SAMPE Journal - November/December 2021 - 14

FEATURE / CONTINUOUS FIBER 3D PRINTING
of contact with the work, the fiber is compacted
with a user or process definable force where it is
simultaneously snap cured by a linearly variable
dose of UV light. Depending on the fiber and resin
combination as well as the initiation package, the
deposited material may be fully cured or B-staged
for end application full conversion methods.
CF3D®
end effectors have been deployed
on both articulated robotic arms and gantry
systems. The motion platform can impact several
capabilities of the system, including build volume,
speed, and accuracy. Continuous Composites
has worked with robotic and numerical control
manufactures as well as precision linear drive
component manufacturers to increase the
accuracy of integrated platforms. Using precision
laser trackers, scanners as well as both static and
dynamic compensation models, Continuous
Composites is approaching industry-leading
accuracy and repeatability in demonstration units.
High accuracy Numeric Controllers are being
utilized over traditional robotic controllers for
increased accuracy and repeatability.
Material Development
CF3D® relies on several different off-the-shelf and
custom material combinations to achieve target
end part performance and properties. The ability to
bring additive into a true 3D Euclidian coordinate
space is enabled, among other factors, by snap
curing photopolymer chemistry. Various matrix
solutions can offer several property optimization
combinations, including fillers and additives, to
augment capabilities including surface properties,
thermal attributes, and electromagnetic
susceptibility. Engineered matrix
solutions
are
being developed to support additional part types
involving phenolic, ceramic, and other atypical
matrix systems. These new material considerations
are enabling CF3D®
application in carbon-ceramic,
carbon-carbon and ceramic-ceramic composites.
To date, CF3D®
has been mostly deployed using
off the shelf fiber solutions including various grades
and sizes of carbon fiber, fiberglass, ceramic fibers,
aramid fibers (Kevlar, Spectra, Xylon, Dyneema),
as well as function fibers like conductive single
core wire, fiber optic cable, and exotic R&D
embedded electronic fibers. This expands the
potential for a wide array of end-user applications.
Carbon fiber and silicon carbide fiber, being black
bodies, absorb wavelengths used to cross-link
photopolymers. Polymers are in development that
harden through the surface of the fiber enough
to hold shape, but that require secondary full
conversion methods such as a thermal postcure
to complete polymerization. In addition to these
14 | SAMPE JOURNAL | NOVEMBER/DECEMBER 2021
polymers, new chemistries are in development that
propagate the reaction to achieve full depth of cure
at room temperature and do not require secondary
full conversion methods.
Through custom resin solution development
with Arkema®
and Sartomer®
combined with a
wide availability of various commercial fibers,
creating products with specific requirements
and enhanced functionality beyond traditional
composites is possible. As a result of the unique
material combinations and fiber orientation
introduced by CF3D®
not fully characterize CF3D®
Software Development
A new approach to software-driven analysis is
needed to leverage the possibilities of CF3D®
, standard ASTM tests may
.
.
Continuous Composites is developing the software
tools that drive CF3D®
- tools that consume material
properties, part geometry and required physical
characteristics to generate motion-platform
specific steered fiber tool paths. Unlike traditional
manufacturing techniques, CF3D®
composites are
composed of steered fibers that can be oriented to
maximize load distribution in specific directions.
This takes advantage of the principal strength axis
of high-performance fiber, without having to rely
solely on the strength of the underlying matrix. By
using techniques grounded in traditional FEA and
topology optimization, CF3D®
software analysis
incorporates physical, geometric, and material
characteristics to create and validate motion plans
for material deposition on a given part.
AEROSPACE APPLICATIONS
Transitioning a new process technology like CF3D®
into aerospace applications can be challenging
even when the technology offers clear cost and
performance advantages. Mature production
programs require considerable returns on
investment before
even considering
replacing
proven technologies. The ideal transition platform
for a new, low cost, composite process like CF3D®
,
would currently be in its conceptual design phase
and would benefit from CF3D®
features including
automation, tool-less processing, low cost raw
materials, and high rate material deposition. A
new vision for future military aircraft operations
championed by AFRL is providing just such an
opportunity.
Application to LCAA
In response to the increased proliferation of
advanced capabilities by adversaries, the US Air
Force has established a vision for a Low Cost
Attritable Aircraft (LCAA) program that calls for
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SAMPE Journal - November/December 2021

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