Geometric and finite element modeling of biopolymer aerogels to characterize their microstructural and mechanical properties

Biopolymer aerogels belong to a class of highly open-porous cellular materials. Their macroscopic mechanical properties (such as elasticity or thermal conductivity) depend on microstructural features (namely pore size distribution (PSD), fiber diameter and solid fraction), which can be tailored by different synthesis and drying routes. The design of modern aerogel materials requires a better perception into the microstructure and its influence on the mechanical properties. To predict the material properties using simulation, it is significant to construct a geometric model which is sufficiently precise to represent the microstructure of real materials. A tessellation approach based on Voronoi diagrams is a powerful tool to model such cellular-like materials. In this contribution, the diversified cellular morphology of aerogels is described computationally using a Voronoi tessellation-based approach [1]. Accordingly, Voronoi tessellations are generated to create periodic representative volume elements (RVEs) resembling the microstructural properties of the cellular network. Stress-strain curves resulting from finite element simulations of these RVEs and experiments of the aerogels under compression are compared. This work is an extension of our previous Voronoi tessellation-based on the 2-d description of biopolymer aerogels [2]

Computational design of biopolymer aerogels and predictive modelling of their nanostructure and mechanical behaviour

To address the challenge of reconstructing or designing the three-dimensional microstructure of nanoporous materials, we develop a computational approach by combining the random closed packing of polydisperse spheres together with the Laguerre–Voronoi tessellation. Open-porous cellular network structures that adhere to the real pore-size distributions of the nanoporous materials are generated. As an example, κ-carrageenan aerogels are considered. The mechanical structure–property relationships are further explored by means of finite elements. Here we show that one can predict the macroscopic stress–strain curve of the bulk porous material if only the pore-size distributions, solid fractions, and Young’s modulus of the pore-wall fibres are known a priori. The objective of such reconstruction and predictive modelling is to reverse engineer the parameters of their synthesis process for tailored applications. Structural and mechanical property predictions of the proposed modelling approach are shown to be in good agreement with the available experimental data. The presented approach is free of parameter-fitting and is capable of generating dispersed Voronoi structures

Mechanics of biopolymer aerogels based on microstructures generated from 2-d Voronoi tessellations

In this paper, the heterogeneous morphology of biopolymer aerogels is described using a 2-d Voronoi tessellation, which accounts for the randomized cell shapes of aerogels and adheres to the pore-size distributions obtained from experimental data. Accordingly, a two-dimensional periodic representative volume element (RVE) has been generated and simulated under compression. In particular, the sensitivity of the varying microstructural parameters within the RVE is analyzed. It is realized that the fiber diameter, the pore-size distribution, and the density of the cells within the aerogel network show a significant influence on their mechanical response. The trends of the model predictions are qualitatively in good agreement with the macroscopic experimental data of biopolymer aerogels