Design of Very High-Strength Aligned and Interconnected Carbon Nanotube Fibers Based on Molecular Dynamics Simulations

The principal objective of this work is to implement a new material development paradigm using atomistic simulations to guide the molecular design of materials. Traditional empirical macroscopic material development studies omit the fundamental insight needed to understand material behavior at the atomic and molecular levels where material response begins. The new paradigm relies heavily on a tight integration between simulation and experimental efforts to design and process new materials with nanometer-scale precision. Exploiting nanotechnology requires atomic-molecular-level material design and the ability to process these materials with atomic-molecular-level precision. Processing materials with nanoscale precision poses formidable theoretical, computational, and experimental challenges to developing advanced materials. High performance computers and advanced physics-based simulations can complement experimental efforts to design, test, synthesize, and analyze novel materials and innovative structural designs. This method can be applied to a wide range of material designs. As a proof of concept, we began our work on the design of novel carbon nanotube-based materials. The mechanical properties of carbon nanotubes such as low-density, high-stiffness, and exceptional strength make them ideal candidates for reinforcement material in a wide range of high performance composites. Molecular dynamics simulations are used to predict the tensile response of fibers composed of aligned carbon nanotubes with intermolecular bonds of interstitial carbon atoms. The effects of bond density and carbon nanotube length distribution on fiber strength and stiffness are investigated. Results indicate that including cross link atoms between the carbon nanotubes in the strands significantly increases the load transfer between the carbon nanotubes and prevents them from slipping. This increases the elastic modulus and yield strength of the fibers by an order-of-magnitude. Carbon nanotube-based materials appear poised to affect civil and military engineering significantly over the next two decades by providing materials with an order-of- magnitude improvement in strength-to-weight and stiffness-to-weight ratios over existing materials.