Objectives

1
Objectives
Polishing
Optical Microscopy
Composite Processing
Microstructural Analysis
Micrographs of Carbon Composites Containing MP
Mesophase Pitch
Micrographs of Carbon Fibers Containing
Multi-Wall Nanotubes (MWNTs)
Concluding Remarks
PROCESSING AND MICROSTRUCTURAL ANALYSIS OF CARBON
COMPOSITES
Juri BassunerUNIVERSITY OF MISSOURI --
COLUMBIAErvis BezatiCOLUMBIA UNIVERSITYOrain
HibbertUNIVERSITY OF MASSACHUSETTS -- AMHERST

• Introduction

• Clear identification of orientation was possible
  at a radial/flow direction of 45/-45 relative
  to the polarizer-analyzer.
• Micrographs reveal three colors blue, yellow,
  magenta.

Carbon fibers and carbon-carbon composites are
advanced materials with unique properties.
Carbon-carbon composites have high thermal
conductivities and a low coefficient of thermal
expansion. The linear thermal expansion of
carbon-carbon composites is approximately 1.1 x
10 -6 C -1 and the thermal conductivity is
approximately 11.5 W/mK. Carbon-carbon materials
also have high tensile strength and modulus and
high chemical stability in inert environments.
These materials generally have a modulus of
elasticity greater than 69 GPa and an ultimate
tensile strength greater than 0.276 GPa. The
density of these materials is less than 2000 kg/m
3 and they have a melting point greater than 4100
C.
T-300 carbon fibers
Casting resin
Mesophase pitch
T-300 carbon fibers

• Processing of novel carbon composites from medium
  purity (MP) mesophase pitch (Mitsubishi Co.) and
  phenol formaldehyde (phenolic).
• Preparation of composite samples using the
  Buehler Ecomet 3000 grinder/polisher for
  microstructural analysis.
• Microstructural investigation of polished samples
  using the Olympus BX60 polarizing microscope with
  cross-polarizers and a first-order red plate.

• T-300 carbon fibers continuous, unidirectional
  and chopped, discontinuous
• Matrix phenol formaldehyde, medium purity (MP)
  mesophase pitch.
• Processing conditions MP mesophase pitch and
  T-300 carbon fibers -- 581 F and 5000 lbf or
  10000 lbf phenol formaldehyde and T-300 carbon
  fibers -- 332 F and 10000 lbf.

0 wt MWNTs
0.1 wt MWNTs
0.3 wt MWNTs
Carbon fibers containing 0.3 wt MWNTs have a
more randomized microstructure than those
containing 0 wt MWNTs.
1 in.
1 in.
1 in.
Epoxy tabs were cut using a hand saw.
Thereafter, samples of carbon fibers/carbon-carbon
composites were glued to the epoxy block.
The samples were embedded in mounting cups
using polyester resin and then placed in the oven
for approximately 12 hours. The solidified
samples were polished using the Buehler Ecomet
Grinder-Polisher. Polishing was done using grit
papers of increasing fineness.

• Compression molding proves to be an effective
  means of cross-linking phenol formaldehyde
  matrices. However, more void spaces were detected
  in phenolic composites than in pitch composites.
• This project establishes a framework for future
  microscopy work and a more in-depth analysis of
  the microstructure of carbon fibers and
  carbon-carbon composites.
• Future work will determine how the orientation of
  carbon fibers changes the physical properties of
  the carbon-carbon composites.

Discontinuous and chopped
Continuous and unidirectional
Continuous and unidirectional
Polyester resin
Micrographs of T-300 carbon fibers compressed
with a phenol formaldehyde matrix
Mounting cup
Sample
Solid epoxy support
Carbon fibers
Void space in phenolic
Phenolic
Carbon fibers
Phenolic
Casting resin
Acknowledgements Dr. Amod Ogale, Clemson
University Rebecca Alway-Cooper and Daniel
Sweeney, Clemson University this work was
supported by the RET program at the National
Science Foundation, Award Number EEC-0602040.