Micromechanics of fiber-reinforced cementitious composites

The strain hardening and tension softening response of short fiber-reinforced cementitious composites under unidirectional tensile/flexural loading is modelled using concepts from fracture and damage mechanics. The tensile strain hardening in these composites is due to the formation of microcracks which ave however prevented from coalescing by the bridging action of the fibers. The density of microcracks increases with increasing tensile/flexural loading until it reaches a saturation level at the tensile load carrying capacity of the composite. Thereafter the fibers progressively debond from the elastic matrix and the deformation begins to localise in the eventual fracture plane, first as unconnected cracks and later as a connected through crack subjected to the residual frictional bridging action by the fibers.