METHOD AND APPARATUS FOR PRODUCING CONTOURED COMPOSITE STRUCTURES AND STRUCTURES PRODUCED THEREBY

• US 20120076973A1
• Filed: 01/25/2011
• Published: 03/29/2012
• Est. Priority Date: 04/17/2008
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Guzman, Juan Carlos, Messinger, Ross, McCarville, Douglas Alan, Sweetin, Joseph L.
• Granted Patent: US 9,278,484 B2
• Time in Patent Office: Days
• US Class Current: 428/113
• CPC Class Codes: B29C 70/207 arranged in parallel planes of fibres crossing at substantial angles
• CPC Class Codes: B29C 70/30 Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
• CPC Class Codes: B29C 70/304 In-plane lamination by juxtaposing or interleaving of plies, e.g. scarf joining
• CPC Class Codes: B29C 70/38 Automated lay-up, e.g. using robots, laying filaments according to predetermined patterns application heads for tyres B29D30/28
• CPC Class Codes: B29C 70/44 using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
• CPC Class Codes: B29L 2031/003 having a profiled transverse cross-section
• CPC Class Codes: B29L 2031/3082 Fuselages
• CPC Class Codes: B32B 37/10 characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
• CPC Class Codes: G06F 30/17 Mechanical parametric or variational design
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 156/1052 with cutting, punching, tearing or severing
• CPC Class Codes: Y10T 156/14 Surface bonding means and/or assembly means with shaping, scarifying, or cleaning joining surface only
• CPC Class Codes: Y10T 428/24124 Fibers
• CPC Class Codes: Y10T 428/24132 including grain, strips, or filamentary elements in different layers or components parallel
• CPC Class Codes: Y10T 428/24628 Nonplanar uniform thickness material

Abstract

A contoured composite structure includes an axis of curvature and at least one curved leg. The structure is fabricated by laying up a flat stack of prepreg fiber plies each having non-zero degree fiber orientations relative to an axis of curvature, and laying up at least one prepreg fiber ply on the stack having a zero degree fiber orientation. Laying up the zero degree ply includes placing prepreg tows in segments arranged end-to-end on at least a portion of the stack. The stack is formed into a web and a curved leg.

Claims

1. A method of fabricating a contoured composite structure having an axis of curvature and at least one curved leg, comprising:

laying up a flat stack of prepreg fiber plies each having non-zero degree fiber orientations relative to an axis of curvature;

laying up a prepreg fiber ply on the stack having a zero degree fiber orientation, including placing prepreg tows in segments on at least a portion of the stack; and

forming the stack including the zero degree ply into a web and a curved leg.

2. The method of claim 1, wherein forming the stack includes forming the portion of the stack to a larger radius.

3. The method of claim 1, wherein forming the stack includes forming the portion of the stack to a smaller radius.

4. The method of claim 1, wherein placing the prepreg tows in segments includes forming gaps between the tow segments.

5. The method of claim 1, wherein placing the tows in segments includes substantially abutting the tow segments.

6. The method of claim 1, wherein placing tows in segments includes overlapping the tow segments.

7. The method of claim 1, wherein laying up the prepreg fiber ply having a zero degree fiber orientation includes placing continuous tows of fiber prepreg on the stack adjacent to the portion having the tows placed in segments.

8. The method of claim 1, wherein placing the tows in segments includes arranging the segments end-to-end.

9. The method of claim 1, wherein placing the tows in segments includes staggering strips of the segments relative to each other.

10. A contoured composite structure fabricated by the method of claim 1.

11. A method of fabricating a contoured composite structure having an axis of curvature and at least one curved leg, comprising:

laying up a flat stack of prepreg fiber plies each having unidirectional fiber tows, including aligning the tows relative to the axis of curvature and segmenting at least certain of the tows in at least a portion of one of the plies; and

forming a curved leg on the stack by forming the portion of the stack containing the tow segments over a curved tool.

12. The method of claim 11, wherein laying up the flat stack includes:

laying up a plurality of non-zero degree plies each having non-zero fiber orientations relative to the axis of curvature, and

laying up at least one zero degree ply on the non-zero plies having a zero degree fiber orientation relative to the axis of curvature.

13. The method of claim 12, wherein the zero degree ply includes the tow segments.

14. The method of claim 11, wherein segmenting the tows includes:

cutting the tows, and

placing the cut tows end-to-end on the ply portion.

15. The method of claim 14, wherein placing the tow segments end-to-end includes forming a gap between the tow segments.

16. The method of claim 14, wherein placing the tows end-to-end includes maintaining the gap between the tow segments substantially constant.

17. The method of claim 14, wherein cutting the tows includes cutting the tows to substantially constant length segments.

18. The method of claim 11, wherein placing the tows end-to-end includes overlapping the tow segments.

19. The method of claim 11, wherein placing the tows in segments includes cutting the tows to a substantially fixed length.

20. The method of claim 11, wherein placing the tows in segments includes cutting the tows to varying lengths.

21. A contoured composite structure fabricated by the method of claim 11.

22. Apparatus for fabricating a curved composite structure having curved legs, comprising:

a mandrel adapted to have a flat composite charge placed thereon and having first and second curved mandrel surfaces against which the charge may be formed respectively into first and second curved legs;

a tool for forming the flat charge against the first curved mandrel surface; and

a flexible vacuum bag adapted to cover the mandrel and the tool for forming the charge against the second curved mandrel surface.

23. The apparatus of claim 22, wherein the mandrel includes a third surface against which the charge may be held by the tool while the charge is being formed against the first and second mandrel surfaces.

24. The apparatus of claim 23, wherein the mandrel includes a fourth surface adjacent the first mandrel surface for supporting the charge prior to being formed.

25. The apparatus of claim 23, wherein the tool is mounted on the mandrel for linear movement toward and away from the third mandrel surface.

26. The apparatus of claim 22, wherein the mandrel, the tool and the vacuum bag are mounted on a common base.

27. The apparatus of claim 22, wherein the tool includes a curved surface to which the bag may conform and through which forming pressure may be applied to the charge.

28. The apparatus of claim 22, further comprising a heater on the mandrel for heating a portion of the charge to be formed into the first leg.

29. The apparatus of claim 22, further comprising:

a plurality of forming aids spaced apart along the second mandrel surface for guiding the movement of the bag toward the second mandrel surface during forming of the charge into the second leg.

30. A method of fabricating a contoured composite structure, comprising:

placing a flat composite charge on a mandrel; and

using the mandrel to form the charge into a pair of curved legs connected by a curved web.

31. The method of claim 30, further comprising:

stabilizing the position of the charge in preparation for forming by holding the charge between a tool and a surface on the mandrel.

32. The method of claim 30, wherein using the mandrel to form the charge includes:

using a tool to form a first portion of the flat charge onto two surfaces on the mandrel.

33. The method of claim 32, wherein using the tool to form the first portion of the flat charge includes moving the tool relative to the mandrel using actuators.

34. The method of claim 32, wherein using the mandrel to form the charge includes:

holding the charge against the two surfaces, and

forming a second portion of the charge against another surface on the mandrel while the charge is being held.

35. The method of claim 30, wherein forming the another portion of the charge is performed using a vacuum bag.

36. The method of claim 30, further comprising heating areas of the charge prior to forming the charge.

37. The method of claim 34, wherein forming the second portion of the charge includes using forming aids to guide movement of the second portion of the charge toward and onto the another surface of the mandrel.

38. A contoured composite structure fabricated by the method of claim 30.

39. Apparatus for fabricating a composite structure having curved legs, comprising:

first and second matched tool halves relatively shiftable from an open position, to a closed forming position,

the first and second tool halves respectively including first and second mandrels over which portions of a flat composite charge may be respectively formed into first and second curved legs.

40. The apparatus of claim 39, wherein the first and second mandrels respectively have opposing surfaces between which a portion of the charge may be held during forming of the legs.

41. The apparatus of claim 39, wherein the first and second mandrels each has a tool surface for forming the charge into one of the legs.

42. The apparatus of claim 39, wherein each of the first and second tool halves include a vacuum bag for forming a vacuum chamber with the opposite halve when in a closed position, the vacuum chamber for forming the charge against the mandrel.

43. The apparatus of claim 39, wherein the first and second tool halves each includes a heater for heating a portion of the charge.

44. The apparatus of claim 39, wherein the first and second tool halves respectively include mating frames within which the mandrels are contained, and the apparatus further includes:

means for forming a vacuum tight seal between the mating frames.

45. The apparatus of claim 39, further comprising:

a set of guides for guiding the first and second tool halves for shifting movement between the open and close positions thereof.

46. The apparatus of claim 42, wherein the first and second tool halves respectively includes forming aids for controlling the shape of the bags during forming.

47. The apparatus of claim 42, wherein the vacuum chambers are located on opposite sides of the mandrel when the tool halves are in the closed position thereof.

48. The apparatus of claim 39, wherein each of the mandrels includes a curved tool surface onto which a portion of the flat charge is formed.

49. A method of fabricating a composite structure, comprising:

holding a flat composite charge between first and second mandrels;

using a first vacuum bag to form a first portion of the charge against the first mandrel; and

using a second vacuum bag to form a second portion of the charge against the second mandrel.

50. The method of claim 49, wherein:

the first and second mandrels are each curved, and the charge is formed into a pair of curved legs connected by a curved web.

51. The method of claim 49, further comprising:

heating the first and second portions of the charge while the charge is being held between the first and second mandrels.

52. The method of claim 49, further comprising:

placing the charge between the first and second mandrel, and

clamping the charge between the mandrels by bringing the mandrels together.

53. The method of claim 49, wherein the first and second portions of the charge are formed substantially simultaneously.

54. A composite structure fabricated by the method of claim 49.