Engineering Fiber Anisotropy within Natural Collagen Hydrogels

It is well-known that biophysical properties of the extracellular matrix (ECM) in- including, stiffness, porosity, composition, and fiber alignment (anisotropy) play a crucial role in controlling cell behavior in vivo. Type I collagen (collagen I) is a ubiquitous structural component in the ECM and has become a popular hydrogel material that can be tuned to replicate the mechanical properties found in vivo. In this review article, we describe popular methods to create 2D and 3D collagen I hydrogels with anisotropic fiber architectures. We focus on methods that can be readily translated from engineering and materials science laboratories to the life science community with the overall goal of helping to increase the physiological relevance of cell culture assays.

Nonlinear dynamic analysis of anisotropic fiber-reinforced dielectric elastomers: A mathematical approach

In this paper, the primary purpose is to have a complete understanding of the importance of fibers in dielectric elastomers due to the influence of fiber orientation in decreasing the applied voltage to simulate the structure and improving mechanical performance. Fibers will also reduce the chance of failure like Wrinkling instabilities and increase the response rate under electric displacement. Implementing the dielectric elastomers with anisotropic structure, despite their great potential, has not adequately analyzed in previous researches. Therefore, based on nonlinear continuum mechanics and large inelastic deformations, the constitutive relationships and equations governing the behavior of viscoelastic dielectric elastomers under harmonic electrical loading are extracted and analyzed in different states. The numerical results, such as phase and frequency-amplitude diagrams and the oscillation, illustrate the dynamic behavior of an anisotropic dielectric elastomer with different fiber orientations. To describe the viscoelasticity behavior of the material, hyperelastic models and the rheological model, are used in conjunction with electrical coupling. Using the theory of anisotropic dielectric elastomers, a geometrically nonlinear formulation under finite deformations is developed by the Euler-Lagrange equations and solved mathematically.

Dynamic stability of anisotropic fiber-reinforced plate

The dynamic stability problem of an anisotropic fiber-reinforced plate under increasing compressing load is considered in a geometrically nonlinear formulation using the Kirchhoff-Love’s shell theory. The problem is solved using the Bubnov-Galerkin method based on a polynomial approximation of the deflections in combination with a numerical method based on quadrature formulas. For a wide range of variations of physical, mechanical, and geometrical parameters, the dynamic behavior of the plate is studied.

A note on the volumetric-deviatoric split on the anisotropic constitutive model for fiber-reinforced materials

In the literature, it has been suggested that for a class of anisotropic constitutive laws for fiberreinforced materials, the volumetric-deviatoric split should only be performed on the isotropic (matrix) term, but not on the anisotropic (fiber) term. In this research note, we follow up on the theoretical and numerical analyses adopted in these early publications with an intuitive example that allows us to directly analyze the effect of this split. We demonstrate that performing such split on the anisotropic term leads to non-physical volume growth of the material sample. Therefore, we consolidate the observation that the volumetric-deviatoric split should not be applied to the anisotropic (fiber) term of the total strain energy.