Acoustic cores with sound-attenuating protuberances
An acoustic core has a plurality of cell walls formed of an additive-manufacturing material and a resonant space defined by the plurality of cell walls. At least some of the resonant cells have sound-attenuating protuberances formed of an excess amount of the additive-manufacturing material having been intentionally introduced to the cell walls and protruding into the resonant space with a semi-random orientation and/or size.
1. An acoustic core, comprising:
an array of resonant cells, wherein respective ones of the resonant cells comprise a plurality of cell walls formed of an additive-manufacturing material and a resonant space defined by the plurality of cell walls, and wherein at least some of the resonant cells comprise sound-attenuating protuberances, the sound-attenuating protuberances comprising an excess amount of the additive-manufacturing material having been intentionally introduced to the cell walls and protruding into the resonant space with a semi-random orientation and/or size.
2. The acoustic core of claim 1 , wherein the sound-attenuating protuberances have an average height, an average width, and/or an average length of from 5 micrometers to 10,000 micrometers.
3. The acoustic core of claim 1 , the acoustic core having been produced by an additive-manufacturing technology comprising a material extrusion technology.
4. The acoustic core of claim 3 , wherein the material extrusion technology comprises fused deposition modeling or fused filament fabrication.
5. The acoustic core of claim 3 , wherein at least some of the sound-attenuating protuberances have one more dimensions that are smaller than a minimum dimensional resolution provided for by the additive-manufacturing technology utilized to produce the acoustic core.
6. The acoustic core of claim 5 , wherein the additive-manufacturing material comprises a filament.
7. The acoustic core of claim 6 , wherein the minimum dimensional resolution is defined at least in part by a cross-sectional dimension of the filament.
8. The acoustic core of claim 6 , wherein the filament comprises polyetherimide, polycarbonate, acrylonitrile, acrylonitrile-butadiene-styrene, aramid fiber, meta-aramid fiber, para-aramid fiber, polyethylene fiber, rayon, polyester, and/or nylon.
9. The acoustic core of claim 1 , wherein the additive-manufacturing material comprises a thermoplastic material or a ceramic material.
10. The acoustic core of claim 1 , wherein at least some of the resonant cells have a polyhedral configuration.
11. The acoustic core of claim 10 , wherein for the at least some of the resonant cells that have the polyhedral configuration, the polyhedral configuration comprises a parallel polyhedral cellular structure; and/or wherein for the at least some of the resonant cells that have the polyhedral configuration, the polyhedral configuration comprises an oblique polyhedral cellular structure.
12. The acoustic core of claim 1 , wherein at least some of the resonant cells have an oblique polyhedral cellular structure, the oblique polyhedral cellular structure comprising a frustum, a rhombohedron, an antiprism, a twisted prism, a cupola, a star cupola, a wedge, and/or a pyramid.
13. The acoustic core of claim 1 , wherein at least some of the resonant cells have an oblique polyhedral cellular structure, the oblique polyhedral cellular structure comprising a frustal polyhedron.
14. The acoustic core of claim 13 , wherein the frustal polyhedron comprises a tetragonal frustum, a pentagonal frustum, a hexagonal frustum, a heptagonal frustum, an octagonal frustum, a nonagonal frustum, a decagonal frustum, a hendecagonal frustum, or a dodecagonal frustum.
15. The acoustic core of claim 1 , wherein at least some of the resonant cells have an oblique polyhedral cellular structure, the oblique polyhedral cellular structure comprising an antiprism, the antiprism comprising a trigonal antiprism, a tetragonal antiprism, a hexagonal antiprism, or an antiprismal polyhedron.
16. The acoustic core of claim 1 , wherein at least some of the resonant cells have an oblique polyhedral cellular structure, the oblique polyhedral cellular structure comprising a twisted prism, the twisted prism comprising a Schönhardt polyhedron, a tetrahedral twisted prism, a hexagonal twisted prism, or a twisted prismal polyhedron.
17. The acoustic core of claim 1 , wherein the plurality of cell walls comprise adjacent contours that have forced the excess amount of the additive-manufacturing material outward to incidentally form at least some of the sound-attenuating protuberances.
18. The acoustic core of claim 1 , wherein the plurality of cell walls comprise adjacent contours that have one or more overlapping toolpath passes.
19. The acoustic core of claim 18 , wherein the one or more overlapping toolpath passes comprise a toolpath gap ratio from 1.0 to less than 2.0.
20. A turbomachine comprising:
a turbine; and
a housing surrounding the turbine, the housing defining a duct wall; and
one or more acoustic liners disposed annularly along the duct wall, at least one of the one or more acoustic liners comprising an acoustic core, the acoustic core comprising:
an array of resonant cells, wherein respective ones of the resonant cells comprise a plurality of cell walls formed of an additive-manufacturing material and a resonant space defined by the plurality of cell walls, and wherein at least some of the resonant cells comprise sound-attenuating protuberances, the sound-attenuating protuberances comprising an excess amount of the additive-manufacturing material having been intentionally introduced to the cell walls and protruding into the resonant space with a semi-random orientation and/or size.