Role of the interphase zone in the effective mechanical properties and fracture modes of multiphase metal matrix composites at microscale

This study conducts a comprehensive numerical analysis to examine how the interphase zone influences the mechanical behavior of multiphase metal matrix composites at the microscale. A unit-cell model is developed within a finite element framework to capture the mechanical response of (a) interphase and particle deformation and damage, (b) a porous metal matrix, and (c) surface separation at two distinct interfaces. The material properties of the composite's key constituents are determined through a calibration process combining experimental testing and literature data. A series of simulations on unit-cell models with varying interphase characteristics are carried out to assess the effect of different plastic properties. Additionally, the role of interphase brittleness is investigated by modifying the failure strain to represent brittle, semi-ductile, and ductile behavior. By systematically varying interphase parameters, the study explores a broad spectrum of potential composite performance scenarios. Parametric studies are also conducted to analyze the behavior of interfaces between composite constituents. By adjusting cohesive strength and fracture energy, the model captures a wide range of bonding conditions—from weak to strong, and from brittle to ductile. The analysis identifies more than six distinct failure modes. Comparative stress-strain responses are used to highlight the influence of specific parameters on composite behavior. Key performance metrics such as toughness, ultimate tensile strength, and ductility are evaluated to illustrate the connection between microscopic features and macroscopic properties.