A phase field damage model for micropolar continuum undergoing finite rotation: application to concrete

The behaviour of concrete is greatly influenced by its internal composition.Unlike brittle materials, concrete and other quasi-brittle materials have a larger fracture process zone due to the presence of microcracks.Traditional analysis methods may fail to account for the effects of its heterogeneous structure.Experimentally, this heterogeneity results in variabilities in the global response, such as peak load and post-peak behaviour.To address this, we propose a novel cohesive phase field model for analyzing quasi-brittle fractures in concrete, treating the material behaviour as a generalized continuum.This model considers the deformation of the material's internal structure at the continuum level, assuming it can undergo finite rigid rotation, characteristic of a micropolar continuum.This framework can be extended to more complex behaviours such as micro stretch and micromorphic continuum.The model's elastic response is insensitive to the smoothing length scale, which is introduced to approximate the sharp crack topology with a continuous scalar field variable.Our model introduces additional length scales related to bending and torsional rigidity, allowing for a better representation of size-dependent effects in concrete.We demonstrate the impact of various parameters in our formulation on matching experimental data.The variation of these parameters highlights the variations in internal structure, offering insights into how the additional parameters relate to the material's varying internal structure.