Simulations reveal the secret to strengthening carbon fiber

Summary

Most high-performance computing clusters used by industry and universities can simulate upwards of a few thousand atoms. But the calculations use approximation techniques that group atoms together instead of calculating them individually. The technique is faster and far less computationally demanding, but it’s also less accurate and can introduce errors.The research team was given a small allocation of time on Frontier via a Director’s Discretionary award to demonstrate the benefits of using a leadership-class supercomputer. Frontier is the world’s most powerful supercomputer for open science, with a peak performance of 2-exaflops per second, meaning it can perform more than a billion-billion calculations per second.Using only a fraction of Frontier’s power, Sohail and Ghosh built a 5-million-atom model of carbon-fiber composites reinforced by PAN nanofibers. This model provided unprecedented molecular-level insights into the fundamental forces that bind the materials together.To find the right fit, the team modeled PAN nanofibers with diameters that ranged between 6 and 10 nanometers by using the Large-scale Atomic/Molecular Massively Parallel Simulator, or LAMMPS. LAMMPS is a powerful, open-source code used for molecular dynamics simulations on supercomputers. It is widely used to model the behavior of atoms in materials such as metals, polymers and biomolecules and investigate how the materials respond to conditions such as stress, temperature and chemical changes over time. The simulations showed that PAN nanofibers with a diameter of approximately 6 nanometers offered the best performance. The thinner fibers aligned more uniformly at the interface, thereby improving both mechanical strength and stress transfer from the carbon fiber to the polymer. “Simulating materials with 5 million atoms would not have been possible without the power of Frontier,” Sohail said. “To our knowledge, this work is the first hierarchical, fully atomistic simulation of a complete bul...