xu, hao2019-09-172019-09-172019-07https://hdl.handle.net/11299/206615University of Minnesota Ph.D. dissertation. July 2019. Major: Aerospace Engineering and Mechanics. Advisor: Traian Dumitrica. 1 computer file (PDF); xxiii, 138 pages.Super strong lightweight material systems comprising carbon nanotubes (CNTs) are especially suitable for aerospace applications. Assembles of CNTs obtained by mechanically stretching the CNT sheets, represent a promising material platform for developing composite materials with mechanical attributes approaching those of individual CNTs. In this quest, the guidance power of computational materials modelling is critical. Ideally one would like to investigate CNT assembles with all atom simulation methods, but this approach is computationally prohibitive. Due to the inherent spatial and temporal limitations of atomistic modeling and the lack of mesoscale models, mesoscopic simulation methods for CNT systems are missing. My work focuses on deriving ultra-coarse-grained models based on mesoscopic dintinct element method (mDEM). Our mDEM model is informed by atomistic data obtained with molecular dynamics (MD) and density functional theory-based tight-binding (DFTB) objective molecular modeling. Our mDEM model is capable of reproducing the atomistic elastic and frictional properties of CNTs. With the mDEM model, tensile tests of mesoscale CNT network were carried out, showing results in good agreement with experiments. The tensile tests revealed nanofriction was a key factor deciding the load transfer of CNT network. Our mDEM model serves as a powerful tool to expand the understanding and guide the development of CNT materials.enCarbon NanotubesDistinct Element MethodMolecular DynamicsThesis or Dissertation