Mechanical behavior of twisted bilayer graphene and titanium nanocomposites

Z Fu and W Zhang and Y Zhang and H Chen and A Amer, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 303, 110616 (2025).

DOI: 10.1016/j.ijmecsci.2025.110616

This study investigates the mechanical behavior of twisted bilayer graphene (TBLG) and its reinforced titanium matrix nanocomposites (TBLG- RT) through molecular dynamics (MD) simulations. Young's modulus and shear modulus of TBLG are systematically calculated for the first time, across twist angles from 0 degrees to 30 degrees with 1 degrees increments. Our results demonstrate that while Young's modulus exhibits minimal angular fluctuations, tensile strength displays anisotropic behavior: decreasing in the zigzag direction yet increasing in the armchair direction with larger twist angles. Furthermore, the shear moduli show negligible angular dependence across the studied range. A critical finding is that TBLG manifests transversely isotropic material properties at a critical twist angle of approximately 29 degrees similar to 30 degrees Consequently, TBLG with a 29.96 degrees twist configuration is selected for titanium reinforcement in uniaxial tensile and shear simulations. and the TBLG with twist angles of 6.01 degrees and 12.90 degrees are used to verify the angle independence of TBLG-RT. The MD simulations reveal that even minimal TBLG volume fractions induce substantial mechanical property enhancements compared to pure titanium. However, significant discrepancies emerge between conventional micromechanical models (Rule of Mixtures and Halpin-Tsai) and MD-derived results at higher reinforcement fractions. To address this divergence, we propose modified versions of these models calibrated against MD simulation data, enabling more accurate predictions of TBLG-RT composite performance. Furthermore, the modified micromechanical models establish a computational framework for tailoring graphene-reinforced composites across length scales, bridging quantum-scale MD insights with macroscopic engineering applications.

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