Integrated aircraft structure in composite material

1. Aircraft fuselage structure made of composite material comprising:

a skin; and mounted thereon:

at least one set of frame feet comprising a plurality of linearly arranged frame feet and

a plurality of stringers disposed orthogonally to said set of frame feet and extending between adjacent frame feet,

wherein said frame feet are formed of U-shaped elements each of which U-shaped element being located between but not extending through adjacent stringers and comprising two L-shaped sections which together with a skin part form said U-shaped element in such a way that these U-shaped elements perform two structural functions in said structure at the same time, acting as frame feet and as skin, providing an integrated fuselage structure without rivets or joints.

2. Aircraft fuselage structure made of composite material according to claim 1 , the U-shaped elements include reinforcements for providing predetermined extra thickness in zones of said elements.

3. Aircraft fuselage structure made of composite material according to claim 1 , wherein the composite material comprises carbon fibres or glass fibres.

4. Aircraft fuselage structure made of composite material according to claim 1 , wherein the resin of the composite material is of the thermosetting or thermoplastic type.

5. Aircraft fuselage structure made of composite material according to claim 1 , wherein the composite material is preimpregnated or is dry fibre.

6. Aircraft fuselage structure made of composite material according to claim 1 , wherein the fuselage is panelled.

7. Aircraft fuselage structure made of composite material according to claim 1 , wherein the fuselage structure is in the form of a complete barrel.

8. Method of manufacture of an integrated aircraft fuselage structure made of composite material according to claim 1 , wherein it comprises the following stages:

a) lay-up of layers of composite material which make up the U-shaped elements;

b) lay-up of the layers of composite material that make up the stringers;

c) folding of the stack obtained in stage a) to form the U-shaped elements;

d) folding of the stack obtained in stage b) to form the stringers;

e) placement of the U-shaped elements in curing tooling together with the stringers, said U-shaped members being arranged orthogonally to said stringers and arranged such that stringers pass between adjacent U-shaped members;

f) lay-up of the skin, and

g) curing of the complete structure by the application of pressure and temperature, ensuring adequate compaction of all the zones of said structure.

9. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein the lay-up of the layers of composite material in stages a) and b) is carried out by a manual or automatic method.

10. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein that the stacks of the U-shaped elements ( 15 ) from stage a) include reinforcements ( 6 ) both longitudinally and transversely for optimizing said stacks.

11. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein in stage c), the folding of the U-shaped elements is carried out by a cycle of temperature and vacuum, using a tooling.

12. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein, in stage e), roving is introduced to prevent hollows, accumulations of resin and to ensure optimum co-curing.

13. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein in stage f), a conical or cylindrical tooling or a sector is used, depending on whether it is a one-shot process or a panelled section.

14. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein the integrated structure is co-cured, co-bonded or secondary bonded.

15. Method of manufacture of an integrated aircraft fuselage structure according to claim 8 , wherein, prior to stage e), in the case when the U-shaped elements have been cured previously, there is an additional stage of curing by Resin Transfer Moulding (RTM) when the composite material is dry fibre.