Experimental characterization of mechanical and tribological properties of composite materials for friction-based force-limiting structural components

This research presents an experimental study to characterize the mechanical properties of composite materials and the tribological properties of composite to low-carbon structural steel friction interfaces for friction-based structural components in earthquake structural engineering applications. A systematic experimental testing program was developed, including the coupon tensile test, the plate bearing test, the bolt relaxation test, and the friction test. The friction test considered the normal load level, loading frequencies, sliding velocities, velocity profiles, and sliding histories as the testing parameters. Six types of phenolic-resin-based fiber-reinforced composite materials were tested. The results revealed the influence of the manufacturing process and the constituents of the composite materials on their mechanical and tribological properties. The flash compression molding process in manufacturing could produce composite materials having a lower concentration of phenolic resin than designed, and these materials exhibited exacerbated through-thickness creep behavior. Friction tests with different sliding velocities showed a general trend where an increase in the sliding velocity overall reduced the coefficient of friction, while lower sliding velocities overall increased the coefficient of friction. The velocity-dependent frictional behavior was found to depend on the material constituents of the composite materials. Among the friction interfaces tested, the friction interface with the composite friction material Gatke 398 (containing glass reinforcing fibers and graphite, Teflon and molybdenum disulfide MoS2 lubricants) in contact with low-carbon structural steel appeared to exhibit the most stable frictional behavior under various sliding velocities and was considered suitable for use in friction-based structural components for earthquake structural engineering applications.