Viscoelastic characterization using instrumented indentation

This work describes the measurement of elastic and viscoelastic properties of polymers using instrumented indentation. A new method for carrying out dynamic nanoindentation for measuring complex modulus is developed and applied successfully to test two polymers. Viscoelastic creep measrements are carried out using Berkovich and spherical indenters. A comparison of the results obtained from nanoindentation techniques with bulk characterization methods is provided. Finally a description of a problem requiring the application of instrumented indentation is discussed. This problem involves the characterization of the surface degradation of epoxy by UV radiation. Since only a few microns of depth are affected by UV radiation, conventional bulk testing methods are ineffective in studying this phenomenon. Instrumented indentation is used to characterize the effects of UV degradation of epoxy. The viscoelastic properties of undegraded and degraded samples are determined using bulk and nanoindentation techniques and a comparison is provided. The depth profile of the degradation is also studied using instrumented indentation. Degradation mechanisms of the epoxy and epoxy clay nanocomposite are studied using FTIR to provide a chemical basis for the properties obtained using mechanical tests.