Microstructural Computational Modelling of Soft Tissues

In this work we numerically implement a previously developed large deformation model for porous fibre-reinforced materials with statistically oriented fibres, including the effect of the presence of the fibres on both the elastic properties and the permeability. The model is microstructural, based on observations made at different length-scales: the microscopic scale of the porous matrix, the mesoscopic scale of the reinforcing fibres, and the macroscopic scale of the system as a whole, and makes use of upscaling techniques. The implementation makes use of the open-source Finite Element package FEBio, which allows for full customisation of the constitutive equations. We first study a benchmark test in which only the effect of the fibre orientation on the permeability is accounted for. Then we simulate an unconfined compression test on a sample of articular cartilage, with realistic histological features, such as the volumetric fractions of the matrix and collagen fibres and fibre orientation.