Model Studies of the Effect of Surface Roughness and Mechanical Interlocking on Adhesion

The apparent strength of adhesion has been measured for a soft elastic layer adhering to model porous substrates, consisting of rigid plates containing regular arrays of cylindrical holes. Two contributions to the apparent strength have been identified and compared with the predictions of a simple theoretical treatment. The first is adhesion to the surface itself. Because “rough” surfaces have greater area for bonding, the strength of adhesion was increased by as much as twenty-fold. The second arises from the work of breaking deeply embedded or entangled strands in order to detach the overlayer. Contributions from this mechanism were as much as several hundred times the (low) intrinsic strength of adhesion. Satisfactory agreement was obtained with theory in both cases. Measurements were also made using cloth substrates, when the adhering layer penetrated the cloth completely. The work of detaching and breaking permeating strands was again much larger than the intrinsic strength of adhesion, in reasonable agreement with theoretical predictions.