JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 37

Bright Lite Structures specifies Hexcel carbon multiaxials for safety-critical application

produced on the A and B sides.

Fig. 2: The chassis
comprises five carbon
composite parts
bonded to a central
aluminium spine.
Hexcel's HiMax fabrics play an integral
role in reinforcing
areas of the floor pan

Fig. 3:
The moulded
Zenos chassis floor

adhesive bonding, resulting in lower assembly costs.

The right combination
Bright Lite Structures, who collaborated
successfully with Hexcel Reinforcements
UK on a number of previous projects,
contacted the company for advice during the E10 chassis design phase. After

Fast, cost-effective manufacture
Bright Lite Structures manufactures the
composite chassis components at its production facilities in Peterborough, UK,
using its proprietary wet compression
moulding process. This technique is capable of moulding complex, deep-draw designs in one step and, because the core can
be compressed, a different surface can be

Bright Lite Structures delivers the cured
parts to a machinist for trimming prior
to delivery to Zenos for assembly. The
total cycle time, including reinforcement and core kit cutting, lay-up and
post-mould trimming, is 15-20 minutes
per part. The exterior of the body sides
and rear bulkhead are painted black to
produce an acceptable aesthetic surface.
This patented technology offers several
advantages over conventional composite manufacturing processes, which rely
on costly preforming techniques and
autoclave equipment. The carbon fibre
components produced are up to 20%
lighter than those manufactured using
conventional processes, yet still meet
stiffness requirements. The parts are
also less expensive and faster to manufacture in high volume, and less carbon
fibre and resin are required, leading to
lower total materials costs. As a result of

Fig. 4: Spraying resin onto the reinforcement/core
stack at Bright Lite Structures

No110 January - February 2017

/ jec composites magazine

Feature Automotive

The chassis is made up of only five parts -
front and rear bulkheads, a floor pan and
left and right body side panels - bonded
to a central aluminium spine. The parts
are manufactured as a sandwich structure.
At the centre of the structure is a sheet of
core material made from hollow tubes of
recycled polycarbonate. Either side of this
core is a laminate based on one ply of recycled chopped carbon fibre in the form
of a multiaxial mat and a resin blend of
polyurethane and RTM-grade epoxy. For
the 1.6 m x 1.7 m chassis floor, two carbon
fibre multiaxial reinforcements produced
by Hexcel Reinforcements UK (formerly Formax) were also specified. Should
the vehicle be involved in a crash, these
reinforcements are engineered to spread
the seat belt pull-out load over the largest
possible area, ensuring the metal seat belt
inserts positioned under the floor remain
in place.

studying the requirements for the additional reinforcement of the chassis floor,
Hexcel recommended a combination of
two multiaxial fabrics that would provide
optimal performance for this challenging
application. Rolls of the chosen materials
were supplied to Bright Lite Structures for
testing purposes. The results were excellent and the two products were specified
for the chassis. On the floor interior, on
top of the recycled carbon mat, one ply of
HiMax™ 300 g/m2 (75 g/m2, 150 g/m2, 75 g/
m2) carbon fibre triaxial is added over the
complete surface of the part. Additionally,
one ply of HiMax™ 0/90° 300 g/m2 carbon fibre biaxial is used in the areas of the
seat belt inserts and seat mounting inserts,
which are co-moulded into the floor.
Although employed primarily to handle
crash loads, the Hexcel fabrics are also
very attractive in visual appearance and
the moulded floor remains unpainted.

In the first step of the process, the dry
materials (cut to shape) are stacked together by hand to form a flat sandwich
(reinforcement/core/reinforcement).
This stack is clamped in a frame, which
is then attached to a robot arm. The robot moves the assembly under a spray
machine and the resin is sprayed onto
the reinforcement. The frame is turned
over and the other side is sprayed. The
part is then placed into a compression
moulding press at 130°C for 8 minutes
at 6 bar pressure.

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