SAMPE Journal - March/April 2023 - 38

FEATURE / HYBRID COMPOSITES
Injection molding was selected as the
manufacturing technique in this study to produce
test specimens from composite (PA66/30CF/10AltF)
pellets, and a small-scale shredder/granulator was
employed as the mechanical recycling technique.
Once a material is shredded and granulated, it is
typically referred to as granulate. To understand
how varying the recycled content affects material
properties, three different formulations with
different recycled contents (33%, 67%, and 100%)
were created by dry blending virgin pellets with
granulate.
The three virgin pellet-granulate
blends were injection molded into test coupons
to assess how the amount of recycled content
affects mechanical and electrical conductivity
performance. A flow diagram of the processing or
recycling pathway is shown in Figure 1.
The processing/recycling pathway utilized in
this study was intended to mimic a likely pathway
that could be utilized by OEMs. Ultimately, the
recycling pathway and the process parameters
for each processing method will have an effect on
the final mechanical performance. For instance,
if the compression molding was substituted for
injection molding or if the screen mesh size was
changed on the shredder/granulator system, the
properties of PA66/30CF/10XF are expected to
change. Therefore, it is important to understand
the mechanisms by which the properties change
rather than simply identifying the percent change
in mechanical properties as the recycled content is
increased.
Utilization of these two strategies provides
OEMs the opportunity to increase certainty in their
CF supply chain that can ease demand and increase
the adoption of CFRPs beyond the aerospace
industry. Here, a CF-based hybrid composite
comprised of PA66/30CF/10AltF is employed to
show how replacing some CF content with an
alternative fiber and how utilizing recycled content
provides the opportunity to lower CF supply chain
risk, potentially decrease cost, and help develop
sustainable manufacturing practices. The potential
mechanisms that change the mechanical properties
as recycled content increase are discussed to allow
for application and understanding beyond the
recycling pathway utilized here.
EXPERIMENTATION
Material Procurement
PA66/30CF/10XF pellets were purchased from The
Materials Group (Rockford, MI). To produce the
pellets, neat PA66 pellets were compounded via
twin screw extrusion with CF and AltF to produce
pellets consisting of 30 wt% CF, 10 wt% AltF, and
60wt% PA66.
Material Processing
Injection Molding
Prior to injection molding, all the materials
were dried in a Heratherm oven (Thermo
Fisher Scientific, Waltham, MA) at 70°C for 18
hours. A BOY 35 E VV injection molding (BOY
Spritzgiessautomaten, Neustadt, Germany) was
employed for molding of the PA66/30CF/10AltF
composites. The BOY 35 E VV is equipped with 5
heating zones to establish a heating profile of 80°C,
276°C, 287°C, 290°C, 293°C, 290°C. The material
was plasticized at a rate of 350 mm/s to create a
32 mm shot. The material was injected into the
mold to produce ASTM D638 Type I dogbones
using a pressure of 12.75 MPa. The pressure was
increased to 15.17 MPa for 6 s after injection. The
molded dogbones were ejected and the process
was repeated until at least six dogbones were
produced. The same injection molding processing
parameters were used for all the specimens.
Mechanical Recycling
After the molded dogbones were tested, the
dogbones, sprues, and runners were fed into a
Shr3d IT shredder/granulator system (3devo,
Utrecht, The Netherlands) with a 4 mm mesh
screen. For the material to pass through the screen,
at least 2 dimensions must be reduced to at least
4 mm. The resulting granulate was collected and
utilized for dry blending to make recycled contentvirgin
pellet blends for injection molding.
Dry Blending
To make dogbones comprised of 33%, 67%, and
100% recycled
content PA66/30CF/10AltF and
virgin PA66/30CF/10AltF pellets were dry blended.
For the 100% recycled content samples with no
virgin pellets were utilized and 100% granulate
was directly fed into the injection molder. For the
33% recycled content blends, a 200 g batch was
Figure 1. A flow diagram of the processing/recycling pathway for the PA66/30CF/10XF hybrid
composites.
38 | SAMPE JOURNAL | MARCH APRIL 2023
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