Fatigue damage propagation models for ductile fracture of ultrahigh toughness cementitious composites

Ultrahigh toughness cementitious composites are a kind of high-performance cementitious material with a characteristic of ductile fracture. Based on the continuum damage mechanics theory and flexural fatigue damage model, two damage propagation models of ultrahigh toughness cementitious composites are built. One is a linear bilogarithmic model with J-integral range as its independent variable, while the other one is a linear model on a semilogarithmic scale with fatigue stress level as its independent variable. However, according to former research, the J-integral depends strongly on specimens' geometry, so the first damage propagation model is deeply influenced by material dimension. As a result, the second damage propagation model is more convenient in application, shows the material fatigue property in comparison with the first model. In order to prove these two models and obtain the parameters, a three-point flexural fatigue experiment on single-edge-notched fracture specimens is carried out. The results shows that the two models fit better with the experimental results, rather than the crack propagation law of ultrahigh toughness cementitious composites.