Design of Fiber-Reinforced DSP Mixes for Minimum Brittleness

The limitations of the traditional material design approach in driving properties to extreme values and handling multiple design criteria and variables can be overcome by applying the optimization approach. Fiber-reinforced cement based composites based on strong aggregates and exhibiting approximately bilinear fiber pullout behavior are optimized in the present study for a given compressive strength f^′_c with a view to maximizing their uniaxial tensile strength f^′_t and fracture energy G_F. Relations for the bridging stresses prior to and during fiber pullout are established using fracture mechanics. The mix design leads to nonlinear, single, or multicriterion maximization problems for the objective functions f^′_t and l_ch = EG_F/f^′_t² (characteristic length), subject to an equality constraint on f^′_c. In this way, optimal values for the microstructural parameters (fracture toughness of paste, length of fiber, and volume fractions and diameters of aggregate and fiber) are obtained.