Atomistic insights into tensile damage of functionally Graded Al-SiC composites

Abstract

The tensile behavior and damage mechanisms of functionally graded (FG) Al-SiC composites are systematically investigated using molecular dynamics (MD) simulations. A comprehensive set of large-scale MD simulations is conducted on FG composites composed of three layers reinforced with different volume fractions of randomly distributed three-dimensional SiC particles. This work introduces a novel approach by modeling the reinforcement ceramic as three-dimensional particles, thereby more accurately representing the FG composite microstructure. Predictions of the model for Young's moduli of composites align with experimental data from the literature. The yield and ultimate tensile strength are overestimated due to the high applied strain rates and idealized crystal structures used in the simulations, which lack common defects such as vacancies and dislocations. The model is utilized to study the influence of reinforcement particle shape, size, orientation, and distribution on the tensile and damage behavior of composites. The FG composites reinforced with cubic particles demonstrate lower yield and tensile strength than those with spherical particles, primarily due to the high-stress concentrations around the corners of the cubic reinforcements. Reducing the size of SiC particles enhances the elastic modulus, yield, and tensile strength of the FG composites. It is shown that the stiffness of the FG composites reinforced with rectangular prisms can be effectively tailored by changing the orientation of the reinforcements. When SiC rectangular prisms are aligned along the tensile direction, the resulting FG composites exhibit higher yield and tensile strength. This work offers fundamental atomistic insights that help design FG composites with better mechanical performance.