Aircraft fastener parts have become more advanced to support a wide variety of metal aircraft and spacecraft structures. The newest addition has been the assortment of lightweight materials used to create different fasteners.
The new Alcoa fastener addition has not only been beneficial but has also raised issues on the compatibility of the lightweight materials such as aluminum. It is useful because it can be used and inserted into certain fasteners but when composites are involved other fasteners need to be created.
The transition from metallic to composite has also been a problematic transition in the aircraft fastener industry because composites structures are not safe against lightning strikes. The traditional metallic aircraft is made of aluminum, it is an ideal conductor of electricity. In any case that the aircraft is struck by lightning, the energy is dispersed through the metal. Most times it is harmless and if any harm occurs only small repairs are necessary.
Alcoa’s Flite-Tite pin fastener was made to get past any situations of composite delamination. Using a stainless steel or titanium sleeve to develop an interference fit without delaminating the composite.
Since composites are more like insulators than conductors. When using aluminum structures, the aluminum is the primary path of conduction. However, when a composite structure is used the fastener becomes the primary path of conduction. Composites are also complicated to deal with because they are sensitive to damage that is caused by delamination. Delamination is the state where composites and steel go under stress. This is caused when the fastener part is pushed into the hole. This separates the composite material which does not create a good electrical connection. In the case of a lightning strike the energy will not pass through the fastener.