Let’s start by defining the different types of loading stress. There are four basic types:
Tensile, Compression, Shear, Peel
- Tensile Stress is pull exerted equally over the entire joint. The pull direction is normal to the adhesive bond.
- Compression Stress is pull concentrated at one edge of the joint, exerting a prying force on the bond.
- Shear Stress is pull directed across the adhesive, parallel to the bond, forcing the substrates to slide over each other.
- Peel Stress is concentrated along a thin line at the edge of the bond where one substrate is flexible.
In construction, shear and compressive loading are optimal types of stress. They require more force to reach shear or compressive failure than peel or tensile failure.
Design your joints so that the bonded areas equally share the load of whatever they carry. Uneven load distribution is the cause of most joint failures.
Use the chart above to see recommended joint designs and designs you should avoid for a successful project.
By understanding the types of joint stresses and avoiding negative stresses, you can create the most robust joint designs with the least amount of adhesive.