Systems and methods for reducing noise in aircraft fuselages and other structures

• US 20060208135A1
• Filed: 03/18/2005
• Published: 09/21/2006
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Montgomery, Joshua M., Liguore, Salvatore L.
• Granted Patent: US 7,837,147 B2
• Time in Patent Office: Days
• US Class Current: 244/117.R
• CPC Class Codes: B29C 70/088 and with one or more layers of non-plastics material or non-specified material, e.g. supports
• CPC Class Codes: B29C 70/342 using isostatic pressure
• CPC Class Codes: B29C 70/865 completely encapsulated
• CPC Class Codes: B29D 99/0014 provided with ridges or ribs, e.g. joined ribs
• CPC Class Codes: B29K 2995/0002 insulating
• CPC Class Codes: B29K 2995/0091 Damping, energy absorption
• CPC Class Codes: B32B 37/12 characterised by using adhesives
• CPC Class Codes: B64C 1/066 Interior liners
• CPC Class Codes: B64C 1/40 Sound or heat insulation , e.g. using insulation blankets
• CPC Class Codes: B64C 2001/0072 from composite materials
• CPC Class Codes: F16F 9/306 of the constrained layer type, i.e. comprising one or more constrained viscoelastic layers
• CPC Class Codes: Y02T 50/40 Weight reduction
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

Systems and methods for reducing noise in aircraft fuselages and other structures are described herein. A noise reduction system configured in accordance with one embodiment of the invention includes an auxetic core, a damping layer, and a constraining layer. In this embodiment, the auxetic core is supported by a structural member, and the damping layer is sandwiched between the auxetic core and the constraining layer. A method for manufacturing a structural assembly in accordance with another embodiment of the invention includes forming a stiffener by positioning a first ply of composite material against a first tool surface, positioning damping material against the first ply, and positioning a second ply of composite material against the damping material to sandwich the damping material between the first and second plies. The method can further include forming a skin by positioning a third ply of composite material against a second tool surface offset from the first tool surface, and attaching the stiffener to the skin by co-curing the first, second and third plies of composite material.

Claims

1. A noise reduction system comprising:

a structural member;

an auxetic core supported by the structural member, the auxetic core having a first surface facing at least approximately toward the structural member and a second surface facing at least approximately away from the structural member;

a constraining layer positioned toward the second surface of the auxetic core; and

a damping layer sandwiched between the constraining layer and the second surface of the auxetic core.

2. The noise reduction system of claim 1 wherein the auxetic core includes a material that expands in a first direction when stretched in a second direction perpendicular to the first direction.

3. The noise reduction system of claim 1 wherein the auxetic core includes a material that expands in a first direction when stretched in a second direction perpendicular to the first direction, and wherein the damping layer includes a viscoelastic material.

4. The noise reduction system of claim 1 wherein the auxetic core includes a honeycomb material that expands in a first direction when stretched in a second direction perpendicular to the first direction, wherein the damping layer includes a viscoelastic adhesive, and wherein the constraining layer includes a fiber-reinforced resin material.

5. The noise reduction system of claim 1 wherein the damping layer includes a viscoelastic adhesive having a first thickness of about 0.01 inch, and wherein the auxetic layer includes a honeycomb material having a second thickness of about 0.05 inch or more.

6. The noise reduction system of claim 1 wherein the structural member includes a first fiber-reinforced resin material and the constraining layer includes a second fiber-reinforced resin material.

7. The noise reduction system of claim 1, further comprising an aircraft skin, wherein the structural member is attached to a portion of the aircraft skin.

8. The noise reduction system of claim 1, further comprising an aircraft skin, wherein the structural member is a stiffener having a first stiffener portion attached to the aircraft skin and a second stiffener portion offset from the aircraft skin, and wherein the auxetic core is supported by the second stiffener portion.

9. The noise reduction system of claim 1, further comprising a fiber-reinforced resin shell structure, wherein the structural member is a fiber-reinforced resin stiffener that is at least partially bonded to the fiber-reinforced resin shell structure.

10. The noise reduction system of claim 1, further comprising a fiber-reinforced resin shell structure, wherein the structural member is a fiber-reinforced resin stiffener that is at least partially bonded to the fiber-reinforced resin shell structure, and wherein the constraining layer is a fiber-reinforced resin layer that is at least partially bonded to the damping layer.

11. The noise reduction system of claim 1, further comprising a fiber-reinforced resin shell structure, wherein the structural member is a fiber-reinforced resin stiffener that is at least partially bonded to the fiber-reinforced resin shell structure, wherein the auxetic core includes a honeycomb material that expands in a first direction when stretched in a second direction perpendicular to the first direction, wherein the damping layer includes a viscoelastic adhesive, and wherein the constraining layer is a fiber-reinforced resin layer that is at least partially bonded to the damping layer.

12. A method of manufacturing a structural assembly with a damping system for noise reduction, the method comprising:

attaching a stiffener to a skin;

attaching an auxetic core to a portion of the stiffener;

covering at least a portion of the auxetic core with a damping layer; and

attaching a constraining layer to the auxetic core by sandwiching the damping layer between the auxetic core and the constraining layer.

13. The method of claim 12 wherein attaching a stiffener to a skin includes attaching a longitudinal stiffener to a portion of an aircraft fuselage skin.

14. The method of claim 12 wherein attaching a stiffener to a skin includes attaching a curved frame to a portion of an aircraft fuselage skin.

15. The method of claim 12 wherein attaching a stiffener to a skin includes bonding a fiber-reinforced resin stiffener to a portion of a fiber-reinforced resin skin during a cocurring process.

16. The method of claim 12 wherein covering at least a portion of the auxetic core with a damping layer includes applying a viscoelastic adhesive to the auxetic core.

17. The method of claim 12 wherein attaching an auxetic core to a portion of the stiffener includes bonding the auxetic core to the portion of the stiffener with a first viscoelastic adhesive, and wherein attaching a constraining layer to the auxetic core includes bonding the constraining layer to the auxetic core with a second viscoelastic adhesive.

18. A method of reducing noise in a structure, the method comprising:

attaching an auxetic core to a portion of the structure;

covering at least a portion of the auxetic core with a damping layer; and

attaching a constraining layer to the auxetic core by sandwiching the damping layer between the auxetic core and the constraining layer.

19. The method of claim 18 wherein covering at least a portion of the auxetic core with a damping layer includes applying a viscoelastic adhesive to the auxetic core.

20. The method of claim 18 wherein attaching an auxetic core to a portion of the stiffener includes bonding the auxetic core to the portion of the stiffener with a first viscoelastic adhesive, and wherein attaching a constraining layer to the auxetic core includes bonding the constraining layer to the auxetic core with a second viscoelastic adhesive.

21. The method of claim 18 wherein attaching a constraining layer to the auxetic core includes attaching a composite material layer to the auxetic core by sandwiching a viscoelastic adhesive between the auxetic core and the composite material layer.

22. A noise reduction system for use with a structural assembly, the noise reduction system comprising:

a structural member;

means for amplifying strain energy, wherein the means for amplifying strain energy are attached to the structural member, and wherein the means for amplifying strain energy expand in a first direction when stretched in a second direction perpendicular to the first direction;

a constraining layer; and

means for attaching the constraining layer to the means for amplifying strain energy.

23. The noise reduction system of claim 22 wherein the means for attaching the constraining layer include means for damping vibration.

24. The noise reduction system of claim 22 wherein the means for attaching the constraining layer include viscoelastic adhesive.

25. The noise reduction system of claim 22, wherein the means for amplifying strain energy include auxetic honeycomb material.

26. The noise reduction system of claim 22, further comprising:

an aircraft skin; and

means for attaching the structural member to a portion of the aircraft skin.

27. The noise reduction system of claim 22 wherein the structural member is a fiber-reinforced resin stiffener, and wherein the noise reduction system further comprises:

a fiber-reinforced resin aircraft skin; and

means for attaching the fiber-reinforced resin stiffener to a portion of the fiber-reinforced resin aircraft skin.

28. A structural assembly having an integral damping system, the structural assembly comprising:

a stiffener, the stiffener including;

a first stiffener portion configured to be attached to a skin panel;

a second stiffener portion spaced apart from the first stiffener portion and configured to be offset from the skin panel, the second stiffener portion including at least first and second plies of fiber-reinforced resin material; and

a layer of damping material sandwiched between the first and second plies of fiber-reinforced resin material.

29. The structural assembly of claim 28 wherein the first ply of fiber-reinforced resin material extends from the first stiffener portion to the second stiffener portion.

30. The structural assembly of claim 28 wherein the first and second stiffener portions are composed of fiber-reinforced resin material.

31. The structural assembly of claim 28 wherein the layer of damping material includes a viscoelastic damping material.

32. The structural assembly of claim 28 wherein the layer of damping material includes a viscoelastic adhesive.

33. The structural assembly of claim 28 wherein the first stiffener portion includes a flange portion configured to be bonded to the skin panel, and wherein the second stiffener portion includes a cap portion offset from the flange portion.

34. The structural assembly of claim 28, further comprising the skin panel, wherein the skin panel is composed of fiber-reinforced resin material and the first stiffener portion is attached to the skin panel.

35. The structural assembly of claim 28, further comprising the skin panel, wherein the skin panel is composed of a first portion of fiber-reinforced resin material, wherein the first and second stiffener portions are composed of a second portion of fiber-reinforced resin material, and wherein the first stiffener portion is bonded to the skin panel.

36. The structural assembly of claim 28, further comprising the skin panel, wherein the skin panel is a portion of aircraft fuselage skin composed of fiber-reinforced resin material, and wherein the first stiffener portion is bonded to the portion of aircraft fuselage skin.

37. The structural assembly of claim 28, further comprising the skin panel, wherein the skin panel is composed of a first portion of fiber-reinforced resin material, wherein the first and second stiffener portions are composed of a second portion of fiber-reinforced resin material, wherein the first stiffener portion includes a flange portion bonded to the skin panel, wherein the second stiffener portion includes a cap portion offset from the flange portion, and wherein the layer of damping material includes a viscoelastic damping material.

38. A method for manufacturing a structural assembly with an integral damping system, the method comprising:

positioning a first portion of fiber-reinforced resin material against a first tool surface to at least partially form a stiffener;

positioning a layer of damping material against the first portion of fiber-reinforced resin material;

positioning a second portion of fiber-reinforced resin material against a second tool surface offset from the first tool surface to at least partially form a skin; and

cocuring the first and second portions of fiber-reinforced resin material to bond the stiffener to the skin.

39. The method of claim 38 wherein positioning a layer of damping material against the first portion of fiber-reinforced resin material includes laminating a viscoelastic material with a ply of fiber-reinforced resin fabric.

40. The method of claim 38 wherein positioning a second portion of fiber-reinforced resin material against a second tool surface to at least partially form a skin includes wrapping fiber-reinforced resin material around a mandrel.

41. The method of claim 38 wherein positioning a second portion of fiber-reinforced resin material against a second tool surface to at least partially form a skin includes wrapping fiber-reinforced resin material around a rotating mandrel.

42. The method of claim 38 wherein positioning a second portion of fiber-reinforced resin material against a second tool surface to at least partially form a skin includes winding a fiber-reinforced resin filament around a mandrel.

43. The method of claim 38 wherein positioning a second portion of fiber-reinforced resin material against a second tool surface to at least partially form a skin includes wrapping fiber-reinforced resin tape around a mandrel.

44. The method of claim 38, further comprising positioning a third portion of fiber-reinforced resin material against the layer of damping material to laminate the damping material between the first and third portions of fiber-reinforced resin material.

45. The method of claim 38 wherein positioning a first portion of fiber-reinforced resin material against a first tool surface to at least partially form a stiffener includes laying at least a first ply of fiber-reinforced resin material in an elongate channel to at least partially form a stiffener with a hat-shaped cross-section.

46. The method of claim 38 wherein positioning a first portion of fiber-reinforced resin material against a first tool surface to at least partially form a stiffener includes laying at least a first ply of fiber-reinforced resin material in an elongate channel, and wherein positioning a second portion of fiber-reinforced resin material against a second tool surface to at least partially form a skin includes laying at least a second ply of fiber-reinforced resin material over the channel and in contact with a portion of the first ply of fiber-reinforced resin material.

47. The method of claim 38 wherein positioning a first portion of fiber-reinforced resin material against a first tool surface to at least partially form a stiffener includes laying at least a first ply of fiber-reinforced resin material in an elongate channel, and wherein the method further includes positioning a bladder in the channel to seal the first ply of fiber-reinforced resin material during a vacuum-bagging process.

48. A structural assembly having an integral damping system, the structural assembly comprising:

a skin, the skin including at least a first ply of fiber-reinforced resin material; and

means for stiffening the skin, the means for stiffening the skin including;

a second ply of fiber-reinforced resin material;

at least a third ply of fiber-reinforced resin material; and

means for damping vibration, wherein the means for damping vibration are sandwiched between the second and third plies of fiber-reinforced resin material.

49. The structural assembly of claim 48 wherein the means for stiffening the skin include a first portion attached to the skin and a second portion offset from the skin.

50. The structural assembly of claim 48 wherein the means for stiffening the skin are bonded to the skin by cocurring the first, second, and third plies of fiber-reinforced resin material.

51. The structural assembly of claim 48 wherein the means for damping vibration are viscoelastic.

52. The structural assembly of claim 48 wherein the skin includes an aircraft fuselage skin.

53. The structural assembly of claim 48 wherein the skin includes an aircraft fuselage skin, and wherein the means for stiffening the skin include a stiffener having a flange portion attached to the skin and a cap portion offset from the skin.

54. The structural assembly of claim 48 wherein the skin includes an aircraft fuselage skin, wherein the means for stiffening the skin include a stiffener having a flange portion attached to the skin and a cap portion offset from the skin, and wherein the means for damping vibration are positioned toward the cap portion of the stiffener.