Cellular-core structure for an acoustic panel

1. A cellular core structure able to be used in an acoustic panel for a turbojet engine nacelle comprising at least one cellular unit, each cellular unit comprising at least one intermediate sheet and two end sheets, wherein said cellular core structure includes a surface that is substantially of revolution, said surface being made by joining together edge to edge end sheets of a cellular unit or several cellular units by joining pads positioned in such a way as to form alveolar cells.

2. The structure as claimed in claim 1 , wherein the joining pads are made of a material comprising at least one of metals, alloys, polymers, and an epoxy-based resin.

3. An acoustic panel for a nacelle, comprising at least one cellular core structure as claimed in claim 1 .

4. The acoustic panel as claimed in claim 3 , wherein it comprises several cellular core structures arranged in layers between which a multi-perforated or porous skin is located.

5. A turbojet engine nacelle comprising an acoustic panel, wherein the acoustic panel is as claimed in claim 3 .

6. A method of preparing a cellular core structure as claimed in claim 1 , comprising at least one cellular unit, comprising:

A—selecting at least one cellular unit in a substantially compacted and substantially flat form, each cellular unit comprising at least one intermediate sheet and two end sheets, wherein said cellular core structure includes a surface that is substantially of revolution;

B—joining the end sheets of a cellular unit or several cellular units edge to edge and positioned the end sheets to face one another using bonding means positioned on one end sheet in such a way as to form substantially compacted alveolar cells;

C—stretching the structure obtained at the outcome of step (B) using expansion means in order to form the substantially expanded alveolar cells.

7. The method as claimed in claim 6 , further comprising a step (D) in which at least one of a perforated acoustic skin and a non-perforated skin are attached to at least one face of the cellular core structure obtained at the outcome of step (C).

8. The method as claimed in claim 6 , wherein the bonding means comprise a polymer, of metal or of alloy used for welding.

9. The method as claimed in claim 6 , wherein the bonding means comprise a material the position and thickness of which are such that the bonding means create a non-negligible air-filled space between two end sheets.

10. The method as claimed in claim 6 , wherein the expansion means are mechanical means able to stretch the structure obtained at the outcome of step (B) in a direction that is substantially perpendicular or radial to internal and external faces.

11. An acoustic panel for a nacelle, comprising at least one cellular core structure obtained by the method as claimed in claim 6 .

12. The acoustic panel as claimed in claim 11 , wherein it comprises several cellular core structures arranged in layers between which a multi-perforated or porous skin is located.

13. A turbojet engine nacelle comprising an acoustic panel, wherein the acoustic panel is as claimed in claim 11 .