JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 34

AUTOMOTlVE

Fig. 5: The demonstrator

Since this newly developed styrenic-based
composite neither contains semi-crystalline
polymer domains nor requires any additional impact modification or plasticizers,
the resulting sheets reinforced with glass
fibre fabrics (50/50) appear translucent
with a high-gloss surface finish. This adds
an interesting feature to the material, which
could be used for backlighted decorated applications at a competitive price level versus
PC, PMMA or a TPU-based thermoplastic
composite. The transparent nature of the
StyLight* SAN matrix, reinforced with a
woven carbon or glass textile, also makes it
an interesting alternative to epoxy for "carbon design" decorative applications (Figure
4). Once a clear coating is applied, this thermoplastic solution offers more design flexibility (at an affordable price) than conventional thermoset systems based on epoxy or
polyurethane matrices produced with RTM
or autoclave processes.
Demonstrator
To validate these promising laboratory results and the manufacturing behaviour of
the material, INEOS Styrolution decided to
invest in a full-size prototype mould made of
steel, combining different features.
A door panel design concept was selected as

it combined different construction and manufacturing challenges and complex shapes to
demonstrate the performance of StyLight*
(Figure 5). Different surface aesthetics and a
semi-structural reinforcement were integrated in the demonstrator design.
A thermoplastic composite sheet with a
thickness of 1.2 mm was chosen to provide
the best compromise between weight saving, good surface quality and high mechanical strength, while allowing the draping of a
complex-shape design.
Manufacturing process
During the manufacturing process of the
demonstrator, the StyLight* sheet was heated
up to about 270°C. At this temperature, the
composite sheet has a semi-rigid behaviour,
allowing a convenient handling, positioning
and draping process despite the relatively
complex and deep shape of the demonstrator surface. The draping phase was designed
with the support and expertise of mould
manufacturer Krumpholz Werkzeuge e. K.
(Grafengehaig). The "clamping drawers"
were accurately positioned in the mould,
following a predefined moving sequence to
prevent wrinkles, minimize the residual stress
and the "locking" of the fibre fabrics during
the part consolidation phase.

jec composites magazine / No110 January - February 2017

The processing parameters of the backmoulded material were optimized to
ensure good adhesion of the ribs to the
demonstrator's surface while filling up the
frame and the overmoulded upper surface
of the demonstrator. The injection moulding process was optimized with a mould
filling analysis. Rib feet were designed to
offer the best surface adhesion while minimizing the visibility of the ribs on the visible side. INEOS Styrolution used Terblend
N NG02EF SL, a high-flow glass fibre-reinforced ABS/PA blend reinforced with 8%
short fibres, offering a great surface quality
combined with structural stiffness, low viscosity and surface adhesion to the sheet.
The optimization of the manufacturing
process parameters and the draping phase
were supported by a draping process simulation performed by ESI (Engineering
System International GmbH) based on a
material card generated by Cikoni (TTI
GmbH - Cikoni Tgu). Based on this material card, basic structural simulations of
static loading were also performed by ESI
with StyLight* on the demonstrator.
Surface decoration
One of the major challenges for the demonstrator was to take advantage of StyLight*'s
surface properties and demonstrate the
feasibility of achieving a decorated surface
in a single manufacturing step. The team
focused on two critical areas of the demonstrator: the lower part, where the composite sheet is directly visible, and the central
part, where the composite is covered and
decorated directly in the mould with an insert developed by Leonhard Kurz Stiftung
& Co. KG (Fürth).
Different surface structures were applied
on the demonstrator: a high-gloss surface
finish around the loudspeaker circle, a fine
grain in the lower part, and a leather-type
grain in the upper part (Figure 6).
Although the StyLight* sheet offers a low
surface waviness measured under ideal
conditions, other types of surface defects
can appear on the sheet surface in a complex-shape, large part. To prevent these defects, the following three conditions need
to be fulfilled:
- During the compression phase, the pressure should be evenly distributed over

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017