Effects of interfacial friction on composites containing nanotube ropes

The present paper develops a constitutive model for the elastic modulus and energy loss of CNT-based polymeric composites. In this study, a close-packed lattice consisting of seven nanotubes in hexagonal arrangement is used to model single-walled carbon nanotubes often found in rope-like bundles in polymers. The composite is described using a multi-phase system composed of a resin and bonded and debonded nanotube ropes. The concept of "stick-slip" motion caused by frictional contacts is proposed to describe the load transfer behavior among the nanotubes and between the nanotube ropes and resin. A micromechanical model is developed to describe inter-tube and tube/resin frictional motions. Modulus change and energy dissipation due to the "stick-slip" interfacial load transfer are determined. The developed method is used to analyze composites with aligned nanotube ropes. The analytical study shows that mechanical properties can be significantly affected by adding small fractions of carbon nanotubes in polymers. The elastic modulus and loss factor are both strain-dependent. Also, to show the inter-tube sliding effects due to nanotube aggregation, results obtained for the composites filled with well-dispersed nanotubes and nanotube ropes are compared.