On the universality of fracture surface roughness

We measure the roughness of fracture surfaces generated in uniaxial tension for model materials in two and three dimensions. We study the effect of disorder, of anisotropy of material properties and of dimensionality on surface roughness. Although the roughness exponent zeta is always found within a narrow range, its value systematically decreases as the extent of disorder is increased. For anisotropic materials the scaling properties are found to be independent of the orientation. These results indicate that the scaling properties of the fracture surface are not universal, but depend, albeit weakly, on material properties. While values of the roughness exponent zeta are independent of dimension, differences in the fracture morphology and in the breakdown characteristics are noted.