A Study on the Wear Behavior of Plasma-Modified Woven
Carbon/Epoxy Laminated Composites
Jae H. Lee a, Jae S. Lee a, Kyong Y. Rhee b,* (corresponding author), Bong H. Lee c
a
School of Mechanical Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea
corresponding author, School of Mechanical Engineering, College of Engineering, Kyung Hee
University, Yongin
446-701, Republic of Korea, ([email protected])
c
Korea Automotive Technology Institute, 74 Yongjeong-Ri, Poongse-Myun,Dongnam-gu, Cheonan-si,
Chungnam 330-912, Republic of Korea
Abstract
In this study, woven type carbon fibers were plasma-treated using oxygen gas to improve wear
properties of woven carbon/epoxy laminated composites. FE-SEM examination was made to determine
the physical changes on the surface of carbon fibers due to the oxygen plasma modification. Wear tests
have been performed using unmodified and plasma-modified carbon/epoxy woven composites to
investigate effect of the plasma treatment on the tribological behavior of carbon/epoxy woven
composites. It was found that the wear properties of plasma-treated carbon/epoxy woven composites
were better than those of unmodified carbon/epoxy woven composites. It was also found that the
improved wear properties of the plasma-treated carbon/epoxy woven composites were attributed to
enhanced adhesive strength, caused by the carbonyl functional groups created on the carbon fibers.
b,*
Keywords: carbon/epoxy woven composites, plasma treatment, wear
1. Introduction
The use of woven fabric reinforced polymer
composites is increasing in automobile,
aerospace, naval, and civil industries because
they exhibit excellent mechanical properties in
both longitudinal and transverse directions.
Among them, carbon/epoxy woven composites
are prominent wear-resistant materials because
carbon fabric offers good strength, stiffness,
and thermal conductivity. Accordingly, many
studies have examined the wear behavior of
carbon/epoxy woven composites [1-3].
Adhesion between the carbon fabric and epoxy
is crucial to the wear properties of
carbon/epoxy woven composites. In general,
carbon/epoxy woven composites suffer from
weak adhesion at the carbon/matrix interface
due to the hydrophobic properties of carbon
fabric [4-9]. Presently, not many studies have
been made to improve wear properties of
carbon/epoxy composites by increasing
interfacial strength between the carbon fiber
and the matrix .
In this study, a carbon woven fabric was
surface-treated by oxygen plasma to improve
adhesive force at the fiber/matrix interface and
its effects on the wear properties of a
carbon/epoxy
woven
composite
were
investigated. Ball-on-disk wear tests were
performed and wear track was analyzed using a
scanning electron microscope (SEM).
2. Experimental
The materials used were carbon plain-woven
fabric (CF332NON, Korea Carbon, Korea),
bisphenol-A type epoxy (YD-115, Kukdo
Chemical, Korea), and D-230 hardener
(Dianiline, Kukdo Chemical, Korea). The
epoxy resin and hardener were mixed in a 6:4
ratio by weight percent. The carbon fabric was
desized and surface treated with lowtemperature atmospheric oxygen plasma using
a Plasma-Preen II (Plasmatic Systems Ltd.,
USA). Oxygen gas was used to induce the
plasma. Chemical changes on the carbon fiber
surface due to treatment were determined using
1
X-ray photoelectron spectroscopy (XPS)
analysis.Wear specimens were made using
four-plied carbon/epoxy woven composites
with a fiber content less than 67% by weight.
The carbon/epoxy woven composites were
cured in an autoclave with a pressure of 2
kgf/cm2 at 130ºC for 6 hr. The cured
composites were cut into 30 ㎜ × 30 ㎜ pieces
using a diamond wheel cutter. Ball-on-disk
wear tests, which used one zirconia (ZrO2) ball,
were conducted at room temperature using a
Neotribo Friction & Wear test machine (NeoPlus, Korea). The applied vertical load and
rotational speed were 19.6 N and 10.6 m/min,
respectively. Sectional shape of the wear track
was measured using a surface profiler (Dektak
150, Veeco Ltd., USA) to determine wear
volume loss.
Figure2. Surface profiler of unmodified and plasmamodified carbon/epoxy composites
Figure 2 shows a comparison of the wear-depth
profile for untreated and plasma-treated
samples. As expected from the change of
friction coefficient, the plasma-treated sample
exhibited better wear-resistant behavior than
the untreated sample. The maximum depth
profiles of untreated and plasma-treated
carbon/epoxy composites were 23 μm and 13
μm, respectively. Worn surfaces of the
untreated and plasma-treated carbon/epoxy
woven composites samples were examined
using SEM to investigate the wear mechanism.
3. Results and discussion
The effect of plasma treatment on the wear
behavior of carbon/epoxy composites was
investigated by determining the change in
friction coefficient as a function of wear
distance.
Figure 3. Worn surface of unmodified composites
Figure 1.Variation of friction coefficient of carbon/epoxy
composites with and without plasma treatment
Figure 1 shows the change in friction
coefficient as a function of wear distance. As
shown
in
the
figure,
plasma-treated
carbon/epoxy woven composites had a lower
friction coefficient compared to untreated
carbon/epoxy woven composites. Specifically,
the fraction coefficients of untreated and
plasma-treated samples were 0.2~0.3 and
0.15~0.2, respectively.
Figure 4. Worn surface of plasma-modified composites
2
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Figures 3 and 4 show the worn surfaces of
untreated and plasma-treated carbon/epoxy
woven composites, respectively. For the
untreated sample, fibers were broken and
dispersed randomly in the epoxy matrix. Fibers
were peeled off from the epoxy, and the
surfaces of the peeled fibers were relatively
clean due to weak adhesion forces between the
carbon fibers and epoxy matrix. On the
contrary, for the plasma-treated sample, the
fibers and epoxy matrix remained well adhered,
despite the presence of local cracking,
indicating that more energy was required to
wear the oxygen plasma-treated specimen than
the untreated specimen.
4. Summary
The effect of oxygen-plasma treatment on the
wear behavior of carbon/epoxy woven
composites was investigated. Ball-on-disk wear
tests were performed on carbon/epoxy
composites that were made of untreated and
plasma-treated carbon fibers. It was found that
oxygen-plasma treatment of the carbon fabric
resulted in improved wear properties of the
carbon/epoxy woven composite. Specifically,
the friction coefficient and wear volume loss of
carbon/epoxy composites were reduced by 26%
and 88%, respectively, by plasma treatment.
The improvement of wear properties of plasmatreated carbon/epoxy composites was caused by
the improvement in interfacial adhesion
strength of the plasma-treated sample was
caused by the formation of new polar functional
groups, especially C=O carbonyl groups.
Ackowledgement
This work was supported by the Center for
Science & Technology Research(CSTR) grant
funded by the Korea government(MEST).
(CSTR-002-100701-03)
References
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Mayer, S. Jeelani, Effect of stitching and weave
architecture on the high strain rate compression
response of affordable woven carbon/epoxy
composites Composite Structures Volume 59,
Issue 4, March 2003, Pages 507-523
3