(Courtesy of 3M)
Adhesive bonding is a very complex, multi-layered process with numerous interacting and unexpected factors that may contribute to bond failure. This section is intended to provide the novice reader with a general summary of the structural bonding process.
Bonding technology is a systemic joining technique that is based on a variety of interrelated processes. Besides the properties of the adhesive film, substrate materials and the stresses and loads on the joint, the fundamental importance for a bond to be effective is its geometric design. Flaws in bonded structures are a common occurrence because key basic principles of bond design have been neglected. Even in the design phase of a component, special relationships must be taken into account. The principle requirement on a bond is to transmit forces and be able to withstand the stresses caused by these forces for a long period of time. When designing bonds, two key requirements must be met in order to create a bond having good long-term stability (meaning in particular resistance to moisture): Firstly, a sufficiently large area must be available for bonding and secondly measures must be taken to prevent mechanical loads causing stress peaks in the bond.