Measurements of Viscoelastic Properties of SWNT/Polymer Composite Films Using Nanoindentation

Abstract

Methods for measuring the mechanical properties of linear viscoelastic materials in both time and frequency domains have been presented using the nanoindentation technique. In the time domain, the viscoelastic functions of materials were measured through the direct differentiation method using the load-displacement curve or the material parameter extraction method by fitting the load-displacement curve. In the frequency domain, the complex creep functions of materials were measured in terms of dynamic load-displacement data under a harmonic loading superimposed upon a ramp loading. As an application, these methods were used to determine the material properties for single-wall carbon nanotube (SWNT)/polyelectrolyte mutilayer films and the neat resin film made of polyelectrolyte under nanoindentation tests. The uniaxial relaxation moduli as a function of time for both SWNT/polymer composite films and the neat resin film have been obtained from quasi-static nanoindentation tests. The complex compliance as a function of frequency for SWNT/polyelectrolyte composite films has been obtained from dynamic nanoindentation tests.