Tribo Performance of T-bfrp Composite Subjected to Dry/Wet Contact Conditions - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 311

effect of sliding on surface roughness
Before test, the average roughness profile of the stainless steel counterface was Ra
= 0.052 μm; Figure 10(a) . After test under both dry/wet contact conditions, there
were slight modifications on the counterface roughness. The roughness profiles of
the counterface are presented in Figures 10(b) and (c). The roughness of the wear
track was measured in the presence of film transfer. The film transfer was removed
by acetone, where the polyester is soluble in acetone and the results are displayed in
Figure 11.
From Figure 11, one can see that the average roughness values were slightly
lower when the T-BFRP composite that was subjected to wet contact condition as
compared to the dry test. As discussed previously, water played an important role to
wash away trapped/generated wear debris between the contacting interface and thus
lowering the Ra values in wet contact conditions. For dry tests, the higher roughness
is due to the trapped wear debris from the fibrous and resinous regions on the coun-
terface which contributed to increase the Ra values for all three orientations. From
Figure 11, it can be said that the counterface roughness increased for both dry and
wet contact conditions after testing the composite in the three orientations. However
in dry contact condition; after cleaning the counterface, the roughness decreased
noting that the counterface roughness is still higher than the virgin one. This indi-
cates the presence of rough film transfer during the sliding. Interestingly, under wet
contact conditions, there were not many changes in the Ra values of the counterface.
It can be observed that the wear track roughness after testing before cleaning and
after cleaning was not highly remarkable. This could have been because of water
introduced at the interface which washed away all trapped wear particles by the
T-BFRP composite test specimen during the sliding. In spite to this, the reduction
of counterface surface roughness under wet contact condition was about 21% as
compared to the dry test.
The optical microscopy images of the virgin counterface and after the test
are shown in Figure 12 for dry/wet contact conditions. In Figure 12(b), compos-
ite experienced film transfer on the counterface. However, there was much worn
polyester debris from the resinous region of the composite which caused greater
surface roughness on the counterface due to the fact that the worn polyester debris
are brittle by nature. When the composite was subjected to wet contact condition,
the counterface was polished with the presence of water during sliding. As a re-
sult, there was no evidence of film transfer which is confirmed by Figures 12(d)
and (e). Therefore, this can be the reason why the specific wear rate under wet
contact condition for the three orientations was significantly lower compared to
the dry test.