Interfacial and mechanical behavior of fiber-reinforced calcium phosphate cement composites

Abstract

One basic drawback of hydrothermally synthesized calcium phosphate cements (CPC) is that they are brittle and fragile. To solve this problem, we investigated the interfacial chemistry, microstructure development, and toughness-related physical properties of CPC composites reinforced with strong fibrous materials (carbon fiber, glass fiber, and Kevlar). The most ideal interfacial structures between fiber and CPC were observed in carbon-fiber-reinforced composites, i.e., intermediate layers that were created by a moderate interfacial interaction of carbon with CPC promoted cross-linking, which tightly interconnects the fibers and thereby significantly improves ductility and toughness. In contrast, an undesirable interfacial mode was identified in Kevlar- and glass-fiber-reinforced CPC composites that were autoclaved at 250°C: the alkali-catalyzed hydrolysis of Kevlar in the composite prevented adherence to the CPC, and an extensive interaction between CPC and glass fiber resulted in the formation of porous intermediate layers. These negative factors were correlated directly to a lack of toughness and to catastrophic failure.