Microwave Heating for Manufacturing Carbon-Fiber Thermoplastics
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MICROWAVE HEATING FOR MANUFACTURING CARBON-FIBER THERMOPLASTICS A.C. LIND*,
L.N. MEDGYESI-MITSCHANG*,
J.E. KURZ**,
F.C. WEAR** *McDonnell Douglas Research Laboratories, **McDonnell Aircraft Company,
P.O.
H.F. MCKINNEY**,
P.O. Box 516,
Box 516,
St.
Louis,
St.
Louis,
AND
MO 63166
MO 63166
ABSTRACT
Traditionally, an
autoclave.
polymeric composite parts are heated and consolidated in
For
large
parts,
such as transport aircraft
submarine hulls, size becomes a limiting factor.
fuselages or
To overcome
this
limita-
tion and to reduce labor costs we are developing an automated tape placement process.
In this process we build composite parts one layer at a time
tape containing carbon fibers impregnated with a thermoplastic. comes into contact with the part, and
apply
pressure
to
we apply heat to
melt
the
consolidate the tape to the part.
thermoplastic To support this
effort we have developed a proprietary microwave applicator that is for
rapidly
process. the
with
As the tape
suitable
heating carbon-fiber composites in an automated tape placement
Small carbon-fiber/poly(aryl-ether-ether-ketone)
microwave
applicator
(14.5 ksi), which is
have
interlaminar
shear
parts made
strengths
almost equal to the 103 MPa (15.0 ksi)
using
of 100 MPa
obtained
using
an autoclave.
INTRODUCTION
Traditionally, techniques. becomes
a
composite
For large parts such limiting factor.
parts as
have
been
transport
formed
using
aircraft
will
build
composite
size
Tape placement employing microwave heating has
been proposed as an alternative to autoclave consolidation. we
autoclave
fuselages,
parts
one
In
this proclss
layer at a time with tape containing
carbon fibers impregnated with a thermoplastic.
As
the
tape
comes
into
contact with the part, we will apply microwaves to heat and melt the thermoplastic and apply pressure to consolidate the tape to the part, Figure
1.
as shown
in
One or more infrared temperature sensors will be used to control
the microwave power to the applicator. The
use of electromagnetic
energy in
the microwave frequency range has
been explored as an energy source for the consolidation posite
materials
in
and
numerous studies over the past decade.
Mat. Res. Soc. Symp. Proc. Vol. 189. 01991 Materials Research Society
cure
of
com-
Perceived ad-
462
-6. Microwave eaergy source 3. Microwave applicator head 7. Infrared temperature sensor
-
-.
Carbon-fiber/
4. Compaction5.
throlsi tape
Figure 1. Concept drawing; showing use of a microwave applicator in a tape-placement part forming device. vantages are more efficient energy use [1,2], and adaptability to artificial
A variety of waveguide and cavity unsuccessfully als (4]. is
parallel
cross aligned fibers, there is
(3]
microwave
applicators
have
been
tried
to heat continuous carbon fiber reinforced composite materi-
The principal impediment is
polarized
shorter processing cycles
intelligence control of the processing cycle.
that when the incident electric
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