SAMPE Journal - July/August 2016 - 37

Feature Article
Several fluoropolymer release films, with different
perforations, were compared to the hand lay-up
baseline release film to determine which best enabled
z-breathing. On average, different perforations in the
release films did impact the porosity levels exhibited
in the 24 ply laminates. The proprietary bag scheme
selected decreased the porosity an average of 0.4%.
Most of the benefit of the porosity reduction was
seen in the outer 8 to 10 plies.
Four different cure cycles were compared to
hand lay-up baseline cure to determine if the cure
could impact void diffusion and volatile extraction.
Cure cycle evaluations resulted in the selection of a
proprietary cure cycle.
Geometric Features on Flat Surfaces
The addition of skin features to a part was quickly
found to increase the frequency of defects formed,
largely since it was not possible to place material at
uniform pressures and surface temperatures. Initial
trials on placing surface features showed uneven
loading on the compaction roller induced bridging
and wrinkling. Moreover, the machine speed varied
greatly as it traveled over the features causing
inconsistent control of heat to the lay-up.
Addressing these defect challenges is particularly
critical with OoA materials for several reasons. First,
the higher temperature and pressure conditions
associated with OoA fiber placement changes not
only the nature of the defects formed but also leads
to more difficulties in manually removing the defects
due to the increased adhesion of the defect to the
plies underneath. Repairs of defects performed
on plies placed above like oriented plies were
susceptible to damage more severe than leaving
the defects alone. In addition, since OoA fiber
placement relies on on-the-fly consolidation, there
is a concern hand laid repairs may impact the final
quality of laminate since they do not benefit from
the same heat and compaction as those placed by
the machine. For these reasons it is imperative the
process envelope is optimized to minimize defects
for OoA AFP.
Optimized Door Joggles. Following process envelope
development, where the objective is to achieve the
highest quality panels on flat surfaces, the focus of
research moves to minimizing defects on features
such as joggles. Initially, the parameters developed
for solid laminates resulted in bridging over joggle
features; defects which were not eliminated by
vacuum compaction. In addition, the tool surface of
the joggle area was found to be resin dry as shown
SAMPE Journal, Volume 52, No. 4, July/August 2016

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