4.4 Stresses on Joints

4.4 Stresses on Joints

Adhesive performance is measured by its resistance to the forces acting on the bonded assembly. Laboratory results on standardised specimens, available in the adhesive manufacturer’s published technical data sheets (TDS), are an excellent tool for identifying candidate adhesives for an application. Adhesive candidates chosen based on these generic results should then be tested rigorously with simulated or actual end-use parts, assembly processes and operating conditions.

The physical forces acting on a joint may be classified as shear, tensile and compression loads, etc. They rarely occur purely as one type; in fact, some combinations are so common that they have their own names, such as peel or cleavage loading. Stress may occur at high speeds in the form of impact or as cyclic fatigue loads, and it may be static or dynamic. Thermal effects may impose stresses with differential expansion and contraction of a substrate or assembly. The more accurately these conditions can be simulated in testing, the better the prediction of the final assembly’s performance.