Fracture Model for Fiber Reinforced Concrete


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Title: Fracture Model for Fiber Reinforced Concrete

Author(s): Kitisak Visalvanich and Antoine E. Naaman

Publication: Journal Proceedings

Volume: 80

Issue: 2

Appears on pages(s): 128-138

Keywords: composite materials; cracking (fracturing); crack propagation; fiber reinforced concretes; metal fibers; models; mortars (material).

Date: 3/1/1983

A fracture model is developed to generate the entire crack growth resistance curve (R-curve) of fiber reinforced cementitious composites, including the steady state fracture energy. The crack growth mechanism in these materials is described in terms of three different zones: stress-free, pseudoplastic, and process. The pseudoplastic zone is the zone where the matrix has cracked, but the fibers bridging the crack still provide some resistance to pullout. The proposed fracture model assumes that the main portion of energy required during the fracturing of the material comes from fiber pullout within the pseudoplastic zone. The model is somewhat similar to the cohesive force crack model of Barenblatt on the linear elastic fracture mechanics theory. It is also assumed that the main crack in the composite propagates with a constant shape while its cohesive force-displacement law is being fully developed. Two pieces of information are required for the model to generate the entire R-curve of the composite. They are the cohesive force-displacement law, described in this study by the law of the composite and the crack shape during the fracturing process. An analytical relationship representing the law of steel fiber reinforced mortar is derived in this study from fitting tests data on notched tensile prisms. This law is shown to be a direct function of the fiber reinforcing index (V l / o) and the equivalent bond properties of the fibers. The crack shape is assumed to have a straight profile with an opening angle equal to the observed critical crack opening angle. Results predicted by the model are shown to be in reasonably good agreement with the experimental data obtained from the double cantilever beam tests.