Three-phase cyanate ester adhesives have been developed using a bisphenol E cyanate ester resin, fumed silica, and negative-CTE
(coefficient of thermal expansion) reinforcements: short carbon fiber or zirconium tungstate (ZrW2O8). Fumed silica was used to impart thixotropic behavior on the resin and decrease settling in the adhesives. The cured composites
were evaluated using various thermal analysis techniques for their thermal-mechanical properties.
Composites with short carbon fiber showed enhanced modulus and decreased thermal expansion (70% reduction for 20 vol%) and
showed little phase separation. While settling of the dense ceramic particles could not be completely eliminated for the zirconium
tungstate composites through rheological modification of the adhesive with added fumed silica, a reduction in CTE of 84% was
achieved in the composite (58 vol%) compared to the neat resin. In addition, the effect of thermal history on the cure and
temperature induced ZrW2O8 phase transitions, and their corresponding influence on thermal strains vs. temperature, are examined by thermomechanical analysis.