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Damage Evolution of Fiber/Mortar Interface During Fiber Pullout

Published online by Cambridge University Press:  21 February 2011

Yiping Geng
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Christopher K.Y. Leung
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Abstract

This study aims at connecting the change in interfacial properties of FRC during fiber pullout to the microstructural features of the interface. The interfaces between steel, polypropylene and nylon fibers and mortar are investigated by SEM and EDXA at four stages during fiber pullout (a) before debonding; (b) right after debonding; (c) pullout 1 mm and (d) pullout 10 mm. Since fiber pullout is found to be sensitive to lateral compression, microscopic studies are carried out on fibers pulled out with and without lateral compression.

For steel FRC, significant damage occurs at the interfacial transition zone (ITZ) of the mortar. Regardless of the presence or absence of lateral compression, it is found that the “abrasion and grinding effect” is the major mechanism leading to the rapid decline of the pullout force and interfacial friction. Based on SEM and EDXA results, an interfacial damage evolution process is proposed.

For polymeric FRC's, the damage occurs mainly on the polypropylene and nylon fibers and the ITZ of the mortar experiences much less damage. The surface of the polypropylene fiber is shaved and abraded during the pullout process. The surface of the nylon fiber is peeled and shaved which contributes to the increase of the pullout force and interfacial friction.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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