DETERMINATION OF PARAMETERS OF VISCOELASTIC MATERIALS BY INSTRUMENTED INDENTATION

Instrumented indentation, called also nanoindentation if very low loads are used, provides information about mechanical properties from indenter load and depth measured during loading and unloading (Fig. 1). Today, these methods are well established for elastic-plastic materials like metals or ceramics. They can also be used for characterisation of polymeric and other materials whose response to load depends also on time. However, specific features of their behaviour must be taken into account in the test preparation and data processing. The pertinent methods are still under development. This paper gives a brief review of basic formulae for instrumented indentation into elastic-plastic materials, then it explains the load response of viscoelastic materials and presents the pertinent formulae, with emphasis on indentation testing. Also, a practical test procedure is described.