JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe - 106

thermoset

neering thermosets) as a function of
temperature. Comparisons were made
against values for a 50% glass fibre reinforced polyphthalamide (PPA) and 40%
and 65% glass fibre reinforced polyphenylene sulphide (PPS) materials [2, 3].
The results indicated a greater resistance
of the engineering thermosets to high
temperatures versus the other material
candidates
Water pump material
dimensional stability
Over time, long-life coolants become
acidic and can deteriorate water pump
materials [4]. Standard die cast aluminium must be post-treated to protect the
component. However, this adds cost,
complexity and sometimes environmental issues with which to contend.
An improved design would not require
post-treatment.
In addition to chemical resistance, dimensional stability as a function of time
and temperature is critical to water pump
operation. Most pumps rely on accurate
movement and precise clearances in
order to function. Materials that have
high thermal expansion coefficients can
cause interferences and premature wear.
The dimensional stability of Bakelite®
engineering thermoset PF 6510 was
measured after 1000 hours of exposure to
coolant mixture at 120°C [5]. Width and
thickness dimensions remained nearly
constant for the engineering thermoset
while total mass absorption was less than
2.5%.
Long-term creep behaviour
Water pump components that are
subjected to sustained loads have a
greater possibility of failure if creep strain
exceeds design limits. Internal components/gears can slip due to dimensional
changes. Housings and attachment
locations can distort, causing leaks,
alignment issues or noise and vibration
(NVH) problems. Figure 2 shows the
long-term creep behaviour of Bakelite®
engineering thermoset PF 6510, PPA,
PPS and AZ91 magnesium. Even at
higher stress loadings, results indicate a

Fig. 2: Creep strain (%) according to ISO:899 of
Bakelite® engineering thermoset PF 6510 (72 MPa)
vs. engineering thermoplastic PPA (60 MPa) and
PPS (30 MPa) at 120 °C, over 1000 hours

superior low-creep strain of the engineering thermoset versus PPA and PPS. In
fact, the measured creep of the engineering thermoset was low enough to avoid
the need for threaded inserts in the water
pump housing. Assembly screws were
able to be directly fastened into threaded
holes, reducing the part complexity and
number of required assembly steps.

Case 2: vacuum pump parts
A vacuum pump produces vacuum for
power brakes and other devices in diesel
cars. It is consequently a critical part that
must operate reliably when subject to the
vibration, dynamic forces and temperature cycles generated by the engine. To fit
closely enough to avoid leakage, vacuum
pump parts must meet design tolerances
as low as 0.1%.
Similar to the water pump example, an
automotive customer sought alternative
materials for a next generation design
that could maintain performance while
reducing weight and cost.

Fig. 3: Fatigue strength of Bakelite® engineering
thermosets PF 1110, PF 6510, PPS (40% and 65%
GF) and PPA 50% GF

Vacuum pump
material dimensional stability
Several materials were considered for the
replacement design based on their thermal expansion behaviour. Table 1 compares the thermal expansion coefficients
of the candidate materials. Bakelite® engineering thermoset material PF 1110 has
coefficients of thermal expansion very
close to those of steel (0.10 vs. 0.11) and
behaves isotropically. By contrast, the
engineering thermoplastic materials have
higher coefficients of thermal expansion
and show anisotropic behaviour.
Long-term fatigue strength
Water and vacuum pumps experience
dynamic loads from the vehicle's engine
and from road conditions, making fatigue
strength an important consideration. Figure 3 compares the fatigue performance
of the candidate engineering thermoset
and thermoplastic materials. After 1
million cycles, the engineering thermoplastic materials lose 35-40% of their

Coefficients of thermal expansion for vacuum for vacuum pump candidate materiald

106 jec composites magazine / No87 March 2014

JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe