SAMPE Journal - July/August 2016 - 50

Feature Article
Rapid Out-of-Autoclave Composite Manufacturing
for Aerospace-Grade Prepregs
A. Haro, B. Lehman, K. Yoshioka, F. N. Nguyen
Toray Composites (America), Inc., Tacoma, WA

B. Luedtke, D. Brosius
Quickstep Composites LLC, Dayton, OH

Abstract
Current state-of-the-art composite manufacturing technologies developed for dual-aisle aircraft are limited to a low volume by
an exclusive use of an autoclave molding method. This method is both time-intensive and costly. Future composite aerospace
applications for primary and secondary aircraft structures could demand a rapid part production rate with void-free quality in addition
to exceptional performance. Notably, single-aisle aircraft would need innovative composite manufacturing technologies that are rapid
and cost competitive enough to compete with current metal alloy processes. Researchers at Toray Composites (America), Inc. have
investigated a rapid out-of-autoclave (OOA) molding method known as the Quickstep process. This process allows rapid heating/
cooling with moderate compaction pressures to fabricate composites from prepregs. Two commercially available aerospace prepregs
were utilized in the present study for a comparison among Quickstep, vacuum bag only (VBO) and autoclave. A non-interlayer
toughened system demonstrated more than 50% total cycle time reduction compared to VBO and autoclave. In addition, a low void
content of less than 1% was achieved with comparable mechanical properties to those from autoclave cure. On the other hand,
an interlayer toughened system showed a marginal reduction in total cycle time but achieved void content of less than 2% and
comparable mechanical properties to those from autoclave cure as well.
Introduction
The autoclave process is well established to
build today's composite aircraft producing high
quality aircraft structures. However, it lacks the
processing speeds needed to serve the future
single aisle aircraft market. Alternative OOA
processing technologies have been investigated
for their viabilities in rapidly producing high quality
composite structures as well as cost effective ones.
VBO processes consisting of curing with a thermal
oven have low ramp rate capabilities and require a
vacuum pump to make aerospace and space quality
composites1-3. However, as part sizes increase,
achieving a desired void content and proper
consistency has been a challenge due to edge
breathing. In addition, cycle time often exceeds
even that of autoclave processing due to long prevacuum times (PVT). These limitations make VBO
infeasible as an alternative method for producing
large composite parts at a high production rate. In
consideration of the foregoing challenges in VBO,
an alternative rapid OOA molding method known
as Quickstep (QS)4-6 with much faster ramp rates
for part fabrication was introduced. Rates as high
as 40°C/min have been achieved. The high heat
transfer rate allowed a lower minimum viscosity of
the resin to be obtained than that observed with a
slower oven heat-up rate. In addition, the weight
of a heating fluid exerted on a material to be cured
provided an additional compaction pressure. As a
result, reaching full consolidation was obtainable,
i.e., a low void content, even at low applied
50

pressures. Furthermore, the PVT before ramping
up was significantly reduced or eliminated. Yet, the
Quickstep process might face a challenge when
used to mold an interlayer toughened prepreg as
the toughening material typically blocks air paths in
both xy plane and z-direction. One solution as done
in VBO is to stage the composite at an intermediate
temperature for a period of time before a final cure
temperature to allow trapped air and volatiles to
be depressed into the resin and/or removed by
vacuum. As a result, cure cycle time increases
but could be optimized to be much less than that
from VBO, owning to faster ramp rates and higher
compaction pressures.
To further investigate the viability of the
Quickstep process for composite manufacturing,
in this study two commercially available prepregs
from Toray Composites (America), Inc., viz., a noninterlayer toughened prepreg (P711AG-15) and
an interlayer toughened prepreg (P2352W-19),
were selected. A series of Quickstep processing
experiments for each prepreg was demonstrated,
and the results of which are presented herein. An
equivalency comparison for cycle time reduction,
laminate quality, and mechanical properties will be
discussed.
Experimentation
Materials
Two commercially available aerospace grade
unidirectional (UD) prepregs manufactured by
Toray Composites (America) Inc. were utilized for
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
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SAMPE Journal - July/August 2016 - Cover3
SAMPE Journal - July/August 2016 - Cover4
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