A network model has been formulated and used for computer simulations of the geometry an mechanical behaviour of cellulose fibre networks. The focus is on the properties needed to proceed with a continuum analysis of fracture, that is stiffness, strength and fracture energy. It is found that the ductility of inter-fibre bonds has a strong effect on the fracture properties. Localization of the fracture zone is also studied. The dependence of elastic stiffness on various micro-level parameters is simulated, and examples are given of Young's modulus dependence on fibre curl and fibre orientation distribution.