Design and mechanical properties of particle-reinforced polymer-matrix functionally graded materials applied on elastic polishing pad

Abstract

Aiming at the functionally graded materials (FGMs) formed by mixing the abrasive particles and rubber with different kinds and mass ratios, the numerical analysis and experimental verification of its mechanical properties were carried out. The FGMs was applied on the elastic polishing pad for obtaining ultra-smooth surfaces of hard and brittle materials, such as glass ceramics and silicon wafers. Its structure and properties changed in the radial direction quasi-continuously. Regarding to the design of the FGMs, the maximum standard deviation of Young's modulus was 1.09 after 6 repeated tests, when the SiC abrasive particles and chloroprene rubber (CR) were mixed with mass ratio less than 50 phr. Furthermore, there are three types of mechanical properties, named edge stress, boundary stress and central stress, when the workpiece was applied to the elastic polishing pad mainly made of the FGMs mentioned above. If using matching module method, the abrupt phenomenon of edge stress was basically eliminated. Increasing the gradient rings could reduce the abrupt change of boundary stress, and the contact stress in the single gradient ring was basically kept constant when the FGMs was up to 8 gradient distribution. Meanwhile, due to the viscoelastic property of rubber, there was a difference of 25% between the dynamic and static stress values of the elastic polishing pad with acrylate rubber (ACM) as the matrix, and the maximum difference was less than 4.7% when using CR as the matrix. Besides, the dynamic mechanical analysis (DMA) showed that the loss factor tanδ was less than 0.1 in the processing temperature range of 20 °C–50 °C. Therefore, the FGMs with SiC or Al2O3 as particle-reinforcement, and CR as polymer-matrix could largely solve the inconsistent problem of central stress under dynamic and static conditions.