JEC COMPOSITES MAGAZINE - Issue #95 - Special JEC Europe - March 2015 - 89

Materials and
mechanical behaviour

Fig. 2: The BMW i3

cycle times around 3 minutes. Other
technologies based on thermoplastic
matrix systems also offer a very high
potential and it can be expected that
there will be a large variety of materials, structural concepts and processes in
the automotive industry of the future.
However, significant steps forward are
needed for efficiency improvements
along the whole process chain and
material and process costs have to be cut
down significantly.
Even though both sectors have different
application requirements, there is for
sure an enormous potential for collaboration. Automotive will profit from the
vast experience of the aerospace sector
and vice versa, aerospace must benefit
from the new material and process developments of low-cost and high-volume
technologies.

The key element for lightweight composite structures is carbon fibre. While
the aerospace industry is focusing on
traditional high-performance 3-12k
rovings with respective qualification
standards ("aerospace grade"), the trend
for automotive applications goes for
lower costs. There are mainly three ways
to achieve this: 1) go for thicker rovings
(48k, 50k or higher), 2) improve the
efficiency of the production process,
or 3) use new and efficient precursors.
The first approach is already established
but it needs adapted textile preforming
processes and, for example, braiding
is not possible with rovings thicker
than 24k and it tends to lead to lower
performance. The second approach is
under development. Laser heating or microwaves are promising technologies to
reach the high temperatures needed and
to replace the large and not so efficient
ovens. The third approach is a long-term
development because the performance
of the fibres is still far away from the
values needed for significant lightweight
design.
On the matrix side, there are very interesting developments, especially in the
field of epoxy resins. On the automotive
side, so-called snap-cure resins promise
a curing time in the range of 2 minutes.

PU resins will also play a role in some
applications. On the other hand, thermoplastic matrix systems will become
very important due to the possibility of
combining different semi-finished products (UD tapes, organic sheets, LFT)
as well as fast cycle times and recycling
opportunities. In addition to advanced
process technologies to produce costefficient semi-finished materials, the
fibre-matrix interface is the key for future applications of this materials class.
For aerospace, the focus is on toughened epoxy prepreg systems providing,
in particular, improved damage tolerance in combination with high stiffness and strength properties. Future
developments are in the direction of
matrix functionalization for enhanced
electrical conductivity, mechanical
properties and fire resistance using filler
materials on the micro- and nano-scale.
Thermoplastic matrix applications in
aerospace are very limited, mainly to
PEEK systems for leading edges, due to
high temperature requirements.

Customized sizing technologies
for thermoplastic materials
SGL Group is conducting a comprehensive research and development programme on customized sizing technologies in order to optimize the fibre-matrix
interaction for different matrix poly-

Fig. 3: Left: Carbon fibre with a standard sizing in a Nylon 6 matrix; carbon fibre with a thermoplastic-compatible TPC sizing; right: Performance of Sigrafil® C30 T050
carbon fibre with different sizings

No95 March 2015 /

jec composites magazine 89

JEC COMPOSITES MAGAZINE - Issue #95 - Special JEC Europe - March 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #95 - Special JEC Europe - March 2015