Modelization of Crack Growth in Brittle, Disordered Materials
  The thesis consists of four main chapters. In Ch.2 we discuss experimental results concerning the scaling behavior and fractality of fracture surfaces. In Ch.3 continuum and discrete models for fracture mechanics are reviewed and partially extended. In Ch.4 we present numerical results for a finite size scaling of the macroscopic fracture stress in the absence of any disorder in the material. We discuss in Ch.5, the main chapter, the technological important problem of hydraulic fracturing of heterogeneous solids. We have performed intensive computer simulations on this problem and discuss the conditions under which the resulting cracks may develop fractal patterns. We also determine the opening volume of the crack and the elastic stress field in the bulk, quantities that are accessible experimentally. postscript file 'ft_phd93.ps.gz' (1.9Mb) only via ftp server 'ftp.gkss.de'.Login as 'ftp', password: 'your-email', cd /pub/doc, binary mode, get ft_phd93.ps.gz, quit, and then decompress with 'gunzip ft_phd93.ps.gz'. The uncompressed postscript file is around 25Mb large, but you can easily preview it with 'ghostview' for example. Hardcopy upon request. 
Frank Tzschichholz