Prashanth Badrinarayanan

Carbon fiber-reinforced cyanate ester/nano-ZrW2O8 composites with tailored thermal expansion.

Fiber-reinforced composites are widely used in the design and fabrication of a variety of high performance aerospace components. The mismatch in coefficient of thermal expansion (CTE) between the high CTE polymer matrix and low CTE fiber reinforcements in such composite systems can lead to dimensional instability and deterioration of material lifetimes due to development of residual thermal stresses. The magnitude of thermally induced residual stresses in fiber-reinforced composite systems can be minimized by replacement of conventional polymer matrices with a low CTE, polymer nanocomposite matrix. Zirconium tungstate (ZrW(2)O(8)) is a unique ceramic material that exhibits isotropic negative thermal expansion and has excellent potential as a filler for development of low CTE polymer nanocomposites. In this paper, we report the fabrication and thermal characterization of novel, multiscale, macro-nano hybrid composite laminates comprising bisphenol E cyanate ester (BECy)/ZrW(2)O(8) nanocomposite matrices reinforced with unidirectional carbon fibers. The results reveal that incorporation of nanoparticles facilitates a reduction in CTE of the composite systems, which in turn results in a reduction in panel warpage and curvature after the cure because of mitigation of thermally induced residual stresses.

Effect of a zirconium tungstate filler on the cure behavior of a cyanate ester resin.

In this work, the effect of a negative thermal expansion zirconium tungstate (ZrW2O8) filler on the cure behavior of a unique low-viscosity bisphenol E cyanate ester (BECy) is characterized by differential scanning calorimetry. The cure rate of BECy is found to increase upon the incorporation of ZrW2O8 particles, and the catalytic effect increases with increasing filler loading. The catalytic effect is primarily attributed to the presence and nature of hydroxyl groups on the ZrW2O8 particle surface. In comparison with BECy/ZrW2O8 composites of the same loading, silane-coated ZrW2O8 particles resulted in a higher value of the glass transition temperature (T(g)) and a delay in the onset of the cure. The ability of a phenomenological reaction model to describe the cure behavior of the composites is also examined.