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short circuits with low energy / long
exposure times), and the burn-though
behaviour of structural materials following
accidents.
New Material Concepts
The most important material for composites
in aerospace is of course the carbon fibre.
Today, the primary focus for new carbon
fibre developments is not the improvement
of fibre performance. Instead, it is the
reduction of costs and the improvement of
processability (e.g. through textile
preforming). 24k fibres are now, more or
less, established and new approaches using
flat bands instead of “round” rovings look
promising for further improvements in
performance and affordability.
In the long term, significant performance
improvements can also be anticipated
through the development and application of
carbon nanotubes (CNTs). These have
considerable potential for enhancing
mechanical performance and functionality.
In Figure 16, the performance of CNTs is
compared to current state of the art
materials. It shows that as well stiffness and
strength increases, improvements in thermal
conductivity and heat transfer open-up new
worlds of opportunity.
Several companies in Europe, the US and
Japan are working on CNTs. Today, only a
limited amount of CNTs are available, and it
may take another five years to produce
CNTs on an industrial scale with high quality
and acceptable costs.
The initial applications for CNTs are likely to
be as a filler material for improving the
Figure 16 – comparison of the performance of
carbon nanotubes and conventional materials
Stiffness Strength Elongation Thermal Specific Strength
Conductivity
Electrical
Conductivity
CNT
Carbon Fibre
(HM)
CNT
Carbon Fibre
(IM)
CNT
Carbon Fibre
(IM)
CNT
Copper
CNT
Copper
CNT
Carbon-Fiberr
(IM)
Steel
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
20 km
400 km
400 W/mK
17 • 10 – 6 Ω/cm
7 GPa
> 50 GPa
> 1000 GPa
> 10 %
1,8 %
> 10 – 4 Ω/cm
> 2000 W/mK
> 2000 km
700 GPa
16
performance of conventional composites
(e.g. with respect to electrical conductivity),
as well as in niche applications such as
reinforced stitching yarns.
In the development of new resin systems,
the main focus is in the field of liquid resin
infusion. Improved processability (low
viscosity, wide processing window) as well
as improved toughness are amongst the
goals. Nevertheless, there are still the
general goals of cost reduction and
obtaining a good balance between high
temperature capability and toughness.
Increasing attention is also being given to
specific topics like fire, smoke and toxicity
(FST).
Interesting developments are on the way in
the field of sandwich structures. Two
examples are new foam core materials
adapted to resin infusion processes through
the use of smaller surface cells, and new
folded structures allowing the automated
and affordable manufacturing of contoured
cores with special features like drainability.
FUTURE RESEARCH PRIORITIES FOR COMPOSITES IN
AEROSPACE
The challenge for all developments in
aerospace is always to find a good
compromise between performance and cost.
Depending on the nature of the mission and
the market, one or the other will dominate.
Figure 17 shows the goals for the next
generation of Airbus planes. Clearly a 40%
cost saving and a 30% weight saving
compared to the state of the art cannot be
reached by small steps. An integrated
approach that takes all disciplines into
account is necessary. With this in mind,
recommendations for future research
priorities are presented here.
Primary Research Priority –
Manufacturing Technologies
Improved manufacturing technologies are
the primary key to better affordability and
quality. Higher degrees of automation, better
quality control, reduced tooling costs and
-40 -30 -20 -10 10 20 30
10
20
-10
-30
-20
Δ Costs [ % ]
Δ Weight [ % ]
CFRP applications
of today
Target for
CFRP fuselage
CFRP using today‘s
technology
Metal tomorrow,
welded fuselage
Metal today
Figure 17 – the goals for weight and cost
reduction on future Airbus planes
shorter cycle times have to be consistently
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