Adhesive Bonding in Aviation

Adhesive bonding is the process of joining two surfaces together. They play an important
role in the aviation industry as they provide fewer stress points compared to faster joints.

The adhesive bonding process is made glue, epoxy, or one of a wide range of plastic agents
which bond through the evaporation of a solvent.

Glues tend to create relatively weak joins but with the use of new self-curing adhesives
these bonds are now close to the strength of the materials themselves. With this in mind,
gluing is now the preferred method of joining for many applications.

The properties of glues mean that they can form both an adhesive and sealant at the same
time, while also resisting vibration and flexing stresses. The ability to act as a seal allows
adhesives to help protect a join from corrosion.

While adhesive bonding can be applied to metal-to-metal, plastic, glass, rubber, ceramic and
many other material combinations, the process can be used to join irregularly shaped
surfaces while offering virtually no change in the dimensions or geometry of the parts.
Adhesives also add very little by way of weight to the materials being joined and can be
used to quickly bond dissimilar substrates and heat-sensitive materials.

One of the greatest advantages of adhesive bonding is its versatility, it allows for joining of a
wide range of items as well as being easy to automate.

The importance of adhesives in the aviation industry becoming increasing important as
composites are being adopted to reduce weight and manufacturing costs.

Adhesive bonding of aircraft primary structures has been in use for over 50 years. Bonding
of stringers to skins for both fuselage and wing construction and of metallic honeycomb to
skins for elevators, ailerons, tabs and spoilers are the main uses for adhesives.

Traditional joining methods can only operate on materials above certain minimum thickness
values to prevent damage (e.g., tearing, bending, burning) in the material during joining,
adhesives are advantageous as they can be applied to materials of any thickness, reducing
the presence of the holes, which results in stress concentrations; these aspects make
bonding a very convenient tool to connect the parts together.