3. Molecular Dynamics Studies of Load Transfer in Nanocomposites Reinforced by Defective Carbon Nanotube

This chapter is concerned with the development of relatively more accurate numerical simulations than those adopted in the literature to investigate the considerable discrepancies between experimental findings and theoretical predictions of the interfacial shear strength (ISS) of nano-reinforced thermoset composites. Those differences are most likely attributed to the presence of various defects, the possible inaccuracies in the system modeling, and the variance between experiments. In this chapter, we present a review of the literature as well as recent work conducted by the authors focusing on the effect of defects and functionalization on the ISS and buckling behavior of carbon nanotube (CNT)-reinforced composites. Different modeling and calculation techniques pertinent to CNT pull-out tests are presented, and proper selection of the simulation parameters are discussed. Unlike earlier studies, which focused on thermoplastics, in this chapter attention is devoted to CNT-reinforced thermoset polymer composites with different degrees of conversion. Pull-out and compressive load simulations were performed on a representative volume element comprising a single-walled CNT embedded in an epoxy matrix. All MD simulations used the consistent valence forcefield (CVFF) to represent the interatomic potential. Our results revealed that different defects can, to some extent, either enhance or degrade the properties of nanocomposites. The findings of this chapter will assist in improving our understanding of the toughening/weakening mechanisms associated with nanoscopic reinforcement and the load transfer capability in epoxy-based nanocomposites and give an insight into the reasons for the discrepancies in ISS.