Interfacial Stresses for Bonded Rubber Blocks in Compression and Shear

When a rubber block is compressed between two rigid surfaces, to which it is bonded, both compressive and shear stresses are set up at the interfaces. These interfacial stresses have been measured for small compressions of four relatively-thin, flat rubber blocks of square and circular cross section. Maximum compressive stresses, nearly twice the average value, were developed in the center of the bonded surfaces. Shear stresses were found to increase continuously from zero at the center to maximum values at the edges. No evidence was detected of a singularity at the edges. For all of the blocks examined, the observed stress distributions agreed satisfactorily with theoretical predictions based on incompressibility of the rubber and a simple superposition of two deformation states. Measurements were also made of the shear stress distribution associated with an overall shear displacement of the block.