Effect of fiber addition on mechanical and tribological properties of a copper/phenolic-based friction material

The purpose of the present work is to compare the effects of addition of different fibers on the mechanical and tribological properties of a copper/phenolic resin-based semi-metallic friction material using the same fiber contents and process conditions. The results indicate that cracks/voids are observed more or less in all post-cured materials. Compared to fiber-free material, materials containing copper and brass fibers have higher compressive strengths, while materials containing cellulose and carbon fibers have lower strengths. After post-curing all materials increase in thickness and decrease in weight and density. Cellulose fiber-added material has the greatest increase in thickness and decrease in density. Except cellulose, all fiber-added materials exhibit higher average COF values than that without fibers. Significant fade occurs to materials containing steel, brass, cellulose and ceramic fibers. Steel fiber-added material has the largest wear, while copper fiber-added material has the smallest wear. A loosely bonded layer of wear debris almost fully covers the worn surfaces of fiber-free as well as brass, cellulose and ceramic fiber-added materials. The debris layer partially covers the surfaces of copper and carbon fiber-added materials, and is substantially absent from the surface of that containing steel fiber. Among all fibers copper fiber appears to be the best candidate due to its relatively high and stable COF as well as low wear.