Delayed failure of the shock compressed inhomogeneous brittle material

Abstract

Inhomogeneous brittle material contains numerous preexisting microcracks and under the shock wave compression they could be activated and grow due to the shear stress effect. This failure property has been studied in this work by using amphibolized olivine websterite (AOW) rock as a representative candidate for the inhomogeneous brittle materials. At stresses much below the Hugoniot elastic limit, the AOW rock specimens have been shock compressed with the impact from a thick copper plate, and the velocity histories at the rear surface of the specimens have been measured. A delayed failure zone has been detected. It expands into the stressed material with a velocity comparable to the shock wave front, and follows the propagation of the shock wave with a time delay that decreases with the increase of shock stress. The time delay is 1.2 μs at shock stress of 0.9±0.2 GPa and 0.5 μs at 3.7±0.2 GPa. A physical explanation considering the in situ activation and growth of the preexisting microcracks by the local shear stress under shock compression is proposed for these observations. The results provide a further understanding for the dynamic fracture of inhomogeneous brittle materials under the shock wave loadings.