SAMPE Journal - July/August 2022 - 70

FEATURE / INVESTIGATION ON MATERIAL EQUIVALENCY
the butt splice positions as uniform as possible in
the laminate. An optimization algorithm is used
to optimize the patch overlaps8
. Each layer with its
subsequent sublayers of same fiber orientation is
created and optimized with a minimum overlap
preset by the user. Figure 7 shows an exemplary
optimized layer configuration with non-repeating
butt splices in thickness direction based on four
sublayers.
The quality of each patch overlap can be
Figure 6. Left: Marker with patches representing corners of the plate
dimension.
Right: Visualization of patch overlap quality using a modeled 45° layer.
Figure 7. Cross section of an overlap optimized patch layer with nonrepeating
butt splices in thickness direction.
visualized using a color plot (see Figure 6 right).
However, an offset in lateral direction is not part
of an optimization, but the layers are shifted to
each other based on the tape width divided by the
number of layers with same fiber orientation.
The associated machine data are created using
the CAM-module MOTION ARTIST. Figure 8 shows
a plane table mounted on the 6-axis robot in order
to deposit patches on it by a Scara robot. The
table is moving during the production to ensure
optimal accessibility and collision-free movement
of the two interacting robots. The output results in
machine data for the patch-based manufacturing.
Figure 8. Offline robot programming with MOTION
ARTIST generating machine data for laminate
manufacturing.
Figure 8. Offline robot programming with
MOTION ARTIST generating machine data for
laminate manufacturing.
is aimed at a patch length which is approximately
half the clamping distance of the specimen based
on the tensile test method. In conclusion, a patch
length of 65 mm is chosen. The width is obtained
based on design criteria for patch-based laminates,
according to which the patch length should be at
least twice the width. Therefore, the patch width
results in 30 mm. Mechanical properties are
influenced, among other things, by the distribution
of butt splices. A local accumulation of such butt
splices in thickness direction can lead to high
stress concentrations, which reduces the resulting
strength. Therefore, it is appropriate to distribute
70 | SAMPE JOURNAL | JULY AUGUST 2022
MANUFACTURING OF SPECIMENS
The manufacturing of specimens required flat
plate laminates in order to cut out all test coupons.
The conventional laminates with endless fibers are
built-up manually, i.e. each layer is stacked on top
of each other, whereas the patch-based laminates
are produced with the SAMBA Pro production
system. Before the manufacturing starts, the
material for SAMBA Pro is slitted to a width of 30
mm. With a tape available, the machine data is
loaded into the machine to start the production.
For consolidation of the manufactured prepreg
laminates the autoclave process is used based on
the curing cycle according to the HexPly 8552®
product data sheet for monolithic components (1st
plateau of 60 min. at 110°C and 7.0 bar, 2nd
plateau
of 120 min at 180°C and 7.0 bar, see Figure 9).
Tabs are applied onto the coupons only for the
appropriate test methods. After the curing process,
the specimens are cut out using a water-cooled saw
followed by drilling for the notched specimens. The
tools are equipped with polycrystalline diamond
(PDC) cutting edges ensuring high quality edges.
TEST RESULTS
The environmental conditions during the tests
measured a temperature of 21°C and a relative
humidity of 65 %. Six samples were used per test
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SAMPE Journal - July/August 2022

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