COMPOSITE STRUCTURE HAVING REINFORCED CORE AND METHOD OF MAKING SAME

• US 20090035510A1
• Filed: 07/31/2007
• Published: 02/05/2009
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Chakrabarti, Buddhadev
• Granted Patent: US 8,512,853 B2
• Time in Patent Office: Days
• US Class Current: 428/116
• CPC Class Codes: E04C 2/296 composed of insulating material and non-metallic or unspecified sheet-material E04C2/288 takes precedence
• CPC Class Codes: E04C 2/3405 spaced apart by profiled spacer sheets
• CPC Class Codes: E04C 2002/3488 spaced apart by frame like structures
• CPC Class Codes: Y02T 50/40 Weight reduction
• CPC Class Codes: Y10T 428/24149 Honeycomb-like
• CPC Class Codes: Y10T 428/249923 Including interlaminar mechanical fastener

Abstract

A polymer-based composite sandwich includes a core bonded between fiber reinforced resin facesheets. The core includes a truss formed by groups of composite pins held in a low density foam. The pins in each group intersect to form nodes adjacent to one of the facesheets. The ends of the pins extend parallel and are bonded to the facesheets.

Claims

1. A composite sandwich, comprising:

first and second fiber reinforced polymer facesheets; and

a reinforced core between the first and second facesheets, the reinforced core including—

(i) a plurality of pins arranged in groups forming a truss, each of the pins including medial portions extending between the first and second facesheets and distal portions respectively extending generally parallel with and bonded to the first and second facesheets, the pins in each group intersecting at a node adjacent one of the first and second facesheets, and

(ii) a carrier surrounding the pins.

2. The composite sandwich of claim 1, wherein:

each of the pins includes carbon fiber reinforced resin, and

each of the first and second facesheets includes laminated plies of carbon fiber reinforced resin.

3. The composite sandwich of claim 2, wherein distal portions of the pins in each of the groups radiate outwardly from the node formed by the pins in the set.

4. The composite sandwich of claim 1, wherein the nodes are spaced substantially equidistant from each other.

5. The composite sandwich of claim 1, wherein each of the groups include at least 3 of the pins.

6. The composite sandwich of claim 1, wherein the pins in each of the groups are inclined relative to the planes of the facesheets approximately 30 degrees.

7. The composite sandwich of claim 1, wherein the carrier includes rigid foam.

8. The composite sandwich of claim 7, wherein the rigid foam includes a polymethacrylimide.

9. The composite sandwich of claim 1, wherein the pins in each of the groups are radially spaced substantially equidistant from each other around the node formed by the set.

10. The composite sandwich of claim 1, wherein the carrier is closed cell foam, and the core has a density of between approximately 6.9 and 12 pounds per cubic foot.

11. The composite sandwich of claim 10, wherein the core has a thickness of between approximately ½

inch and 1 inch.

12. The composite sandwich of claim 1, wherein the nodes are spaced from each other between approximately 0.168 and 0.191 inches.

13. The composite sandwich of claim 1, wherein the core has a coefficient of thermal expansion generally matching the coefficient of thermal expansion of the first and second facesheets.

14. An aircraft structure incorporating the composite sandwich of claim 1.

15. A reinforced polymer composite structure, comprising:

a pair of fiber reinforced polymer facesheets; and

,

a reinforced core between the facesheets, the reinforced core including a plurality of structural pins arranged in groups thereof, the pins in each of the groups substantially intersecting with each other and being spaced around a central axis extending generally normal to the facesheets.

16. The composite structure of claim 15, wherein the pins in each of the groups are symmetrically arranged around the central axis.

17. The composite structure of claim 15, wherein each of the pins includes distal portions extending substantially parallel with and bonded to the facesheets.

18. The composite structure of claim 15, wherein each group of the pins includes at least 3 of the pins.

19. The composite structure of claim 15, wherein the pins and the facesheets are formed of graphite fibers held in an epoxy binder.

20. The composite structure of claim 15, wherein the core has a coefficient of thermal expansion generally matching the coefficient of thermal expansion of each of the facesheets.

21. The composite structure of claim 15, wherein each of the pins is inclined relative to the planes of the facesheets at an angle of approximately 30 degrees.

22. The composite structure of claim 15, wherein:

each of the first and second facesheets includes laminated plies of carbon fiber reinforced resin, and

the pins include distal portions extending substantially parallel to the facesheets and bonded between the plies.

23. The composite structure of claim 15, wherein:

each of the pins includes medial portions extending generally transverse to the facesheets, and distal portions extending generally parallel to the facesheets, and

wherein the pins in each of the groups intersect each other at a junction generally between the medial and distal portions of the pins.

24. The composite structure of claim 15, wherein the pins in each of the groups includes distal portions symmetrically arranged around and radiating from the central axis.

25. The composite structure of claim 15, wherein the core has a density generally between 6.9 and 12 pounds per cubic foot.

26. The composite structure of claim 25, wherein the thickness of the core is generally between ½

and 1 inch.

27. The composite structure of claim 25, wherein each of the pins includes graphite fiber reinforced epoxy and has a diameter between approximately 0.020 and 0.028 inches.

28. The composite structure of claim 25, wherein the central axes of adjacent groups of the pins are spaced from each other between approximately 0.169 and 0.191 inches.

29. The composite structure of claim 25, wherein the core includes a polymethacrylimide foam surrounding the pins.

30. An aircraft subassembly incorporating the composite structure of claim 15.

31. A method of fabricating a reinforced composite sandwich, comprising the steps of:

(A) fabricating a core by—

(i) forming a layer of foam, and

(ii) forming groups of intersecting structural pins in the foam layer;

(B) bending the ends of the pins; and

(C) bonding the core to a pair of fiber reinforced facesheets by bonding the bent ends of the pins to the facesheets.

32. The method of claim 31, wherein step (A) (ii) includes inserting the pins into the foam layer along intersecting trajectories.

33. The method of claim 31, further comprising the steps of:

(D) poltruding a length of graphite epoxy composite material;

(E) partially curing the length of graphite epoxy material; and

,

(F) forming the pins by cutting the length of graphite epoxy material.

34. The method of claim 31, wherein step (A)(ii) includes:

inserting the pins into the foam layer,

flaying the ends of the pins.

35. The method of claim 31, further comprising the step of:

(D) curing the structural pins after step (A) has been completed.

36. The method of claim 31, further including the step of:

(D) compacting and curing the facesheets and the core after step (C) has been completed.

37. An aircraft subassembly fabricated by the method of claim 31.

38. Performing maintenance and repair of an aircraft using the method of claim 31.

39. Assembling vehicles using the reinforced composite sandwich produced by the method of claim 31.