TOUGHENING OF HIGH-STRENGTH CEMENTITIOUS MATRIX REINFORCED BY DISCONTINUOUS SHORT FIBERS

High strength cementitious materials are more brittle than conventional cement-based materials. The brittleness of high strength cementitious materials can be reduced by using fibers. Toughening of high strength cementitious matrices reinforced by discontinuous short fibers is studied in this paper using nonlinear fracture mechanics. An R-curve-based approach is proposed to describe the matrix toughening due to fiber reinforcement. The effect of fiber bridging is modeled by a closing pressure which depends on length, diameter, and volume fraction of fibers, and the fiber-matrix interfacial bond. Results predicted by the proposed R-curve approach match quite well with experimental data from different studies. It is found that use of fibers in relatively high volume fractions not only reduces the brittle nature of high strength cementitious matrices, but also increases the maximum matrix strength.