Composite flange, duct incorporating a flange and method of making a flange

1. A flange comprising composite material, wherein

the flange comprises a curved hollow member having a substantially triangular cross-section; and

said cross-section includes a substantially right-angled triangle, wherein

a first side of the triangle is substantially perpendicular to a second side of the triangle that follows a curve; and

a third side of the triangle comprises substantially pentagonal shaped holes.

2. A flange according to claim 1 , wherein the curved hollow member defines a section of a closed figure having a curved perimeter.

3. A flange according to claim 2 , wherein the section is one quarter to one third of the closed figure having the curved perimeter.

4. A flange according to claim 1 , wherein a plurality of the curved hollow members are combined to form a closed figure having a curved perimeter.

5. A flange according to claim 4 , wherein the closed figure is a circle.

6. A flange according to claim 4 , wherein the closed figure is an ellipse.

7. A flange according to claim 1 , comprising fiber reinforced composite material.

8. A flange according to claim 7 , wherein the fiber reinforcement is carbon fiber.

9. A flange according to claim 7 , wherein the composite material is laminated.

10. A duct comprising composite material including a flange according to claim 1 .

11. A duct according to claim 10 , wherein the cross-sectional shape of the duct is a closed figure having a curved perimeter.

12. A duct according to claim 10 , wherein the duct is an open channel having a curved perimeter.

13. A duct according to claim 10 , wherein the material of the duct and the material of the flange are chemically compatible and thermally compatible.

14. A duct according claim 10 , wherein the material of the duct and the material of the flange are the same material.

15. An aircraft comprising the duct of claim 10 .

16. A method of making a flange comprising composite material, wherein the method comprises the steps of:

a) applying composite material to external surfaces of a curved mandrel that comprises a substantially triangular cross-section;

b) curing the composite material to produce a flange comprising a curved hollow member having a substantially triangular cross-section; and

c) machining substantially pentagonal shaped holes on the face of the flange corresponding to the hypotenuse side of the substantially triangular cross-section, wherein the sides of the pentagonal shaped holes are arranged to align with fibers in the composite material comprising the flange.

17. A method according to claim 16 , further comprising the step of: d) removing the mandrel from the hollow member.

18. A method according to claim 17 , wherein the mandrel can be dismantled and removal of the mandrel comprises dismantling the mandrel.

19. A method according to claim 18 , wherein the mandrel comprises two or more parts which are assembled to form a substantially triangular cross-section, wherein the two or more parts are dismantled for removal from the hollow member.

20. A method according to claim 19 , wherein the mandrel comprises two or more segments which are dismantled by sliding segments relative to each other.

21. A method according to claim 18 , wherein the mandrel comprises a plurality of tessellating sections that join together to provide the mandrel a substantially triangular cross-section when assembled and separate for removal from the hollow member.

22. A method according to claim 16 , wherein the mandrel is made of soluble material that is dissolved to remove the mandrel from the formed hollow member.

23. A method of making a structure comprising composite material, wherein the method comprises providing a duct of composite material with a flange of composite material, wherein the flange is produced from the method according to claim 16 , further comprising the step of attaching the flange to at least an end of the duct.

24. A method according to claim 23 , wherein an end section of the material of the duct is darted to allow the material to fold into contact with one side of the flange; applying the flange to the surface of the duct proximate the darting; folding the darted section of the composite material making the duct into contact with the side of the flange to attach the flange to the duct.

25. A method according to claim 24 , further comprising the steps of: applying filler at the junction of a vertex of the triangular cross-section provided by a surface of the flange in contact with the duct and a hypotenuse side of the triangular cross-section; and adding plies of composite material to overlay the duct, the filler and at least part of the hypotenuse side of the triangular cross-section.

26. A method according to claim 24 , including the step of bagging the structure and curing the composite material providing the structure.

27. A method according to claim 26 , further comprising machining fixing holes on exposed faces of the flange and wherein the substantially pentagonal shaped holes are access holes.

28. A mandrel for use in the method of making a flange according to claim 16 , wherein the mandrel is curved and comprises a solid triangular cross-section.

29. A mandrel according to claim 28 , wherein the mandrel comprises two or more parts configured to be assembled together to provide the substantially triangular cross-section.

30. A mandrel according to claim 29 , wherein two segments comprising mitred surfaces are arranged one on top of the other to provide the curved member having a substantially triangular cross section.

31. A mandrel according to claim 30 , further comprising one or more end plates attachable to one or both ends of the segments.

32. A mandrel according to claim 28 , wherein the mandrel is made of iron nickel alloy.

33. A mandrel according to claim 28 , wherein the mandrel is made of composite material.

34. A mandrel according claim 28 , wherein the mandrel is coated with a release agent.

35. A mandrel according to claim 28 , wherein the mandrel is coated with PTFE.