SAMPE Journal - July/August 2016 - 30

Feature Article
days above -18°C. Because MTM®45-1 tack is so
highly sensitive to prepreg outlife, it is desirable to
be able to quickly and quantitatively assess the
tack level of the material prior to placement.
Experimentation
LM Aero Mongoose Machine
The developments described in this paper were
conducted using an Ingersoll Mongoose gantry
fiber placement machine installed in Palmdale,
CA in 2011. The machine, shown in Figure 1, is a
uniquely capable production scale AFP machine
with a head that gives access to tighter concave
surfaces than other machine designs. This made
the Mongoose the best suited to varied complex
shapes of wing skins, fuselage skins, and ducts of
most interest to Lockheed Martin. Other notable
features include bi-directional placement, cut/add
on the fly, dynamic speed proportioned heat control,
high acceleration rates for improve productivity,
and interchangeable fiber placement heads. The
machine's work envelope is 24 m along the X-axis,
9 m along the Y-axis, and 3 m along the Z-axis with
185° of C-axis rotation. Interchangeable heads for
use with both 0.3175 cm and 0.635 cm wide slit
tape were acquired.

LM Aero ADP Building Block Development
While AFP is well suited to fabricate large unitized
assemblies, there are producibility challenges with
OoA materials above those with standard autoclave
materials. These challenges are magnified when
applied to multi-feature articles that include
complex curvatures, skin joggles (offsets allowing
for an outside flush fit of components such as
access doors), and core stiffening. To address
these challenges, Lockheed Martin uses a building
block approach (Figure 2), incrementally adding
complexity to manufacturing articles, to verify the
parameters and efficacy of process improvements
at each stage. This section describes the building
block development conducted to transition IM7/
MTM®45-1 composite to the AFP manufacture
of next generation wing skin structures. At all
levels of complexity laminates are inspected by
C-scan (ASTM E25806) followed by sectioning
for photomicroscopy, laminate physicals (ASTM
D31717), and thermal analysis (ASTM D70288).
Lockheed Martin uses this combination of tests
because conventional C-scan alone does not
provide comprehensive quality assessments (QA);
in particular it does not identify the location of
porosity (e.g. within tows versus between tows, tool
side versus bag side plies, or evenly distributed,
etc.). By using multiple QA methods, the feedback
can help ascertain how effective the chosen
process parameters were prior to applying those to
more complex parts.
Process Envelope Development
AFP building block development begins with
work on simple monolithic panels; identifying
optimal machine parameters, bagging techniques,
and cure methods unique to the fully impregnated
AFP product form.

Figure 2. AFP building block development approach.
30

Environmental Impacts
One of the fundamental factors affecting
consolidation of plies is the tackiness of the
material. How well the material sticks to itself is vital
to achieving good consolidation, yet material with
too much tack can negatively impact productivity
as it will stick to machine parts and cause unwanted
resin build-up in the machine tow path. Typically, a
quick evaluation of tack on the shop floor is done
using the qualitative levels as defined in Table
1. Between level 3 and 4 is ideal for OoA fiber
placement.
The handling capabilities of epoxy systems during
SAMPE Journal, Volume 52, No. 4, July/August 2016



Table of Contents for the Digital Edition of SAMPE Journal - July/August 2016

Contents
SAMPE Journal - July/August 2016 - Cover1
SAMPE Journal - July/August 2016 - Cover2
SAMPE Journal - July/August 2016 - Contents
SAMPE Journal - July/August 2016 - 2
SAMPE Journal - July/August 2016 - 3
SAMPE Journal - July/August 2016 - 4
SAMPE Journal - July/August 2016 - 5
SAMPE Journal - July/August 2016 - 6
SAMPE Journal - July/August 2016 - 7
SAMPE Journal - July/August 2016 - 8
SAMPE Journal - July/August 2016 - 9
SAMPE Journal - July/August 2016 - 10
SAMPE Journal - July/August 2016 - 11
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SAMPE Journal - July/August 2016 - 19
SAMPE Journal - July/August 2016 - 20
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SAMPE Journal - July/August 2016 - Cover3
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