JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 33

housings. It has now turned its attention to
the cylinder housing, a critical, complexshaped component currently made from
cast iron or aluminium. In a recent collaboration with the Fraunhofer Project Group
- New Drive Systems, in Karlsruhe, Germany, SBHPP set out to demonstrate the
benefits of replacing die-cast aluminium
cylinder housings with phenolic composite
parts manufactured by injection moulding,
a standard mass production process.

Demonstrator cylinder housing

warm-up time. Both of these factors will
lead to lower emissions when cold starting
the engine. Improved noise, vibration and
harshness (NVH) behaviour was found
to be a further benefit of composites, with
initial acoustic tests showing a 5 dB noise
emission reduction for the composite
housing compared with the aluminium
reference part. Because of their excellent
chemical resistance to engine oil, fuels
and coolant, composites also offer a lower
corrosion risk than metals. This will lead
to longer service life and reduced maintenance requirements.

Performance benefits

Weight and cost savings

The composite cylinder housing passed all
the tests successfully and demonstrated that
it could deliver the same performance as the
aluminium part. During full-load testing -
designed to prove the mechanical integrity
of the part at full load - the composite cylinder maintained full functionality during the
entire test programme and its peak power
value (30.6 kW at 6000 rpm) was identical
to that of the aluminium reference cylinder.
In short durability testing (ESC European
Stationary Cycle), the composite housing
maintained full functionality during the entire five-hour test programme, performance
values such as torque and power remained
constant during the test, and no leakage of
oil or water occurred. Repeated full-load
tests conducted at the end of the ECS test
confirmed that the power performance
values of the engine could be maintained.
The testing programme also revealed
some notable advantages of the composite cylinder housing over the aluminium
part. Thermal tests verified reduced heat
radiation from the composite part to the
surrounding environment, and a faster

Weight and manufacturing cost calculations were performed for the composite and
aluminium components. For the weight
comparison, a die-cast aluminium cylinder
housing was compared with composite
housings employing various combinations
of stud and insert materials. Compared
with the aluminium part, the glass fibrereinforced phenolic component delivered
weight savings of up to 20% (Figure 4). The
cost analysis (Figure 5) proves the competitiveness of the composite concept versus the
aluminium reference cylinder. Costs per part
are approximately 10% lower for a production run of up to 30,000 parts/year. The
higher the production volumes, the more
significant this cost reduction will become.
A very significant cost reduction for the
composite part is in the area of tooling -
tooling costs are lower and tooling lifetime
is longer. In an aluminium die-casting machine, molten aluminium at a temperature
of around 660°C is shot into the mould at
high speed and pressure, and to achieve
a short cycle time (<60 seconds), the
mould is cooled down rapidly using liquid

Fig. 2: The composite cylinder housing showing the metal inserts and liner

No102 January - February 2016 / jec

Feature Automotive

The project involved the manufacture of
a proof-of-concept composite cylinder
housing for a single-cylinder 650 cc engine
(Figure 1). During the development phase,
various simulation tools were employed to
optimise the part's design and the injection
moulding process for its manufacture. A 55
vol% short glass fibre-reinforced phenolic
moulding compound (Vyncolit® X6952/
Vyncolit® BXE6952) from SBHPP was
selected to manufacture the part. This material, supplied in powder form for use in
injection, transfer and compression moulding processes, exhibits superior mechanical
properties, a high impact strength and excellent retention of mechanical properties
at elevated temperatures. Metal inserts are
employed to provide support and wear resistance in highly loaded areas (e.g. around
the stud bolts) and an aluminium cylinder
liner is required in order to disperse the
heat of combustion (Figure 2). A serial production specification mould was manufactured for the production of prototype parts,
and composite cylinder housings with various insert configurations were produced
(Figure 3). A cycle time of 90 seconds was
achieved. With further optimisation of the
process, this could potentially be reduced.

The injection-moulded parts required
some post-processing, including removal
of the sprue and runners, and milling of the
head and foot gasket surfaces. To validate
its functionality and performance, the composite cylinder housing was installed in the
engine and subjected to a battery of tests
using a state-of-the-art engine test bench.
After testing, no damage was observed to
the composite part and no issues relating
to the bolts, inserts or liner were found.
The same tests were carried out on the
aluminium reference part to enable a direct
comparison between the two components.

composites magazine 33

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016