ON WEAR SYNERGISM IN HYBRID COMPOSITES

The dry-wear behavior of several polymer composite materials (unidirectional glass, carbon, or Aramid fibers in epoxy, PEEK, or PA matrix) sliding against smooth ball-bearing steel counterparts has been investigated. Results of specific wear rates of the different composites as a function of sliding direction (normal, parallel, and antiparallel fiber orientation) were referenced to the wear rate of the unfilled epoxy (as a standard). This database was then utilized in the design of an optimum wear-resistant composite material for specified wear conditions (hypothetical model). The structure of the model material was approached in step-wise fashion by making and testing hybrid composites consisting of various layers of glass, Aramid, or carbon fibers under different orientations. Synergistic effects were found with respect to the wear-resistance of the hybrid composites in comparison with the monolithic systems, indicating that the hypothetical model was a prediction in the right direction. The best achievement was observed with hybrid composites containing inner layers of Aramid fibers with normal orientation relative to the contact surface and outer layers of carbon fibers oriented parallel to the sliding direction. The wear studies were complemented by SEM-studies of the wear mechanisms, the final objective being to develop a wear model that helps to predict the wear-resistance of composites as a function of their microstructural composition.