Mechanical Response and Fracture Mechanisms of ψ-Graphene Containing Elliptical Defects: Effects of Aspect Ratio and Orientation.

Using molecular dynamics (MD) simulations, we systematically investigate the mechanical response and failure mechanisms of ψ-graphene containing elliptical nanoholes. The mechanical reliability of ψ-graphene is significantly influenced by the complex interplay between defect geometry and lattice anisotropy. Our findings reveal that for loading along the x-axis, mechanical properties are severely degraded at an aspect ratio (AR) of 1 but unexpectedly recover as the defect becomes more elongated (AR = 1 to 8). In contrast, loading along the y-axis leads to a persistent degradation of the mechanical properties for all AR values. Furthermore, we have investigated the influence of the elliptical defect's orientation on the mechanical properties relative to the tensile axis. The results reveal a pronounced orientation-dependent anisotropy; notably, the mechanical performance reaches its minimum at a critical tilt angle of 75° rather than the expected 90°. This anomalous behavior is driven by a mixed-mode (shear-tension) failure mechanism, where the elliptical tips align with the lattice's intrinsic failure planes, significantly lowering the energy barrier for bond rupture. These results provide a new perspective for understanding and modulating the mechanical properties of ψ-graphene, serving as quantitative guidance for the potential application of carbon-based two-dimensional materials in nano-devices.