SAMPE Journal - May/June 2016 - 17
Feature Article
Figure 11. Infrared thermography image of the doublecurvature region of the IML skin.
Figure 12. Infrared thermography image of the doublecurvature region of the OML skin.
Void Content Estimation
Thermography images were evaluated at different
time stamps for the demonstrator. Figure 12 shows a
voidage map of the local void content estimation in the
honeycomb core inserts for both OML and IML skins.
The void content was only estimated for the regions
Conclusions
An aircraft demonstrator with honeycomb core
inserts was manufactured using OoA prepregs and
VBO processing technology. The demonstrator was
instrumented with miniature pressure sensors to
investigate the evolution of honeycomb core pressure
throughout lay-up, ply de-bulking, the extended precure vacuum hold, and the elevated temperature
curing cycle of a complex aircraft part.
appears as a bright region in the upper right-hand
corner of Figure 11. The bright regions at the skin-tocore transition indicate possible ply-bridging, which
is most prevalent in the female 90° corners (bottom
left and right of Figure 11) and near the flat bottom
depression on the mid left-hand side of Figure 11.
This corresponds to the region where core springback was observed after core forming process.
The thermal image of the OML surface in Figure
12 also shows the presence of discontinuities in the
part. The surface ply-bridging observed in Figure
10C appears as bright regions, most notably in the
curved corners in the upper right- and left-hand side
of Figure 12. The bright ellipse identifies the poor
consolidation in the flat-bottom depression. The plybridging visually observed in Figure 10D and as a
bright region in the upper right-hand corner of Figure
11, appears as a dark region in the upper left-hand
corner of Figure 12. A region of low skin consolidation
was expected and confirmed with thermography. No
visual indication of this defect was observed when
examining the OML surface by eye. The outline of the
honeycomb core appears as a dark region in Figure
12. The visible core-to-skin transition indicates poor
consolidation in these regions and the worst regions
again appear in the female corners of the honeycomb
core insert. Finally, the core region where spring-back
was observed after forming is the only dark region
that spans across the width of core insert (to the left
of the bright ellipse).
SAMPE Journal, Volume 52, No. 3, May/June 2016
with honeycomb insert to illustrate the variation in
porosity within those regions, and avoid confusion
with the monolithic section.
Heterogeneous levels of porosity are found
throughout the sandwich sections on both sides of
the door. Except the top of the flat region, the OML
skin exhibits an acceptable internal skin quality with
skin voidage close to, or below 1%. The dark region
observed in the upper third of the OML skin was the
region of surfacing film pieces overlapped, and as a
result, was not mapped for voidage. In addition, the
white region in the upper right-hand corner was not
mapped because this was where the surfacing film
remained on the mould.
A lower skin quality was observed in the IML skin.
Intuitively, this was expected because all gas flow
observed during the constant temperature dwell
in Figure 9 must pass through the IML skin for the
pressure to decrease in within the honeycomb core.
Higher voidage remained in the regions where gas
flow paths contained volatiles at resin gelation. No
correlation was observed between the pressure sensor
readings and the voidage map. Higher void content,
above 1.5%, was found in the areas of abrupt curvature,
core chamfer, and core spring-back. In the doublecurvature region, only the bottom area of the close-out
near the edge breathing had a void content below 1%.
17
Table of Contents for the Digital Edition of SAMPE Journal - May/June 2016
Contents
SAMPE Journal - May/June 2016 - Cover1
SAMPE Journal - May/June 2016 - Cover2
SAMPE Journal - May/June 2016 - Contents
SAMPE Journal - May/June 2016 - 2
SAMPE Journal - May/June 2016 - 3
SAMPE Journal - May/June 2016 - 4
SAMPE Journal - May/June 2016 - 5
SAMPE Journal - May/June 2016 - 6
SAMPE Journal - May/June 2016 - 7
SAMPE Journal - May/June 2016 - 8
SAMPE Journal - May/June 2016 - 9
SAMPE Journal - May/June 2016 - 10
SAMPE Journal - May/June 2016 - 11
SAMPE Journal - May/June 2016 - 12
SAMPE Journal - May/June 2016 - 13
SAMPE Journal - May/June 2016 - 14
SAMPE Journal - May/June 2016 - 15
SAMPE Journal - May/June 2016 - 16
SAMPE Journal - May/June 2016 - 17
SAMPE Journal - May/June 2016 - 18
SAMPE Journal - May/June 2016 - 19
SAMPE Journal - May/June 2016 - 20
SAMPE Journal - May/June 2016 - 21
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SAMPE Journal - May/June 2016 - 25
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SAMPE Journal - May/June 2016 - 27
SAMPE Journal - May/June 2016 - 28
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SAMPE Journal - May/June 2016 - 30
SAMPE Journal - May/June 2016 - 31
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SAMPE Journal - May/June 2016 - 33
SAMPE Journal - May/June 2016 - 34
SAMPE Journal - May/June 2016 - 35
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SAMPE Journal - May/June 2016 - 37
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SAMPE Journal - May/June 2016 - Cover3
SAMPE Journal - May/June 2016 - Cover4
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