SAMPE Journal - March/April 2017 - 38

Feature Article
of the Company SAERTEX GmbH &
Co. KG, Saerbeck, Germany, with an
areal weight of 248 g/m² was used.
In total, 12 single unidirectional
layer of this material were used for
one preform with the orientations
[0° / 90° / 0°]4. The used chopped
strands mat was provided from the
Company Owens Corning, Battice,
Belgium. The chopped strands mat
from the type M123 375, has an areal
weight of 375 g/m². In total, 8 layers
of the chopped strands mat were
used for each preform. All properties
of the comparative preforms are
summarized in Table 1.
RTM Part Manufacturing
The preforms were processed
to structural parts in a RTMprocess. Therefore, the preforms
are impregnated with the epoxy
resin system EPIKOTE Resin 05475
/ EPIKURE Curing Agent 05443
(Momentive Specialty Chemicals
GmbH, Duisburg, Germany) in a
RTM-mold with a cavity of 500 x

500 mm². To increase the laminate
quality a post pressure of 5 bar was
applied after the injection of the resin
system. During the injection and for
the curing, the mold was heated
isothermal to 80°C. Altogether, three
parts were manufactured from each
preform type.
Comparative Investigations
To get an objective comparison
of the mechanical properties of the
different parts, quasi static and
dynamic tests were carried out. In
this paper the flexural properties,
tensile properties, Charpy impact
properties and flexural properties
after impact are presented for each
preform type.
Determination of the Flexural Properties
The flexural properties were
determined according to DIN EN
ISO 14125. According the testing
standard, specimens with the
dimensions 60 x 15 x 3 mm³ were
prepared. The flexural properties

were determined parallel and
perpendicular to the aspired fiber
orientation. Five specimens were
tested in each direction to determine
the average and standard deviation
of the flexural strength and flexural
modulus.
Determination of the Tensile Properties
According to DIN EN ISO 527-4,
the tensile properties of the laminates
were determined. Therefore, five
specimens for each direction with
the dimensions 250 x 25 x 3 mm³
were prepared and tested. To
optimize the force transmission into
the specimens and to prevent the
specimens from slipping out of the
clamps of the testing machine, cap
strips were glued at both ends of the
specimens.
Determination of the Charpy Impact
Properties
To evaluate the material behavior
under dynamic stresses, the Charpy
impact properties were determined
according to DIN EN ISO 179.
Five specimens parallel and five
specimens perpendicular to the
aspired fiber orientation were tested
with an energy of 25 J. The specimens
have the dimensions 75 x 15 x 3 mm³.
Determination of the Flexural Properties
After Impact
Another important mechanical
parameter of FRP is the mechanical
behavior after impacts. Commonly
the
compression
strength
of
specimens with an impact damage
are
determined
to
analyze
the mechanical behavior after
impacts. The determination of
the compression strength of the
manufactured laminates is not
possible. Investigations on the
compression strength of specimens
without impact failures show, that
the specimens tend to buckling.
This failure do not allow for getting
objective results for the compression
properties. Therefore, the flexural
properties of the laminates after
impact were determined13,14. For the
premature damage of the specimens,
150 x 100 x 3 mm³ sized specimens

38

SAMPE Journal, Volume 53, No. 2, March/April 2017
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