A novel damage model based on micromechanics for hybrid fiber reinforced cementitious composites under uniaxial compression

A novel damage model based on micromechanics is proposed for hybrid fiber reinforced cementitious composites under uniaxial compression. In this model, a multilevel homogenization method is presented to predict the overall elastic properties of hybrid fiber reinforced cementitious composites. To account for the contribution of microcracks on its macrocompliance under compression, hybrid fiber reinforced cementitious composite is considered equivalent to the microcrack-weakened solid, whose overall compliance consists of the compliance of the matrix and the additional compliance by sliding, propagating and kinking cracks. The bridging effects of hybrid fibers on restraining crack growth are simplified based on the reality that the average sliding displacement of microcracks is much less than the length of reinforcing fibers. The evolutional domains of microcrack growth under loads where the microcracks are sliding, propagating and kinking are discussed in detail. In addition, the weakening effects of fibers upon compressive behavior are captured by introducing two functions, which consider the influences of fiber geometrical parameters, the microcrack density and the distance between two nearest microcracks with the same oriented angle. Simulation results by our evolutionary damage model render reasonable agreements with available experimental data of fiber reinforced cementitious composites and hybrid fiber reinforced cementitious composites with various fiber contents. The new micromechanical damage model would be beneficial to elucidating the strengthening and weakening mechanisms of hybrid fiber reinforcement.