CarbonMide carbon fiber-reinforced LS composite, with a greater
concentration of fibers aligned on the X axis.
In order to minimize the inconsistencies to move toward
isotropic reinforcement, the orientations of the fibers need to be
more evenly distributed throughout the part.
LS material developers are discovering new methods for
producing LS carbon fiber composites that randomly orient the
fibers throughout X, Y, and Z to achieve better isotropy. One
method is encapsulating the fiber within the plastic particles
which has shown significant improvements in fiber orientation
distribution (Fig. 2).
The carbon fibers are encapsulated in the plastic in varying
orientations to prevent them from aligning with the recoating
blade along the X axis. As the laser hits the powder, the particles
are spread in every direction in the melt pool (Fig. 3a). A
micrograph of a cross-section of a finished part reveals carbon
fibers oriented randomly in and out of the plane (Fig. 3b).
The result is more uniform reinforcement. The table below
shows a comparison between EOS CarbonMide, a dry-blended
carbon fiber-reinforced LS composite, and EOS HP11-30, an
encapsulated carbon fiber-reinforced LS composite. While both
materials use a Nylon 12 as their base polymer, the method
of carbon fiber reinforcing creates a notable difference in
DEVELOPING AN ISOTROPIC HIGH-PERFORMANCE THERMOPLASTIC
While isotropy is universally beneficial for all applications, it’s
in high demand for functional end-use applications in aerospace,
transportation, and energy. The Boeing Company recognized
a gap in isotropic LS materials for advanced applications and
approached EOS, a manufacturer of LS systems; ALM, the
materials development arm of EOS NA; and Stratasys Direct
Manufacturing, one of Boeing’s additive manufacturing service
providers. The companies formed a team to develop an isotropic
reinforced high performance LS thermoplastic.
PEKK (polyetherketoneketone) is a semi-crystalline
thermoplastic from the polyaryletherketone (PAEK) family with
high heat deflection temperature, excellent chemical resistance,
and strong mechanical properties. While most LS materials
require a heavy molecular additive to achieve flame retardancy,
PEKK is naturally flame retardant and lightweight.
ALM formulated PEKK for LS with encapsulated carbon fibers
to run on a EOSINT P 800 machine. EOS provided hardware
and software modifications to its standard EOSINT P 800
machine as well as optimized process parameters in order to
process the carbon fiber reinforced PEKK and account for the
unique material processing challenges. After EOS pinpointed
the initial machine modifications, Stratasys Direct Manufacturing
and The Boeing Company began testing the new material and
process. The table below shows normalized data comparing
carbon fiber encapsulated PEKK (HT- 23), carbon fiber
encapsulated Nylon 11 (HP11-30), and flame retardant Nylon
11 (FR-106). HT- 23 exhibits isotropic properties combined
with improved strength, stiffness, flame retardancy, and glass
The team is continuing to test and validate encapsulated
carbon fiber PEKK for LS and has already used some parts
for Boeing’s ecoDemonstrator program, which tests new
technologies to reduce aviation’s environmental impact.
Figure 2: Encapsulated carbon fiber composite (a). A single powder particle with
encapsulated carbon fiber (b). Images courtesy of EOS.
Figure 3: Encapsulated carbon fibers during (a) and after laser sintering (b).
Images courtesy of EOS.
Table 2: Courtesy of Stratasys Direct Manufacturing.
This article was written in partnership with Andreas Pfister,
Senior Scientist, EOS; Sybille Fischer, Material & Process
Developer, EOS; Rick Booth, Chemist, Advanced Laser
Materials; Brett Lyons, Product Development, Materials
Integration, Boeing; and Chris Robinson, 3DSIM.