Computational and Topological Modeling of Mesophase Computational and Topological Modeling of Mesophase Carbon Composites 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 o er arrangements, (2) processing flows , and (3) wetting and interfacial anch sophase Pitch : polycyclic aromatics with viscoelastic anisotropic discotic nematic phase; 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 Key Characteristics 1. Orientation 2. Defect density 3. Anchoring 1. Fiber arrangements (topology) Array strength Core Structur e Triangul ar Square Pentagon al Hexagona l -1/2 -1 -3/2 -2 Singular Escape Singular Escape 2. Liquid Crystal Coating Flows (collaboration with M. Srinivasarao (Georgia Tech) Soft Matter 5, 2277, 2009)) 3. Wetting and Anchoring on Fiber Bundl Theory shows that the defect charge around N fibers is –(N-2)/2. n Coating thickness:h V/ isotropic:n 2/3,liquidcrystal:n 1 Anisotropic fluids have cross couplings. Shear deformation creates extensional stress! 2 1 /8 0 c c LCb f LC ib LS r L:elastic constant S:order parameter rf:fiber radius LC:inter. tensiom c LCb : c LC critical LC spreading parameter : c i critical isotropic spreading parameter Liquid crystals always wet fiber bundles. The critical spreadin parameter is larger for LCs than for isotropic fluids.

Computational and Topological Modeling of Mesophase Carbon Composites

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Key Characteristics Orientation Defect density Anchoring. Computational and Topological Modeling of Mesophase Carbon Composites. Alejandro D. Rey, Dept. of Chemical Engineering, McGill University, Montreal, Quebec, Canada H3A2B2. - PowerPoint PPT Presentation

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Page 1: Computational and Topological Modeling of Mesophase Carbon Composites

Computational and Topological Modeling of Mesophase Carbon CompositesComputational and Topological Modeling of Mesophase Carbon CompositesAlejandro 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 CharacteristicsKey Characteristics1. Orientation

2. Defect density

3. Anchoring

1. Fiber arrangements (topology)

Array strength Core

Structure

TriangularSquarePentagonalHexagonal

-1/2-1-3/2-2

SingularEscapeSingularEscape

2. Liquid Crystal Coating Flows(collaboration with M. Srinivasarao (Georgia Tech)Soft Matter 5, 2277, 2009))

3. Wetting and Anchoring on Fiber Bundles

Theory shows that the defect charge around N fibers is –(N-2)/2.