JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 57

Tab. 1: Endurance test of the demonstrator (configuration 2)
Torque

Number of cycles

Test results

-274 / +137 N·m

30,000

No failure

10% increase for every 30,000 cycles reached
-548 / +274

30,000

No failure

-500 / +250 N·m

2,000,000 cycles

No failure

Test results for the demonstrator

Fig. 6: Pin positions in Configurations 1 to 5

was then prepared to try to limit the number of pins and to better understand the
effect of the pin number and position on the
mechanical performance of the assembly.
Five configurations were prepared:
- Configuration 1:
168 pins - pin height = 2 mm
- Configuration 2:
168 pins - pin height = 3 mm
- Configuration 3:
120 pins - pin height = 3 mm
- Configuration 4:
117 pins - pin height = 3 mm
- Configuration 5:
78 pins - pin height = 3 mm
The pins were uniformly positioned in
configurations 1, 2, and 3. They were
grouped in 6 sectors comprising 3 and 2
rows, respectively, in configurations 4 and 5,
as shown in figure 6.

The demonstrators were tested for their
ultimate resistance to torque. A test bench
was designed to test the samples in torque
to failure. The torque was recorded as a
function of the angle until failure of the
assembly.
The samples were tested at room temperature without ageing, the results are shown
in figure 7. The torque at failure and the
stiffness of the assembly were compared.
The first conclusion was that, from a 1200
N·m baseline for a non-textured metal disk,
the demonstrator's torque at failure can be
increased by 100-200% when textured disks
are used (2500-3550 N·m). Similarly, the
assembly's stiffness is improved by more
than 200% from 500 N·m/°.
For new samples at room temperature, two
technologies yield very comparable results
in terms of torque at failure and stiffness:
adhesive bonding combined with overmoulding and CMT pins in configuration 2.
The effect of the pins' height (2-3 mm) can
be compared between configurations 1
and 2. The main effect relates to stiffness,
which increases with pin height. It was also
demonstrated that the number of pins can
be reduced without significantly decreasing

Fig. 7: Torque at failure and stiffness of the "triangle" demonstrator. The tests
were conducted at room temperature in "new" conditions

performance (configurations 2 and 4) and
that the number of pins can be tuned to the
desired performance (configurations 4 and
5). Also, the technology with collars does
not perform as well as CMT pins but still
significantly improves performance while
being much simpler and cost effective.
The samples were then tested to evaluate
the influence of moisture and temperature
on the assembly performance. Some samples were tested after conditioning at 70°C
and 62% relative humidity for 10 days and
new samples were tested at 80°C.
Due to the fact that a polyamide composite
was used, the effects of moisture and temperature were both important.
Two types of technologies were compared:
CMT pins (configuration 2 with 168 pins
of 3 mm) and adhesive bonding plus overmoulding. For the samples with CMT pins,
the effect of moisture was under 5% due
to the high fibre content in the polyamide, whereas torque at failure at 80°C was
reduced by about 25%. Such values can be
expected when polyamide is used.
For the bonded solutions, the samples'
performance decreased more significantly
with a 27% decrease after the conditioning
step and 75% at 80°C.

Fig. 8: Torque at failure of the "triangle" demonstrator. The tests were conducted
at room temperature in "new" conditions and compared with conditioned
samples and samples tested at 80°C

No104 April - May 2016 / jec

composites magazine 57
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016
