Discontinuous FE approach and lattice models to describe cracking behaviour in fibre-reinforced brittle materials

The numerical evaluation of the mechanical behaviour of quasi-brittle materials like rocks, concrete, ceramics etc. is difficult from the computational point of view due to complex highly nonlinear phenomena occurring in the fracture failure mechanism, and the material softening behaviour due to the cracking process usually leads to a strong mesh dependence. The use of reinforcing fibres is an efficient and economic method to enhance the mechanical behavior of such materials. For a quasi-brittle multiphase material, such as a fibre-reinforced concrete (FRC), several phenomena must be considered in the computational simulation, such as matrix cracking, fibre bridging effects, fibre debonding, fibre breaking and so on. Continuum mechanics approaches as well as micromechanical ones have been developed for the computational solution of such problems. In the present paper, the mechanical behaviour of fibrereinforced materials is analysed by adopting both a new discontinuous-like FE approach and a lattice model. The main phenomena involved, such as crack formation and propagation, crack fibre bridging, fibre debonding, fibre breaking, etc., are taken into account and examined using the above two models. The basic assumptions and theoretical background of such approaches are outlined and, finally, some experimental data related to notched plain or fibre-reinforced concrete specimens under mixed-mode monotonic loading are analysed.