SAMPE Journal - July/August 2022 - 40

FEATURE / HIGH-RATE AIRCRAFT MANUFACTURING
As a result of these identified focus areas and
further input from the commercial aircraft airframe
and engine manufacturers, NASA has partnered
with the United States aerospace industry and
academia through the Advanced Composites
Consortium (ACC) to develop manufacturing
and composite materials technologies to reach
the goal of a 4 to 6x increase in manufacturing
rates over the existing aircraft rates. Under the
HiCAM project the ACC has expanded to include:
original equipment manufacturers and Tier 1
suppliers (Boeing, Raytheon, Northrop Grumman,
Lockheed Martin, Spirit Aerosystems, GE Aviation,
Aurora Flight Sciences, Advanced Thermoplastic
Composites), material suppliers (Toray, Hexcel,
and Solvay), automated equipment manufacturer
(Electroimpact (EI)), software developers (CGTech,
Collier Aerospace, Convergent Manufacturing
Technologies US), government agencies (NASA,
FAA) and academia (Wichita State University,
University of South Carolina). The NASA HiCAM
project currently has collaborative research teams
(CRTs) investigating technology focus areas, or
tasks, to compare qualitatively and quantitatively
with
the baseline, or state-of-the-art
(SoA),
manufacturing rates for fabricating composite
fuselage and wings. These CRTs are comprised of
NASA and ACC subject matter experts investigating
the following proposed CFRP structure materials
and manufacturing technologies:
* Non-destructive evaluation (NDE), including
in-situ inspection during the fabrication
process
* Rapid cure resin infusion thermoset resins
* Stitched resin infusion of wing and fuselage
including unitization of structural elements to
the skin using stitching technologies
* Thermoplastic forming of continuous reinforcing
elements such as stringers,frames, and
spars
* Thermoplastic assembly of reinforcing
structural elements via welding technologies
such as induction, ultrasonic, and resistance
* Thermoplastic automated fiber placement
(TP-AFP), including, in-situ consolidation
AFP of thermoplastics (ICAT) and TP-AFP with
post-consolidation in an oven or autoclave.
* High-rate thermoset AFP, including increased
lay-down rates exceeding the SoA of
1058 mm/s (2500 in/min), and introducing
new rapid-cure thermoset slit-tape materials
to reduce the autoclave cure cycle.
In addition to the composites materials and
manufacturing technologies listed above and
currently under investigation, the HiCAM project
also includes significant efforts in defining the
rates of the current manufacturing processes
based on the proposed design for a Boeing 737
type commercial aircraft replacement including
factory footprint and recurring and non-recurring
costs. These variables are considered in developing
methodologies to accurately compare the new,
or proposed, manufacturing technologies to the
baseline to determine which of these proposed
technologies, after development, can attain the
goal of a 4 to 6x increase in shipset rate. While each
of these proposed technologies possess significant
merit and address issues identified as focus areas
at the NASA manufacturing workshop, one area
that NASA is currently focused on demonstrating
potential as part of the ongoing qualitative and
quantitative analysis is the ICAT process to
fabricate carbon-fiber reinforced thermoplastic
wing
and
fuselage
structure
out-of-autoclave
(OoA). Thermoplastic matrix composites offer
attractive solutions to rapid manufacturing due
to their ability to be formed and consolidated
without the lengthy autoclave cure cycle required
for crosslinking, or " cure " associated with the
more commonly used thermoset epoxy and
bismaleimide materials. NASA and ACC partners
are also investigating thermoplastic forming of
structural elements, various welding technologies
to assemble these structural elements, and
thermoplastic AFP to fabricate large acreage
skins for wing and fuselage. Employing a recently
developed laser
heating
system,
in
the ICAT
process, the thermoplastic matrix carbon fiber
reinforced slit-tape can be quickly and efficiently
heated above the polymer melt temperature and
fusion-bonded, or consolidated, ply-by-ply over
rigid, heated tooling in an automated fashion
utilizing existing AFP robotic placement machines.
Two semi-crystalline polyaryletherketone
thermoplastic matrix tape materials were downselected
for initial study based on the quality of the
supplied materials. The thermal properties of these
thermoplastic tape materials were provided by the
material suppliers to estimate the ICAT process
parameters necessary to fabricate consolidated
laminates at AFP placement speeds approaching
423 mm/s (1000 in/min). The laser power settings
to
achieve the desired material temperatures
were determined in the Electroimpact, Inc. laserassisted
AFP lab, measuring the substrate and
incoming tape temperatures utilizing FLIR thermal
imaging cameras and thermocouples during an
initial ICAT process characterization study.
40 | SAMPE JOURNAL | JULY AUGUST 2022
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