# US 12,109,793 B2 · Composite skins having variable hole sizes and shapes formed using photomachining > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,109,793 B2 - Document ID: US12109793B2 - Status: Granted - Kind: B2 - Application number: 16/690,519 - Filed: 2019-11-21 - Published: 2021-05-27 - Granted: 2024-10-08 - Earliest claimed: 2019-11-21 - Assignees: Rtx Corporation - Applicants: United Technologies Corporation - Inventors: Brian Kenneth Holland; Bruce L Morin; Michael Joseph Murphy; Steven H. Zysman - Web page: https://patentgrep.com/patent/US12109793B2 ## CPC - F02K 1/827: {Sound absorbing structures or liners} - B24C 1/04: for treating only selected parts of a surface, e.g. for carving stone or glass - B24C 1/045: {for cutting (energy dissipating devices therefor B26F3/008)} - B32B 3/12: characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure - B32B 3/266: {characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12} - B32B 5/02: characterised by structural features of a {fibrous or filamentary} layer {(layer formed of metallic wires B32B15/02; layer formed of natural mineral fibres B32B19/02; layer formed of wood fibres B32B21/02)} - B32B 5/142: {Variation across the area of the layer} - B32B 15/04: comprising metal as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042)} - B32B 15/18: comprising iron or steel {(B32B15/011, B32B15/012 and B32B15/013 take precedence)} - B32B 15/20: comprising aluminium or copper {(B32B15/016 and B32B15/017 take precedence)} - B32B 27/38: comprising epoxy resins - B32B 37/146: {whereby one or more of the layers is a honeycomb structure} - B32B 37/18: involving the assembly of discrete sheets or panels only - B32B 38/10: Removing layers, or parts of layers, mechanically or chemically - B64C 1/40: Sound or heat insulation {, e.g. using insulation blankets} - B64D 29/00: Power-plant nacelles, fairings or cowlings - B64D 33/02: of combustion air intakes - G10K 11/168: Plural layers of different materials, e.g. sandwiches - G10K 11/172: using resonance effects - B32B 2250/03: 3 layers - B32B 2262/101: Glass fibres - B32B 2262/106: Carbon fibres, e.g. graphite fibres - B32B 2305/02: Cellular or porous - B32B 2307/102: Insulating - B32B 2315/00: Other materials containing non-metallic inorganic compounds not provided for in groups B32B2311/00 - B32B2313/04 - B32B 2419/04: Tiles for floors or walls - B32B 2605/18: Aircraft - B32B 2607/00: Walls, panels - B64D 2033/0206: {comprising noise reduction means, e.g. acoustic liners} - F05D 2230/10: by removing material - F05D 2250/14: elliptical - F05D 2250/141: circular - F05D 2300/603: Composites; e.g. fibre-reinforced - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - F02K: JET-PROPULSION PLANTS (features of jet-propulsion plants common to gas-turbine plants, air intakes or fuel supply control of air-breathing jet-propulsion plants F02C7/00, F02C9/00) - B24C: ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - B64C: AEROPLANES; HELICOPTERS - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A face skin for an acoustic panel may comprise a sheet defining a first surface and a second surface. A plurality of slots may be formed through the face skin using abrasive blasting. Each slot of the plurality of slots may comprise a first semi-circular wall and a second semi-circular wall opposite the first semi-circular wall. ## Claims ### Claim 1 A method of fabricating a face skin for an acoustic panel of a nacelle configured to surround a central longitudinal axis of a gas turbine engine, the method comprising: locating a masking film over a first surface of a sheet configured to form the face skin for the acoustic panel of the nacelle and thus, configured to surround the central longitudinal axis of the gas turbine engine, the masking film defining a plurality of openings; forming a plurality of slots in the sheet using abrasive blasting, wherein each slot of the plurality of slots has a length dimension and a width dimension, the length dimension being greater than the width dimension, and wherein each slot is oriented such that the length dimension is substantially perpendicular to an expected direction of airflow through the gas turbine engine and over the slot, the plurality of slots configured to be oriented at an angle relative to the central longitudinal axis of the gas turbine engine, where the central longitudinal axis is different from the expected direction of airflow through the gas turbine engine, wherein the angle is defined by a centerline of each slot of the plurality of slots and the central longitudinal axis, wherein a first end of a first semi-circular wall of at least one first slot in the plurality of slots through the face skin is at least one of axially offset or circumferentially offset from a second end of a second semi-circular wall of the at least one first slot though the face skin based upon a degree of a first angle, wherein a first end of a first semi-circular wall of at least one second slot in the plurality of slots through the face skin is at least one of axially offset or circumferentially offset from a second end of a second semi-circular wall of the at least one second slot though the face skin based upon a degree of a second angle, wherein the first angle is different from the second angle, wherein the plurality of slots in the sheet comprises forming at least three regions with a first region of the sheet having a first percentage of open area and a first number of slots that is greater than a second percentage of open area and a second number of slots in a second region of the sheet and greater than a third percentage of open area and a third number of slots in a third region of the sheet, wherein the second percentage of open area and the second number of slots in the second region of the sheet is greater than the third percentage of open area and the third number of slots in the third region of the sheet, and wherein a percentage of open area and a number of slots in each of the first region, the second region and the third region is selected based on an expected velocity of the airglow over a respective region and acoustic characteristics experienced in the respective region; and wherein the first number of slots is offset from the second number of slots; and removing the masking film. ### Claim 2 (depends on 1) The method of claim 1, further comprising determining a pattern of the plurality of openings in the masking film based on an airflow velocity experienced by the face skin. ### Claim 3 (depends on 1) The method of claim 1, wherein an expected airflow velocity in the first region is different from the airflow velocity in the second region. ### Claim 4 (depends on 3) The method of claim 3, wherein the sheet comprises a fiber reinforced composite that is at least one of a fiberglass reinforced composite and a carbon fiber reinforced composite, the fiber reinforced composite includes at least one of glass, carbon, ceramic, and a polymer, the fiber reinforced composite includes a matrix with at least one of a thermoset material and a thermoplastic material. ### Claim 5 (depends on 4) The method of claim 4, further comprising forming each slot of the plurality of slots having: a first planar wall; a second planar wall oriented toward the first planar wall; a first semi-circular wall extending between the first planar wall and the second planar wall; and a second semi-circular wall opposite the first semi-circular wall and extending between the first planar wall and the second planar wall, wherein a centerline of the slot is substantially perpendicular to the expected flow direction over the slot, the centerline being located midway between the first planar wall and the second planar wall and extending from the first semi-circular wall to the second semi-circular wall. ### Claim 6 (depends on 1) The method of claim 1, wherein the first slots of the plurality of slots are configured to be oriented at a first angle relative to the central longitudinal axis of the gas turbine engine, wherein second slots of the plurality of slots are configured to be oriented at a second angle relative to the central longitudinal axis of the gas turbine engine, and wherein the first angle is different from the second angle. ### Claim 7 A method of fabricating an acoustic panel for a gas turbine engine, comprising: locating a masking film over a face skin of the acoustic panel configured to surround a central longitudinal axis of the gas turbine engine, the masking film defining a plurality of openings; forming a plurality of slots in the face skin using abrasive blasting, wherein each slot of the plurality of slots has a first dimension and a second dimension, the first dimension being greater than the second dimension, and wherein each slot is oriented such that the first dimension of the slot is substantially perpendicular to an expected direction of airflow through the gas turbine engine and over the slot, the plurality of slots configured to be oriented at an angle relative to the central longitudinal axis of the gas turbine engine, where the central longitudinal axis is different from the expected direction of airflow through the gas turbine engine, wherein the angle is defined by a centerline of each slot of the plurality of slots and the central longitudinal axis, wherein a first end of a first semi-circular wall of at least one first slot in the plurality of slots through the face skin is at least one of axially offset or circumferentially offset from a second end of a second semi-circular wall of the at least one first slot though the face skin based upon a degree of a first angle, wherein a first end of a first semi-circular wall of at least one second slot in the plurality of slots through the face skin is at least one of axially offset of circumferentially offset from a second end of a second semi-circular wall of the at least one second slot though the face skin based upon a degree of a second angle, wherein the first angle is different from the second angle, wherein the plurality of slots in the face skin comprises forming at least three regions with a first region of the face skin having a first percentage of open area and a first number of slots that is greater than a second percentage of open area and a second number of slots in a second region of the face skin and greater than a third percentage of open area and a third number of slots in a third region of the face skin, wherein the second percentage of open area and the second number of slots in the second region of the face skin is greater than the third percentage of open area and the third number of slots in the third region of the face skin, and wherein a percentage of open area and a number of slots in each of the first region, the second region and the third region is selected based on an expected velocity of the airflow over a respective region and acoustic characteristics experienced in the respective region; and wherein the first number of slots is offset from the second number of slots; and coupling the face skin to a core structure, the core structure defining a plurality of cells, wherein the face skin and the core structure are curved such that the face skin and the core structure surround, at least partially, the central longitudinal axis of the gas turbine engine. ### Claim 8 (depends on 7) The method of claim 7, further comprising: removing the masking film; and coupling a back skin to the core structure opposite the face skin, wherein the back skin is a solid layer. ### Claim 9 (depends on 7) The method of claim 7, further comprising determining a pattern of the plurality of openings in the masking film based on an airflow velocity experienced by the face skin. ### Claim 10 (depends on 7) The method of claim 7, wherein the face skin comprises a fiber reinforced composite that is at least one of a fiberglass reinforced composite and a carbon fiber reinforced composite, the fiber reinforced composite includes at least one of glass, carbon, ceramic, and a polymer, the fiber reinforced composite includes a matrix with at least one of a thermoset material and a thermoplastic material. ### Claim 11 (depends on 7) The method of claim 7, wherein the acoustic panel forms, at least, a portion of a nacelle configured to the surround the gas turbine engine. ### Claim 12 (depends on 7) The method of claim 7, wherein the acoustic panel forms, at least, a portion of at least one of an inner inlet barrel, an inner fixed structure of a thrust reverser, a translating sleeve of a translating sleeve type thrust reverser, or an exhaust system for the gas turbine engine. ### Claim 13 (depends on 7) The method of claim 7, wherein the acoustic panel is configured to form, at least, a portion of at least one of an inner inlet barrel, an inner fixed structure of a thrust reverser, a translating sleeve of a translating sleeve type thrust reverser, or an exhaust system for the gas turbine engine. ### Claim 14 (depends on 7) The method of claim 7, wherein first slots of the plurality of slots are configured to be oriented at a first angle relative to the central longitudinal axis of the gas turbine engine, wherein second slots of the plurality of slots are configured to be oriented at a second angle relative to the central longitudinal axis of the gas turbine engine, and wherein the first angle is different from the second angle.