Adhesive Stress Testing
It’s vital that adhesives are tested thoroughly before they are made available to the market. This ensures that their characteristics and properties, namely their bonding strength, is accurately determined and therefore able to be matched to customer specifications.
Adhesive stress tests determine how effective an adhesive will be at bonding to different substrates. Other factors that affect this include the substrates being bonded, mechanical forces involved, temperatures, thermal cycling, and chemical exposure.
Common Adhesives Stress Modes
Structural adhesives are commonly stress-tested through 4 main types of stress modes. Here we explore these main stress modes routinely used in adhesive stress testing.
Tensile
Tensile stress is the load that a material can withstand in a direction perpendicular to the bonding plane, under stress or deformation, without failure. It is a force applied equally across the entire bond area, acting away from the adhesive bond.
Compression stress differs from tensile stress as it is in the opposite direction, with the substrates being pushed together perpendicular to the bond plane.
Shear
Shear stress is the load that a material is able to withstand in a direction parallel to the face of the material. Shear stress is pull directed across the adhesive, forcing the substrates to slide past one another. Here the force is in the same plane as the bond and distributed across the entire area.
Cleavage
Cleavage stress is the load that a material is able to withstand concentrated at one edge of the joint. In this case, while that end of the adhesive bond is experiencing concentrated stress, the other edge of the joint is theoretically under zero stress. Cleavage stress typically occurs between two rigid substrates.
Peel
Peel stress is the load that a material is able to withstand along a thin line at the edge of the bond where one substrate is flexible. Peel stress results in even more concentration at the leading edge than cleavage stress, pointing out where an adhesive would separate if the flexible surface were peeled away from its mating surface.
If you are unsure about the type of adhesive stress modes in relation to your application, get in contact with our technical experts for a detailed analysis.
