JEC COMPOSITES MAGAZINE - Issue #131 - Novembre/December 2019 - 39

Fast-curing epoxy prepreg system for automated processes with short cycle times

joining processes in the later phases of
automotive production. A Tg of 165°C
can even be achieved with a special formulation. The typical curing cycle in a press
is 8 minutes at 140°C and a minimum
pressure of 6 bar. A further advantage of
the resin system is its service life of up to
21 days when stored in an air-conditioned
room (21°C).
The resin's higher viscosity is required
to prevent it from being rinsed out of
the mould during the high pressure and
temperature rise in the rapid cure cycle.
The stickiness of the prepreg is adapted to
the customer's requirements to facilitate
processing and handling. The prepreg's
low tack allows easier and faster stacking
of the prepreg layers and opens up the
possibility of process automation early in
the production cycle. Another important
feature of this specific resin system is
the "hot in/hot out" function, which
simplifies demoulding. This is crucial to
keep pace with the short-term processing
standard in the automotive industry.

Characteristic

Value

Name

CPO12

Cure temperature

120-180°C

Cure time

3-15 Min

Pressure

2-6 Bar

Viscosity

High

TG

135°C/165°C

Shelf life

3 weeks @RT

Textile

UD/Fabric/MX/Scrim

Unlike other manufacturers, c-m-p gmbh
can supply the fast-curing semi-finished
product with various textiles, including
unidirectional or woven reinforcements,
and can thus react flexibly to specific
customer requirements.
Application example: the Porsche 911
GT3RS suspension system
Together with its partner Dongguan
Action Composites, c-m-p gmbh devel-

oped carbon fibre-reinforced composite
stabilizers for the front and rear axles of
the Porsche 911 GT3RS series (Figure 1).
These stabilizers are now used commercially, which means that for the first time
in a production vehicle, the stabilizers on
the front and rear axles as well as their
coupling rods are made of carbon. In 2018,
Dongguan Action Composites, together
with its partners Porsche AG, c-m-p gmbh,
KLK Motorsport GmbH, IAB GmbH,
FLURO-Gelenklager GmbH and Zund
Thailand, received a JEC Asia Award in the
Automotive category for this innovation.
The main advantage of the composite
material for this specific vehicle component is a weight saving of 55% compared
to the steel version. Dongguan Action
Composites, together with c-m-p gmbh,
was able to prove to Porsche AG that the
CFRP component is suitable for use as
a semi-structural component in the car
suspension system. Above all, the project
also confirmed that composite parts can
be manufactured according to the automotive industry's production standards.
The new high-speed prepreg compression
moulding process with the c-m-p resin
system allows a cycle time of less than 3
minutes. This makes it possible to produce
220 components per day, i.e. about 70,000
parts a year. This is a significant difference
with conventional matrix systems, where
the cycle time is 10 to 20 minutes, depending on the component size.
Prepreg pressing processes significantly reduce production cycle times
Pressing technologies are indispensable for
mass production in automotive engineering. The goal is to minimize cycle times.

With the autoclave technologies previously used, the manufacturing processes
were very complex, while being among
the most expensive and labour-intensive
processing methods. The production of
CFRP high-performance components was
therefore very labour- and resource-intensive and did not allow economical
production in large series. For this reason,
the automotive sector used primarily light
metals and high-strength steels, while
CFRPs' main area of application was niche
production: components for upmarket
vehicle classes, special models as well as
luxury and electric cars.
Compared to the established autoclave
process, rapid curing technologies have
several advantages. Depending on the
matrix material, Press Compression
Moulding (PCM) or Resin Transfer
Moulding (RTM) are used. PCM is
used for semi-finished products such
as those manufactured by c-m-p gmbh,
RTM is used for dry textiles that are not
pre-impregnated. Compared to autoclave
processes, both pressing processes enable
faster and more cost-effective production
of high-quality components. The high
process reliability and possible automation with little manual effort make these
solutions suitable for series production.
Hydraulic prepreg presses with heatable
dies achieve significantly shorter cycle
times than the autoclave process. In this
established method, manual assembly
takes longer and the heating and hardening cycle lasts up to 7 hours.
These significant advantages are offset by
relatively high investment costs for the
corresponding infrastructure and high
mould costs. In addition, not every geometry can be produced.

Feature Automotive

Main characteristics
of the epoxy resin system

Fig. 1: CFRP stabilizers on the front and rear axle

/ jec composites magazine

39

N°131 November - December 2019
JEC COMPOSITES MAGAZINE - Issue #131 - Novembre/December 2019

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