Tensile Force vs. Shear Force
When it comes to determining if a particular tape is right for your construction project, there are two forces to consider: tensile force and shear force.
Tensile force influences the elastic property of the adhesive. Specifically, it will first stretch the adhesive before finally pulling it away from the surface. If a tensile force causes a failure, it will most likely be in the adhesive at the surface. Therefore, adhesion testing that measures the elastic character of the adhesive, and how much force it can take, will help you select the right tape.
A shear force works parallel to the surface – it is the major force at work in double-sided tapes. Shear force resistance testing – often called “Holding Power” – is an effective way to measure the internal strength of the adhesive (known as “cohesion”).
Most adhesive failures or separation occur as a combination of both tensile and shear forces, it is extremely helpful to know what forces could potentially affect your tape. Keep in mind that if the outside force is large enough, and is continuously applied, all tapes will eventually fail. It’s not a matter of “if,” but “when” – it may take an hour, a week, a year, or more, but if a tape isn’t designed to withstand the outside forces, it will eventually fail.