The geometry of vacuum assisted interface adhesion: Resistance to axial moment

Many engineering applications require joining two surfaces by temporary methods that do not harm either surface. The need for non-destructive surface bonding includes the need to resist axial moments. Suction cups in two different arrangements, in pairs at 180° apart and in fours at 90° apart, were pressed onto a polymerized thermoset polyester surface and then subjected to an axial moment. Defining failure as either sliding or complete loss of adhesion, the maximum torque applied before adhesive failure at the cup–plate interface was quantified using an MTS materials testing system. A linear relationship existed between the distance from the centroid of the cups and the applied torque at failure; also a linear relationship existed between the contact area of the cups and the tangential reaction force. Experiment verified that the applied load is distributed among the cups such that the tangential reaction force on each cup is proportional to its distance from the centroid; a coefficient of static friction between polyvinylchloride and polymerized thermoset polyester of 1.24 was calculated from the data.