The
objective of many hundreds of such computations is to develop
correlations which relate the permeability of unidirectional fibrous
media to their microstructure. This involves differentiating between
various hard-core arrays (currently lumped together under the heading
"random") as well as identifying the exact point in microstructure
evolution at which a fibrous medium's resistance to flow is
significantly affected by clustering. A large part of this effort
involves proposing and testing microstructural metrics that correlate
with the observed trends in permeability.
Figure 1:
Speed contours of creeping flow across unidirectional fiber arrays
assuming regular (upper left), hard-core (upper right and lower left)
and clustered (lower right) spatial distributions. The computations
were carried out using an in-house boundary element code [X. Chen, PhD
Thesis, 2005].
Figure 2:
Speed contour during creeping flow across a disordered unidirectional
fiber array consisting of 900 individual filaments. The simulation was
carried out on Loslobos (an IBM cluster) at the High Performance
Computing Center at the University of New Mexico, using a parallel
version of an in-house boundary element code. This research is
currently co-sponsored by NSF/DMII and by DOE/Automotive Lightweight
Materials program.
2. Stress Distribution in Transversely Loaded Continuous Fiber Composites
Figure 3:
Contours of first principal stress in transversely loaded continuous
fiber composites Uniform tensile loading is applied in the horizontal
direction.
Notice the difference between the
stress distribution in a square array (left) and the stress
distribution in an otherwise identical (in terms of constituent
properties and ratios) hard-core array (right). This research is
motivated by the need to quantify the stress enhancement caused by
microstructural variations and correlate it to quantitative measures of
the composite microstructure. (X. Chen and T. D. Papathanasiou, 2004).
3. A Master Curve for Permeability of Structured Dual-Porous Fibrous Assembly
Figure 4:
A large number of simulations in geometries describing deterministic
dual porosity fibrous media has revealed a relationship between the
geometry of the medium (expressed by Ks and Ktow in the above equation) and the permeability of the overall medium (Kp) [T. D. Papathanasiou, 2001].
