Integral structural shell component for an aircraft and method of manufacturing the same

#The invention relates to a structural panel component, and particularly a curved structural shell component that is especially for an aircraft fuselage, and that includes at least one skin sheet as well as stiffening elements thereon. The invention further relates to a method of manufacturing such a structural component.

#The present day conventional fabrication of large format structural components, and particularly the fuselage shell components for aircraft, typically uses skin sheets having dimensions of approximately 2.5 m by 10 m. The maximum largest possible size of the skin sheets is typically used for fabricating the fuselage shell, in order to minimize the number of the longitudinal and circumferential or transverse joints of the finished fuselage, and thereby reduce the weight and the fabrication effort and expense of the aircraft fuselage. Minimizing the structural weight of the fuselage is a very important factor in the manufacture of aircraft, with regard to the ever present effort to reduce the fuel consumption and therefore improve the economy of operating the aircraft.

#Such a weight minimization of the fuselage requires a structure-mechanical optimization of the fuselage shell structure, so that, for example, the skin sheets must have different thicknesses at different areas depending on the respective loads that will prevail at each respective area. This aims to avoid the weight penalty of otherwise having an unnecessary excess thickness at any given area of the fuselage shell that will be subjected to below-average loading. Similarly, areas of the fuselage shell that will be subjected to above-average loading can be provided with a thicker fuselage skin (and/or stronger stringers and frames), without unnecessarily thickening other areas of the fuselage shell. For example, it may be necessary to provide a thickening of the fuselage skin metal sheet in the area of each stringer joint for proper load introduction.

#In order that the invention may be clearly understood, it will now be described in connection with an example embodiment, with reference to the accompanying drawings, wherein:

#FIG. 1 is a schematic perspective view of a structural component according to the invention;

#FIG. 2 is a schematic perspective view of the structural component according to FIG. 1, with a frame member ready to be joined thereon;

#A portion of a conventionally fabricated aircraft fuselage shell 10 has been described above in connection with FIG. 3. That structure should be contrasted with the inventive structure shown in FIGS. 1 and 2. While FIGS. 1 and 2 show a substantially flat planar structural panel component, it should be understood that the present invention also applies to two- and three-dimensionally curved or contoured structural shell components, such as the aircraft fuselage shell component 1′ as shown in FIG. 4.

#FIG. 1 schematically shows such a large-format structural component 1 that essentially comprises a skin sheet 2 with longitudinally extending stiffening elements 3 and crosswise or transverse extending stiffening elements 4 arranged thereon. The structural component 1 is integrally embodied as one monolithic piece, i.e. it is apparent that the stiffening elements 3 and 4 integrally protrude from and are integral extensions of the same material as the skin sheet 2, and the elements 3 integrally intersect and are integrally joined with the elements 4 at respective integral, solid, continuous intersections. Thus, the elements 3 and 4 are each single-ply, solid, continuous uninterrupted elements, and the skin sheet 2 is a continuous, imperforate, uninterrupted sheet without gaps and with a continuous, uninterrupted outer surface. This is achieved by forming the structural component 1 from a one-piece semi-finished part in the form of a monolithic solid plate which may have dimensions of 10 m by 2.5 m by 35 mm, for example, corresponding substantially to the maximum finished dimensions of the structural component. The type of large-format structural component to be manufactured according to the invention has a minimum size of, for example, 1 m by 3 m by 20 mm.

#Material is removed from this plate-shaped semi-finished part to result in the configuration shown in FIG. 1. The material removal is achieved by means of high speed milling, which is characterized by a significant increase of the spindle rotational speed as well as the drive power of the milling equipment. Such high speed milling directly achieves an increase of productivity or production output. For example, the present conventional speed milling is characterized by a spindle rotational speed of 3000 r.p.m. versus the high speed milling especially for the invention has a rotational speed in the range between 10,000 and 40,000 rpm.