Path differences between quasistatic and fatigue cracks in anisotropic media

We report experimental observations demonstrating that, in anisotropic media, fatigue cracks under cyclic loading follow strikingly different paths than quasistatic cracks under monotonic loading. We find a qualitatively similar behavior in a computational model, which suggests that this path difference is a general phenomenon. In both experiments and computations, quasistatic cracks follow paths governed by the anisotropy of the fracture energy, as theoretically expected. In contrast, fatigue cracks follow paths predominantly dictated by the symmetry of the loading with the microstructure playing a negligible or subdominant role. Those results pave the way for future studies aimed at elucidating the failure mechanisms underlying this surprising behavior.