The comparison of measurement of mechanical properties of viscoelastic material by dynamic and creep nano indentation with spherical tip

This study investigated the characterization of viscoelastic materials by nano-indentation experiments which were performed using the home-made facility, Tribology Probe Microscopy (TPM). Both dynamic and creep indentation were performed on PTFE and styrene rubber sample. The dynamic indentation can directly output the storage and loss modulus. By fitting the displacement-time curve obtained in creep test, instantaneous modulus and long term modulus can be generated to calculate the storage and loss modulus, which can be compared to the value obtained in dynamic indentation. It was found that the differences in these results from two approaches indicated simple model was inadequate to get accurate and reliable results. It is suggested that more complex model should be developed to produce equivalent results among different methods.