Application of Simple Notch to Selective Separation of Adherend Bonded with Resin Adhesive by Pulsed Discharge in Air

This study reports the application of a simple conical notch punched on a bonded structure set in air for the selective separation of an adherend by pulsed discharge, with the discharge passage inside the adhesive bonding adherend. A simulation of the electrical field indicated that the field around the notch tip was highest compared with that at the edge where the field concentrated in the normal model without the notch. The tilted model with the sloped adherend resulted in real adhesion during bonding. The optical visualized images of the discharge passage showed that the notch allowed discharge passage control inside the adhesive because of the concentration of electrical field that was presented by the simulation. In the normal model without the notch, separation did not occur because the current passed only on the surface structure because of the lower dielectric breakdown voltage of the air that surrounded the structure compared with the adherend. The adherend with the notch was liberated under the same discharge conditions. The separation of adherend with the notch was investigated by optical visualization and displacement measurement of the surface on the notched adherend. The separation mechanism using the notch was that the adherend was detached by cohesive fracture of the adhesive that was caused by expansion of the gasified adhesive induced by discharge around the notch. These results and mechanism indicate that the notch on the adherend is useful for the selective separation of adherends from bonded structures by adhesive peeling.