Wear of Tire Tread/Carcass Composites

A multi-axial dynamic test instrument was designed to perform wear testing of actual aircraft tires as well as tread/carcass composite specimens under laboratory loading conditions which simulate the elements of take-off, landing and taxiing operations. The wear tester consists of a self-spinning abrading head, mounted on the actuator of a servo-hydraulic test system, which faces either (1) the tread surface of a composite specimen clamped by a horizontal stretch frame or (2) the tread region of actual inflated tires. The test concept has been partially proven in the case of tread/carcass composite specimens by building a proto-type test apparatus and operating it successfully. In the current test set-up, the specimen is subjected to static tension to simulate a circumferential load in the tire footprint and the tread surface is in periodic contact with an abrading head under a specific level of pressure. A swirling mode of motion is superimposed to a spinning action of a circular disk type head to induce the wear of the tread side of the specimen in a constantly changing direction. This ensures the elimination of ‘abrasion pattern’ and allows ‘intrinsic abrasive wear’ under varied contact pressure. Repeatable trends of thickness reduction and weight loss characteristics were observed for each case of tread/carcass composites tested thus far in this study. In the case of automotive tire materials, our preliminary wear test results were found to be consistent with the field experience. The wear rate appeared to be governed by the particle size and the degree of agglomeration of carbon black fillers. The wear phenomenon may therefore be interpreted as a process of filler-matrix debonding under contact fatigue loading. One interesting observation was that, well below a critical temperature, higher temperatures tended to be associated with lower wear rates. The results clearly suggest that less hysteresis of tread compound causes more rapid tread wear, which is consistent with the model proposed by Schallamach and Turner.