THERMAL-EXPANSION OF METAL-CERAMIC COMPOSITES - A 3-DIMENSIONAL ANALYSIS

The thermal expansion response of macroscopically isotropic metal-cera mic composites is studied through micromechanical modeling. Three-dime nsional finite element analyses are carried out for the entire range o f phase concentration from pure metal to pure ceramic, using the alumi num-silicon carbide composite as a model system. Particular attention is devoted to the effects of phase connectivity, since other geometric al factors such as the phase shape and particle distribution play a ne gligible role in affecting the overall coefficient of thermal expansio n (CTE) of the composite. Three types of phase connectivity, i.e. meta l-matrix, ceramic-matrix and interpenetrating (where both phases form a continuous network in space), are considered. It is found that for f ixed phase concentrations, the composite CTE depends strongly on the p hase connectivity, with the metal- and ceramic-matrix cases showing th e highest and lowest CTE values, respectively. The numerical results a re 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 yi elding and the composite CTE is identified. The three-dimensional anal ysis allows the thermal deformation behavior of interpenetrating compo sites to be examined in a realistic manner. The results presented in t his paper are important in the design and characterization of composit es in applications such as electronic packaging and functionally grade d materials. (C) 1998 Elsevier Science S.A. All rights reserved.