Materials Testing
5 // Schematic diagram of
the thermoplastic
composite system and
obtaining technology
6 // Mechanical properties
increase of nanofilled
thermoplastic composite
hybrid system compared to
the unfilled hybrid system
7 // Mechanical properties
increase of nanofilled
thermoplastic composite
hybrid system compared to
the unfilled hybrid system
54 SHOWCASE 2020 \\ AEROSPACETESTINGINTERNATIONAL.COM
activation of the carbon fiber fabric by
chemical oxidation, highlights the
importance of the interaction between all
the phases of the ternary system. The
composites in which the phases were
compatible represent the substantial
growth or mechanical properties, showing
less destructive modes of yielding, where
the degree of delamination is very low.
HYBRID COMPOSITE QUALIFICATION
INCAS’s interest in this test campaign was
to evaluate the mechanical strength with
the increase of the nanofiller percentage.
In order to qualify the process, a series
of samples were tested, each of them
simulating a single selected loading
condition and analyzing the breaking
mode. The data obtained were compared
with the theoretical or the admissible data,
as appropriate.
The mechanical tests illustrate the
increase of the properties in both, tensile
and bending, with the increase of the
nanofiller percentage. 4% nanofiller
imposes increases of the resistance of
30-40% and of the module of 40-70%.
Following the study, it was observed
that the control sample yielded mainly by
delamination a phenomenon whose
incidence decreases with the increase of
the percentage of nanofillers in the matrix.
The samples with 4% nanofiller had a
main yield by tensioning the fiber, which
shows a more efficient transfer of loads in
the composite material.
Through a comparative study, the nonsilane
nanofiller determined an increase of
mechanical properties of about 20%
compared to the control sample. The use of
the silanized nanofiller results in a higher
growth, in traction having an
improvement of up to 30% whereas in
bending of 25% compared to the control
sample.
These results demonstrate that the
nanofiller surface silanization was
effective in its compatibilization with the
polymeric matrix.
Analyzing the breaking mode of the
samples based on modified fiber, it is
observed that the sample yielded
exclusively by tensioning the fibers,
without the appearance of delamination. It
was thus confirmed that the interface was
strengthened by the formation of
hydrogen bonds between the polymeric
matrix and the oxidized surface of the
carbon fiber.
The test results illustrate the positive
effect of the addition of nanofiller in the
thermoplastic polymer matrix on the
properties of carbon fiber hybrid
composites. The nanofiller has the role of
stiffening the matrix – a more resistant
matrix is able to take on a greater amount
of mechanical loading and therefore
improves the properties of the composite
materials as a whole.
The need to develop materials that can
operate under severe conditions is
increasing with accelerated technological
development and the demand for efficiency
in the energy, transport and aerospace
sectors. Hybrid polymeric composites that
use reliable and low cost manufacturing
technology could be a future solution for a
new aerospace reality. \\
Dr. Phys. Adriana Stefan is head of advanced
materials and tribology at INCAS
fiber, chemically compatible with the
polymeric matrix, can increase the
mechanical strength but can also improve
their tribological properties.
INCAS studied the modification of the
fiber surface using an oxidation medium
compatible with the polymeric matrix
used. Morpho-structural analyzes
highlight both, the change of the surface
roughness and the presence of functional
groups. The SEM (electronic scanning
microscopy) analysis showed that the
modification of the fiber surface had a
positive effect on the interface area
between the carbon fiber and the
polymeric matrix. A reactivity of the
surface was observed by the creation of
micro-pores or adherent areas on the
surface of the carbon fiber fabric filaments.
By forming these areas, the number of
contact points on the surface of the
filaments increases, thus increasing the
adhesion to the matrix from a physical
point of view. In conclusion, the chemical
treatment changes the morphology and
increases the roughness of the fiber
surface. In this way, adhesion is improved
by increasing the wettability of the
filament surfaces by the polymeric matrix.
The method of modifying carbon fiber
is simple and efficient, it can be used on a
large scale with an indicative importance
for industrial production. The interfacial
adhesion strength between the fiber and
the matrix greatly affects the properties of
the carbon fiber (CF)–reinforced composite.
Through an extensive study, the used
nanofiller was silanized in an ethanol /
water medium at 75°C, to functionalize the
grouped surface of the area with groups
that can interact with the thermoplastic
matrix groups.
The compatibilizing phase of the
elements with the polymeric matrix
consist of nanofiller silanization and
5
6 7
/AEROSPACETESTINGINTERNATIONAL.COM