There is a wide range of methods of joining materials, some of which are suited to general use and some which are specific to certain materials or material forms. Common methods are:
o riveting
o bolting
o bonding
o welding
Aerospace Rivets
This is the most common method of joining sheet materials in aircraft. A hole is drilled through the sections to be joined. A suitably sized rivet is put into the hole and set – the tail of the rivet is deformed so that it expands sideways and grips the sides of the hole, clamping the material together. They may be set by hand, but more often a powered riveter is used. Rivets are available with a variety of head shapes, including mushroom, snap rivets and countersunk head rivets. Where access is available to only one side, blind rivets are employed. These are hollow rivets, which are set by drawing a mandrel through the hollow rivet from the same side as the head… the mandrel then breaks off. Because blind rivets are hollow, they must generally be sealed separately. The rivet is pushed into the drilled hole, then set – the tail is deformed so that it expands sideways. The deformed tail clamps the sheets together and retains the rivet in the hole. The blind rivet may be used when access is restricted to one side. Pulling the mandrel through the rivet expands the rivet to set it, and the mandrel breaks off to leave a neat fastener. Blind rivets are hollow, and need to be plugged after setting, if sealing is required.
There is a wide variety of special rivets, each for a specific application. Aerospace Rivets may be made from any deformable material, but light alloy rivets are almost universal. An exception is the high-shear rivet, which uses a steel stem for very high shear strength, with an aluminium alloy collar that is deformed during setting to hold the rivet in place. All rivets are designed to be used in shear, and have limited strength in tension.
Alcoa Fastening Systems has through a series of aggressive acquisitions the monopoly on this particular industry, on Kaynar fasteners, Tridair fasteners, Camloc fasteners and Rosan products.
Aerospace Bolts
This is most useful where high shear loads or significant tensile loads will occur at the joint. Aluminium bolts are available for shear applications, but generally steel bolts are preferred for most applications. In most airframe applications, the fasteners must be locked to ensure that the nut and bolt do not loosen under vibration or temperature changes. A variety of methods can be used, including split pins, wire locking and clinch nuts. For bolts fitted to blind holes, wire locking is the most common method.
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