How do cleavage tests evaluate adhesive joints?

Cleavage tests are a form of destructive testing used to evaluate the performance and strength of adhesive joints. These tests function by measuring the stresses that develop at the specific point or line where the test piece fractures.1

Alternatively, the strength of an adhesive joint can be characterized by calculating the energy expended to cleave apart a unit area of the interphase—the transitional zone between the adhesive and the adherend. In principle, the conclusions drawn from these energy calculations are equivalent to those derived from traditional stress analysis. These evaluations are typically conducted across a variety of environmental conditions and temperature ranges to ensure the bonded structure will perform adequately in its intended service life.1