Orientation distribution of polyvinyl alcohol fibers and its influence on bridging capacity and mechanical performances for high ductility cementitious composites

Fibers spatial orientation distribution has a profound impact on the fiber bridging capacity and mechanical properties of high ductility cementitious composites (HDCCs), and the affected extent need to be quantitatively evaluated to provide guidance for engineering application of HDCCs. For this purposes, this study aims to clarify the micromechanical mechanism of fiber orientation distribution in the fiber rupture effect and bridging capacity based on the fiber bridging theory. In addition, experimental programs were conducted, including uniaxial tension test and four-point bending test. The fiber orientation distribution was detected using backscatter electron imaging (BSE) and digital image processing. The HDCC specimens were prepared with three types of fiber orientation distribution. Studies have shown that the fibers in HDCC with larger orientation present lower bridging stress sigma(0), weaker complementary energy J(b)', and higher probability of fiber rupture during the crack-bridging process. The first cracking strength of the composites showed a slight decline, and the flexural properties and tensile properties exhibited a significant decline. The strain/deflection hardening behaviour even disappeared in some specimens with larger fibers orientation. Thus, it need to be note that the degradation of mechanical properties caused by fiber orientation distribution should be considered in HDCC structure designs. (C) 2020 Elsevier Ltd. All rights reserved.