THE LARGE-DEFORMATION OF A SINGLE MICRO-ELASTOMERIC SPHERE

This paper reports on an experimental and theoretical study Of the mec hanical response of microscopic (about 300 mu m) elastomer spheres com pressed between two smooth parallel platens over a wide range of impos ed deformations. An experimental arrangement for obtaining these data is described. Experimental results presented for these elastomeric mic ro-spheres confirm the theoretical predictions oi various models for t he dependence of the reaction force on the compressive deformation of a sphere. at values of the dimensionless approach [(compressive displa cement)(initial particle diameter)] up to 10%, the classical Hertz the ory was found to be in good agreement with experimental results and co nfirms that the load is a function oi the approach to the power 3/2. A t larger deformations (dimensionless approaches in the cases 10-37%), a numerical implementation of Tatara's large deformation model for the compression of an elastomeric sphere gives good agreement with experi mental results. The Tatara analysis provides a numerical solution in w hich the load depends on the approach cubed for large deformations and follows the fifth power of the approach far even larger deformations. The good agreement between the experimental results and theoretical p redictions described facilitates the determination oi a number. of mec hanical properties of these microscopic particles from the experimenta l load versus displacement curves. The Tatara-based analysis, combined with experimental data for a 37% dimensionless approach, allows the e xplicit estimation oi the Poisson ratio for these elastomeric particle s. An application of the Hertz or Tatara analyses, depending upon the dimensionless approach regime investigated experimentally, also allows the plane strain modulus oi a single particle to be determined.