SAMPE Journal - January/February 2023 - 61

better control of consolidation force and pressure
during printing and would allow for high aspect
ratio stiffener beam samples to be produced with
more consistent quality through their height. Such
a system could be used to better determine the
relationships between the consolidation force, the
consolidation pressure, and the void content of
printed layers.
FUTURE WORK
Continued research is underway on the composite
placement system to improve the quality of
manufactured high aspect ratio stiffener beams.
Future work with the composite placement
system includes the investigation of methods or
mechanisms to improve the quality of print layer
edges as well as the implementation of a feedbackcontrolled
consolidation force system which would
supply the means for a more accurate analysis of
the relationship between consolidation force per
layer and composite quality.
CONCLUSIONS
This study demonstrates that the use of the
composite placement system for the manufacture
of high aspect ratio grid stiffener beams with
radically reduced tooling is effective. 80 layers of
tow were able to be placed one on top of another
without sagging or lateral deviations. The quality
of grid stiffener beam samples was evaluated in
terms of constituent volume fraction data as well
as through micrograph analysis. Average fiber
and void volume fractions determined by burn
off tests suggested little variation over the height
of the 80-layer beams. However, micrograph
inspection and consolidation force data told a
different story, indicating an increase in void
concentration, within the center of the tow, with
increasing distance from the build surface. Thus,
it is clear that future efforts must focus on directly
utilizing measured consolidation information, in
the control of the placement head, to maintain
uniform layer thickness and to generate a minimal
void fraction variation through the thickness.
ACKNOWLEDGMENT
This material is based upon work supported by
the U.S. Department of Energy's Office of Energy
Efficiency and Renewable Energy (EERE) under
the Advanced Manufacturing Office, Award
Number DE-EE0009404. The views expressed
herein do not necessarily represent the views of
the U.S. Department of Energy or the United States
Government.
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