Tensile tests for the improvement of adhesion between rubber and steel layers in elastomeric isolators

Steel reinforced elastomeric isolators are currently the most used bearings for seismic isolation purposes. In their manufacturing process, the steel reinforcements are cut in the desired shape, sandblasted, cleaned with acid, and coated with bonding compound. Then the elastomer and steel layers are stacked in a mold and subjected to vulcanization so as to be glued together and to constitute a single body. Good adhesion between the layers is very important for the correct functioning of the device. Adhesion conditions become critical when the isolators are subjected to tensile stresses, which arise under direct tensile actions or large shear strains. To analyze the influence of manufacturing process changes on the isolator adhesive behavior, the authors, instead of expensive shear test on full scale isolators, propose to perform tensile tests on square shaped small scale specimens. Hence, the adhesion behavior between elastomer and steel layers is investigated through tensile tests herein. Among the influencing parameters considered, it is found that vulcanization time increase does not improve the adhesion, but it may even worsen the isolator capacity in terms of strength. Moreover, it is found that, using elastomer without oily component improves the adhesion between the layers and increases the isolator dissipative capacity.