An atomistic investigation of the mechanical behavior of aluminum matrix composites reinforced by intragranular and intergranular carbon nanotubes

Carbon nanotube (CNT) reinforced aluminum composites (CNT/Al composites) are renowned for their remarkably low density and high strength. However, the underlying physical mechanisms by which intergranular and intragranular CNTs reinforce the aluminum matrix remain barely explored, primarily due to challenges in direct experimental observation. In this study, using molecular dynamics simulations, we systematically investigate the mechanical behavior of CNT/Al composites, with emphasis on distinguishing the reinforcement roles of intragranular and intergranular CNTs, as well as their sensitivity to other effects, like CNT size. Our results demonstrate that the composite reinforced with intragranular CNT exhibited higher peak stress than the one reinforced with intergranular CNT, which can be attributed to the structurally weaker effect of overlapped grain boundary and embedded CNT in the intergranular model. Increasing CNT size modifies the peak stress through coupled size and volume-fraction effects but does not alter the distinct failure sequences of the intragranular and intergranular configurations. These findings clarify the physical origins of CNT strengthening in aluminum composites and provide guidance for optimizing the microstructure and processing, thereby supporting the development of predictive continuum models.