Alsayednoor, Jafar
(2013)
Modelling and characterisation of porous materials.
PhD thesis, University of Glasgow.
Full text available as:
Abstract
Porous materials possessing random microstructures exist in both organic (e.g.
polymer foam, bone) and in-organic (e.g. silica aerogels) forms. Foams and
aerogels are two such materials with numerous engineering and scientific
applications such as light-weight cores in sandwich structures, packaging, impact
and crash structures, filters, catalysts and thermal and electrical insulators. As
such, design and manufacture using these materials is an important task that can
benefit significantly from the use of computer aided engineering tools. With the
increase in computational power, multi-scale modelling is fast becoming a
powerful and increasingly relevant computational technique. Ultimately, the aim is
to employ this technique to decrease the time and cost of experimental
mechanical characterisation and also to optimise material microstructures. Both
these goals can be achieved through the use of multi-scale modelling to predict
the macro-mechanical behaviour of porous materials from their microstructural
morphologies, and the constituent materials from which they are made. The aim of
this work is to create novel software capable of generating realistic randomly
micro-structured material models, for convenient import into commercial finite
element software. An important aspect is computational efficiency and all
techniques are developed paying close attention to the computation time required
by the final finite element simulations. Existing methods are reviewed and where
required, new techniques are devised. The research extensively employs the
concept of the Representative Volume Element (RVE), and a Periodic Boundary
Condition (PBC) is used in conjunction with the RVEs to obtain a volume-averaged
mechanical response of the bulk material from the micro-scale. Numerical
methods such as Voronoi, Voronoi-Laguerre and Diffusion Limited Cluster-Cluster
Aggregation are all employed in generating the microstructures, and where
necessary, enhanced in order to create a wide variety of realistic microstructural
morphologies, including mono-disperse, polydisperse and isotropic microstructures
(relevant to gas-expanded foam materials) as well as diffusion-based
microstructures (relevant for aerogels). Methods of performing large strain
simulations of foams microstructures, up to and beyond the onset strain of densification are developed and the dependence of mechanical response on the
size of an RVE is considered. Both mechanical and morphological analysis of the
RVEs is performed in order to investigate the relationship between mechanical
response and internal microstructural morphology of the RVE. The majority of the
investigation is limited to 2-d models though the work culminates in extending the
methods to consider 3-d microstructures.
Actions (login required)
 |
View Item |
Download Statistics
Download Statistics