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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.

Current phase of the study was undertaken to examine tensile fatigue behavior of cord-rubber composites representing bias tire carcass under various frequencies up to the level which closely simulates loading during high-speed take-off of aircraft. At a given stress amplitude, the use of higher cyclic frequency was found to affect strain response and heat build-up characteristics of composites significantly. The lower level of initial strain observed at higher frequency stems clearly from strain rate dependence of deformation of rubber matrix composites. The temperature profile of the specimens subjected from 20 to 30 Hz loading showed that hysteretic heating under these conditions may lead to thermal fatigue failure as well as chemical degradation influencing both fiber-matrix adhesion strength and matrix strength.

An aircraft tire durability study is underway to investigate the deformation and fracture behavior of cord-rubber composites. This study will identify the important parameters responsible for the structural failure of aircraft tires by the use of analytical and laboratory prediction methods. These methods will also identify the interaction between material property degradation and damage accumulation in cord-rubber composites. Preliminary results using coupon specimens of tire carcass have revealed that prolonged static and cyclic loading sequences produce extensive interply shear deformation at the free edges resulting in cord-matrix debonding followed by delamination type failure. These loading sequences represent the circumferential tension in the footprint region of aircraft tires. It was also determined experimentally that a fatigue endurance limit can be established for cord-rubber composites.