  We investigate the influence of fractal structure on material properties. We
calculate the statistical correlation functions of fractal media defined by
level-cut Gaussian random fields. This allows the modeling of both surface
fractal and mass fractal materials. Variational bounds on the conductivity,
diffusivity and elastic moduli of the materials are evaluated. We find that a
fractally rough interface has a relatively strong influence on the properties
of composites. In contrast a fractal volume (mass) has little effect on
material properties.
