Inter-relationships between mechanical properties of glassy polymers from nanoindentation and uniaxial compression

This is a report of the inter-relationships between mechanical properties of glassy polymers, obtained from nanoindentation and uniaxial compression. The deformation states and molecular phenomena are different in the two experiments. Nanoindentation enables determination of local mesoscale properties, which at low strain rates, exhibit a greater deformation rate sensitivity than the corresponding uniaxial deformation properties. At high rates, the nanoindentation properties are rate-independent. In nano indentation, the stresses decrease radially outward from the indenter tip. The progressively less deformed chains away from the nanoindenter tip, constrain the yield flow beneath the tip. These ideas form the bases of our understanding of the experimental observations from the perspectives of continuum mechanics and molecular phenomena. These experimental observations are enabled by refinements in nanoindentation data analyses: (i) LOWESS method on the unloading P-h curve for accurate stiffness estimates and (ii) quadratic drift correction method to account for nonlinear drift. (C) 2018 Elsevier Ltd. All rights reserved