Method for applying a vacuum bag around a fuselage barrel made of composite material to be polymerized

1. A method for applying a vacuum bag around a body made of composite material to be polymerized, comprising a fuselage barrel formed by lamination on at least a part of the outer surface of a mandrel having the form of a solid of rotation about a longitudinal axis, the method comprising:

a) providing, alongside said surface of the mandrel, a bag material in the form of a sheet with a transverse width corresponding to a longitudinal length of the fuselage barrel,

b) fastening or sealing a first transverse end portion of the sheet onto the outer surface of the barrel or the mandrel,

c1) rotating the mandrel about said longitudinal axis, to wrap the sheet around the barrel,

c2) sealing opposite axial end edges of the sheet on the mandrel while the mandrel rotates about said axis, and

d) sealing a second transverse end portion of the sheet on said outer surface of the barrel or the mandrel.

2. A method according to claim 1 , wherein the sheet is a single multi-layer sheet consisting of three superimposed layers: an innermost layer of separating film for making contact with the composite material to be polymerized, an intermediate, porous, breather layer, and an impermeable outer layer.

3. A method according to claim 2 , wherein the three layers are joined together by adhesive or a biadhesive agent.

4. A method according to claim 2 , wherein at least the second transverse end portion of the sheet consists solely of the impermeable outer layer.

5. A method according to claim 4 , wherein the first transverse end portion of the sheet also consists solely of the impermeable outer layer.

6. A method according to claim 1 , wherein

during said steps c1) and c2) the opposite axial end edges of the sheet are sealed gradually while the mandrel rotates to wrap the sheet around the barrel and wherein said steps c1) and c2) are performed simultaneously.

7. A method according to claim 1 , wherein the step a) includes:

providing, adjacent to the mandrel, a static support structure, where the structure comprises at least one longitudinal platform which extends parallel to the outer surface of the mandrel and close thereto, substantially over the entire longitudinal length of the mandrel.

8. A method according to claim 7 , wherein the structure comprises two opposite and parallel longitudinal platforms which extend alongside the opposite longitudinal sides of the mandrel, substantially along the entire longitudinal length of the mandrel.

9. A method according to claim 7 , wherein at least one longitudinal platform of the structure is situated at a level about halfway along the height of the mandrel to allow an operator to reach manually a middle zone of the outer surface of the fuselage barrel on the mandrel.

10. A method according to claim 7 , wherein the structure comprises, alongside each of the axial ends of the mandrel, a respective platform level with the top of the mandrel.

11. A method according to claim 1 , wherein said step a) includes:

providing, alongside the mandrel, a carriage extending in the longitudinal direction and oriented parallel to the longitudinal axis of the mandrel, wherein the carriage contains the sheet folded or rolled up in an orderly manner.

12. A method according to claim 1 , wherein the step b) is preceded by the step of:

raising vertically, by a gripping and raising device which can be operated independently of the mandrel, the first end portion of the sheet to arrange the end portion alongside the outer surface of the barrel at a height close to that of the axis of rotation of the mandrel.

13. A method according to claim 1 , wherein the step c) is preceded by:

cutting transversely the sheet above a sealing or fastening line of the first transverse end portion of the sheet onto the outer surface of the barrel or the mandrel.

14. A method according to claim 1 , wherein during the steps c1) and c2) the mandrel is rotated by same operating means used to rotate the mandrel about said axis during the previous step of formation of the barrel by deposition of composite strips on the outer surface of the mandrel.