Next, the invention will be described in greater detail with reference to an embodiment shown in the accompanying figures. In the figures:
FIG. 1 shows a window frame in perspective view;
FIG. 2 shows a detail section through the installation position of a window frame according to FIG. 1;
FIG. 3 shows a part of a molding tool for making a window frame of FIG. 1 in an opened position;
FIG. 4 shows the molding tool of FIG. 3 in a closed position;
FIGS. 5 and 6 show a representation of the main directions with a window frame of FIG. 1, wherein FIG. 6 is a detail representation of the region in FIG. 5 designated with VI;
FIG. 7 shows the structure of a first perform in a sectional view;
FIG. 8 shows the structure of a second preform in a sectional view; and
FIG. 9 shows the structure of a third perform in a sectional view.
The window frame 1 shown in FIG. 1 is made with a fiber construction and, like the known aluminum forged frames, also has an outer flange 2, an inner flange 3, as well as a vertical flange 4 arranged between these two flanges. In contrast to conventional aluminum window frames, the outer flange 2 in this case, however, has a uniform circumferential edge. Further, this outer flange 2, in contrast to a corresponding aluminum forged part has a varying thickness in different radial regions. This leads to a substantially improved material utilization in the region of the riveting and the shell cut-out. FIG. 2 more clearly shows this in a detail section, in which the installation position of such a window frame 1 in the outer shell 5 of an aircraft is shown. Indicated in this figure are also the rivet positions 6 for the connection of the frame with the outer shell 5, as well as two window panes 7 and 8, which together with a sealing 9, form the window element.
The window frame 1 is manufactured by means of the so-called “resin-transfer-molding” or RTM technology. In this connection, first a mold part 10, the so-called perform, is made from fibers. This is next placed in a two-part molding tool 11, as shown in FIGS. 3 and 4. Within a lower molding tool 12 and an upper molding tool 13, an inner core 14 and an outer core 15, in this case formed in two parts, are arranged. The perform 10 is inserted between the two cores 14 and 15, the molding tool 11 is closed, and under pressure and temperature, resin is injected into the molding tool. The complete component 1 is subsequently hardened within the molding tool 11.
The perform 10 can therefore be made either as a complete part or in the so-called sub-preform technology, in which the complete window frame 1 is combined from individual substructure elements or sub-preforms. In each case, however, the perform 10 comprises individual layers, which in principle can be made from three different types:
- from a web semifinished part,
- from fiber bundles,
- from a combination of web semifinished parts and fiber bundles.
The direction of the individual fiber layers is critical for the weight savings achievable with the window frame 1 described here, which enable a load-suitable layer structure. A fiber direction, which is not circumferential in the frame, could not achieve the weight savings that are achieved with the arrangement described herein. The principle layer direction with the main directions 0°, 45°, and 90° are shown in FIGS. 5 and 6. The 0° direction therefore represents the circumferential direction of the window frame 1, the 90° direction runs in the radial direction, and the 45° direction runs in the region of the transition from the vertical flange 4 to the outer flange 2.
FIG. 7 shows a section through the layer structure of the window frame 1 comprising the web semifinished parts. In this figure, reference numeral 20 designates the 0° winding core in the inner flange, reference numeral 21 designates the ±60° layers in all outer regions as well as the ±60° layers extending from the outer flange 2 to the inner flange 3, and reference numeral 22 designates the 0° and 90° layers in the region of the vertical flange 4. These layer directions are measured on the interface of the outer flange 2, inner flange 3, and vertical flange 4. Outside of this region, the following facts are provided for the curvilinear placed web semifinished parts:
Vertical Flange 4:
- All fibers remain in the direction, in which they were measured; Inner flange 3 and outer flange 2:
- 0° fibers remain in the direction, in which they were measured;
- ±45° fibers remain in the direction, in which they were measured, but are curved;
- ±60° fibers remain in the direction, in which they were measured, but are curved.
FIG. 8 shows a load-suitable layer structure with fiber bundles, wherein, again, a section through the layer structure of the fiber bundle is shown. In this figure, reference numeral 20 designates the 0° winding core in the inner flange, reference numeral 23 designates the fiber bundle with a ±60° layer in all outer regions, as well as the ±60° layer extending from the outer flange 2 to the inner flange 3, reference numeral 24 designates the fiber bundle with 0° and 90° layers in the region of the vertical flange 4, and reference numeral 25 represents the fiber bundle with ±45° layers in the region of the outer flange 2. These layer directions are measured on the interface of the outer flange 2, inner flange 3, and vertical flange 4. In order to achieve a fiber progression, in which the fibers follow the load direction, a structure is selected for the window frame 1, which is summarized as follows:
Outer Flange 2:
- Quasi-isotropic, radial structure in the region of the riveting;
Vertical Flange 4:
- 0° core for receiving the primary load;
- ±60° layers on the outer sides.
Inner Flange 3:
- 0° direction predominantly;
- ±60° layers on the outer sides;
- 90° for reinforcement.
In this manner, the following details are provided for the respectively placed fiber:
Vertical Flange 4:
- All fibers remain in the direction, in which they were measured.
Inner Flange 3 and outer Flange 2:
- 0° fibers remain in the directions in which they were measured;
- ±45° fibers change their angle to ±60°;
- ±60° fibers change their angle to ±70°.
Finally, FIG. 9 shows a layer structure with a combination of webbing and fiber bundles. Here, again reference numeral 20 designates the web layer of 0° winding core in the inner flange, while reference numeral 27 designates the 0° coiled push, 28 designates the ±60° web layer, and 29 designates the 0°/90° web layers.
The window frame 1 made in this manner has an approximately 50 percent weight savings with approximately the same manufacturing costs compared to the common aluminum window frames. Its tolerances are essentially lower than the tolerances of the corresponding aluminum components. Simultaneously, the frame offers higher safety and better thermal insulation than the common aluminum window frame.
Patent Application
20080078878
