DYNAMIC MIXED-MODE FRACTURE OF CONCRETE

The transient moire fringe patterns surrounding a rapidly propagating crack in an impacted three-point bend concrete specimen with an offset precrack were recorded by two IMACON 790 ultra-high speed framing cameras. The fracture parameters associated with this mixed mode fracture event were determined by driving a dynamic finite element model of the concrete specimen in its application mode with the recorded load and the crack propagation histories. The fracture process zone (FPZ), which trails the rapidly propagating crack, was characterized and the mixed modes I and II dynamic stress intensity factors were determined. The fracture energy dissipated at the FPZ increased with crack extension and reached a constant dissipation rate toward the final phase of fracture. Under mixed mode loading, the crack kinked and propagated according to the Ramulu-Kobayashi criterion.