Theoretical analysis on optimal fiber-matrix interfacial bonding and corresponding fiber rupture effect for high ductility cementitious composites

High ductility cementitious composites (HDCCs) exhibit robust tensile ductility accompanied by multiple cracking and a tight crack width. The constitutive relations of fiber/matrix interfacial bonding has a great influence on the mechanical properties of HDCCs. Appropriate interfacial bonding can give full play to the bridging effect of fibers, whereas improper interfacial bonding only achieves inferior, or even no ductility. The purpose of this study is to elaborate on the optimal range of the fiber/matrix interfacial bonding strength based on the micromechanics theory with consideration to fiber rupture. As typical fibers used in HDCCs, like PVA fiber, PET fiber, PE fiber and steel fiber were selected as case studies. Furthermore, a source of confused question is clarified if all the fibers in HDCCs exhibit pullout behavior rather than rupture behavior, which is the optimal case. The analysis results show that moderate volume fractions of fibers ruptured can contribute to obtain stronger fibers bridging capacity and can achieve higher ductility for HDCCs. Finally, the experimental value of fiber/matrix interfacial friction tau(0) is shown to be in an optimal range, and the ductility of the PVA-HDCC and PE-HDCC can reach 2.7 +/- 0.3% and 4.8 +/- 1.0%, respectively. These research findings can be used as an important guide on fiber surface treatment and fiber/matrix interface tailoring. (C) 2019 Elsevier Ltd. All rights reserved.