Adhesive joints may be subjected to the following types of mechanical stress: A) Peel stress, B) Tensile stress, C) Shear stress, D) Torsional stress. Peel stress induces high linear loading on adhesive joints, which far exceeds the strength of most adhesives. During the structural design of adhesive joints, it is imperative to avoid subjecting the joints to such peel stress. When under tensile loading, the applied force is perpendicular to the adhesive interface. Force transmission occurs across the entire bonding surface; in principle, there is no inherent issue with adhesive joints bearing tensile stress. Tensile stress is generally only encountered in butt joints, which typically have a small bonding area. The bonding area can only be increased by adjusting the thickness of the base material. Since the strength of the base material usually exceeds the tensile strength of the adhesive, it is not feasible to design a joint that fully utilizes the strength of the base material. The optimal type of stress for adhesive joints is shear stress, as this stress acts parallel to the adhesive interface. Shear stress occurs in bonded lap joints, which generally have a sufficiently large bonding area. If the existing bonding area is insufficient to withstand the applied load, it is relatively easy to enhance the load-bearing capacity of the joint by increasing the bonding area. Torsional stress is similar to shear stress, and adhesive joints are not sensitive to compressive stress. Over time, any type of mechanical stress can cause aging of adhesive joints, such as permanent deformation (creep) or crack formation. Mechanical stress may also exacerbate the effects of other aging factors (e.g., joint failure caused by moisture).