Effect of Thermal Residual Stresses on the Stress-Strain Behavior of Metal-MatrixComposites

摘要

A phenomenological and parametric study was conducted to assess the effect ofthermal residual stresses on the stress-strain response of a discontinuous fiber-reinforced metal-matrix composite in tensile and compressive loading. The material chosen for this investigation was the silicon carbide whisker reinforced aluminum 6061. The difference between composite flow behavior in tension and compression, as well as the effects of volume fraction, fiber aspect ratio and fiber spacing were analyzed within the framework of axisymmetric finite element models to determine the overall constitutive response of the composite and to solve for local field quantities in the fiber and the matrix. The composite was modeled as a periodic array of cylindrical fibers with perfect interfacial bonding and complete fiber alignment with the tensile/compressive axis. It was found that the presence of residual stresses affected the stress-strain behavior of the composite by influencing the load transfer characteristics between the matrix and the fiber as well as the initiation and growth of the plastic deformation in the matrix. The results of the study indicated that a significant strength differential exists between tensile and compressive loading and that this effect diminishes with increasing volume fraction. The results also indicated that composite stiffness, yield strength and work-hardening rate increase with increasing volume fraction and fiber aspect ratio.