European Fighter Aircraft (EFA)

For the European Fighter Aircraft (EFA) currently under development, the projected target for composites utilization is 35% involving the main wing, the forward fuselage, and the fin and rudder. For any structure or subassembly it is likely that a combination of materials will be used, each applied so that its individual set of properties can be used to best advantage. As an example a scale test section of a proposed fuselage design is shown below where a number of combinations of materials are employed. 

Test section of proposed fuselage design for European Fighter Aircraft EFA (units-inches)

It incorporates carbon and Kevlar reinforced epoxy, aluminium honeycomb and unidirectional and woven reinforcements. Parts integration is also a key factor. The imaginative design of tooling and the taking advantage of the flexibility available in composites design allows parts lists, compared with the equivalent metal fabrication, to be much reduced. The design of an integrated composite horizontal stabilizer, offering an overall 15% weight-saving is shown below.

Composite horizontal stabiliser design for European Fighter Aircraft EFA (units-inches)

Although the basic material cost is more expensive, this is more than offset by reduction in substructure and assembly costs due to the smaller number of component parts. Overall the production cost savings are projected to be 18% over an equivalent all-metal stabilizer. Taking this concept to the limit, designs are now being proposed for an entire filament-wound aircraft fuselage. 

Two methods of providing the required stiffness characteristics have been studied. The first employs a filament wound isogrid network. Here skins are initially wound at [±45/90] and then split. A geodesic reinforcement is then bonded to the two skin sections. The second method uses a honeycomb stiffened structure with CFRP skins. Lightweight composite tooling is used which is capable of outward expansion and allows consolidation of the part during cure in the female mould.