Title:
Polymer and Steel Fiber-Reinforced Cementitious Composites under Impact Loading—Part 1: Bond-Slip Response
Author(s):
V. Bindiganavile and N. Banthia
Publication:
Materials Journal
Volume:
98
Issue:
1
Appears on pages(s):
10-16
Keywords:
bond; cementitious; fiber-reinforced concrete; polymer.
DOI:
10.14359/10155
Date:
1/1/2001
Abstract:
In this two-part paper, the response of polymer and steel fiber-reinforced cement-based composites to impact loading is investigated. In Part 1, single-fiber pullout tests were conducted and the fiber-matrix bond-slip responses were obtained. In Part 2, results from toughness tests performed on fiber-reinforced concrete beams under impact are reported and correlated with the bond-slip responses. A straight, undeformed polyolefin fiber, two lengths of a sinusoidally deformed polypropylene fiber, and a flat-end steel fiber were investigated. For the impact fiber pullout tests, a newly designed, instrumented impact machine was used. With the load applied in the direction of fiber alignment, two rates of impact pullout and one rate of quasistatic pullout were investigated. It was found that the mode of fiber failure itself may change from a complete pullout under quasistatic loading to fiber fracture under impact loading. Sinusoidal deformations placed on polymeric fibers improve their pullout resistance. This increase in the resistance may, however, cause fiber fractures at normal fiber lengths and thus reduce the energy absorption capacity. Scanning electron micrograph (SEM) observation reveals extensive damage in both steel and polymer fibers during pullout, and in the case of the latter, one sees significant fibrillation and longitudinal splitting. The pronounced viscoelastic behavior of polypropylene is reflected in the higher stiffness of the prepeak pullout curve at higher loading rates. With proper deformations and length, energy absorption capacity of polymeric fibers may approach that of steel fibers. In Part 2 of this paper, further evidence of the benefits of the viscoelastic nature of polymeric fibers towards enhancing the impact resistance of the composites will be presented.