Patent Application
20080283668
The present invention relates to a single piece, closed composite material structure for aircraft fuselage and to the process for manufacturing such a structure.
The structures used in aeronautic fuselages comprise an outer panel, stiffeners and/or inner stringers. Since weight is a fundamental aspect in the aeronautic industry, the structures used in optimized aeronautic fuselages are manufactured in composite materials, these composite material structures thus prevailing over the more traditional metallic structures.
In the process for optimizing this type of structures, maximal weight reduction and the integration of a larger number of individual parts into larger parts are sought so as to reduce both the duration of the manufacturing process and the handling and assembly of smaller elements.
The application of the previous aspects to aeronautic fuselages leads to integrating the outer panels with their stiffeners in the smallest possible number of operations. Examples of this are found in documents EP 1151856, where the previously cured panels are assembled on each of the outer panels, and U.S. Pat. No. 5,242,523, where the crossed framework of composite material stiffeners is assembled in several operations on the outer panels forming the structure. In these cases, the panels together with their stiffeners are manufactured in several successive operations, the addition of parts to subsequently join these panels to one another with joints ensuring the tightness between panels further being necessary.
The object of the present invention is a composite material structure for aircraft fuselage solving the drawbacks of the prior art, as well as a process for manufacturing such a structure.
The present invention therefore provides a closed composite material structure for aircraft fuselage formed on a male jig from which it can be separated in a certain direction, said structure comprising a single outer panel and a plurality of inner longitudinal stiffeners integrated in said panel, such that the expansion coefficient of the male jig is greater than the expansion coefficient of the composite material of the structure, thus being able to remove the already manufactured structure, formed by the panel and the integrated inner stiffeners, in a single operation.
The present invention further proposes a process for manufacturing such a closed structure comprising the following steps:
Other features and advantages of the present invention will emerge from the following detailed description of an illustrative embodiment of its object in relation to the attached figures.
The present invention proposes a closed structure 1 for aircraft fuselage manufactured in composite material comprising an outer panel 3 and a plurality of inner longitudinal stiffeners 4 integrated on said panel 3. These stiffeners 4 have a honeycomb shape, preferably an omega (Ω) shape, each of which comprises in turn webs 5, which are parts of the stiffener 4 separated from the panel 3, and legs 6, which are the parts of the stiffener 4 joined to the panel 3.
The closed structure 1 will preferably have a cylindrical or frustoconical shape.
The closed composite material structure 1 is shaped on a leak-tight male jig 2 in turn comprising a body 7 and slots 8, such that the material of the male jig 2 has a thermal expansion coefficient that is greater than that of the composite material forming the structure 1.
The outer surface of the male jig 2 has a shape similar to the inner surface of the closed structure 1, such that the slots 8 of the male jig 2 house the webs 5 of the stiffeners 4.
The closed structure 1 must have a shape allowing its separation from the male jig 2 in a certain direction 11, and in direction 12.
After the curing process, a clearance 10 occurs which allows removing the shaped structure 1 from the male jig 2, in direction 11 and in direction 12. The clearance 10 which occurs after the curing process can be observed in
The present invention further proposes a process for manufacturing a closed composite material structure 1 comprising the following steps:
A closed structure 1, the geometry of which is greater than the initial geometry and having a clearance 10 with respect to the taping and curing male jig 2, is obtained after this process.
The closed structure 1 is separated from the male jig 2 in a manner parallel to the longitudinal separation direction 11, and in direction 12, according to its geometric features and aided by the clearance 10 generated in the curing process.
The design of the stiffeners 4, the skin 3 and the jig 2 will be such that there are no mechanical interferences during the demolding process, further considering the clearances 10 generated in the process. In the event of interferences occurring in the design process, if said interference is less than the local clearance 10 generated in the process for curing the closed structure 1, said closed structure 1 can also be demolded.
According to another preferred embodiment of the invention, at least one inner element 14 inside the outer panel 3 can be introduced in the closed structure 1, which element is not designed according to the longitudinal separation direction 11. The removal of the closed structure 1 according to the longitudinal separation direction 11 is then achieved if the size of this inner element 14 is smaller than the clearance 10 generated in the curing process.
The hold-down plates 9 provide the closed structure 1 with the required surface quality.
According to another variant of the invention, the male jig 2 can be formed by a leak-tight tubular element 81 on which a series of detachable elements 82 completely or partially shaping the inner surface of the closed structure 1 are placed.
Those modifications comprised within the scope defined by the following claims can be introduced in the preferred embodiments which have just been described.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/ES07/70022 | Jan 2007 | ES | national |
