Inelastic Thermal Response of Gr/Cu with Nonuniform Fiber Distribution

Abstract

An analytical model for the thermomechanical response of metal matrix composites was developed based on the method of cells micromechanics model and classical lamination theory. The inelastic behavior of the matrix material is modeled using either the classical incremental plasticity theory or the Freed-Walker viscoplasticity theory, which is a more recent development designed for use with copper and copper alloys. The composite model was subsequently used to investigate the effect of the matrix constitutive model and the effect of nonuniform fiber distribution, on the thermal expansion of unidirectional graphite/copper (Gr/Cu) composites. Results illustrate that when the viscoplastic model is used, stress relaxation decreases the ability of the copper matrix to support load, and the predicted longitudinal thermal response of the composite resembles that of the graphite fiber. The effect of nonuniform fiber distribution on the longitudinal thermal expansion is more pronounced when the plastic constitutive model is used. In addition, the effect of the nonuniformity is more pronounced for the longitudinal thermal expansion of Gr/Cu than the transverse thermal expansion. The model predictions were compared with experimental thermal expansion data for Gr/Cu, and the use of the viscoplastic constitutive model was found to provide better correlation than the plastic constitutive model.