Bending of a bonded beam as a test method for adhesive properties

A strength of materials type solution is obtained for the shear stress state in the adhesive layer of a bonded cantilever beam subjected to an end load.

The shear stress is constant through the thickness of the adhesive layer and varies from zero at the fixed end to a maximum value at the free end. This maximum value can, under certain conditions, be calculated from knowledge of the load and the beam geometry only. The adhesive's shear modulus can then be determined from a measurement of the shear strain in the adhesive layer.

An expression for the beam deflection is also obtained. It contains a coefficient of adhesion which is potentially useful to evaluate surface treatments or other factors leading to different states of adhesion.

Fracture mechanics application of the specimen, nonlinear and viscoelastic adhesive behavior are briefly mentioned.