Method for measuring shear stress-strain relationship of thin adhesive layer

This paper uses the combined bonding disc specimen, with a round end surfaces at both ends of the longitudinal adhesive joint and chamfered steel substrates hither, forms a shear stress distribution of uniform coefficient more than 0.97 and controls the normal tension stress along the bonding surfaces to a very low level. By means of the built-in high accuracy displacement measuring system of uniaxial INSTRON servo equipment, it eliminates the measuring system deformation from the measured total deformation, and then obtains the shear deformation of the joint, and eventually converts into the shear strain of the adhesive joint. The results of experiments using adhesive samples show that the bonding disc specimens are characterized by shear failure of the adhesive joint layers, so it can be thought that the method of combined bonding disc specimens can reveal the right shear properties of adhesives. The measured shear strength can be used as material strength criterion and the measured shear stress-strain relationship can be used in the load capacity analysis of bonded structural members. Because of the simplicity, the combined bonding disc specimen test method is suitable to be adopted in laboratories having displacement-controlled servo systems.