1. Computational and Topological Modeling of Mesophase Carbon Composites
Alejandro D. Rey, Dept. of Chemical Engineering, McGill University, Montreal, Quebec, Canada H3A2B2
Textures in mesophase pitch carbon/carbon fiber composites are a function of :
(1) fiber arrangements, (2) processing flows , and (3) wetting and interfacial anchoring.
Mesophase Pitch: polycyclic aromatics with
a viscoelastic anisotropic discotic nematic phase;
n is the average orientation.
C/C composites : carbon fibers randomly dispersed in a mesophase pitch are an example of anisotropic colloids. Inserting fibers into a liquid crystal creates a texture; the specific textural features depend on the topology of the fiber arranegement (see 1).
Key Characteristics
Orientation
Defect density
Anchoring
1. Fiber arrangements (topology)
2. Liquid Crystal Coating Flows
(collaboration with M. Srinivasarao (Georgia Tech)
Soft Matter 5, 2277, 2009))
3. Wetting and Anchoring on Fiber Bundles
Array
strength
Core Structure
Triangular
Square
Pentagonal
Hexagonal
-1/2 -1
-3/2 -2
Singular
Escape
L:elastic constant
S:order parameter
rf:fiber radius
gLC:inter. tensiom
Theory shows that the defect charge around
N fibers is –(N-2)/2.
Anisotropic fluids have cross couplings.
Shear deformation creates extensional stress!
Liquid crystals always wet fiber bundles. The critical spreading
parameter is larger for LCs than for isotropic fluids.