Void dominated fracture and plastic localization in Cu/Al laminated composites revealed by molecular dynamics simulations

Abstract

Cu/Al laminated composites are promising for lightweight conductive and thermal-management applications, but tensile reliability is strongly affected by deformation incompatibility and damage localization near heterogeneous interfaces. Molecular dynamics simulations were performed to reveal the void-dominated fracture behavior of idealized Cu/Al laminated composites with Cu volume fractions of 15%, 30%, and 50%, in this study. Tensile response and atomistic damage evolution were characterized by stress–strain analysis, polyhedral template matching (PTM), dislocation extraction analysis, local atomic shear strain, and PTM-based root-mean-square deviation (PTM-RMSD). All models exhibit rapid hardening, abrupt post-peak stress release, serrated load-bearing fluctuations, and final through-thickness fracture. As the Cu volume fraction increases from 15% to 50%, the peak stress decreases from approximately 13–11 GPa, while the average post-peak plateau stress decreases from approximately 8.0–6.4 GPa. This inverse trend indicates that the system-level tensile strength is not governed by a simple rule-of-mixtures relationship. Instead, increasing Cu content localizes Shockley partial dislocations, lattice distortion, and high-shear-strain bands. This localization facilitates void nucleation, coalescence, and crack penetration. Interfacial stress analysis further shows that the reduced load-bearing stability of the high-Cu-fraction model is not caused by weakened average interfacial stress continuity, but by localized accommodation of transferred load in defect-rich regions. These results identify plastic localization as the atomistic origin of Cu-fraction-dependent void-dominated fracture.