Project Title:

A Controlled Interfacial Bond Strength Process for Carbon-Phenolic

04.02-2800
Project Title:A Controlled Interfacial Bond Strength Process for Carbon-Phenolic
and Carbon-Carbon Composites
Company:PDA Engineering
Santa Ana, CA 92705
Principal Investigator:H>M> Stoller

Abstract:

Carbon/phenolic composites suffer from low interfacial bond strengths, the result
of poor secondary bonding and the failure to develop covalent bonds at the fiber-matrix
interface.  The consequences are a composite material system with major limitations
due to low interfacial shear and transverse tensile strengths.  The conversion of
carbon/phenolic into a carbon/carbon material further reduces interfacial bond strengths.
 This limits the structural usages of carbon/carbon because of very low off-axis
mechanical properties.  Plasma treatment processes utilizing ammonia as a source
gas have demonstrated the capability of establishing reactive amine groups on aramid
and carbon fibers which can form covalent bonds with epoxy resins.  Mechanical testing
of the plasma-treated aramid/epoxy composites have demonstrated major increase in
off-axis mechanical properties and resistance to moisture absorption, confirming
the strengthening of interfacial bonds.  The feasibility of improving the interfacial
bond strength of a carbon/phenolic composit through a plasma treatment process will
be investigated.  Water vapor will be the plasma source gas to provide hydroxyls
for surface deposition on the carbon fibers.  The ability to control the hydroxyl
group concentration as a function of plasma treatment condition will be investigated.
 Mechanical testing of composites and fracture surface morphology studies will indicate
the degree of covalent bonding attained.  Maintenance of the covalent bonding through
a carbon/phenolic carbonization cycle will also be addressed via mechanical testing.