Nanoscale Structure-Property Relationships of Cyanate Ester as a Function of Extent of Cure.

Cyanate esters are key thermosetting resins for composite materials that require structural integrity and resistance to elevated temperatures. Because cyanate ester composites require relatively high processing temperatures, they are susceptible to the formation of process-induced residual stresses, which compromise their overall strength and durability. Process modeling is a key strategy for optimizing processing parameters to minimize such residual stresses. A necessary component of effective and efficient process modeling of composites is computationally established resin property evolution relationships for a range of processing parameters. In this study, the physical, mechanical, and thermal properties of a cyanate ester resin are established as a function of processing time and temperature using experimentally validated molecular dynamics modeling. The results show that the properties are strongly dependent on the processing temperature. At processing temperatures above 160 °C, the properties quickly approach their fully cured values, whereas at processing temperatures below 140 °C, the chemical cross-linking is significantly inhibited, and processing times to complete cure are relatively long. The evolution of the physical, mechanical, and thermal properties as a function of processing time is established, which is critical data needed as input into multiscale process modeling and optimization of cyanate ester composites for computationally driven composite design.