SAMPE Journal - July/August 2016 - 7

Feature Article
Process Selection and Optimization for
Out-of-Autoclave Prepreg Structures
C. Ridgard
Cytec Aerospace Materials, Tulsa, OK
Abstract
Out-of-autoclave (OOA) or vacuum bag only (VBO) prepregs depend on the physical extraction of entrapped air and volatiles to
achieve low levels of porosity, a tim e dependent process. Strategies for minimizing the total cure duration are discussed in several
scenarios including cures completed exclusively in-tool, cures in which part of the process involves a freestanding postcure after
demolding and sandwich parts in which the characteristics of both the prepreg and the film adhesive need to be considered. The use
of short 'super-ambient' temperature dwells to replace previously used long dwells at room temperature is a focus of current work.
Kinetic models provide a powerful tool in the development of optimum process conditions and examples involving CYCOM® 5320-1
prepreg and FM®309-1 adhesive are discussed.
Introduction
Prepregs capable of being processed by nonautoclave techniques such as vacuum bag oven
curing, have been developed over the last two
decades and the latest generation systems now offer
comparable part quality and mechanical performance
to those of traditional autoclave materials. Materials
such as CYCOM® 5320-1 have been successfully
used to manufacture large structures1,2, however
much of the reported work had been carried out
under developmental programs and has involved
prototype or limited production parts. The cure cycles
used to produce such parts often involved long, low
temperature cure cycles on low cost tooling followed
by demolding and a freestanding postcure to develop
an acceptable degree of cure and optimum properties.
In addition, a 16 hour or more vacuum dwell at room
temperature has been a feature of much of the
published work. The use of such long cure cycles
in the published literature has inevitably created the
perception that the cure cycles for VBO prepregs are
of necessity long and therefore unsuitable for rate
production. Recent work involving the use of short
low temperature 'super-ambient' dwells to replace the
long room temperature dwell has shown this not to be
the case and significantly shortened cure cycles are
possible without compromising laminate quality. This
paper explores the types of VBO process and cure
cycles appropriate for both limited production parts
and rate production parts respectively. Kinetic models
such as those supplied with the Raven® software
available from Convergent Manufacturing Technologies
are powerful tools which can aid in the development of
application specific cure cycles, particularly in cases
where the structure contains more than one material,
such as a prepreg and a film adhesive, each with
different processing characteristics.
SAMPE Journal, Volume 52, No. 4, July/August 2016

Basic VBO Processing for Monolithic
Laminate Parts
Laminate Quality, Air and Volatile Extraction, Prepreg Breathing
Characteristics
Prepreg materials designed for VBO processing in
general have dry fiber paths or evacuation channels
designed to extract entrapped air and any volatiles
dissolved within the resin such as moisture. The
materials inherently 'breathe' more readily in the

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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
SAMPE Journal - July/August 2016 - 13
SAMPE Journal - July/August 2016 - 14
SAMPE Journal - July/August 2016 - 15
SAMPE Journal - July/August 2016 - 16
SAMPE Journal - July/August 2016 - 17
SAMPE Journal - July/August 2016 - 18
SAMPE Journal - July/August 2016 - 19
SAMPE Journal - July/August 2016 - 20
SAMPE Journal - July/August 2016 - 21
SAMPE Journal - July/August 2016 - 22
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SAMPE Journal - July/August 2016 - 25
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SAMPE Journal - July/August 2016 - 27
SAMPE Journal - July/August 2016 - 28
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SAMPE Journal - July/August 2016 - Cover3
SAMPE Journal - July/August 2016 - Cover4
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