How does mechanical interlocking strengthen an adhesive bond?

Mechanical interlocking is one of several mechanisms that contribute to the strength of an adhesive bond. This process occurs when the liquid adhesive flows into the pores of an adherend’s surface or wraps around projections on that surface.1

By penetrating these surface irregularities, the adhesive creates a physical anchor once it hardens. This interlocking mechanism helps secure the materials together, often working in conjunction with other processes—such as adsorption, interdiffusion, or electrostatic attraction—to achieve the desired level of bond strength and durability. The effectiveness of this bond is ultimately influenced by the nature of the surface pretreatment and the ability of the adhesive to properly wet and spread across the interface.1