SAMPE Journal - November/December 2021 - 62

FEATURE / STRUCTURAL COMPONENTS
of these products depend on the amount and
position of incorporated carbon fibers. For tensile
loading, increase in the fiber content results in
a linear dependency of the tensile modulus. The
experimentally obtained values are lower than
theoretically expected, in particular for products
with high fiber content. This was attributed to
imperfections in the printing process and possibly
poor packing of the fibers, leading to sample
thickness higher than designed along with porosity
inside the sample. No significant differences in
stiffness were found for different positions of
the fibers inside the samples, but it should be
noted that samples printed in sandwich layout
showed less deviations in the print geometry
than perimeter samples. For flexural modulus,
a larger deviation between experimental results
and numerical model was found, which seemed
to be irrespective of fiber content. Again, moduli
increased with fiber content, but in this case the
fiber layout had a much more pronounced effect. A
large difference was measured and also predicted
for flexural modulus when comparing sandwich
and perimeter layouts. For perimeter layout,
flexural modulus increased linearly with carbon
fiber fraction. In the case of sandwich layouts the
modulus is not only dependent of fiber volume fraction but also how the
sequence of filled layers are stacked. When the stacking sequence favors
filled layers further away from the center of the geometry the increase in the
modulus is higher than for perimeter layout with the same fiber content, while
the opposite is true when increasing carbon content by filling layers closer to
the midsection. Mechanical characterization of bicycle lugs showed that also
in 3D geometries good mechanical performance is obtained, reaching in first
trials over 50% of stiffness and strength of conventional products based on
thermoset composite with high fiber content. Further optimization of fiber
content, fiber layout and strength perpendicular to the fiber direction are
in progress, supported by numerical modeling, to further improve stiffness
and strength, as well as implementation of this design strategy in other 3D
structural components such as brackets to make full use of the potential to
produce lightweight parts.
ACKNOWLEDGMENTS
Part of this research was financially supported by the European Union
through the European Fund for Regional Development in the framework of
the innovation program OpZuid. This work was also financially supported by
the Province of Limburg.
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MicroGrid®
Lightning Strike Protection for
Carbon Fiber Aircraft, Blades & Structures
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AS9100:D Certified * Tested and Proven
Technology * www.dexmet.com * (203) 294-4440
For more information on Lightning Strike Technologies
Contact: Brett Macdonald * Email: BMacdonald@ppg.com
62 | SAMPE JOURNAL | NOVEMBER/DECEMBER 2021
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