5

Composite Structural Components and Mathematical Formulation

5.1 Overview of Composite Airframe

A section of a fuselage structure, showing some of the typical parts that make it up, is shown in Figure 5.1. Similar part types are used to make up a wing structure.

Figure 5.1 Typical fuselage part break-down

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The types of parts that make up an airframe (fuselage and/or wing) are the same for metal and composite structures. In fact, it is possible to replace, part for part, an aluminium airframe by an equivalent composite airframe. This would typically be a skin-stiffened built-up structure with fasteners connecting the different parts. In general, such a one-for-one replacement does not make full use of composite capabilities and results in minor weight reductions (<15%) with relatively high fabrication cost because the different parts are made separately and assembled together with fasteners. Such a construction, especially when the skin lay-up is quasi-isotropic is referred to as ‘black aluminium’ to emphasize the fact that the design imitates or closely matches the aluminium design and little or no attempt is made to use composites to their fullest potential.

Each part or component in an airframe structure serves a specific purpose (or, sometimes, multiple purposes) so that the ensemble is as efficient as possible. Efficiency typically refers to the lowest weight, given a set ...

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