Multiscale damping model for polymeric composites containing carbon nanotube ropes

A novel multiscale model is developed for describing the damping characteristics of polymeric composites containing aligned or randomly oriented carbon nanotube (CNT) ropes. This is the first known model of damping behavior of CNT-based composites incorporating length scales from atomic to structural. The shear strengths at the inter-tube and tubeĝresin interfaces are calculated using molecular dynamics simulations of nanotube pull outs. The calculated shear strengths are then applied to a micro-mechanical damping model in which the composite is described as a three-phase system composed of a resin, a resin sheath acting as a shear transfer zone, and a CNT rope. The resin is modeled as a viscoelastic material using a three-element standard solid model. The concept of stick-slip motion is used to describe the load transfer behavior between carbon nanotubes in a rope as well as between nanotubes and the surrounding sheath. Energy dissipation from the viscoelastic polymer matrix and from the stick-slip motion contributes to the overall structural damping characteristics. This model is used to study the damping behavior of CNT/polymer composites under tensiong-tension and tensiong-compression cyclic loads. The effects of volume fraction and aspect ratio of the nanotube ropes on damping are illustrated and good insights are gained by analyzing the model.