Any one or more of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, for example, may be constructed from polymer material, fiber reinforced composite (e.g., fiberglass composite, carbon fiber composite, aramid fiber composite, composite reinforced by any combination of glass, carbon, aramid or other fibers), metal (e.g., sheet metal), metal matrix composite, ceramic and ceramic matrix composite, or a combination of any two or more of the foregoing materials.

In some embodiments, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of the acoustic panel <NUM> are constructed from similar or like materials; e.g., the same materials. However, in other embodiments, one or more or each of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be constructed from different materials. For example, the first skin <NUM> may be constructed from a first material and the second skin <NUM> may be constructed from a second material that is different from the first material. The first skin <NUM>, for example, may be constructed from an industrial / aesthetically unfinished material such as sheet metal or a fiber-reinforced composite. By contrast, the second skin <NUM> may be constructed from an aesthetically finished material such as wood (e.g., solid wood or wood laminate / veneer) or textured polymer (e.g., plastic). Thus, the first skin material may be selected for cost reduction whereas the second skin material may be selected for aesthetic appearance, which may be particularly advantageous where the second skin <NUM> forms an exposed surface in the aircraft cabin as shown, for example, in <FIG>.

In some embodiments, the first cellular core <NUM> and the second cellular core <NUM> have substantially (e.g., +/- <NUM>%) or exactly equal thicknesses <NUM> and <NUM> as shown in <FIG>. Thus, each first cavity <NUM> may have a height (e.g., same as <NUM>) that is substantially (e.g., +/- <NUM>%) or exactly equal to a height (e.g., same as <NUM>) of each second cavity <NUM>. However, in other embodiments, the thickness <NUM> of the first cellular core <NUM> may be greater than the thickness <NUM> of the second cellular core <NUM> as shown in <FIG>. Thus, the height of each first cavity <NUM> may be greater than the height of each second cavity <NUM>. In still other embodiments, the thickness <NUM> of the first cellular core <NUM> may be less than the thickness <NUM> of the second cellular core <NUM> as shown in <FIG>. Thus, the height of each first cavity <NUM> may be less than the height of each second cavity <NUM>. This enables each core <NUM>, <NUM> and its cavities <NUM>, <NUM> to be tuned for a frequency / frequencies of sound that core is intended to attenuate. Of course, this tuning may also involve selecting perforations hole sizes, selecting perforation spacings and/or selecting the number of perforations (e.g., density of perforation per unit of area - percent open area (POA)).

The acoustic panels <NUM> are described above with reference to an aircraft application. However, such acoustic panels <NUM> may also be configured for non-aircraft applications; e.g., building applications. The acoustic panels <NUM> of the present disclosure therefore are not limited to any particular application.

Claim 1:
A wall structure (<NUM>) for an aircraft, the wall structure (<NUM>) comprising an exterior fuselage skin (<NUM>) and an acoustic panel (<NUM>), the acoustic panel comprising:
a first skin (<NUM>);
a second skin (<NUM>);
a core structure (<NUM>) connected to and forming a plurality of cavities (<NUM>,<NUM>) between the first skin (<NUM>) and the second skin (<NUM>), the cavities (<NUM>,<NUM>) including a first cavity (<NUM>) and a second cavity (<NUM>), the first cavity (<NUM>) fluidly coupled with one or more first perforations (<NUM>) in the first skin (<NUM>), and the second cavity (<NUM>) fluidly coupled with one or more second perforations (<NUM>) in the second skin (<NUM>); and
a plurality of vibration isolating mounts (<NUM>) that attach the acoustic panel (<NUM>) to the exterior fuselage skin (<NUM>),
wherein the acoustic panel (<NUM>) is arranged with the exterior fuselage skin (<NUM>) and separated from the exterior fuselage skin (<NUM>) by an air gap (<NUM>),
wherein the air gap (<NUM>) provides a resonance chamber between the exterior fuselage skin (<NUM>) and the acoustic panels (<NUM>),
wherein the core structure (<NUM>) comprises a septum (<NUM>) that partially defines and is between the first cavity (<NUM>) and the second cavity (<NUM>), wherein the septum (<NUM>) fluidly isolates the first cavity (<NUM>) from the second cavity (<NUM>), and wherein the septum (<NUM>) is a non-porous solid septum.