Abstract :
The scaling properties of post-mortem fracture surfaces of brittle (silica glass), ductile (aluminum
alloy) and quasi-brittle (mortar and wood) materials have been investigated. These surfaces,
studied far from the initiation, were shown to be self-affine. However, the Hurst exponent measured
along the crack direction is found to be different from the one measured along the propagation direction.
More generally, a complete description of the scaling properties of these surfaces call for the
use of the two-dimensional (2D) height-height correlation function that involves three exponents ζ
0.75, β 0.6 and z 1.25 independent of the material considered as well as of the crack growth
velocity. These exponents are shown to correspond to the roughness, growth and dynamic exponents
respectively, as introduced in interface growth models. They are conjectured to be universal.
