Indentation responses of a graded zirconium phosphate-filled epoxy resin

The effects of load and time on the Vickers indentation responses of a grad ed zirconium phosphate (ZP)-filled epoxy resin are described. The hardness of this material is dependent on the concentration of ZP dispersed within t he epoxy matrix. In the region poor in ZP, the hardness response is indepen dent of load. In contrast, the hardness response in the region rich in ZP i s profoundly load-dependent as a combined result of particle agglomeration and an indentation-size effect. When compared with the ZP-rich-epoxy, the Z P-poor epoxy exhibits a larger creep and a more pronounced elastic recovery in the Vickers impression. The nature and degree of deformation in the vic inity 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 pus h-out. (C) 2001 John Wiley & Sons, Inc.