Multiscale simulation of vacancy-induced defects in carbon nanotube nanocomposites: Mechanical implications

Carbon nanotubes (CNTs) are increasingly utilized as reinforcements in polymer composites for aerospace, mechanical, and automotive applications. However, a comprehensive understanding of the relationship between their nanostructure and resulting mechanical properties remains limited. In industrial-scale manufacturing, random defects and structural imperfections are inevitable and can significantly impact these relationships. This study investigates the effects of such defects, specifically vacancy-induced imperfections within CNTs, on the mechanical behavior of Carbon-Nanotube-Reinforced Polymer Composites (CNTRPCs). Therefore, the present work concentrates on vacancy defects within the SWCNT and at the CNT–polymer interface, aiming to isolate their direct mechanical effects. By excluding additional sources of variability, such as polymer micro-voids, CNT orientation, and dispersion, which are relevant at the mesoscale,the analysis focuses solely on the specific contribution of vacancy defects to the composite’s behavior. Due to the challenges associated with experimental evaluation, a computational material modeling approach is adopted. A multiscale finite element model of a Representative Volume Element (RVE) is developed to characterize the nanocomposite’s mechanical properties. The model includes a Single-Walled Carbon Nanotube (SWCNT), an interfacial region, and a polymer matrix. The SWCNT is modeled as a space nano-frame using a modified Morse potential; the polymer matrix is represented via the Mooney-Rivlin strain energy function; and the interface is described using van der Waals interactions modeled by the Lennard-Jones potential. Vacancy defects and corresponding disruptions in van der Waals interactions are introduced through Monte Carlo simulations. The mechanical response of the nanocomposite is then predicted, and the influence of nanoscale defects on its overall performance is analyzed. The findings offer valuable insights for practical nanomaterial design and optimization. • Vacancy defects in CNTs and their effect on composite strength. • Multiscale finite element modeling of a nanocomposite RVE. • Monte Carlo simulations introduce defects and predict performance variations.