Computational design of carbon nanotube network materials and polymer matrix nanocomposites

Carbon nanotube (CNT) network materials constitute a broad class of multifunctional materials that possess a unique combination of structural, mechanical and transport properties, making them attractive for various aerospace applications. The complexity of the hierarchical multiscale organization of the CNT materials, wide diversity of material structures and variability of physical properties present a challenge for theoretical evaluation of the structure-properties relationships and define the critical role the computational modeling can play in designing the advanced CNT materials. A team of researchers from the University of Virginia and University of Alabama has developed an advanced mesoscopic model capable of bridging the gap between the behavior and properties of nanoscale structural features of CNT-based materials revealed in atomistic simulations and the effective macroscopic properties defined by the collective behavior of thousands of interacting nanotubes. The model is incorporated into a popular open-source code LAMMPS and applied for investigation of structural, mechanical, and transport properties of the CNT network materials. The results obtained in the multiscale modeling and theoretical analysis include the establishment of a new mechanism of compressive deformation of vertically aligned CNT forests, elucidation of the mesoscopic mechanisms that control impact resistance and mechanical stopping power of CNT films subjected to bombardment by high-velocity nanoparticles, development of a novel mesoscopic model of covalent cross-links between carbon nanotubes parameterized based on result of atomistic simulations, insights into the mechanisms of load transfer during the mechanical deformation of CNT films composed of nanotubes of different chirality and density, as well as with different degrees of chemical cross-linking between the nanotubes, design of analytical description of the inter-tube conductance based on predictions of atomistic simulations and suitable for incorporation into mesoscopic model, as well as the development of an analytical model of thermal transport properties of nanofibrous materials. Overall, the outcomes of this computational project contribute to the development and design of multifunctional low-density materials with unique combination of mechanical and transport properties tailored for aerospace applications. The results are reported in 3 key-note, 8 invited, and 12 contributed conference presentations, 2 invited university seminars, and 9 published papers.