Indentation responses of viscoelastic materials

Vickers indentation is arguably one of the most widely used techniques for characterizing the mechanical properties of materials because it is easy, inexpensive, and nondestructive. However, its popularity has so far been Limited to ceramics and metals, and very little literature information is available on the Vickers indentation properties of high or rigid polymers. In this article, the Vickers indentation responses of an epoxy and acrylic polymer have been studied. The hardness of these materials is found to be time-dependent as a result of viscoelastic flow and relaxation processes. Unlike ductile metals, the microhardness is not dependent on the indentation load. The elastic recovery in the Vickers impression takes place only along the side faces but not along the diagonals. Thus, the use of Vickers indentation as a convenient tool for evaluating the hardness and viscoelastic responses of rigid polymers is justified. (C) 1998 John Wiley & Sons, Inc.