Patent Description:
An aircraft may include an acoustic panel for attenuating noise. The acoustic panel may be configured as a single-degree of freedom (SDOF) acoustic panel or a multi-degree of freedom (MDOF) acoustic panel; e.g., a double degree of freedom (DDOF) acoustic panel. A multi-degree of freedom acoustic panel may include a plurality of perforated septums, where each of the perforated septums is disposed within a respective cavity of the multi-degree of freedom acoustic panel and separates that cavity into fluidly coupled sub-cavities. Various types and configurations of multi-degree of freedom acoustic panels and septums are known in the art. While these known acoustic panels and septums have various benefits, there is still room in the art for improvement. For example, forming septums using known processes is typically time and labor intensive and thereby increases manufacturing costs of the acoustic panel. There is a need in the art therefore for methods for forming multi-degree of freedom acoustic panels which are less time and/or labor intensive; e.g., formation methods which may be substantially automated.

<CIT> discloses a soundproof structure body and sound absorbing panel. In the process of forming the panel, first a sheet member is manufactured with a method having a coating film forming step in which coating film forming treatment is performed on one main surface of an aluminum base material to form an aluminum hydroxide coating film, a through-hole forming step in which the through-holes are formed by performing electrolytic dissolution treatment after the coating film forming step so that through-holes are formed in the aluminum base material and the aluminum hydroxide coating film and a coating film removing step in which the aluminum hydroxide coating film is removed after the through-hole forming step; then a metal coating step is performed for coating the surface of the aluminum base material including the inner wall of the through-holes with a metal other than aluminum after the coating film removing step described above, the metal coating is obtained by electroplating. The panel is then formed by assembling a first sheet member, a first spacer, a second sheet member, a second spacer and third sheet member that are laminated in this order.

<CIT> discloses a superplastic forming/diffusion bonding structure for attenuation of noise from airflow.

<CIT> discloses a method of making a noise attenuation panel.

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

The following optional features may be applied of the above aspect.

Optionally, and in accordance with any of the above, the cellular core may be configured as or otherwise include a honeycomb core.

Optionally, and in accordance with any of the above, the first cavity may extend along a centerline through the cellular core. The first cavity may have a polygonal cross-sectional geometry in a plane perpendicular to the centerline.

Optionally, and in accordance with any of the above, the formation method may also include: attaching the metal substrate to a tool; inserting the tool into the first cavity to dispose the metal substrate within the first cavity; and holding the metal substrate within the first cavity using the tool during the electroplating.

Optionally, and in accordance with any of the above, the formation method may also include detaching the tool from the metal substrate subsequent to the bonding of the septum to the cellular core.

Optionally, and in accordance with any of the above, the metal substrate may be attached to the tool using a vacuum.

Optionally, and in accordance with any of the above, the tool may include a base and a protrusion. The metal substrate may be abutted against the base. The protrusion may project out from the base through a perforation in the metal substrate.

Optionally, and in accordance with any of the above, the formation method may also include: disposing the cellular core and the metal substrate into an electroplating bath; and applying an electric charge to the metal substrate to electroplate the metal substrate within the electroplating bath.

Optionally, and in accordance with any of the above, the metal substrate may be electrically decoupled from the cellular core within the electroplating bath.

Optionally, and in accordance with any of the above, the formation method may also include heating an assembly subsequent to the electroplating to activate bonding material and bond the septum to the cellular core. The assembly may include the cellular core and the septum.

Optionally, and in accordance with any of the above, the bonding material may be or otherwise include an adhesive.

Optionally, and in accordance with any of the above, the formation method may also include disposing the bonding material with the cellular core prior to disposing the metal substrate within the cavity.

Optionally, and in accordance with any of the above, the formation method may also include applying the bonding material to an edge of a wall of the cellular core that at least partially forms the first cavity.

Optionally, and in accordance with any of the above, the first cavity may extend along a centerline through the cellular core. The septum may be angularly offset from the centerline by an acute angle.

Optionally, and in accordance with any of the above, the formation method may also include: disposing a second metal substrate within a second cavity, where the cavities include the second cavity; electroplating the second metal substrate to form a second septum within the second cavity; and bonding the second septum to the cellular core.

Optionally, and in accordance with any of the above, the formation method may also include forming an acoustic panel. The acoustic panel may include a core structure between a perforated first skin and a second skin. The core structure may include the cellular core and the septum.

The present invention may include any one or more of the individual features disclosed above and/or below alone or in any combination thereof, insofar as they are according to the scope of the invention that is defined by the accompanying claims.

<FIG> is a partial perspective schematic illustration of a structural, acoustic panel <NUM> for attenuating sound; i.e., noise. This acoustic panel <NUM> is a multi-degree of freedom (MDOF) acoustic panel; e.g., a double-degree of freedom (DDOF) acoustic panel. The acoustic panel <NUM> is configured to attenuate sound generated by an aircraft propulsion system such as, for example, a turbofan propulsion system or a turbojet propulsion system. With such a configuration, the acoustic panel <NUM> may be configured with a nacelle of the propulsion system. The acoustic panel <NUM>, for example, may be configured as or otherwise included as part of an inner or outer barrel, a translating sleeve, a blocker door, etc. Alternatively, the acoustic panel <NUM> may be configured with another component / structure of the aircraft such as its fuselage or a wing. Furthermore, the acoustic panel <NUM> may be configured to also or alternatively attenuate aircraft related sound other than sound generated by the propulsion system. The acoustic panel <NUM> of the present disclosure, of course, may alternatively be configured for non-aircraft applications.

The acoustic panel <NUM> extends laterally in a first lateral direction (e.g., an x-axis direction) along an x-axis. The acoustic panel <NUM> extends laterally in a second lateral direction (e.g., a y-axis direction) along a y-axis. The acoustic panel <NUM> extends vertically in a vertical direction (e.g., a z-axis direction) along a z-axis. Note, the term "lateral" may be used herein to generally describe the first lateral direction, the second lateral direction and/or any other direction within the x-y plane. Also note, the term "vertical" may be used herein to describe a depthwise panel direction and is not limited to a gravitational up/down direction. Furthermore, for ease of illustration, the x-y plane is shown as a generally flat plane. However, in other embodiments, the x-y plane and, thus, the acoustic panel <NUM> may be curved and/or follow an undulating geometry. For example, the x-y plane and, thus, the acoustic panel <NUM> may be arcuate, cylindrical, conical, frustoconical, or tapered with or without radial undulations. In such embodiments, a solely vertical direction (e.g., z-axis direction) is defined relative to a position of interest on the x-y plane. For example, on a spherical x-y plane, the vertical direction (e.g., z-axis) direction is a radial direction.

The acoustic panel <NUM> includes a perforated face skin <NUM>, a solid (e.g., non-perforated) back skin <NUM> and a core structure <NUM>. This core structure <NUM> is arranged and extends vertically between the face skin <NUM> and the back skin <NUM>. The core structure <NUM> is also connected to the face skin <NUM> and/or the back skin <NUM>. The core structure <NUM>, for example, may be welded, brazed, fused, adhered or otherwise bonded to the face skin <NUM> and/or the back skin <NUM>.

The face skin <NUM> may be a relatively thin sheet or layer of material that extends laterally within the x-y plane. This face skin material may be or otherwise include a metal, a polymer (e.g., a thermoplastic or thermoset material) or a fiber reinforced composite (e.g., fiber reinforcement such as fiberglass, carbon fiber and/or aramid fibers within a polymer matrix). The face skin <NUM> has a vertical thickness <NUM>. This face skin vertical thickness <NUM> extends vertically between opposing side surfaces <NUM> and <NUM> of the face skin <NUM>. The face skin <NUM> includes a plurality of perforations <NUM>; e.g., apertures such as through-holes. Each of these face skin perforations <NUM> extends generally vertically through the face skin <NUM> between the face skin side surfaces <NUM> and <NUM>.

The back skin <NUM> may be a relatively thin sheet or layer of (e.g., continuous and uninterrupted) material that extends laterally within the x-y plane. This back skin material may be the same as or different than the face skin material. The back skin material, for example, may be or otherwise include a metal, a polymer (e.g., a thermoplastic or thermoset material) or a fiber reinforced composite (e.g., fiber reinforcement such as fiberglass, carbon fiber and/or aramid fibers within a polymer matrix). The back skin <NUM> has a vertical thickness <NUM>. This back skin vertical thickness <NUM> extends vertically between opposing side surfaces <NUM> and <NUM> of the back skin <NUM>. The back skin vertical thickness <NUM> may be equal to or different (e.g., greater or less) than the face skin vertical thickness <NUM>.

The core structure <NUM> extends laterally within the x-y plane. The core structure <NUM> has a vertical thickness <NUM>. This core structure vertical thickness <NUM> extends vertically between opposing sides <NUM> and <NUM> of the core structure <NUM>, which core structure sides <NUM> and <NUM> are respectively abutted against the interior back skin side surface <NUM> and the interior face skin side surface <NUM>. The core structure vertical thickness <NUM> may be substantially greater than the face skin vertical thickness <NUM> and/or the back skin vertical thickness <NUM>. The core structure vertical thickness <NUM>, for example, may be at least ten to forty times (<NUM>-40x), or more, greater than the face skin vertical thickness <NUM> and/or the back skin vertical thickness <NUM>; however, the acoustic panel <NUM> of the present disclosure is not limited to such an exemplary embodiment.

The core structure <NUM> of <FIG> includes a cellular core <NUM> and one or more perforated septums <NUM>. The cellular core <NUM> is configured to form one or more core cavities <NUM> (e.g., internal chambers, acoustic resonance chambers, etc.) vertically between the face skin <NUM> and the back skin <NUM>. The cellular core <NUM> may be configured as a honeycomb core. The cellular core <NUM> of <FIG>, for example, includes a plurality of corrugated sidewalls <NUM>. These corrugated sidewalls <NUM> are arranged in a side-by-side array and are connected to one another such that each adjacent (e.g., neighboring) pair of the corrugated sidewalls <NUM> forms an array of the core cavities <NUM> laterally therebetween. The cellular core <NUM> and its corrugated sidewalls <NUM> are constructed from or otherwise include core material such as a metal; e.g., sheet metal. The present disclosure, however, is not limited to such an exemplary core material nor cellular core construction.

Each of the core cavities <NUM> of <FIG> extends vertically within / through the cellular core <NUM> along a centerline <NUM> of the respective core cavity <NUM> between and to the face skin <NUM> and the back skin <NUM>. One or more or all of the core cavities <NUM> may thereby each be fluidly coupled with a respective set of one or more of the face skin perforations <NUM>. Referring to <FIG>, each of the core cavities <NUM> has a cross-sectional geometry (e.g., shape, size, etc.) when viewed in a reference plane; e.g., a plane perpendicular to the cavity centerline <NUM> of the respective core cavity <NUM>. This cavity cross-sectional geometry may have a polygonal shape; e.g., a hexagonal shape, a rectangular shape, a triangular shape, etc. The present disclosure, however, is not limited to foregoing exemplary cellular configuration. For example, one or more or all of the core cavities <NUM> may alternatively each have a circular, elliptical or other non-polygonal cross-sectional geometry. Furthermore, various other types of honeycomb cores and, more generally, various other types of cellular cores for an acoustic panel <NUM> are known in the art, and the present disclosure is not limited to any particular ones thereof.

Referring to <FIG>, each of the septums <NUM> is disposed within a respective one of the core cavities <NUM>. Each septum <NUM> is configured to separate / divide the respective core cavity <NUM> into a plurality of fluidly coupled sub-cavities 52A and 52B. The face skin sub-cavity 52A extends vertically within the cellular core <NUM> between and to the face skin <NUM> and the respective septum <NUM>. The back skin sub-cavity 52B extends vertically within the cellular core <NUM> between and to the back skin <NUM> and the respective septum <NUM>. Each septum <NUM> includes one or more perforations <NUM>; e.g., apertures such as through-holes. Each of these septum perforations <NUM> extends through the respective septum <NUM> and thereby fluidly couples the face skin sub-cavity 52A with the back skin sub-cavity 52B.

Each septum <NUM> of <FIG> extends laterally across the respective core cavity <NUM>. Each septum <NUM> of <FIG>, for example, extends longitudinally between and to a face skin end <NUM> (e.g., edge) of the respective septum <NUM> and a back skin end <NUM> (e.g., edge) of the respective septum <NUM>. The septum face skin end <NUM> is disposed at (e.g., on, adjacent or proximate) an interface between the face skin <NUM> and the cellular core <NUM>; e.g., between the face skin <NUM> and a respective corrugated sidewall <NUM>. This septum face skin end <NUM> is also bonded to the face skin <NUM> and/or the cellular core <NUM> and its respective corrugated sidewall <NUM>. The septum back skin end <NUM> is disposed at (e.g., on, adjacent or proximate) an interface between the back skin <NUM> and the cellular core <NUM>; e.g., between the back skin <NUM> and a respective corrugated sidewall <NUM>. This septum back skin end <NUM> is also bonded to the back skin <NUM> and/or the cellular core <NUM> and its respective corrugated sidewall <NUM>. Each septum <NUM> of <FIG> extends laterally between and to opposing sides <NUM> and <NUM> (e.g., edges) of the respective septum <NUM>. The septum first side <NUM> is disposed at (e.g., on, adjacent or proximate) a first side of the respective core cavity <NUM>; e.g., along one of more of the corrugated sidewalls <NUM>. This septum first side <NUM> may also be bonded to the cellular core <NUM> and its respective corrugated sidewall(s) <NUM>. Of course, in other embodiments, the septum first side <NUM> may be unattached to the cellular core <NUM> and its respective corrugated sidewall(s) <NUM>. The septum second side <NUM> is disposed at (e.g., on, adjacent or proximate) a second side of the respective core cavity <NUM>; e.g., along one of more of the corrugated sidewalls <NUM>. This septum second side <NUM> may also be bonded to the cellular core <NUM> and its respective corrugated sidewall(s) <NUM>. Of course, in other embodiments, the septum second side <NUM> may be unattached to the cellular core <NUM> and its respective corrugated sidewall(s) <NUM>.

Referring to <FIG>, each of the septums <NUM> may be canted within the cellular core <NUM>. Each septum <NUM> of <FIG>, for example, is angularly offset from the centerline <NUM> of the respective core cavity <NUM> in which that septum <NUM> is disposed by an included angle <NUM>; e.g., an acute angle. This angle <NUM> may be between ten degrees (<NUM>°) and eighty degrees (<NUM>°), or between thirty degrees (<NUM>°) and sixty degrees (<NUM>°); e.g., exactly or about (+/- <NUM>°) forty-five degrees (<NUM>°). The present disclosure, however, is not limited to the foregoing exemplary angles. Furthermore, in other embodiments, it is contemplated the angle <NUM> may be exactly or about ninety degrees (<NUM>°).

Referring to <FIG>, each septum <NUM> may be configured with a multi-layered construction. The septum <NUM> of <FIG>, for example, includes a first layer <NUM> (e.g., a metal substrate <NUM>) and a second layer <NUM> (e.g., an electroplated coating <NUM>) disposed on and overlapping (e.g., completely covering) a side of the first layer <NUM>. Each of these layers <NUM> and <NUM> may be constructed from metal. The first layer metal, however, may be different than the second layer metal. For example, the first layer metal may be or otherwise include copper (Cu), whereas the second layer metal may be another metal that is compatible with (e.g., which can be electroplated onto) the first layer metal; e.g., the second layer metal may be or otherwise include copper (Cu), nickel (Ni) and/or platinum (Pt). The present disclosure, however, is not limited to any particular septum layer materials or formation techniques.

The first layer <NUM> has a first layer thickness <NUM>. The second layer <NUM> has a second layer thickness <NUM> which may be different (e.g., thicker) than the first layer thickness <NUM>. The first layer <NUM>, for example, may be configured as a thin metal foil substrate and the second layer <NUM> may be configured as a thick coating that takes on a configuration of and stiffens the first layer <NUM>. The present disclosure, however, is not limited to the foregoing dimensional and/or functional relationship.

The septum perforations <NUM> of <FIG> are collectively formed by the septum layers <NUM> and <NUM>. Each septum perforation <NUM>, for example, extends through and, thus, is formed by the first layer <NUM> and the second layer <NUM> between opposing sides of the respective septum <NUM>.

<FIG> is a flow diagram of a method <NUM> for forming an acoustic panel. For ease of description, the formation method <NUM> is described below with reference to the acoustic panel <NUM> and the acoustic panel components <NUM>, <NUM> and <NUM> described above. The formation method <NUM> of the present disclosure, however, is not limited to forming any particular types or configurations of acoustic panels.

In step <NUM>, the face skin <NUM> is formed and/or otherwise provided.

In step <NUM>, the back skin <NUM> is formed and/or otherwise provided.

In step <NUM>, the cellular core <NUM> is formed and/or otherwise provided.

In step <NUM>, one or more of the metal substrates <NUM> are formed and/or otherwise provided. Each metal substrate <NUM> includes one or more perforations <NUM> (see <FIG>); e.g., apertures such as through-holes. Each substrate perforation <NUM> extends through the respective metal substrate <NUM> between opposing sides <NUM> and <NUM> of the metal substrate <NUM> (see <FIG>).

In step <NUM>, bonding material <NUM> is disposed with the cellular core <NUM>. Referring to <FIG>, this bonding material <NUM> may be applied onto one or both of the core structure sides <NUM> and <NUM>. The bonding material <NUM> of <FIG>, in particular, is applied to one or more or all edges <NUM> and <NUM> of one or more or all of the corrugated sidewalls <NUM>. Here, each corrugated sidewall <NUM> extends vertically between and to its respective opposing sidewall edges <NUM> and <NUM>; e.g., on each wall forming a respective cavity <NUM>. The bonding material <NUM> may be applied onto an entire length of each respective sidewall edge <NUM>, <NUM>. The bonding material <NUM> may alternatively be applied onto one or more discrete portions of each respective sidewall edge <NUM>, <NUM> along its length; e.g., on one or more select walls forming a respective cavity <NUM>. Examples of the bonding material <NUM> include, but are not limited to, an adhesive (e.g., a heat activated adhesive) and brazing compound.

In step <NUM>, each metal substrate <NUM> is attached to a respective septum formation tool <NUM>. The formation tool <NUM> of <FIG> includes a tool base <NUM> and one or more tool protrusions <NUM>. The tool base <NUM> extends vertically along a centerline <NUM> of the respective formation tool <NUM> to a substrate land <NUM>; e.g., an end surface. The tool centerline <NUM> may be arranged parallel with (e.g., coaxial with) the cavity centerline <NUM> of the core cavity <NUM> (see <FIG>) into which the formation tool <NUM> is to be inserted. The substrate land <NUM> of <FIG> is angularly offset from the tool centerline <NUM> by an included angle <NUM>; e.g., an acute angle. This angle <NUM> is selected to be equal to the angle <NUM> of <FIG>. The angle <NUM> of <FIG>, for example, may be between ten degrees (<NUM>°) and eighty degrees (<NUM>°), or between thirty degrees (<NUM>°) and sixty degrees (<NUM>°); e.g., exactly or about (+/- <NUM>°) forty-five degrees (<NUM>°). The present disclosure, however, is not limited to the foregoing exemplary angles. Furthermore, in other embodiments, it is contemplated the angle <NUM> may be exactly or about ninety degrees (<NUM>°). Each of the tool protrusions <NUM> is connected to (e.g., formed integral with) the tool base <NUM>. Each of the tool protrusions <NUM> projects vertically out from the tool base <NUM> and its substrate land <NUM> to a respective distal end.

Each of the tool protrusions <NUM> may be mated with a respective one of the substrate perforations <NUM>. Each tool protrusion <NUM> of <FIG>, for example, projects vertically through a respective one of the substrate perforations <NUM> so as to partially or completely fill that respective substrate perforation <NUM>. The substrate land <NUM> is engaged with (e.g., contacts, abutted against, etc.) the exterior side <NUM> of the respective metal substrate <NUM>. This metal substrate <NUM> may be attached to the respective formation tool <NUM> using a vacuum. Fluid (e.g., gas), for example, may be drawn out of a conduit <NUM> in the formation tool <NUM> to apply a vacuum and draw the metal substrate <NUM> against the substrate land <NUM>. The present disclosure, however, is not limited to any particular attachment techniques.

In step <NUM>, each metal substrate <NUM> is disposed within the cellular core <NUM>. Each formation tool <NUM> of <FIG>, for example, is inserted partially into a respective one of the core cavities <NUM>. The metal substrate <NUM> attached to each formation tool <NUM> is thereby also inserted into the respective core cavity <NUM>.

In step <NUM>, each metal substrate <NUM> is electroplated to form a respective septum <NUM>. For example, referring to <FIG>, an assembly of the cellular core <NUM>, the metal substrates <NUM> and the formation tools <NUM> holding and positioning the metal substrates <NUM> within the cellular core <NUM> may be disposed (e.g., submerged) into an electroplating bath <NUM>. An electric current may be applied to each of the metal substrates <NUM> (or a select number of the metal substrates <NUM>) to electrically charge those metal substrates <NUM> to facilitate an electroplating process. This electroplating process may form the electroplated coating <NUM> onto at least (or only) the interior side <NUM> of the metal substrate <NUM>, where the metal substrate <NUM> (e.g., the first layer <NUM>) and the electroplated coating <NUM> (e.g., the second layer <NUM>) may collectively form a respective septum <NUM>. Other components (e.g., <NUM> and <NUM>) of the assembly, however, may not be electroplated. Each metal substrate <NUM>, for example, may be electrically isolated / decoupled from the cellular core <NUM>. Each metal substrate <NUM>, for example, may be (e.g., completely) laterally separated from the cellular core <NUM> and its corrugated sidewalls <NUM> by a (e.g., annular) gap. Furthermore, each formation tool <NUM> (or at least portions of the formation tool <NUM> exposed to the electroplating bath <NUM>) may be constructed from a non-conductive material.

In step <NUM>, each septum <NUM> is bonded to the cellular core <NUM>. For example, referring to <FIG>, an assembly of the cellular core <NUM>, the septums <NUM> and the formation tools <NUM> holding and positioning the septums <NUM> within the cellular core <NUM> may be removed from the electroplating bath <NUM>. This assembly may subsequently be heated to an elevated temperature at which the bonding material <NUM> is melted and/or otherwise activated. This activated bonding material <NUM> interacts with each septum <NUM>, and bonds the septums <NUM> to the cellular core <NUM>. The activated bonding material <NUM> may remain substantially at the core structure sides <NUM> and <NUM> so as to bond (e.g., only) the ends <NUM> and <NUM> of each septum <NUM> to the cellular core <NUM>. Alternatively, the activated bonding material <NUM> may flow along the corrugated sidewalls <NUM> to as to bond the ends <NUM> and <NUM> and the sides <NUM> and <NUM> (see <FIG>) of each septum <NUM> to the cellular core <NUM>. Following the bonding, each septum <NUM> may be detached from the respective formation tool <NUM> (e.g., vacuum suction may be released), and the formation tool <NUM> may be removed from the cellular core <NUM> to provide the core structure <NUM>.

In step <NUM>, the acoustic panel <NUM> is assembled. For example, referring to <FIG>, the core structure <NUM> is arranged vertically between the face skin <NUM> and the back skin <NUM>, and the core structure <NUM> is bonded and/or otherwise attached to the face skin <NUM> and/or the back skin <NUM>.

Claim 1:
A formation method, comprising:
providing a cellular core (<NUM>) comprising a plurality of cavities (<NUM>) that include a first cavity (<NUM>), each of the plurality of cavities extending through the cellular core (<NUM>);
disposing a metal substrate (<NUM>) within the first cavity (<NUM>);
the method being characterized by comprising :
electroplating the metal substrate (<NUM>) while the metal substrate (<NUM>) is disposed within the first cavity (<NUM>) to form a septum (<NUM>) within the first cavity (<NUM>), the septum (<NUM>) comprising one or more perforations (<NUM>); and
bonding the septum (<NUM>) to the cellular core (<NUM>).