An atomistic-to-continuum approach to modeling size effects in polymer-carbon nanotube composites

We propose a computational procedure to assess size effects in polymer-carbon nanotube (CNT) composites. The characteristic dimension of CNTs, in the order of nanometers in the radial direction, calls for a detailed analysis of the atomic structure of the polymer in the region surrounding the CNT. This region, known as the interphase layer, plays a central role in the overall response of polymer-CNT composites [1] and can be related to the occurrence of size effects. In this contribution, the interphase layer and the CNTinduced size effects are characterized by means of Molecular Dynamics (MD) simulations on a polymerCNT representative unit. An optimization procedure is then employed to define a mechanically equivalent continuum model which describes the CNT, the polymer-CNT interface, and the interphase as a threedimensionalequivalentfiber[2]. Havingestablishedthemechanicalequivalencebetweentheatomisticand thecontinuummodel,weinvestigatesizeeffectsinthemechanicalpropertiesofaCNT-polymercomposite with realistic CNT volume fractions. In particular, we use the Generalized Finite Element Method [3] to efficiently handle the inclusion of the equivalent fibers in a polymer matrix.