Using the Kelvin-Voigt model for nanoindentation creep in Sn-C/PVDF nanocomposites

In the present work, nanoindentation was used to examine the creep behaviour of nanostructured Sn-C/polyvinylidene fluoride composites, which are promising anodes for next generation Li ion batteries. Modifying the Kelvin-Voigt model using the stresses and strains that develop upon constant load nanoindentation allowed for an analysis that fits the experimental data. The resulting fits provided estimates for the elastic modulus and viscosity. The modulus and viscosity are found to vary significantly with position on the sample but are within range of accepted values. A comparison of the Kelvin-Voigt derived modulus with the Maxwell solid derived creep corrected Oliver-Pharr method was of the same order, but the trends did not match between the two models. The dissipated creep strain energy (DCSE), which has been used as a measure of damage in viscous-elastic composites, was examined for the Kelvin-Voigt model derived modulus and viscosity. The DCSE may be a relevant parameter for Li ion anode lifetime prediction.