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Fracture Toughness of Fiber Reinforced Concrete.
Final rept. Jun 82-Aug 85,
NORTHWESTERN UNIV EVANSTON IL DEPT OF CIVIL ENGINEERING
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A fracture mechanics based theoretical model is presented to predict the crack propagation resistance of fiber reinforced cement based composites. Mode I crack propagation and steel fibers are treated in the proposed model. The mechanism of fracture resistance for FRC can be separated as subcritical crack growth in matrix and beginning of fiber bridging effect post critical crack growth in matrix such that the net stress intensity factor due to the applied load and the fiber bridging closing stresses remain constant and a final stage where the resistance to crack separation is provided exclusively by fibers. The response of FRC during all these stages was successfully predicted from the knowledge of matrix fracture properties and the pull-out load vs. slip relationship of single fiber. The model was verified with the results of experiments conducted on notched beams reported here as well as by other researchers. Beams were loaded in a closed-loop testing machine so as to maintain a constant rate of crack mouth opening displacement.
APPROVED FOR PUBLIC RELEASE