SAMPE Journal - May/June 2017 - 20

Feature Article
I. Swentek, B. Beck and V. Ugresic
Fraunhofer Project Centre for Composite Research at the Western University, Canada
T. Potyra
Zoltek Automotive, Toray International, Germany
F. Henning
Department of Polymer Engineering, Fraunhofer Institute for Chemical Technology ICT, Germany

Impact of HP-RTM Process Parameters on
Mechanical Properties with Epoxy and
Polyurethane Systems
Abstract
High pressure resin transfer molding is a method for processing continuous fiber reinforced composites at industrial production
rates. This paper examines the more common HP-IRTM variant, where the 'I' stands for injection. To achieve a composite with
the best mechanical properties, a combination of the fiber, resin and processing parameters must be understood. Two different
matrix materials, epoxy and polyurethane, and two different fibers, glass and carbon, are processed on a KraussMaffei HP-RTM
system at the Fraunhofer Project Center in London, Ontario, Canada. Several processing parameters are investigated during the
manufacturing of these polymer matrix composites including the press force during injection, the press force during cure, and the
injection rate. Subsequently, the manufactured parts are characterized and their mechanical properties are evaluated. The results
of this study shed light on the critical properties and process settings in HP-RTM production.

Background
The effective use of composite
materials in structural automotive
applications
requires
robust
understanding of process-property
relationships. One major technology
used to manufacture structural
parts is high-pressure resin transfer
molding (HP-RTM) as it utilizes
continuous fibers in a stitched or
woven fabric form.
Resin transfer molding has long
been used to create structural
composites. The main drawback of
the process is the long infusion time
coupled with a slow cure reaction.
Recently, high-pressure infusion
has been tested as a method to
dramatically reduce the cycle time,
as reported1,2. These past studies
have examined the different process
variants and the effect of pressure on
the resulting quality of the produced
material.
This paper continues the study of
the injection variant of high pressure
resin transfer molding process by
examining some of the influences
of the processing conditions on the
composite mechanical properties.
20

Two of the most common matrix
materials, epoxy and polyurethane,
are compared in a parametric study
of the main processing parameters:
the injection rate, the press force
during injection, and the press force
during cure.
To manufacture the samples, a
new KraussMaffei Rimstar 8/4/8
high-pressure RTM system at
Fraunhofer Project Centre (FPC) was
used. In this study 20, 40 and 60 g/s
injection flow rates used were used,
while the press forces were varied
between 1000-5000kN. The nominal
part thickness was 2.3 mm, while
the fiber volume fraction was set to a
target value of 60%.
The results of this study shed light
on the critical forming properties and
process settings required to attain
the peak performance. The influence
of processing parameters on the
material properties were determined
with this study.
Experimental Setup
The process flow of the highpressure injection RTM (HP-IRTM) is
similar to the standard RTM process.

The main difference is injection of
material system at high pressure
within a short period of time. The
high-pressure injection thus implies
that a significant amount of force
is required to maintain the mold
closed. In this process, the mold
remains completely closed before
the injection starts, thus defining the
fiber volume content and the final
part thickness. A preform is placed
into mold before closing. The major
impregnation of the preform is in the
direction of width and length (x-y
axis) and should be completed before
the reactive resin starts to cure. A
vacuum unit can be connected to
the mold to further improve the part
quality and to reduce the amount of
voids3. The main process steps of the
HP-IRTM cycle are shown in Figure
1.
The main advantage of HPIRTM, compared to the standard
RTM process, is the ability to use
fast curing resin systems. This is
particularly needed for high volume
productions of automotive parts.
However, high injection-pressure
and high flow rates can lead to "fiberSAMPE Journal, Volume 53, No. 3, May/June 2017



Table of Contents for the Digital Edition of SAMPE Journal - May/June 2017

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