Thermal expansion of metal–ceramic composites: a three-dimensional analysis

The thermal expansion response of macroscopically isotropic metal–ceramic composites is studied through micromechanical modeling. Three-dimensional finite element analyses are carried out for the entire range of phase concentration from pure metal to pure ceramic, using the aluminum–silicon carbide composite as a model system. Particular attention is devoted to the effects of phase connectivity, since other geometrical factors such as the phase shape and particle distribution play a negligible role in affecting the overall coefficient of thermal expansion (CTE) of the composite. Three types of phase connectivity, i.e. metal-matrix, ceramic-matrix and interpenetrating (where both phases form a continuous network in space), are considered. It is found that for fixed phase concentrations, the composite CTE depends strongly on the phase connectivity, with the metal- and ceramic-matrix cases showing the highest and lowest CTE values, respectively. The numerical results are compared with analytical predictions. The combined effects of phase connectivity and metal plasticity are examined by numerically varying the thermal history. The correlation between the constrained metal yielding and the composite CTE is identified. The three-dimensional analysis allows the thermal deformation behavior of interpenetrating composites to be examined in a realistic manner. The results presented in this paper are important in the design and characterization of composites in applications such as electronic packaging and functionally graded materials.