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New method for foam-���lled honeycomb
Foam-filling via curtain coating
source: m.c. gill
a unique system for filling honeycomb
with foam was presented by m.c. gill (el
monte, calif.). called gillfists, it features
a liquid coating applied by a curtaincoating apparatus (below) to ensure that
it uniformly coats the honeycomb���s cell
surfaces.
During a subsequent thermal process (standard to
processing), the coating foams and fills the cells. the
foam can be pre-expanded for use in applications
such as Vartm or dried at a lower temperature and
stored for thermal foam-fill processing at a later date.
Said to be extremely damage tolerant, HexMC can be molded into a variety of geometries, reported Bruno
Boursier, Hexcel���s R&T; manager. Attainable shapes include sharp angles, deep
draws, box corners, curves and gussets.
Tension, compression and ���exure moduli are 90-plus percent that of quasi-isotropic UD tapes, but in-plane strength
drops to 50 percent.
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Hexcel has developed proprietary
mold designs and processes that it says
will preserve the transverse isotropy of
the HexMC material in critical areas of
parts and ensure minimum ���ber distortion. Currently, a special epoxy formulation is used for parts that need to comply
with FST requirements (but not heat-release requirements) of FAR 25. A structural thermoset formulation that will
high-performance composites
source: m.c. gill
Tailorable foam expansion
meet FAR 25 OSU requirements (65/65
heat release) can be produced, but it will
not perform as well for OSU as thermoplastics, explained Boursier, who sees
OSU as the factor that currently limits
HexMC use in interior applications.
Also of interest was a presentation
on recycled carbon ���ber given by Jim
Stike, CEO, Materials Innovation Technologies-RCF (MIT-RCF, Lake City, S.C.).