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such as packaging, structural performance
and aerodynamics.
Intensive research is also needed in the field
of crash simulation. Material damage
models and approaches to the simulation of
structural failure need to be developed to
facilitate design optimisation.
Manufacturing
Important issues relating to the research and
development of new manufacturing methods
for aerospace applications include:
• Improved affordability (e.g. automation,
tooling costs).
• Improved part performance (e.g. lightweighting,
damage tolerance).
• Quality assurance.
• Concurrent engineering.
The most interesting technologies with a
high potential to fulfil these needs are:
• Textile preforming.
• Automated tape laying / fibre placement.
• Liquid moulding technologies (especially
non-autoclave).
• Advanced curing technologies.
• Thermoplastic technologies.
• New sandwich technologies.
Textile preforming is particularly relevant to
the automated manufacturing of structural
composites with a high degree of integration
and optimisation, and in which threedimensional
fibre reinforcement is required.
Important technologies are non-crimp
fabrics, braiding, textile fibre placement
(embroidery) and stitching. These
technologies have been developed for
composite applications over the last ten
years and their potential has been
demonstrated in many development
programs. First series applications are
13
planned for the A380 and the A400 M
(pressure bulkhead, ribs, flap-track, etc).
Some examples showing complex preforms
(based on non-crimp fabrics, braids and
textile fibre placement) that have been
stitched together by robot-controlled singlesided
stitching are shown in Figure 15.
Nevertheless, there is still the need for
further improvement. The stiffness and
strength properties of components based on
such preforms are currently significantly
below prepreg levels. Furthermore, design
guidelines and calculation methods are still
only on an academic (rather than industrial)
level.
Liquid moulding techniques are, when used
in combination with textile preforming, an
interesting alternative to prepreg technology.
Many different approaches to liquid
moulding have been developed for different
purposes (e.g. resin transfer moulding -
RTM, Seeman Composites Resin Infusion
Moulding Process - SCRIMP, vacuum
assisted resin infusion - VARI, differential
pressure resin transfer moulding – DP-RTM,
etc.). In all cases the dry fibre preform is
placed in a mould and a low viscosity liquid
resin is injected with or without pressure. Of
special interest is the opportunity for low
cost tooling. For some liquid moulding
technologies, only one stiff tool side is
necessary, the other side being realised with
film. This is especially relevant for big, highly
integrated structures which are typical for
wing or fuselage applications. An additional
benefit is the possibility for non-autoclave
curing because, even with only one bar
consolidation pressure, high quality
impregnation and fibre volume fractions of
close to 60% can be realised.
In parallel with the thermosetting
technologies described above,
thermoplastics have now been developed to
a stage where the first significant structural
applications are starting to emerge. An
example is the A380 J-nose, a sheet-formed
and welded structure that exploits the
benefits of thermoplastics. Of particular
importance for this application is the good
damage tolerance of thermoplastics. It can
be expected that this development will lead
to new advances in thermoplastic
technology.
For the affordable manufacturing of
sandwich structures, newly developed
folded cores offer some interesting
opportunities. They can be produced
automatically into near net shapes, and they
offer much more flexibility in their
performance compared to honeycombs.
Their functionality with respect to drainage,
acoustic damping and signature is also
higher. Nevertheless, the technology is still
relatively new and only small-scale lab
samples have been manufactured up until
now.
Lightweighting
Lightweighting is still one of the most
important driving forces in aerospace
development programs. However, in
attempting to reduce weight, many other
aspects also have to be taken into
consideration. These include:
• Affordability.
• Quality assurance.
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