Numerical techniques for the analysis of crack propagation in cohesive materials

The aim of the paper is the development, assessment and use of suitable numerical procedures for the analysis of the crack evolution in cohesive materials. In particular, homogeneous as well as heterogeneous materials, obtained by embedding short sti bres in a cohesive matrix, are considered. Two-dimensional Mode I fracture problems are investigated. The cohesive constitutive law is adopted to model the process zone occurring at the crack tip. An elasto-plastic constitutive relationship, able to take into account the processes of bre debonding and pull-out, is introduced to model the mechanical response of the short bres. Two numerical procedures, based on the stress and on the energy approach, are developed to investigate the crack propagation in cohesive as well as bre-reinforced materials, characterized by a periodic crack distribution. The results obtained using the stress and energy approaches are compared in order to evaluate the e ectiveness of the procedures. Investigations on the size e ect for microcracked periodic cohesive materials, and on the bene cial e ects of the bres in improving the composite material response, are developed