Ultra-high speed X-ray imaging of dynamic fracturing in cementitious materials under impact

In this work the dynamic fracturing of an ultra-high strength cementitious material is probed with in-situ ultra-high speed X-ray phase-contrast diagnostics to investigate the phenomenology of dynamic fracture. Gas gun experiments were conducted on two characteristic samples with two different impact speeds, namely 80 and 190 m/s using the edge-on impact test configuration. The samples were placed within the intense X-ray beam providing an observation field of 12.8 mm in width and 8 mm in height. Thanks to equispaced 16 bunches of short X-ray pulses, the samples were imaged through an indirect detector arrangement using the Shimadzu HPV-X2 camera lens-coupled to a fast scintillator capturing through-thickness measurements with an interframe time of 1.06 µs. The comparison of fragmentation patterns between two samples revealed an important insight into velocity dependant spall formation as well as the effects of crack closure and bridging