Patent Application
20200309028
The present disclosure pertains to acoustic cores that have enhanced acoustic absorption and reduced drag characteristics, as well as methods of making such acoustic cores and liners.
Acoustic liners may be used to dampen or attenuate sound waves. For example, acoustic liners are commonly used to dampen or attenuate noise from turbomachines such as turbofan engines. Typical acoustic liners include an acoustic core positioned between a perforated acoustic screen and a substantially imperforate back sheet. The perforated acoustic screen allows sound waves to enter the acoustic core. The acoustic core includes a plurality of resonant cells intended to dampen or attenuate sound waves. However, existing perforated acoustic screens may affect acoustic absorption to varying degrees, which may differ across a spectrum of frequencies. In fact, some acoustic cores may have perforated acoustic screens that exhibit unsatisfactory acoustic absorption properties generally, or with respect to at least certain absorption frequencies. Additionally, existing perforated acoustic screens may cause undesirable drag to varying degrees. Further, the extent and nature in which existing perforated acoustic screens affect acoustic absorption and drag also may vary depending on the speed of grazing flow across the surface of the perforated acoustic screen, as well as depending on the configuration of the acoustic core, such that some existing perforated acoustic screens may be less suitable at certain speeds and/or for certain acoustic core configurations.
Accordingly, there exists a need for improved acoustic liners, including improved acoustic screens for acoustic liners that exhibit enhance acoustic absorption and/or reduce drag. Additionally, there exists a need for improved methods of forming acoustic liners that have such improved acoustic absorption and/or reduced drag characteristics.
Aspects and advantages will be set forth in part in the following description, or may be obvious from the description, or may be learned through practicing the presently disclosed subject matter.
In one aspect, the present disclosure embraces acoustic liners. An exemplary acoustic liner may include an acoustic core having an array of resonant cells, and an acoustic screen disposed across the array of resonant cells. The resonant cells include a plurality of cell walls and a resonant space defined by the plurality of cell walls. The acoustic core may include a folded acoustic core. Additionally, or in the alternative, at least some of the resonant cells may include an oblique polyhedral cellular structure and/or a multitude of sound-attenuating protuberances. The acoustic screen may include a reticulate membrane and a support lattice. The support lattice may include a plurality of apertures extending therethrough.
The reticulate membrane may include a multitude of reticulations passing through a membrane matrix. The reticulate membrane may have a thickness of from 0.1 millimeters to 2.0 millimeters. The multitude of reticulations may have a cross-sectional width of from 1.0 micron to 2.0 millimeters. The reticulate membrane may be rigid or flexible. The resonant cells include a resonant space, and the apertures of the support lattice may provide an open area of from 20% to 100% of the surface area of the resonant space.
In some embodiments, the support lattice and/or the reticulate membrane may include a curved surface, and the curved surface may include an aerodynamic profile and/or a Coanda surface. In other embodiments, the reticulate membrane may additionally or alternatively include intra-membrane resonant cells and/or intra-membrane curved surfaces.
At least a portion of the acoustic core and/or at least a portion of the acoustic screen may be integrally formed using an additive manufacturing technology. By way of example, the reticulate membrane and/or the support lattice may be formed of a polymeric material, a metal alloy, and/or a composite materials. The reticulate membrane comprises a first reticulate membrane-material and a second reticulate membrane-material, the first reticulate membrane-material differing from the second reticulate membrane-material.
In another aspect, the present disclosure embraces turbomachines that include an acoustic liner. An exemplary turbomachine may include a turbine, a fan rotor, a housing or nacelle defining a duct wall surrounding the turbine and/or the fan rotor, and one or more acoustic liners disposed annularly along the duct wall. At least one of the one or more acoustic liners may include an acoustic core having an array of resonant cells, and an acoustic screen disposed across the array of resonant cells. The resonant cells include a plurality of cell walls and a resonant space defined by the plurality of cell walls. The acoustic core may include a folded acoustic core. Additionally, or in the alternative, at least some of the resonant cells may include an oblique polyhedral cellular structure and/or a multitude of sound-attenuating protuberances. The acoustic screen may include a reticulate membrane and a support lattice. The support lattice may include a plurality of apertures extending therethrough.
In yet another aspect, the present disclosure embraces methods of forming an acoustic liner. An exemplary method may include attaching an acoustic screen to an acoustic core. The acoustic screen may inclue a reticulate membrane and a support lattice, and the acoustic core may include an array of resonant cells having a plurality of cell walls and a resonant space defined by the plurality of cell walls. The acoustic core may include a folded acoustic core. Additionally, or in the alternative, at least some of the resonant cells may include an oblique polyhedral cellular structure and/or a multitude of sound-attenuating protuberances.
In some embodiments, an exemplary method may include forming the reticulate membrane and/or the support lattice at least in part using an additive manufacturing technology. Additionally, or in the alternative, an exemplary method may include forming the acoustic core at least in part using an additive manufacturing technology. Further, exemplary methods may additionally or alternatively include forming sound-attenuating protuberances on at least a portion of the acoustic screen and/or forming sound-attenuating protuberances on at least a portion of the resonant cells. In still further embodiments, exemplary methods may additionally or alternatively include forming the acoustic core at least in part using a folded core technology.
These and other features, aspects and advantages will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and, together with the description, serve to explain certain principles of the presently disclosed subject matter.
A full and enabling disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended Figures, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure.
Reference now will be made in detail to exemplary embodiments of the presently disclosed subject matter, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation and should not be interpreted as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Acoustic liners for damping or attenuating sound waves are described herein. Acoustic liners may be used, for example, to dampen or attenuate noise generated by or emanating from various aspects or components of turbomachines, such as turbofan engines commonly used in aircraft, including commercial, military, and civilian aircraft. Acoustic liners may be used for damping and attenuating noise from a wide variety of turbomachines, including, turbojets, turbofans, turboprops, turboshafts, ramjets, rocket jets, pulse-jets, turbines, gas turbines, steam turbines, marine engines, and the like. More broadly, acoustic liners may be used to dampen or attenuate sound waves from any source that might be within the contemplation of those skilled in the art.
The presently disclosed acoustic liners include an array of resonant cells having a plurality of cell walls and a resonant space 207 defined by the plurality of cell walls, and an acoustic screen disposed across the array of resonant cells. The acoustic screen includes a reticulate membrane and a support lattice. The presently disclosed acoustic screens may be configured to provide a relatively constant acoustic impedance across a spectrum of frequencies, meaning that the acoustic impedance of the acoustic screen is generally unaffected by the amplitude of the sound pressure level and the gazing flow Mach number.
The presently disclosed acoustic liners are in contrast with conventional acoustic liners that have a perforated acoustic screen, such as those with numerous small perforations or holes, which are known to exhibit an acoustic impedance that can be greatly affected by both sound pressure level and the grazing-flow Mach number. The presently disclosed acoustic liners are also in contrast with conventional acoustic liners that have a wiremesh acoustic screens adhered to an array of resonant cells with no supporting perforated acoustic screen, which may provide a relatively linear acoustic impedance but generally require undesirably small resonant cells and the wiremesh may be prone to becoming damaged or dislodged by debris, and the adhesive used to adhere the wiremesh tends to become partially blocked by adhesive materials used for adhering the wiremesh to the resonant cells. A conventional perforated acoustic screen may be placed on top of a wiremesh to provide support; however, such a conventional perforate acoustic screen may undesirably introduce variable acoustic impedance properties that depend on sound pressure level and grazing-flow Mach number.
Exemplary embodiments of the presently disclosed acoustic liners may be produced at least in part using an additive manufacturing technology. The use of an additive manufacturing technology allows for novel resonant cell configuration, geometries, and/or features, as well as novel acoustic screens that avoid the aforementioned shortcomings with conventional acoustic liners. In exemplary embodiments, an acoustic screen may be integrally formed with an array of resonant cells using an additive manufacturing technology, thereby eliminating the need for an adhesive while also permanently securing the acoustic screen to the array of resonant cells. For example, an additive manufacturing technology may be used to provide an additively-manufactured acoustic core or an additively-manufactured acoustic core segment that includes an additively-manufactured array of resonant cells and/or an additively-manufactured acoustic screen. The additively-manufactured acoustic screen may include an additively-manufactured reticulate membrane and/or an additively-manufactured support lattice. In some embodiments, the additively-manufactured array of resonant cells and the additively-manufactured acoustic screen may be formed using the same additive manufacturing technology and/or as part of the same additive build process.
It is understood that terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. It is also understood that terms such as “top”, “bottom”, “outward”, “inward”, and the like are words of convenience and are not to be construed as limiting terms. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Here and throughout the specification and claims, range limitations are combined and interchanged, and such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.
Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems.
Exemplary embodiments of the present disclosure will now be described in further detail. As shown in
In operation, a turbofan engine 102 generates a tremendous amount of noise. To illustrate a typical source of turbofan engine 102 noise, it will be appreciated that the fan rotor 108 rotates within the fan casing portion 122, producing discrete tonal noise predominately at a blade passage frequency (BPF) and multiples thereof. During take-off of the aircraft, the fan blades 110 reach transonic and supersonic rotational velocities, generating noise that propagates out of the fan duct into the surrounding environment. In exemplary embodiments, one or more acoustic liners 100 are configured and arranged to suppress noise resonating at the BPF and harmonics of the BPF. The one or more acoustic liners 100 or various portions thereof may be configured to dampen or attenuate sound waves and thereby reduce the sound at specific frequencies or across a range of frequencies. Some aspects of an acoustic liner 100 may be configured to reflect incident sound waves multiple times before the sound waves escape the acoustic liner 100. These multiple reflections may reduce the amplitude of the sound waves. Additionally, some aspects of an acoustic liner 100 may be configured to cause sound waves to become out-of-phase. When sound waves become out-of-phase, various portions of the sound waves tend to cancel one another, thereby reducing at least some of the energy in the sound waves.
The reticulate membrane 208 may include a multitude of reticulations 400 passing through a membrane matrix 401 (
The reticulate membrane 208 may be rigid or flexible and may include one or more layers which may differ from one another. In some embodiments, the reticulate membrane 208 may include pre-loaded tension, such as by stretching the reticulate membrane 208 across the array of resonant cells 206 and/or by subjecting the reticulate membrane 208 to a thermal or chemical curing process that introduces such pre-loaded tension. Such pre-loaded tension may increase the acoustic absorption properties of an acoustic liner 100. For example, grazing flow (such as from air flow 116) and/or fluid within the resonant cells 206 may interact with the pre-loaded reticulate membrane 208, and the pre-loaded tension may allow the reticulate membrane 208 to absorb a greater amount of acoustic energy and thereby provide enhanced acoustic impedance. Additionally, or in the alternative, energy absorption may be enhanced by providing a degree of flexibility in the reticulate membrane 208 such that grazing flow (such as from air flow 116) and/or fluid within the resonant cells 206 activate the flexibility of the reticulate membrane 208 and thereby provide enhanced acoustic impedance. The reticulate membrane 208 may be formed of polymeric materials (e.g., a thermoplastic and/or elastomeric material), metal alloys, and/or composite materials, and may be in the form of a wire mesh, a web, or a woven or nonwoven fibrous material (e.g., synthetic fibers) that has reticulations applied thereto or that has reticulate characteristics as formed.
The reticulate membrane 208 may have a thickness of from about 0.1 millimeters (mm) to about 2.0 mm, such as from about 0.1 mm to about 1.0 mm, such as from about 0.1 mm to about 1.0 mm, such as from about 0.5 mm to about 1.5 mm, such as from about 1.0 mm to about 2.0 mm, or such as from about 1.5 mm to about 2.0 mm. The reticulate membrane 208 may have a thickness of at least about 0.1 mm, such as at least about 0.5 mm, such as at least about 1.0 mm, or such as at least about 1.5 mm. The reticulate membrane 208 may have a thickness of less than about 2.0 mm, such as less than about 1.5 mm, such as less than about 1.0 mm, or such as less than about 0.5 mm.
The reticulations in the reticulate membrane 208 may have a cross-sectional width of from about 1.0 micron (μm) to about 2.0 millimeters (mm), such as from about 1 μm to about 1,000 μm, such as from about 50 μm to about 1,000 μm, such as from about 100 μm to about 500 μm, such as from about 250 μm to about 750 μm, such as from about 750 μm to about 1.5 mm, such as from about 1.0 mm to about 2.0 mm, or such as from about 1.5 mm to about 2.0 mm. The reticulations in the reticulate membrane 208 may have a cross-sectional width of at least about 1.0 μm, such as at least about 50 μm, such as at least about 100 μm, such as at least about 250 μm, such as at least about 500 μm, such as at least about 750 μm, such as at least about 1.0 mm, or such as at least about 1.5 mm. T The reticulations in the reticulate membrane 208 may have a cross-sectional width of less than about 2.0 mm, such as less than about 1.5 mm, such as less than about 1.0 mm, such as less than about 0.5 mm, such as less than about 1.0 mm, such as less than about 750 μm, such as less than about 500 μm, such as less than about 250 μm, such as less than about 100 μm, such as less than about 50 μm.
The support lattice 210 provides support for the reticulate membrane 208 and may also be formed of polymeric materials (e.g., a thermoplastic material or elastomeric polymers), metal alloys, and/or composite materials. The support lattice 210 includes a plurality of apertures 212 extending therethrough so as to allow sound waves to interact with the reticulate membrane 208 and enter the resonant cells 206 of the acoustic core 200. The apertures 212 may be positioned and arranged in at least one of a repeating pattern and a random pattern. In an exemplary embodiments, the apertures 212 may be positioned and spaced in a manner that corresponds to the positioning and spacing of the array of resonant cells 206 that make up the acoustic core 200. The apertures 212 and resonant cells 206 may have a one-to-one or many-to-one relationship. For example, in some embodiments, an acoustic liner 100 may include one aperture 212 positioned adjacent to a respective resonant cell 206 so as to allow fluid to interact with the reticulate membrane 208 and enter such resonant cell 206. Other embodiments may include a plurality of apertures 212 positioned adjacent to a respective resonant cell 206.
The reticulate membrane 208 and/or the support lattice 210 may be formed as part of an additive manufacturing technology or any other suitable process, separately or concurrently with one another. The reticulate membrane 208 and/or the support lattice 210 may additionally or alternatively be formed as part of an additive manufacturing technology separately or concurrently with the acoustic core 200. Additionally, or in the alternative, the reticulate membrane 208 may be combined with the support lattice 210 and/or the acoustic core 200 using an adhesive process, and/or the support lattice 210 may be combined with the reticulate membrane and/or the acoustic core 200 using an adhesive process. Alternatively, the reticulate membrane 208 may be secured to the acoustic screen 202 using an adhesive process. For example, a thermal, sonic, or electric welding process may be used. As another example, diffusion bonding may be used. Alternatively, an adhesive formulation such as a thermosetting or pressure sensitive adhesive or an adhesive tape may be used to secure the reticulate membrane 208 to the support lattice 210. Such an adhesive process may also be used to secure the support lattice and/or the reticulate membrane 208 to the acoustic core 200.
Exemplary acoustic screens 202 may include a support lattice 210 with apertures 212 that are sufficiently large so as to provide linear acoustic impedance properties while minimizing or eliminating undesirable dependency on sound pressure level and grazing-flow Mach number. For example, an acoustic screen 202 may include a support lattice 210 with apertures 212 that provide for an open area of at least 20% up to or approaching 100% of the surface area of the resonant space 207, such as an open area from about 20% to about 100%, such as from about 20% to about 90%, such as from about 20% to about 80%, such as from about 20% to about 60%, or such as from about 20% to about 40% of the surface are of the resonant space 207 of the resonant cells 206.
The support lattice 210 may include apertures 212 that have any desired shape, including elliptical and/or polyhedral shaped apertures 212. For example,
A thickness or height of the acoustic core 200 may be defined by a distance taken along an axis R 214 (also shown in
The acoustic screen 202, the back sheet 204, and the acoustic core 200 may together form an arcuate cylindrical acoustic liner 100 (see, e.g.,
In still other embodiments, the acoustic screen 202, the back sheet 204, and the acoustic core 200 may together form a complexly curved acoustic liner 100. For example, and without limitation, one or more complexly curved walls or other aspects of a nacelle or a noise source-containing room or space may be at least partially lined with a complexly curved acoustic liner 100, such as shown in
Now turning to
The acoustic liners 100 shown in
In some embodiments, as shown in
In still further embodiments, as shown in
While acoustic liners 100 that have a support lattice 210 with a curved surface 300 are described with reference to
Still referring to
In exemplary embodiments, an acoustic liner 100 may be formed entirely using an additive manufacturing technology. For example, sequential layers of the acoustic core 200, the reticulate membrane 208, and the acoustic screen 202 may be additively manufactured using a suitable additive manufacturing technology. Such additive manufacturing technology may allow for configurations such as a support lattice 210 disposed flush with at least a portion of the reticulate membrane 208, for example, as shown in
In some embodiments, a reticulate membrane 208 may be applied to a top face 216 of an acoustic core 200, such as from a roll or sheet of reticulate membrane material, and then a support lattice 210 may be additively printed thereon. The support lattice 210 may penetrate through the reticulate membrane material and integrally bond with the cell walls of the acoustic core 200 as well as the reticulate membrane material, providing an acoustic liner 100 that includes an acoustic core 200 and an acoustic screen 202 integrally formed with one another. Such an integrally formed acoustic liner 100 may include a reticulate membrane 208 integrally formed with a support lattice 210 and the acoustic core 200, as well as a support lattice 210 integrally formed with the acoustic core 200.
In exemplary embodiments, the acoustic core 200, the reticulate membrane 208, and the support lattice 210 may be additively manufactured in such a manner so as to be one and the same component without seams or the like separating elements from one another. However, the reticulate membrane 208 may be recognized by reticulations present therein and the support lattice 210 may be recognized by non-reticulated material disposed above the cell walls of the acoustic core 200 and/or between portions of the reticulate membrane 208.
Now turning to
As shown in
As shown in
In some embodiments, the intra-membrane curved surfaces 414 may have an aerodynamic profile that reduces drag from grazing flow (such as from air flow 116). While convex aspects are shown, it will be appreciated that the intra-membrane curved surfaces 414 may include convex and/or concave aspects. In some embodiments, the intra-membrane curved surfaces 414 may include a Coanda surface, which may direct grazing flow (such as from air flow 116) through reticulations 400 in the reticulate membrane-material 404 and into an intra-membrane resonant space 407 defined by intra-membrane resonant cell 406, and/or into a resonant space 207 defined by a resonant cell 206.
As shown in
The exemplary reticulate membrane 208 shown in
Now turning to
The surface 500 and/or the pathways 500 may be formed using an additive manufacturing technology and/or a subtractive manufacturing technology, or a combination thereof. For example, the surface 500 may be formed using an additive manufacturing technology, leaving pathways 502 extending therethrough.
Additionally, or in the alternative, a subtractive process may be used to form pathways 502 extending through the surface 500.
As shown in
The pathways 502 may be arranged about the surface 502 in any desired orientation, including an ordered or random or semi-random orientation. The pathways 502 may be oriented in an array, including an equidistant array (e.g., as shown with surfaces 500 (a) and (c), having adjacent pathways 502 in perpendicular directions equidistant from one another), or a staggered array (e.g., as shown with surface 500 (l) and (m), having adjacent pathways 502 in perpendicular direction of unequal distance from one another).
Now turning to
The acoustic cores 200 may include resonant cells 206 with any polyhedral configuration, including parallel polyhedral cellular structures and/or oblique polyhedral cellular structures. Parallel polyhedral cellular structures generally have geometric characteristics reflecting a right prism or a substantially right prism. A right prism refers to a polyhedron composed of an n-sided polygonal top face 216, a bottom face 218 which is a translated copy of the top face 216 without rotation, and n-number of rectangular lateral faces bisected by the top face 216 and the bottom face 218. Given these characteristics of a right prism or substantially right prism, parallel polyhedral cellular structures have lateral faces that are substantially parallel to a normal line 214 represented by an axis R. For example,
As shown in
In contrast with parallel cellular structures, oblique polyhedral cellular structures have polyhedral cells with least one lateral face that either converges or diverges relative to the normal line 214 represented by the axis R at a convergence angle θ (theta) 220 greater than zero degrees. A wide variety of convergence angles and/or divergence angles may be provided. For example, in various embodiments, a convergence angle θ (theta) 220 may fall within a range from greater than zero to 45 degrees, such as from 1 to 10 degrees, such as from 1 to 20 degrees, such as from 1 to 30 degrees, or such as from 1 to 45 degrees. In some embodiments, a convergence angle θ (theta) 220 may fall within a range from 2 to 30 degrees, such as from 2 to 10 degrees, such as from 5 to 15 degrees, such as from 10 to 20 degrees, or such as from 15 to 30 degrees. The convergence angle θ (theta) 220 may be greater than zero degrees, such as greater than 1 degrees, such as greater than 2 degrees, such as greater than 5 degrees, such as greater than 10 degrees, such as greater than 15 degrees, such as greater than 20 degrees, such as greater than 25 degrees, such as greater than 30 degrees, such as greater than 35 degrees, or such as greater than 40 degrees. The convergence angle θ (theta) 220 may be less than 45 degrees, such as less than 40 degrees, such as less than 35 degrees, such as less than 30 degrees, such as less than 25 degrees, such as less than 20 degrees, such as less than 15 degrees, such as less than 10 degrees, such as less than 5 degrees, or such as less than 1 degrees.
The exemplary acoustic core shown in
The converging polyhedral cells 802 and/or diverging polyhedral cells 804 have asymmetry in respect of at least one such converging or diverging lateral face and/or in respect of a differing cross-sectional area as between two substantially parallel planes that bisect the cell (i.e., the top face 806 and the bottom face 808). The substantially parallel planes of the top face 806 and the bottom face 808 may bisect an oblique polyhedral cell as a plane, as a line, or as a point, depending on the configuration of the particular cell. As a convenience, such a plane, line, or point may sometimes be referred to more generally as a face. For example, the top face 806 bisects both the converging polyhedral cells 802 and the diverging polyhedral cells 804 as a plane, and the bottom face 808 bisects the converging cells 802 as a line and the diverging cells 804 as a plane.
In addition to the exemplary oblique polyhedral cellular structures shown in
As shown in
An antiprism includes a polyhedron composed of a polygonal top face 216, a polygonal bottom face 218, and a sequence of adjacent trigonal lateral faces with alternating orientations, bisected by the top face 216 and the bottom face 218. By way of example, an antiprism may include a trigonal antiprism, a tetragonal antiprism, a hexagonal antiprism, an antiprismal polyhedron, and combinations of these. An antiprismal polyhedron includes an antiprism combined with another polyhedron. In some embodiments, an antiprism may include an n-sided top face 216 and an n-sided bottom face 218. Alternatively, an antiprism may include an n-sided top face 216 and a bottom face 218 with greater than or less than n-sided.
A twisted prism includes a polyhedron composed of a polygonal top face 216, a polygonal bottom face 218, and a plurality of lateral faces including at least some lateral faces bisected on a diagonal, with the top face 216 and the bottom face 218 twisted relative to one another, causing at least some adjacent lateral faces to be concave relative to one another. By way of example, a twisted prism may include a Schonhardt polyhedron, a tetrahedral twisted prism, a hexagonal twisted prism, a twisted prismal polyhedron, and combinations of these. A twisted prism has one or more lateral faces bisected on an adjacent diagonal or on a subsequent diagonal. For example,
A cupola includes a polyhedron composed of a polygonal top face 216, a polygonal bottom face 218, and a plurality of lateral faces including an alternating sequence of trigonal lateral faces and tetragonal lateral faces. In some embodiments, a cupola has a top face 216 with twice as many edges as that of its bottom face 218, or vice versa. By way of example, a cupola includes a trigonal cupola, which has a tetragonal top face 216 and a hexagonal bottom face 218, or a hexagonal top face 216 and a tetragonal bottom face 218; and a pentagonal cupola, which has a pentagonal top face 216 and a decagonal bottom face 218, or vice versa. A cupola also includes star cupola, which is a cupola in which tetragonal lateral faces are replaced with adjacent concave trigonal lateral faces. Star cupola include a pentagrammic cuploid and a heptagrammic cuploid. A pentagrammic cuploid has a pentagonal bottom face 218 and a pentagrammic top face 216, or vice versa. A heptagrammic cuploid has a heptagonal top face 216 and a heptagrammic bottom face 218, or vice versa. As a further example, a cupola includes cuploidal configurations with numerous lateral faces, including configurations which approach frustoconical as the number of lateral faces increases. For example, a cupola includes an octacontagon, which has eighty lateral faces. A cupola also includes a cuploidal polyhedron, which includes a cupola or cuploid combined with another polyhedron.
A wedge includes a polyhedron with a polygonal top face 216 and a plurality of polygonal lateral faces that converge into a line. By way of example, a wedge may include a tetrahedral wedge, an obtuse wedge, an acute wedge, and a wedged polyhedron, and combinations of these. A tetrahedral wedge has two trigonal lateral faces and two tetragonal lateral faces. The lateral faces are bisected by a tetragonal plane on one side and converge into a line on the other. An obtuse wedge converges into a line that is wider than the opposing tetragonal plane. An acute wedge converges into a line that is narrower than the opposing tetragonal plane. A wedged polyhedron includes a wedge combined with another polyhedron.
A pyramid includes a polyhedron with a polygonal base bisected by a plurality of trigonal lateral faces that converge into a point. By way of example, a pyramid includes a tetragonal pyramid composed of a tetragonal face bisected by four trigonal lateral faces which converge into a point. A pyramid also includes a star pyramid, composed of a star polygonal base and a plurality of trigonal lateral faces that converge into a point. As an example, a star pyramid includes a pentagonal star pyramid.
Any one or more of these oblique polyhedral configurations (including combinations or portions thereof) may be included in various exemplary oblique cellular structures. In one aspect, the converging polyhedral cells 802 shown in
The acoustic core 200 may be formed of polymeric materials (e.g., a thermoplastic material or elastomeric polymers), synthetic fibers, metal alloys, or composite materials, and may be formed as part of an additive manufacturing technology or any other suitable process, separately or concurrently with the reticulate membrane 208 and/or the support lattice 210. Additionally, the back sheet 204 may be formed of any one or more such materials, as part of an additive manufacturing technology or any other suitable process, separately or concurrently with the acoustic core 200, the reticulate membrane 208 and/or the support lattice 210. Alternatively, the acoustic core 200 may be secured between the acoustic screen 202 and the back sheet 204 using an adhesive process. For example, a thermal, sonic, or electric welding process may be used. As another example, diffusion bonding may be used. Alternatively, an adhesive formulation such as a thermosetting or pressure sensitive adhesive or an adhesive tape may be used to secure the acoustic core 200 in position. Additionally, acoustic cores may be formed from any other suitable technology and/or material known in the art, all of which are within the scope of the present disclosure.
Exemplary polymeric materials may include thermoplastic materials, and/or thermosetting materials. Exemplary thermosetting materials include, for example, epoxies, resins, acrylics, phenolics, polyesters, polyurethanes, polyimides, polyamide-imides (PAI), polysiloxanes bismaleimides, cyanate esters, phenolics, benzoxazines, phthalonitriles. Exemplary thermoplastic materials include, for example, acrylonitrile butadiene styrene (ABS), polyesters, polyamide-imides (PAI), polyetherimide (PEI), polyphenylsulfone (PPSF), polycarbonate (PC), polylactic acid (PLA), high-impact polystyrene (HIPS), thermoplastic polyurethane (TPU), aliphatic polyamides (nylon), polyaryletherketone (PAEK), polyetherketoneketone (PEKK), or polyether ether ketone (PEEK), as well as combinations thereof.
Exemplary synthetic fibers include extruded polymer filaments such as polyetherimide (PEI), polycarbonate, acrylonitrile, acrylonitrile-butadiene-styrene, aramid fiber, meta-aramid fiber, para-aramid fiber, polyethylene fiber, rayon, polyester, or nylon, as well as combinations of these.
Exemplary metal alloys include aluminum alloys, steel alloys, titanium alloys, or nickel alloys (e.g., superalloys, such as austenitic nickel-chromium-based superalloys), as well as combinations of these.
Exemplary composite materials include ceramic matrix composite (CMC) materials and/or polymer matrix composite (PMC) materials. CMC materials include a ceramic matrix material and reinforcing fibers or cloth. Exemplary ceramic matrix materials include silicon carbide (SiC) and/or carbon (C). Exemplary CMC materials include carbon-fiber-reinforced carbon (C/C), carbon-fiber-reinforced silicon carbide (C/SiC), or silicon-carbide-reinforced silicon carbide (SiC/SiC). PMC materials include a polymeric matrix material and reinforcing fibers or cloth. Exemplary PMC materials include fiber-reinforced plastics and advanced composites. Exemplary polymeric matrix materials include thermosets, such as epoxies, phenolics, polyurethanes, polyimides, bismaleimides, cyanate esters, phenolics, benzoxazines, phthalonitriles. In some embodiments, polyimides may be particularly suitable. Exemplary polyimides include phenylethynyl-terminated imide (PETI) oligomers, biphenyl dianhydride-based 2,2′-dimethylbenzidine, ultrahigh-temperature HFPE. In some embodiments, exemplary polyimides may include end caps, such as 4-phenylethynylphthalic anhydride (PEPA) and/or asymmetric oxydipththalic anhydride (a-ODPA) end caps.
Exemplary reinforcing fibers or cloth that may be utilized in CMC or PMC materials include carbon fibers, ceramic fibers, fiberglass, graphite fibers, and aramid fibers. Exemplary reinforcing fibers include monofilaments, yarns, chopped whiskers or fibers, and/or particles. In some embodiments, ceramic fibers may be formed of materials such a silicon carbide (SiC), carbon fiber (C), sapphire, alumina silicates, and/or oxides of Si, Al, Zr, Y, as well as combinations thereof. The reinforcing fibers may additionally include inorganic fillers, such as silica, quartz, pyrophyllite, wollastonite, mica, talc, kyanite, and/or montmorillonite, as well as combinations thereof.
Any suitable additive manufacturing technology may be utilized to manufacture various aspects of the presently disclosed acoustic liners 100. Exemplary additive manufacturing technologies include, but are not limited to: directed energy deposition (DED) systems, such as chemical vapor deposition (CVD) systems, laser metal deposition (LMD) systems, directed metal deposition (DMD) systems, laser engineered net shape (LENS) systems, electron beam additive melting (EBAM) systems, or rapid plasma deposition (RPD) systems; powder bed fusion (PBF) systems, such as direct metal laser melting (DMLM) systems, electron beam melting (EBM) systems, directed metal laser sintering (DMLS) systems, selective laser melting (SLM) systems, or selective laser sintering (SLS) systems; laminated object manufacturing (LOM) systems, such as ultrasonic manufacturing (UAM) systems; mater extrusion (ME) systems, such as fused deposition modeling (FDM) systems or fused filament fabrication (FFF) systems; material jetting (MJ) systems, such as smooth curvatures printing (SCP) systems, multi jet modeling (MJM) systems; and 3D printing, such as by inkjets and laserjets, including binder jetting (BJ) systems; photopolymer jetting (PJ) systems, stereolithographic (SLA) systems, and hybrid processes (HP).
Other suitable technologies that may be used to manufacture various aspects of the presently disclosed acoustic liners 100 include, without limitation, forming (e.g., rolling, stamping, joining, etc.), extruding (e.g., sheet extruding), subtractive manufacturing (e.g., machining, drilling, laser cutting, etc.), forging or casting, as well as a combination thereof, or any other manufacturing technology. As shown in
Now turning to
In one embodiment, the acoustic core 200 shown in
Core material strips 1000 such as those shown in
It will be appreciated that in some embodiments it may be advantageous to avoid waste or unused material when cutting core material strips 1000 from a larger supply of core material. In some embodiments, core material strips 1000 having a circular, spiral, or curvilinear configuration may result in waste or unused material. However, in some embodiments core material strips 1000 can be cut from a larger supply of core material such as a roll to provide oblique polyhedral cellular structures that reduce waste material. For example, in some embodiments oblique polyhedral cells may be cut from wavy or oscillating core material strips 1000 configured such that the respective edges of subsequently cut strips 1000 align with one another Additionally, in some embodiments oblique polyhedral cells may be cut from linear core material strips 1000.
Now turning to
The intentionally incidental nature of the sound-attenuating protuberances 1200 or the formation thereof may provide for a random or semi-random orientation and/or size of sound-attenuating protuberances 1200 over at least a portion of the acoustic core 200, such as at least a portion of the cell walls making up the resonant cells 206 of the acoustic core 200. This random or semi-random orientation and/or size may not necessarily be achievable by other means, such as directly additively manufacturing each individual protuberance 1200. For example, in some embodiments, at least a portion of the sound-attenuating protuberances 1200 may have one or more dimensions (e.g., height, width, and/or length) that are smaller than a corresponding minimum dimensional resolution provided for by the additive manufacturing technology utilized to produce the acoustic core 200.
As shown in
The sound-attenuating protuberances 1200 take the form of the additive manufacturing material of the cell walls integrally protruding into the resonant space 207 with a random or semi-random orientation about at least a portion of the cell walls. Exemplary sound-attenuating protuberances 1200 may include any one or more of a combination of protuberant features having a variety of shapes and configurations, including nodules, loops, hooks, bumps, burls, clots, lumps, knobs, projections, protrusions, swells, enlargements, outgrowths, accretions, blisters, juts, and the like. These sound-attenuating protuberances 1200 occur in a random or semi-random fashion as a product of the particular manner in which the resonant cells 206 are formed. However, the particular configuration, arrangement, or orientation of the sound-attenuating protuberances 1200 may be selectively controlled or modified by adjusting the manner in which the resonant cells 206 are formed.
Regardless of their shape, sound-attenuating protuberances 1200 may be provided in any desired size. The sound-attenuating protuberances 1200 protrude from the nominal surface 1202 of a cell wall in respect of a height (h) 1204, a width (w) 1206, and a length (l) 1208. In some embodiments, a multitude of sound-attenuating protuberances 1200 may have an average height, width, and/or length of from about 5 to 10,000 micrometers. The size of the sound-attenuating protuberances 1200 may be selected based on the desired sound-attenuation properties of the resonant cells 206.
A multitude of sound-attenuating protuberances 1200 may have an average height, (h) 1204 of from about 5 to 10,000 micrometers, as measured from the nominal surface 1202 of the cell wall from which the sound-attenuating protuberances 1200 protrude. For example, the average height 1204 of the sound-attenuating protuberances 1200 may be from about 10 μm to 5,000 μm, such as from about 10 μm to 1,000 μm, such as from about 10 μm to 500 μm, such as from about 10 μm to 500 μm, such as from about 25 μm to 300 μm such as from about 50 μm to 200 μm, or such as from about 75 μm to 150 μm. The multitude of sound-attenuating protuberances 1200 may have an average height 1204 of 10,000 μm or less, such as 5,000 μm or less, such as 1,000 μm or less, such as 500 μm or less, such as 500 μm or less, such as 300 μm or less, such as 200 μm or less, such as 100 μm or less, such as 75 μm or less, such as 50 μm or less, such as 25 μm or less, or such as 10 μm or less. The multitude of sound-attenuating protuberances 1200 may have an average height 1204 of 10 μm or more, such as 25 μm more, such as 50 μm more, such as 75 μm more, such as 100 μm more, such as 150 μm more, such as 200 μm more, such as 300 μm, more, such as 500 μm more, such as 500 μm more, such as 1,000 μm more, or such as 5,000 μm more.
A multitude of sound-attenuating protuberances 1200 may have an average width, (w) 1206 of from 5 to 500 micrometers, as measured laterally across the surface of the cell wall from which the sound-attenuating protuberances 1200 protrude. For example, the average width 1206 of the sound-attenuating protuberances 1200 may be from 10 μm to 5,000 μm, such as from 10 μm to 1,000 μm, such as from 10 μm to 500 μm, such as from 10 μm to 500 μm, such as from 25 to 300 μm such as from 50 μm to 200 μm, such as from 75 μm to 150 μm. The multitude of sound-attenuating protuberances 1200 may have an average width 1206 of 10,000 μm or less, such as 5,000 μm or less, such as 1,000 μm or less, such as 500 μm or less, such as 500 μm or less, such as 300 μm or less, such as 200 μm or less, such as 100 μm or less, such as 75 μm or less, such as 50 μm or less, such as 25 μm or less, or such as 10 μm or less. The multitude of sound-attenuating protuberances 1200 may also have an average width 1206 of 10 μm or more, such as 25 μm more, such as 50 μm more, such as 75 μm more, such as 100 μm more, such as 150 μm more, such as 200 μm more, such as 300 μm more, such as 500 μm more, such as 500 μm more, such as 1,000 μm more, or such as 5,000 μm more.
A multitude of sound-attenuating protuberances 1200 may have an average length, (l) 1208 of from 5 to 500 micrometers, as measured longitudinally along the surface of the cell wall from which the sound-attenuating protuberances 1200 protrude. For example, the average length 1208 of the sound-attenuating protuberances may be from 10 μm to 5,000 μm, such as from 10 μm to 1,000 μm, such as from 10 μm to 500 μm, such as from 10 μm to 500 μm, such as from 25 μm to 300 μm such as from 50 μm to 200 μm, or such as from 75 μm to 150 μm. The multitude of sound-attenuating protuberances 1200 may have an average length 1208 of 10,000 μm or less, such as 5,000 μm or less, such as 1,000 μm or less, such as 500 μm or less, such as 500 μm or less, such as 300 μm or less, such as 200 μm or less, such as 100 μm or less, such as 75 μm or less, such as 50 μm or less, such as 25 μm or less, or such as 10 μm or less. The multitude of sound-attenuating protuberances 1200 may have an average length 1208 of 10 μm or more, such as 25 μm more, such as 50 μm more, such as 75 μm more, such as 100 μm more, such as 150 μm more, such as 200 μm more, such as 300 μm more, such as 500 μm more, such as 500 μm more, such as 1,000 μm more, or such as 5,000 μm more.
Now referring to
As shown in
Regardless of where the additional additive manufacturing material is introduced, as shown in
The extent of the overlap as between two toolpath passes (e.g., the first toolpath pass 1302 and the second toolpath pass 1304) in the toolpath overlap zone 1306 may be described with reference to a toolpath gap 1308, which describes a distance between a first pass centerline 1310 and a second pass centerline 1312. The toolpath gap 1308 may be described in relation to a toolpath pass width 1314 and/or a contour width 1316. A toolpath pass width 1314 refers to the average width of a toolpath pass, such as the first toolpath pass 1302, without regard to the presence of sound-attenuating protuberances 1200. A contour width 1316 refers to the average width of a plurality of toolpath passes defining the toolpath overlap zone 1306, such as that of the first toolpath pass 1302 and the second toolpath pass 1304, without regard to the presence of sound-attenuating protuberances 1200. In some embodiments, the amount of additional additive manufacturing material introduced to the acoustic core 200 may be proportional to the toolpath gap 1308.
The integral formation of the sound-attenuating protuberances 1200 may depend on providing a toolpath gap 1308 of sufficient size so as to introduce to the acoustic core 200 sufficient additional additive manufacturing material. The size of the toolpath gap 1308 may be described with reference to a toolpath gap ratio, which refers to a ratio of the contour width 1316 to the toolpath pass width 1314. In some embodiments, the amount of sound additional additive manufacturing material introduced may be depend at least in part on the toolpath gap ratio. The particular toolpath gap ratio that may be suitable for a given acoustic core 200 may be selected by evaluating the sound-attenuation properties of the sound-attenuating protuberances 1200 resulting therefrom.
A toolpath gap ratio may range from 1.0 to less than 2.0. A toolpath gap ratio of 1.0 corresponds to fully overlapping toolpath passes. A toolpath gap ratio of 2.0 corresponds to adjacent and abutting toolpath passes that do not overlap. In some embodiments, sound-attenuating protuberances 1200 may be integrally formed by providing a toolpath gap ratio from 1.0 to less than 2.0, such as from 1.1 to 1.9, such as from 1.1 to 1.8, such as from 1.1. to 1.5, such as from 1.1 to 1.3, such as from 1.2 to 1.7, such as from 1.5 to 1.9, such as from 1.5 to 1.7. The toolpath gap ratio may be 1.0 or more, such as 1.1 or more, such as 1.2 or more, such as 1.3 or more, such as 1.4 or more, such as 1.5 or more, such as 1.6 or more, such as 1.7 or more, such as 1.8 or more, or such as 1.9 or more. The toolpath gap ratio may be less than 2.0, such as less than 1.9, such as less than 1.8 such as less than 1.7, such as less than 1.6, such as less than 1.5, such as less than 1.4, such as less than 1.3, such as less than 1.2, or such as less than 1.1.
Sequential contours of an acoustic core 200 that includes sound-attenuating protuberances 1200 may be formed by orienting the additive manufacturing tool with respect to sequential toolpaths 1300. The sequential contours may be applied on top of one another, incrementing in a stepwise manner to additively build the acoustic core 200. All or a portion of the sequential toolpaths 1300 may include overlapping toolpath passes providing for a toolpath overlap zone 1306. However, it is not necessary that every toolpath 1300 provide for a toolpath overlap zone 1306, and it also is not necessary that a toolpath overlap zone 1306 exist with respect to the entirety of a toolpath 1300. In fact, the toolpath overlap zone 1306 may be present in an intermittent or variable manner. Additionally, or in the alternative, additional additive manufacturing material may be introduced within the toolpath overlap zone 1306 in an intermittent or variable manner. As examples, an additive manufacturing tool may follow a variable or irregular toolpath 1300 or toolpath passes such that the toolpath overlap zone 1306 exhibits a variable or irregular nature. As further examples an additive manufacturing tool may cause the introduction of additive manufacturing material to occur in a variable or irregular manner, such as by cycling a tool speed or material introduction rate.
The specific nature in which sound-attenuating protuberances 1200 are integrally formed in an intentionally incidental manner may depend on the particular additive manufacturing technology used. Additive manufacturing technologies may be grouped by the nature of the input from the additive manufacturing tool. For example, an additive manufacturing tool may introduce an additive manufacturing material and/or a beam of additive energy to additively manufacture an acoustic core 200. The additive manufacturing material may be an amorphous material such as a powder, a liquid, a gel, a polymer, etc. The additive manufacturing technology includes conforming the amorphous material to a solid acoustic core 200 through a process such as melting, fusing, curing, etc.
Additive manufacturing technologies which utilize an additive manufacturing tool that introduces an additive manufacturing material are sometimes referred to herein as additive material technologies. Additive material technologies includes material extrusion (e.g., fused deposition modeling (FDM), fused filament fabrication (FFF), etc.), material jetting (MJ) (e.g., smooth curvatures printing (SCP), multi jet modeling (MJM), etc.), binder jetting (BJ), and directed energy deposition (DED) (e.g., laser metal deposition (LMD), laser engineered net shaping (LENS), directed metal deposition (DMD), etc.).
In the case of material extrusion, the additive manufacturing material may be provided in the form of a filament. The filament may include a thermoplastic material or a ceramic material, for example. In the case of material jetting (MJ), the additive manufacturing material may include a photosensitive material, such as a thermosetting material. The photosensitive material may be supplied in the form of a liquid, gel, or the like, and may solidify when exposed to an additive energy source such as ultraviolet light. In the case of binder jetting (BJ), the additive manufacturing material may include a binder material which is jetted into a bed of powder material. The binder material may be applied in the form of a liquid, gel, or the like. Exemplary binder materials include thermosetting materials or thermoplastic materials. Exemplary powder material for binder jetting (BJ) may include, for example, metal or metal alloys, thermoplastic materials, and ceramics. In the case of directed energy deposition (DED), the additive manufacturing material may be provided in the form of a wire, a filament, or powder. Exemplary material for directed energy deposition (DED) may include, for example, metal or metal alloys, thermoplastic materials, and ceramics.
Additive manufacturing technologies which utilize an additive manufacturing tool that introduces a beam of additive energy to solidify (e.g., melt, fuse, cure, etc.) an amorphous additive manufacturing material (e.g., a powder, a liquid, a gel, etc.) are sometimes referred to herein as additive energy technologies. Additive energy technologies include powder bed fusion (PFB) (e.g., selective laser sintering (SLS), direct metal laser sintering (SLM), laser melting (LM), electron beam melting (EBM), selective heat sintering (SHS), multi-let fusion (MJF), etc.), and vat photopolymerization (e.g., stereolithography apparatus (SLA), digital light processing (DLP), scan, spin, and selectively photocure (3SP), continuous liquid interface production (CLIP), etc.). In the case of powder bed fusion (PFB), the additive manufacturing material may be provided in the form of a powder. Exemplary powder material for powder bed fusion (PFB), may include, for example, metal or metal alloys, polymeric materials (e.g., thermosetting materials and/or thermoplastic materials), and ceramics. In the case of vat photopolymerization, the additive manufacturing material may include a photosensitive material. Exemplary photosensitive materials that may be utilized with additive manufacturing technologies (e.g., additive material technologies or additive energy technologies) include a formulation containing, for example, a binder, a monomer, and a photoinitiator. Exemplary binders include styrenes, methacrylates, vinyl alcohols, olefins, clycerols, and propylenes. Exemplary monomers include acrylic acids, methacrylic acids, isodecyl acryalates, and N-vinyl pyrrolidone. Exemplary photoinitiators include free radical photoinitiators such as isopropylthioxanthone, benzophenone, and 2,2-azobizisobutyronitrile, and cationic photoinitiators such as diaryliodonium salts and triarylsulfonium salts.
In some embodiments, sound-attenuating protuberances 1200 may be integrally formed in an intentionally incidental manner using an additive material technology. One suitable additive material technology includes fused deposition modeling (FDM) or fused filament fabrication (FFF), however other additive material technologies also may be used. With an additive material technology, the additive manufacturing tool introduces an additive manufacturing material to the acoustic core 200. The overlapping toolpath passes cause an excess of additive manufacturing material to be introduced into a domain 1201 occupied by the contour defined by the toolpath 1300. As additional contours are applied to the acoustic core 200, adjacent contours force excess additive manufacturing material outward from the respective contours, causing incidental protuberances 1200 of additional additive manufacturing material to be intentionally formed with a random or semi-random orientation. For example, with fused deposition modeling (FDM) or fused filament fabrication (FFF), excess material is extruded and deposited in the overlapping toolpath passes, causing an accumulation of excess material in the toolpath overlap zone 1306, forcing extruded material outward from the respective contours. The additive manufacturing material making up the protuberances 1200 may come from any portion of the additive manufacturing material, including any one or more toolpaths 1300 and/or any one or more toolpath passes 1302, 1304, and including material originating from within or outside of the toolpath overlap zone 1306. In some embodiments, at least a portion of the sound-attenuating protuberances 1200 may have one or more dimensions that are smaller than a corresponding minimum dimensional resolution provided for by the additive manufacturing technology used to produce the acoustic core 200. For additive material technologies, the dimensional resolution may be defined by the dimensions of the material introduced. For example, with fused deposition modeling (FDM) or fused filament fabrication (FFF), the dimensional resolution may be defined by the cross-sectional dimension of filaments as extruded during the fused deposition modeling process.
In some embodiments, sound-attenuating protuberances 1200 may be integrally formed in an intentionally incidental manner using an additive energy technology. One suitable additive energy technology includes selective laser sintering (SLS), however, other additive energy technologies also may be used. With an additive energy technology, the additive manufacturing tool introduces a beam of additive energy to the acoustic core 200, which solidifies an amorphous additive manufacturing material. The overlapping toolpath passes causes excess of additive energy to be introduced into a domain 1201 occupied by the contour defined by the toolpath 1300. This excess energy propagates outward from the respective contours, causing incidental protuberances 1200 of additional additive manufacturing material to be intentionally formed with a random or semi-random orientation. For example, with selective laser sintering (SLS), heat generated by a laser melts a powder material. To form sound-attenuating protuberances 1200, excess laser energy is intentionally introduced by providing overlapping toolpath passes, and this excess laser energy incidentally melts adjacent powder particles outside of the domain 1201 occupied by the respective contours with a random or semi-random orientation. In some embodiments, at least a portion of the sound-attenuating protuberances 1200 may have one or more dimensions that are smaller than a corresponding minimum dimensional resolution provided for by the additive manufacturing technology used to produce the acoustic core 200. For additive energy technologies, the dimensional resolution may be defined by the cross-sectional dimensions of the amorphous additive manufacturing material and/or the cross-sectional dimensions of the beam of additive energy. For example, with selective laser sintering (SLS), the dimensional resolution may be defined by the cross-sectional dimension of the particles of the amorphous additive manufacturing material and/or the cross-sectional dimension of the laser beam used to melt the particles. As another example, for vat photopolymerization, the dimensional resolution may be defined by the cross-sectional dimension of a laser or other energy beam used to cure the photopolymer.
In some embodiments, sound-attenuating protuberances 1200 may be integrally formed using a combination of additive material technology and additive energy technology. For example, it will be appreciated that directed energy deposition (DED) utilizes an additive manufacturing tool that introduces both an additive manufacturing material and an additive energy. Additionally, or in the alternative, different additive manufacturing technologies may be combined with one another, such as by using different additive manufacturing technologies for different portions of an acoustic core 200, and/or by using different additive manufacturing technologies simultaneously, sequentially, or otherwise in combination, to integrally form sound-attenuating protuberances 1200 in an acoustic core 200.
Now referring to
The present disclosure provides numerous configurations for cellular structures that may be included in an acoustic core 200. It will be appreciated that numerous additional configurations are within the spirit and scope of the present disclosure. In some embodiments, an array of resonant cells 206 may include a combination of differently configured polyhedral cells. The combination may include both oblique polyhedral cells and parallel polyhedral cells, and various different configurations of these. For example,
Now turning to
As shown in
In exemplary methods 1600, forming an acoustic core, at block 1602, may include, at block 1610, forming the acoustic core 200 at least in part using an additive manufacturing technology. Additionally, or in the alternative, block 1602 may include, at block 1612, forming the acoustic core 200 at least in part using a folded core technology. In some embodiments, block 1602 may include, at block 1614, forming sound-attenuating protuberances 1200 on at least a portion of the resonant cells 206.
Still referring to
Now turning to
Exemplary methods may further include, at block 1624, concurrently or subsequently folding the plurality of core material strips 1000. The respective core material strips 1000 may be thereby separated from one another or expanded at a multitude of expansion regions 1004. Such expansion regions 1004 may be respectively located between the multitude of adherence regions 1002. Such folding and/or expanding may provide an array of oblique polyhedral cellular structures 800. For example, the core material strips 1000 may be configured in accordance with the present disclosure to provide an array of resonant cells 206 that includes a plurality of converging polyhedral cells and a plurality of diverging polyhedral cells.
Now turning to
The overlapping toolpath passes may be configured such that, at block 1628, the overlapping toolpath passes 1302, 1304 intentionally introduce an amount of additive manufacturing material that exceeds a domain 1201 occupied by the contour. As the amount of additive manufacturing material intentionally introduced exceeds the domain 1201 occupied by the contour, at block 1630, a portion of the additive manufacturing material may incidentally form a plurality of sound-attenuating protuberances 1200 having a random or semi-random orientation and/or size.
Sequential contours of an acoustic core 200 and/or an acoustic screen 202 may be formed by orienting an additive manufacturing tool with respect to sequential toolpaths in which at least a portion of the sequential toolpaths include overlapping toolpath passes. The formation of the sound-attenuating protuberances 1200 may be intentionally incidental to the formation of the acoustic core 200. In some embodiments, the additive manufacturing tool may utilize an additive manufacturing technology that introduces an additive manufacturing material to form the sequential contours of the acoustic core 200 and/or the sequential contours of the acoustic screen 202. The overlapping toolpath passes may cause an excess of additive manufacturing material to be introduced into the respective domains 1201 occupied by the respective contours corresponding to the overlapping toolpath passes 1302, 1304. Adjacent contours may force excess additive manufacturing material outward to incidentally form the plurality of sound-attenuating protuberances 1200. The additive manufacturing technology may include material extrusion, material jetting, binder jetting, and/or directed energy deposition. For example, the additive manufacturing technology may include fused deposition modeling (FDM) or fused filament fabrication (FFF).
In other embodiments, the additive manufacturing tool may utilize an additive manufacturing technology that introduces an additive energy to an amorphous additive manufacturing material. The additive energy may solidify a portion of the amorphous additive manufacturing material to form the sequential contours of the acoustic core 200 and/or the acoustic screen 202. The overlapping toolpath passes 1302, 1304 may cause excess additive energy to be introduced into the respective domains 1201 occupied by the respective contours corresponding to the overlapping toolpath passes 1302, 1304. Excess additive energy may propagate outward from the respective contours to incidentally form the plurality of sound-attenuating protuberances 1200. The additive manufacturing technology may include powder bed fusion or vat photopolymerization. For example, the additive manufacturing technology may include selective laser sintering.
The presently disclosed acoustic liners may be utilized, for example, in a turbomachine, such as a turbofan engine 102. An exemplary turbomachine may include a turbine 106 and a fan rotor 108, and a housing or nacelle 104 surrounding the turbine 106 and/or a fan rotor 108, the housing or nacelle 104 defining a duct wall 114, and one or more acoustic liners 100 disposed annularly along the duct wall 114. At least one of the one or more acoustic liners 100 may include an acoustic core 200 comprising an array of resonant cells 206. At least some of the resonant cells 206 may include an oblique polyhedral cellular structure 800 and/or a multitude of sound-attenuating protuberances 1200. The acoustic liner 100 may further include an acoustic screen 202 disposed across the array of resonant cells 206, and the acoustic screen 202 may include a reticulate membrane 208 and a support lattice 210.
This written description uses exemplary embodiments to describe the presently disclosed subject matter, including the best mode, and also to enable any person skilled in the art to practice such subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the presently disclosed subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
