Where two components are to be connected, it is conventional to provide each component with a flange which abuts with the opposing flange and provides a means for connecting the two components. In addition, the flanges may also provide additional strength and stiffness to the components.
As shown in FIG. 1, flanges are often used with tubular components, particularly cylindrical components. However, the components may be hemispherical, conical or other similar structures. The component 2 of FIG. 1 has a flange portion 4 projecting substantially perpendicularly to a portion 6 of the component 2. The flange portion 4 is provided with a plurality of holes 8 passing therethrough for connection with an abutting flange. FIG. 2 shows a partial cross-section through the component 2, with the dashed line representing a central axial axis of the component.
The component 2 may be a casing component of a turbomachine. Conventionally, such a casing component would be manufactured from a metal, such as a titanium or a nickel alloy. Advantageously, metallic components usually have near homogeneous material properties irrespective of the component shape and method of manufacture.
The same can not be said for composite materials, particularly fibre reinforced organic matrix composites, which are highly heterogeneous. The properties of these materials depend on the local fibre orientation and the strength and stiffness of the material may vary greatly between regions of the component. It is however desirable to use such composite materials since they are generally lighter than metallic materials and may be cheaper than high-strength low-density metals, such as titanium. Furthermore, particular directionality of strength can be tuned by appropriate selection of ply material and orientation.
A composite component may be designed to ensure that it has the desired properties by selectively aligning the fibres in the composite material with the directions of anticipated loads. This may be performed on a local scale such that localised regions of the component are provided with appropriately oriented fibres to produce the desired properties for that region.
For example casing components are often designed to withstand pressure vessel loads, to provide roundness stability, and to guarantee containment of a blade in the event of a blade-off. The main body of the component therefore has to have good hoop and axial strength and stiffness.
The flange portion of the component must maintain its shape under asymmetric loading to prevent leakage from the interface between the two components.
The present invention provides a composite flange having a ply layup which provides desirable properties for the flange and which enables the metal flange to be replaced by a composite material.