Crack growth modelling: enriched continuum vs. discrete models

Abstract

Failure in quasi-brittle materials usually appears in the form of narrow bands called fracture process zones, where all inelastic deformation takes place, while the surrounding bulk material outside those areas typically unloads elastically. This localised nature of failure is the main source of size effects in these materials, since the width of the fracture process zone is a material property that does not scale with the size of the material volume. An adequate description of localised failure and associated size effects requires both size and behaviour of the fracture process zone and neighbouring material to be properly taken into account. In this study, we present two alternative approaches for modelling localised failure and simulating fracture propagation using finite element methods. In the first approach, an embedded crack appears at a constitutive level by enriching the kinematics of constitutive models, while in the second one this is done at the finite element level using cohesive interface elements. The advantages and shortcomings of both are presented through one numerical example on the failure of fibre-reinforced composite materials.