Unexpected Dynamics in the Propagation of Fracture Fronts

Abstract Fractures are ubiquitous and lead to catastrophic failure of materials. While fracture in a two-dimensional plane is well understood, all fractures are, in fact, extended and propagate in a three-dimensional space and their behavior is more complex. Here we show that forward propagation of a fracture front always occurs through an initial rupture, nucleated at some localized position, followed by very rapid transverse expansion at velocities as high as the Rayleigh-wave speed. We study a circular geometry to achieve an uninterrupted extended fracture front and use fluid to control the loading conditions that determine the amplitude of the forward jump; we find this amplitude correlates with the transverse velocity. Dynamic rupture simulations capture the observations for only high transverse velocity. These results highlight the importance of transverse dynamics in the forward propagation of extended fracture.