An Atomistic Investigation of the Strengthening Mechanism of Aluminum Matrix Composites Reinforced by Intergranular and Intragranular Carbon Nanotubes

The mechanical characteristics of CNTs/Al composites are widely reported to be reinforced by carbon nanotubes (CNTs), but intergranular and intragranular CNTs play different roles in strengthening, whose detailed effects are hard to be directly observed and are not fully clear. In this paper, the strengthening mechanisms of aluminum matrix composites (AMC) reinforced by CNTs at different positions (intragranular or intergranular) are explored on an atomic scale. Molecular dynamics (MD) simulation models for AMC reinforced by intragranular and intergranular CNTs are constructed. The uniaxial tensile deformation tests are carried out at the temperature of 300K, using periodic boundary conditions (PBCs) in all three directions. The results show that adding CNTs in the aluminum can significantly strengthen the mechanical properties of the AMC. The improvement in tensile strength of the CNTs-reinforced materials is respectively 29.7% and 25.4% when compared with defective single-crystal aluminum (SA) and double-crystal aluminum (DA). Moreover, the strengthening mechanism of AMC reinforced by intragranular and intergranular CNTs is further explored through the MD simulations, including dislocation density and lattice structure transformation.