The subject of adhesive bonding covers everything from gluing on postage stamps to aircraft structural bonding. This report confines itself to metal-to-metal organic adhesive bonding which is structurally competitive with other modern joining processes such as brazing, welding, soldering and mechanical fastening. The advantages and limitations are discussed, as well as materials, processing, tooling and design techniques.
Adhesion is a function of the surface effect (surface free-energy) of atoms and molecules. The proximity of the adhesive molecule in respect to the metal adherend significantly affects the attraction strength. The cohesive strength of the adhesive is influenced by factors which include chemical structural formation, environmental exposure and internal stresses. The most critical processing factor influencing bond integrity and durability is surface preparation and the protection of the surface prior to bonding.
Formal education in this discipline and design manuals are practically nonexistent in an art which is less than thirty-five years old. Design engineers must prepare realistic functional requirements and rely upon adhesive specialists in the industry to keep pace with the current information explosion.