The Effect of Adhesive Thickness on Joint Strength

The hypothesis that the weakness of thick joints is due to stresses caused by contraction of the adhesive on setting requires a linear relation between the strength of a joint and the adhesive thickness. However it is statistically preferable to describe our experimental data by relating either log strength or linear strength to log thickness. The predicted slopes or thickness-dependences of the joint strengths are at least three orders greater than those observed. Both the preferred relations have a possible theoretical basis, namely the statistical nature of rupture.