Stress enhancement in the vicinity of brittle cracks makes the macro-scale
failure properties extremely sensitive to the micro-scale material disorder.
Therefore: (i) Fracturing systems often display a jerky dynamics, so-called
crackling noise, with seemingly random sudden energy release spanning over a
broad range of scales, reminiscent of earthquakes; (ii) Fracture surfaces
exhibit roughness at scales much larger than that of material micro-structure.
Here, I provide a critical review of experiments and simulations performed in
this context, highlighting the existence of universal scaling features,
independent of both the material and the loading conditions, reminiscent of
critical phenomena. I finally discuss recent stochastic descriptions of crack
growth in brittle disordered media that seem to capture qualitatively - and
sometimes quantitatively - these scaling features.Comment: 38 pages, invited review for J. Phys. D cluster issue on "Fracture:
from the Atomic to the Geophysics Scale
