Effects of Particle Characteristics on the Fracture Behavior of A359/SiC Composites Based on a Micromechanical Method

Abstract

The mechanical and fracture behaviors of A359/SiC composites are profoundly influenced by their complex microstructural characteristics, which are not fully understood. Existing micromechanical models often oversimplify particle geometry, neglecting nonconvex shapes, and fail to comprehensively capture the interplay between particle aspect ratio, particle volume fraction, stress distribution, and damage mechanisms. In this study, a novel microstructure-based micromechanical finite element modeling method that incorporates nonconvex particle shapes is proposed to accurately represents the realistic geometry of SiC particles. This approach enables the analysis of how particle characteristics, such as aspect ratio and volume fraction, influence the stress distribution, damage initiation, and fracture propagation in A359/SiC composites. The model accounts for all potential fracture modes, including brittle cracking of SiC particles, ductile damage of the aluminum matrix, and particle–matrix interface debonding. Results demonstrate that the tensile strength and elongation both increase as the particle aspect ratio rises. Needle-shaped particles exhibit superior load bearing capacity and serve as more effective reinforcements compared to stubby-shaped particles. Although increasing the particle volume fraction enhances the fracture strength of the composite, the elongation is reduced concurrently due to the brittleness of the particles and the intensified stress concentration. This study provides a significant advancement over previous models by incorporating realistic particle geometries and offering new insights into the role of microstructure in governing the mechanical and fracture behaviors of A359/SiC composites. The findings are critical for property optimization and material design of A359/SiC composites.