SAMPE Journal - July/August 2016 - 14

Feature Article

Figure 9. Comparison of CYCOM 5320-1
and FM309 for a typical 177°C
in-tool cure cycle.

Since the cure is conducted with the part supported
by a tool and under a vacuum bag throughout, the
fact that both materials effectively gel and achieve
an acceptable Tg only after 177°C has been reached
is acceptable.
Conclusions
Out of autoclave (OOA) or vacuum bag only (VBO)
prepregs such as CYCOM 5320-1 or MTM45-1
depend on the physical extraction of entrapped air
and volatiles to achieve low levels of porosity. In such
latest generation resin systems the principal volatile
is usually atmospheric moisture, which while present
at a low percentage in terms of weight, can provide
a significant volume and potential source of porosity
when in gaseous form. The principal extraction of
entrapped air and volatiles in VBO parts is via the
laminate edge because of the inherent permeability
characteristics of the uncured materials although
some through thickness transport has to take place
to evacuate internally terminated plies.
The use of relatively long cure cycles reported in
the published literature for developmental prototype
parts has created a possibly erroneous impression
that VBO cure cycles are of necessity long compared
with those used for autoclave cured parts. Cure
cycles conducted exclusively with the part supported
within a high temperature tool significantly shorten
the cure cycle duration to a point where part
production rates are comparable to those of those
made from autoclave cured materials. In addition, the
use of short 'super-ambient' dwells has been shown
14

to remove the need for the 16 hour or longer room
temperature dwells that some have used to achieve
the optimum part quality.
For the CYCOM 5320-1 prepreg system, an in-tool
VBO cure involving a 2 hour dwell at 121°C plus a
two hour dwell at 177°C has been demonstrated to
be an effective and efficient production cure cycle.
The addition of a super-ambient dwell in the range of
50°C to 60°C to this cure cycle should be considered
for large parts. The amount of time required for the
super-ambient dwell at 50°C or 60°C is the subject
of a current investigation; 4 hour dwells at these
temperatures have been effective in achieving
low levels of porosity however it is possible that a
significantly shorter super-ambient dwell time may
be sufficient. A further possibility for shortening the
cure cycle is the use of a super-ambient dwell while
eliminating the standard 121°C cure and ramping
straight to 177°C. Work is in progress to investigate
these production cure cycle optimization possibilities
and will be the subject of a future paper.
Cure cycles for CYCOM 5320-1 involving initial
cures at 93°C or 121°C followed by demolding and
a slow ramped postcure to 177°C have been used to
produce large parts. Raven kinetic models for these
established cure cycles indicate that these cure
cycles do slightly deviate from the guidelines of not
exceeding the Tg during the postcure and ensuring
at least a 50% degree of cure prior to demolding,
but are nonetheless successful and have been used
for prototype and limited production parts.
Prepreg based on ultra-high modulus fibers
SAMPE Journal, Volume 52, No. 4, July/August 2016



Table of Contents for the Digital Edition of SAMPE Journal - July/August 2016

Contents
SAMPE Journal - July/August 2016 - Cover1
SAMPE Journal - July/August 2016 - Cover2
SAMPE Journal - July/August 2016 - Contents
SAMPE Journal - July/August 2016 - 2
SAMPE Journal - July/August 2016 - 3
SAMPE Journal - July/August 2016 - 4
SAMPE Journal - July/August 2016 - 5
SAMPE Journal - July/August 2016 - 6
SAMPE Journal - July/August 2016 - 7
SAMPE Journal - July/August 2016 - 8
SAMPE Journal - July/August 2016 - 9
SAMPE Journal - July/August 2016 - 10
SAMPE Journal - July/August 2016 - 11
SAMPE Journal - July/August 2016 - 12
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SAMPE Journal - July/August 2016 - 14
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