DETERMINATION OF INTERFACIAL DEBOND MODE FOR FIBER-REINFORCED CEMENTITIOUS COMPOSITES

Theoretical models of mechanical properties of fiber reinforced cementitious composites require assumptions of fiber-cement interfacial behavior. In this paper, strength-based and fracture-based fiber debonding criteria are reviewed. To determine whether interfacial debonding is governed by the bond strength or critical energy release rate of the fiber-matrix interphase, fiber pull-out experiments were conducted using steel and brass wires of various diameters. The bond properties, including effective bond strength and frictional stress, were interpreted through a theoretical model of fiber pull-out. It was found that, for the material systems tested, interfacial debonding is dominated by frictional stress which is independent of the fiber diameters. Therefore, the debond mode of these material systems is categorized as strength-based. In general, the debond mode is a material characteristic and is dependent on the specific fiber and matrix types. In order to precisely predict the mechanical response of a fiber reinforced cementitious composite, it is necessary to determine the debond mode for a particular material system following the methodology proposed in this paper.