Meshfree modeling of the dynamic mixed-mode fracture in FRC through an eigensoftening approach

This work is concerned with the numeric study of dynamic mixed-mode fracture in fiber reinforced concrete (FRC). A recently developed eigensoftening algorithm to deal with the fracture of quasi-brittle materials is employed in a meshfree framework. Three point bending tests on notched beams reinforced with steel fibers carried out through a drop weight device at two loading velocities are modelled. Since the notch was placed with an offset from the middle section, mixed-mode crack formation was facilitated. Assuming a linear softening stress-equivalent crack opening relation, the numerical methodology is first validated against experimental results on plain concrete. Subsequently, it is applied to study the dynamic fracture of fiber reinforced concrete with a newly-proposed bilinear relation. The studies reveal that the total fracture energy dissipation plays an important role on the peak reaction load, whereas the transitional point between the two branches has a significant influence on the crack patterns. Parametric studies on the notch position are also carried out. The results show that the notch position has a significant influence on the crack patterns.