The investigation of carbon nanotube based polymers for improved structural damping

In this paper, experimental and analytical investigations are conducted on the energy dissipation of polymeric composites containing carbon nanotube fillers. The specimens are fabricated by directly mixing single-walled carbon nanotubes into two types of representative polymers, a stiff resin system (Epon 9405/Epodil 749/Ancamine 9470) and a soft resin system (D.E.R. 383/Epodil 748/Ancarez 2364/Ancamine 2384), with high-power ultrasonic agitation. To characterize loss factors, uniaxial testing with harmonic loading is conducted to directly measure the phase lag between stress and strain. The loss factors are measured using different material deformations. The present paper also presents an energy loss model by addressing nanotube/resin interfacial friction. The concept of "stick-slip" motion caused by frictional contacts between nanotubes and resin is proposed to describe the load transfer behavior. Energy dissipation and loss factor are characterized through the work done by interfacial friction. The trends of strain-dependent loss factors obtained from experiments and analysis are compared.