Current trends in biologics delivery to restore intervertebral disc anabolism.

In this paper, a micromorphic, non-linear 3D model aiming to describe internal friction phenomena in concrete is considered. A reduced two-degrees-of-freedom model is employed for the sake of easy handling to explain dissipative loops which have been observed in some concrete specimens tested under cyclic uniaxial compression loading with different frequencies and having various amplitudes but never inducing large strains. As (linear or non-linear) viscoelastic models do not seem suitable to describe neither qualitatively nor quantitatively the measured dissipation loops, we propose to introduce a multi-scale micromechanism of Coulomb-type internal dissipation associated to the relative motion of the faces of the microcracks present in the material and to the asperities inside the microcracks. We finally present numerical simulations showing that the proposed model is suitable to describe some of the available experimental evidence.

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Multi-scale concrete model with rate-dependent internal friction

Elastic, permeability and swelling properties of human intervertebral disc tissues: A benchmark for tissue engineering

Mechanical properties are investigated for a class of microstructured materials with promising applications. Specifically, we consider a composite material with orthogonal, mutually interconnected fibers building a pantographic substructure. In order to predict the behavior of such a system in three-dimensional continuum, a reduced-order model is introduced by means of a bi-dimensional elastic surface accurately describing large deformations. The properties of this reduced-order model are characterized by an elastic energy density that involves second space derivatives of the displacement for capturing the resistance of twisted and bent fibers in plane as well as out of plane. For determining the coefficients in the elastic energy of the reduced-order model, we utilize a numerical inverse analysis and make use of ad hoc computational experiments performed by a direct numerical simulation on the microscale with detailed modeling of the pantographic substructure. This reduced-order model represents a homogenized material on macro-scale with its substructure on microscale. The homogenized model is capable of describing materials response at a significantly less computational cost than the direct numerical simulations.

Numerical identification of constitutive parameters in reduced-order bi-dimensional models for pantographic structures: application to out-of-plane buckling

https://spiral.imperial.ac.uk/bitstream/10044/1/25633/7/COMMAT-D-15-00257R1.pdf

Modelling the damage and deformation process in a plastic bonded explosive microstructure under tension using the finite element method

http://eprints.gla.ac.uk/89714/1/89714.pdf

Mechanical modeling of incompressible particle-reinforced neo-Hookean composites based on numerical homogenization

Although the mechanical behaviour of the human annulus fibrosus has been extensively studied, the interaction between the collagen fibres and the ground matrix has not been well understood and is therefore ignored by most constitutive models. The objective of this study is to identify the significance of the fibre–matrix interaction in the human annulus fibrosus by careful investigation of the experimental data, the theoretical constitutive models, and the numerical simulation results in the literature. Based on the experimental results from biaxial and uniaxial tests, it is shown that the mechanical behaviour of the matrix can be well simulated by an incompressible neo-Hookean type model, but the effective stiffness of the matrix depends on fibre stretch ratio, which can only be explained by fibre–matrix interaction. Furthermore, we find that this interaction takes place anisotropically between the matrix and the fibres distributed in different proportions in different directions. The dependence of the tangent stiffness of the matrix on the first invariant of the deformation tensor can also be explained by this fibre orientation dispersion.

Xiaohao Shi

Papers

Mechanical modeling of incompressible particle-reinforced neo-Hookean composites based on numerical homogenization

Fibre-matrix interaction in the human annulus fibrosus.

A Hyperelastic Constitutive Model for Chain-Structured Particle Reinforced Neo-Hookean Composites

Shear stiffness of neo-Hookean materials with spherical voids