Indentation responses of a graded zirconium phosphate–filled epoxy resin

Abstract

The effects of load and time on the Vickers indentation responses of a graded zirconium phosphate (ZP)-filled epoxy resin are described. The hardness of this material is dependent on the concentration of ZP dispersed within the epoxy matrix. In the region poor in ZP, the hardness response is independent of load. In contrast, the hardness response in the region rich in ZP is profoundly load-dependent as a combined result of particle agglomeration and an indentation-size effect. When compared with the ZP-rich-epoxy, the ZP-poor epoxy exhibits a larger creep and a more pronounced elastic recovery in the Vickers impression. The nature and degree of deformation in the vicinity of Vickers contacts are also studied. During indentation the ZP-rich epoxy exhibits no contact-induced cracks but displays microscale plasticity, which can be associated with intergrain sliding, debonding, and grain push-out.