Anisotropic fracture mechanisms and crack-mediated mechanical degradation in trigraphene nanosheets: A molecular dynamics study

This study investigates the anisotropic fracture mechanisms and mechanical degradation of trigraphene nanosheets (TNS) with central cracks using molecular dynamics (MD) simulations. The elastic modulus, ultimate stress, fracture strain, toughness, and stress intensity factor (Kc) are systematically evaluated as functions of crack angle (0°-90°), crack length (30-60 Å), and temperature (200-1000 K) under uniaxial tension along armchair (X) and zigzag (Y) directions. Key findings reveal direction-dependent failure modes: X-loading causes brittle, mode-I fracture with symmetric crack propagation and high stress concentration at tips, while Y-loading induces crack deflection toward boundaries due to diffuse stress distribution and tip shielding. Mechanically, the armchair (X) direction exhibits higher elastic modulus, whereas zigzag (Y) demonstrates superior ultimate stress, fracture strain, toughness, and fracture toughness but greater sensitivity to crack orientation. Elevated temperatures lead to significant thermal softening, reducing stiffness, strength, and fracture resistance, with the Y direction experiencing more pronounced deterioration.