Composite beam chord between reinforcement plates

1. An article comprising a composite beam chord between first and second reinforcement plates, the beam chord including a first ply of reinforcing fibers with a fiber orientation of +α degrees with respect to a longitudinal axis of the beam and a second ply of reinforcing fibers with a fiber orientation of −α degrees with respect to the longitudinal axis, where α=2 to 12 degrees.

2. The article of claim 1 , wherein α=2 to 8 degrees.

3. The article of claim 1 , wherein α=3 to 5 degrees.

4. The article of claim 1 , wherein α=3 degrees.

5. The article of claim 1 , wherein the number of reinforcing fibers oriented at ±αdegrees is at least 60% of the total number of reinforcing fibers in the composite beam chord.

6. The article of claim 1 , wherein the composite beam chord includes carbon fibers in a polymer matrix.

7. The article of claim 1 , wherein the beam further includes third and fourth plies of reinforcing fibers oriented at ±β degrees with respect to the longitudinal axis, where β is between 15 and 85 degrees.

8. The article of claim 7 , wherein β is between 50 and 75 degrees.

9. The article of claim 7 , wherein 0% to 40% of all fibers in the beam chord are oriented at ±β degrees.

10. The article of claim 1 , wherein the plies extend in an x-y plane, wherein holes are drilled through the beam in a z-direction; and wherein fasteners extend through the holes to clamp the plates to the beam chord.

11. The article of claim 1 , wherein at least one of the first and second reinforcement plates includes a plurality of z-pin members extending into a respective first side and second side of the beam chord.

12. The article of claim 1 , wherein the plates are metal plates.

13. The article of claim 1 , wherein the article is an aircraft keel beam.

14. The article of claim 1 , wherein the beam chord consists of a matrix and reinforcing fibers oriented at ±α degrees.

15. The article of claim 1 further comprising at least one attachment plate positioned between the beam chord and at least one of the first and second reinforcement plates, the attachment plate including a plurality of apertures for attaching to external structures.

16. A beam assembly comprising a first article according to claim 1 ; a second article according to claim 1 ; a splicing plate for splicing the first and second articles together; and a plurality of fasteners extending through the splicing plate and the articles.

17. An aerospace vehicle, comprising:

a fuselage;

wing assemblies and an empennage coupled to the fuselage; and

an article of claim 1 in at least one of the wing assemblies, the fuselage and the empennage.

18. The vehicle of claim 17 , wherein the fuselage includes a keel beam, the keel beam including the article of claim 1 .

19. An article comprising first and second metal reinforcement plates, a composite beam chord between the first and second plates, and a plurality of fasteners extending through the beam chord for clamping the first and second plates to the beam chord, the beam chord including a first ply of reinforcing fibers with a fiber orientation of +α degrees with respect to a longitudinal axis of the beam chord and a second ply of reinforcing fibers with a fiber orientation of −α degrees with respect to the longitudinal axis, where α=2 to 12 degrees, the fasteners perpendicular to the plies.

20. The article of claim 19 , wherein α=3 to 5 degrees.

21. A method of manufacturing an article, the method comprising:

fabricating a composite beam chord, including laying up plies of reinforcing fibers on a tool, wherein the fibers in at least some of the plies have an orientation of ±α with respect to a uni-axial load bearing direction of the article, where α=2 to 12 degrees;

forming through holes in the composite beam chord; and

using the through holes to fasten reinforcement plates to opposite sides of the beam chord.

22. The method of claim 21 , wherein α=3 to 5 degrees.