Friction performance assessment of Non-Asbestos Organic (NAO) composite-to-steel interface and Polytetrafluoroethylene (PTFE) composite-to-steel interface: Experimental evaluation and application in seismic resistant structures

This paper presents an experimental research program for assessing the mechanical performance of two types of friction interfaces: i.e. Non-Asbestos Organic (NAO) friction composite against steel and Polytetrafluoroethylene (PTFE) composite against steel. A shear device was designed for testing the friction interface, and the compressive force on the interface was realized by a pretension high strength bolt. Cyclic loading tests were conducted for evaluating the friction performance of the interfaces, and loading frequency, loading amplitude, and magnitude of compressive force on the interface were considered as main influencing parameters. Experimental results showed that with the same magnitude of compressive force on the interface, the sliding shear force of the PTFE-steel interface was much smaller than that of the NAO-steel interface. An average friction coefficient of 0.12 was obtained for the NAO-steel interface, while an average friction coefficient of 0.025 was obtained for the PTFE-steel interface. Both friction interfaces exhibited stable and predictable behavior. The interfaces were further utilized in a slip friction damping device developed for upgrading the seismic performance of a novel timber-steel hybrid seismic resistant structure, and analytical results revealed that both structural damage and unrecoverable deformation of the structure were significantly decreased with the application of the damping devices.