Elasto-plastic deformation of silica glass and glassy carbons with different indenters

Abstract

Abstract Nanoindentation of glassy carbons, which had been heat treated at different temperatures, and silica glass was carried out with a spherical tipped indenter and three triangular pyramidal indenters with decreasing apical angles (Berkovich, 45° and corner cube). The effect of the face angle on the elasto-plastic deformation was investigated. The Meyer hardness or contact pressure of these materials increased with decreasing apical angle of the indenters. The dependence of the Meyer hardness on the face angle was consistent with the analysed relation of pressure P/πa 2-face angle sin−1 (a/R) curves obtained with a spherical indenter of 1 μm radius. A nonlinear response for the plots of contact pressure P/πa2 versus contact strain a/R, resulting from elasto-plastic deformation, was characterized by power-law fitting. It is concluded that the power-law fitting constant k is an alternative measure of the ‘true’ hardness of a material.