Coefficients of thermal expansion of some laminated ceramic composites

The coefficients of thermal expansion (CTE) were determined for several non-fibrous alumina-based laminated ceramic composites. The results were compared with the CTE values predicted by the modified equations of Schapery and Chamis. Both models are identical in the longitudinal direction and showed differences from experimental CTE of 2.3 and 4.1% for alumina/barium zirconate (Al2O3/BaZrO3) and alumina/tin dioxide (Al2O3/SnO2) composites, respectively. For Al2O3/BaZrO3 in the transverse direction, Schapery's model showed a 1.9% difference while Chamis' model showed a 7.5% difference. For the Al2O3/SnO2 in the transverse direction, Schapery's model had an 8.2% difference while Chamis' model showed only a 2.3% difference. Results for alumina/calcium titanate (Al2O3/CaTiO3) laminates showed larger differences, 27.6% in longitudinal CTE and differences of 9.6 and 19.8% transverse CTE for the Schapery and Chamis models, respectively. These differences were attributed to the formation of cracks that occurred in this composite system during processing because of the large CTE mismatch between Al2O3 and CaTiO3. Results for Al2O3/BaZrO3 and Al2O3/SnO2 composites showed that for continuous laminae both the Schapery and Chamis models were adequate predictors of CTE for the systems. (C) 2001 Elsevier Science Ltd. All rights reserved.