SAMPE Journal - July/August 2022 - 42

FEATURE / HIGH-RATE AIRCRAFT MANUFACTURING
(a)
(b)
Figure 2. LaRC HH-ATP head process elements including front-view of torches, tape feeder mechanism,
and three heated and chilled compactors (a) and bottom-view perspective (b).
The Advanced Materials and Processing
Branch (AMPB) at NASA LaRC has developed
aerospace capable thermoplastic composite
materials and the accompanying thermoplastic
composite processing techniques. Under a
NASA Small Business Innovative Research (SBIR)
Phase II contract completed in 2007, Accudyne.
Inc. (Newark, DE) designed and fabricated a
developmental version HH-ATP placement head
(Figure 2) with the capabilities to conduct material
evaluation and process development experiments
of in-situ consolidation of thermoplastic ATP
placing both commercial-off-the-shelf (COTS)
CF/thermoplastic supplied tape as well as LaRC
developed materials. The NASA LaRC HH-ATP
facility utilizes a high-rail gantry system providing
1.8 m (~6 ft) of linear motion, a 1 m x 1 m (~3 ft
x 3 ft) flat tool controlled by X and Y direction
stepper motors, and a heated tape placement
head. The HH-ATP process is fully automated with
process and machine control software developed
by Accudyne. Coordinated gantry/head motion
together with the on-head tape consolidation
process enables the fabrication of open section
flat laminates without requiring an autoclave.
As described in the processing steps above, the
equipment was designed so that the deposition
head preheats the CF/thermoplastic tape and the
pre-placed, or substrate, laminate to the melting
temperature using hot gas torches (HGT), welds
them together under heat and pressure until the
composite material is fused and consolidated
in place and maintains pressure while cooled to
temperatures below the Tg
3. Figure 2(a) shows the
processing elements used in the thermoplastic
composite fabrication including: 1) four gas
combustion torches (HGT) to preheat the preplaced
composite " substrate " layers to near the
process temperature, 2) a mini-HGT to rapidly heat
both tape surfaces at the contact, or " nip- point " , to
the process temperature where compaction load is
applied via a line-compactor to establish intimate
contact between the incoming and substrate tape
plies using up to 800 N (~180 lb.), 3) immediately
following the " nip-point " , a heated conformable
area-compactor capable of applying force of up to
1330 N (~300 lb) over an area of 11.4 cm x 10 cm (4.5
in x 4 in), and 5) a chilled area conformable areacompactor
that can apply forces of up to 2200N
(~500lb) at 10°C over an area of 12.7 cm x 10 cm (5
in x 4 in). Figure 3(b) provides a view of the head
from the perspective of the flat placement tool. The
conformable " area-compactors " are comprised of
vertical heated shims capable of applying uniform
load to both flat part surfaces or to parts with padups
and pad-downs3
. This novel approach of using
conformable area-compactors requires a travelling
sheet of brass shim stock between the head
compaction elements and the placed thermoplastic
tape to prevent material sticking and allows the
heated and cooled compactors to conform up to the
approximate contour of a basketball3
, i.e., double
curvature with a radius of about 12 cm (4.8 in).
These conformable area-compactors provide an
increased area of compaction force in comparison
to the single flexible roller commonly utilized
during AFP of thermoset tapes (see Figure 1) and
provides a larger area, or more importantly longer
heated-compaction time to the thermoplastic tape
to fusion-bond the incoming tape to the substrate
tape ply.
The equipment arrangement described above
provides a highly capable solution for conformable
compaction that has been demonstrated to
investigate the in-situ process of flat and simple
contour CF/thermoplastic parts fabricated from
various LaRC amorphous and non-optimum
commercially available semi-crystalline CF/
thermoplastic tape materials. However, the
HH-ATP equipment configuration is unlikely to
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