Study on wear mechanisms of copper impregnated C/C composite under electrical current

Pantograph contact strips made of carbon-based materials have been widely used on Japanese railway lines. However, carbon-based materials are low in fracture toughness and there are still concerns about brittle fracture of strips in use. Hence, we have developed copper-impregnated carbon fiber reinforced carbon composites (C/C composites). In order to evaluate the wear performances and wear mechanisms of developed C/C composites, block-on-disk type wear tests were performed applying electrical current. Two kinds of C/C composites with different strength of carbon fiber were adopted for the test pieces. The test was carried out under the following conditions: contact force is 59N; electrical current, 100 to 500A; arc-discharging ratio, 0 to 15%. The arc-discharging rate is defined as the ratio of arc-discharging time to test time. From the experimental results, the following have been found out: the wear of copper impregnated C/C composite strips is proportional to the amount of heat generation at contact points which can be calculated from the measurement value of contact voltage drop and electric current; strengthening carbon fiber is not effective for reducing the wear of C/C composites.