The thickness of adherends is just as crucial as their strength, especially in applications where the adhesive’s elastic modulus is related to joint design. Flexible materials—such as rubber, thin metal sheets, and plastic films—are prone to bending during use and should not be bonded with rigid, brittle adhesives, as such adhesives may crack and reduce bond strength. Differences in the flexibility or thermal expansion of adherends can induce internal stress within the adhesive layer. This stress may cause premature joint failure even before the joint bears any external load, and such joints are particularly risky for use at sub-zero temperatures. To a certain extent, stress can be minimized through joint design, but residual stress will still exist in the cured adhesive layer. The lowest stress inherently occurs when bonding identical materials. By adjusting the adhesive composition and selecting the appropriate adhesive, one can achieve a product whose rheological properties, thermal expansion, and chemical stability are similar to those of the adherends. If one of the joint materials swells in a chemical medium (gas or liquid), stress will concentrate at the interface between the adhesive and the adherend.