A physically-based abrasive wear model for composite materials Page: 8 of 22
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To provide some degree of experimental verification of the proposed model, abrasive wear
tests were conducted with a model composite system involving an epoxy matrix with spherical
aluminum alloy particulate reinforcement. In order to minimize the effect of the mismatch in
coefficient of thermal expansion, a room temperature curing epoxy was selected as the matrix
material; this was DER 331 epoxy resin and DEH 24 hardener from Dow Chemical, Midland, MI
USA. The epoxy was reinforced with 6061aluminum metal particles provided by Valimet Inc.,
Stockton, CA USA; the particles were nominally spherical with an average size of ~100 m.
In order to vary the contribution coefficient C in Eq. (15), tests were performed for
composites with different matrix/reinforcement interfacial toughnesses and with different relative
sizes of reinforcement. A "strong" interface was achieved by reinforcing the epoxy with
uncontaminated particles, whereas a "weak" interface was achieved by prior coating of the
particles with a thin layer of silicone. By conducting tests on different sizes of abrasive (35 ~ 326
m), the relative size of reinforcement was varied.
Tests were performed for the specimens with 0, 20, 40 and 100 vol.% of reinforcement. The
composites were fabricated by the stir-casting method, specifically involving the mixing of metal
particles in a liquid epoxy followed by casting in an open mold (9.5 mm diameter and 20 mm
length) in a vacuum.
B. Abrasive wear test
Two-body abrasive wear tests were conducted on a pin-on drum abrasive wear tester,
designed for standard wear tests described ASTM standard D5963-97a. In this method, the test
specimen moves over the surface of an abrasive, which is located on a revolving drum, the
resulting wear of the material being expressed as the volume loss . The test setup is
schematically illustrated in Fig. 6.
An alumina (A1203) abrasive was used which is substantially harder than the matrix and
reinforcement. The pin specimen, which was 0.95 mm diameter and 20 mm long, was placed on
the top of the drum, which was then rotated at a fixed angular speed of 25 RPM; this gives a
tangential velocity at the contact surface of 200 mm/s. While the drum was rotating, the
specimen moves at the speed of 4.2 mm/rev along the axis of rotation. Thus, the specimen is
continuously in contact with new abrasive surface. A static normal load, L, was applied directly
above the specimen to press it against the center of the drum (Fig. 6); its magnitude was varied
from 1 to 5 N, corresponding to normal stress from 13.8 to 68.8 kPa. Throughout the test, the
sliding distance was fixed at 39.2 m (80 revolutions). All tests were carried out in dry ambient air
RESULTS AND DISCUSSION
A. Prediction with the new model
Predicted wear rates from Eq. (15) for the two ideal composites with different contribution
coefficients and volume fractions are shown in Fig. 7. The two composites, termed composite 1
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Lee, Gun Y.; Dharan, C.K.H. & Ritchie, Robert O. A physically-based abrasive wear model for composite materials, article, May 1, 2001; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc780737/m1/8/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.