Effect of Lateral Stress on the Debonding and Pullout of Steel Fibers in a Cementitious Matrix


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Title: Effect of Lateral Stress on the Debonding and Pullout of Steel Fibers in a Cementitious Matrix

Author(s): C. K. Y. Leung and Y. Geng

Publication: Special Publication

Volume: 156


Appears on pages(s): 153-172

Keywords: composite materials; fiber reinforced concretes; pullout tests; stresses; Materials Research

Date: 9/1/1995

In many practical engineering applications of fiber reinforced concretes (FRC), fibers are subjected to significant lateral loading. The lateral stress may have a significant effect on fiber debonding and pullout, thus affecting the performance of FRC. In this investigation, a novel experimental set-up was developed to carry out fiber pullout tests under various levels of lateral compression. Interfacial properties for steel fiber in mortar were derived from the measured fiber load versus displacement curves, based on a unified fiber debonding theory. As expected, the interfacial friction at the onset of sliding increases with applied compressive stress. Surprisingly, the pre-sliding interfacial resistance (which can be either the interfacial strength or the interfacial fracture energy, depending on whether interfacial debonding is strength or fracture governed) is also found to increase with lateral compressive stress. Also, with higher compression, there is a more rapid decay of interfacial friction when the fiber is sliding out of its groove. As a result, while lateral compression can significantly increase the peak pullout load, the increase in total energy absorbed during the pullout process is much less drastic.