Strengthening Mechanisms and Mechanical Characteristics of Heterogeneous CNT/Al Composites by Finite Element Simulation

The refined explicit finite element scheme considering various strengthening mechanisms and damage modes is proposed for simulation of deformation processes and mechanical properties of carbon nanotube (CNT)-reinforced bimodal-grained aluminum matrix nanocomposites. Firstly, the detailed microstructure model is established by constructing the geometry models of CNTs and grain boundaries, which automatically incorporates grain refinement strengthening and load transfer effect. Secondly, a finite element formulation based on the conventional theory of mechanical-based strain gradient plasticity is developed. Furthermore, the deformation and fracture modes for the nanocomposites with various contents and distributions of coarse grains (CGs) are explored based on the scheme. The results indicate that ductility of the composites first increases and then decreases as the content of CGs rises. Moreover, the dispersed distribution exhibits better ductility than concentrated one. Additionally, grain boundaries proved to be the weakest component within the micromodel. A series of interesting phenomena have been observed and discussed upon the refined simulation scheme. This work contributes to the design and further development of CNT/Al nanocomposites, and the proposed scheme can be extended to various bimodal metal composites.