Bonding strength of adhesives and surface roughness of joined parts

The bonding strength of adhesives is influenced by the surface roughness of the joining parts. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this paper, it is found that an optimum value of the surface roughness exists with respect to the tensile strength of the adhesion. On the other hand, the peel strength shows no clear relationship with the surface roughness. The shear strength of the adhesion lies in the middle of the above two tendencies.