Flexural fatigue damage model of ultra-high toughness cementitious composites on base of continuum damage mechanics

Ultra-high toughness cementitious composite is a fiber reinforced cementitious material, with the characteristics of strain hardening and multiple cracking under uniaxial tension. It could be applied in some structures to sustain complicated loading conditions, such as fatigue loads. This paper presents an experimental and theoretical investigation on the flexural fatigue damage property of ultra-high toughness cementitious composites. Based on continuum damage mechanics and elastic-plastic isotropic damage model, a flexural fatigue damage model of ultra-high toughness cementitious composites is developed. The parameter of starting damage D _s is introduced, which equals to the damage amount happening in fatigue stage I. Meanwhile, the plastic strain ɛ _p on the bottom surface of the standard specimen is employed to calculate fatigue damage, D. The fitted parameters of the damage model are obtained with the experimental data. The research result shows that the starting damage amount and the cumulative damage degree drop with the decrease of stress levels. It is proved that this fatigue damage model is applicable to calculate the fatigue damage of ultra-high toughness cementitious composites.