Establishing Physical and Chemical Mechanisms of Polymerization and Pyrolysis of Phenolic Resins for Carbon-Carbon Composites

The complex structural and chemical changes that occur during polymerization and pyrolysis critically affect material properties but are difficult to characterize in situ. This work presents a novel, experimentally validated methodology for modeling the complete polymerization and pyrolysis processes for phenolic resin using reactive molecular dynamics. The polymerization simulations produced polymerized structures with mass densities of 1.24 & PLUSMN; 0.01 g/cm3 and Young's moduli of 3.50 & PLUSMN; 0.64 GPa, which are in good agreement with experimental values. The structural properties of the subsequently pyrolyzed structures were also found to be in good agreement with experimental X-ray data for the phenolic-derived carbon matrices, with interplanar spacings of 3.81 & PLUSMN; 0.06 & ANGS; and crystallite heights of 10.94 & PLUSMN; 0.37 & ANGS;. The mass densities of the pyrolyzed models, 2.01 & PLUSMN; 0.03 g/cm3, correspond to skeletal density values, where the volume of pores is excluded in density calculations for the phenolic resin-based pyrolyzed samples. Young's moduli are underpredicted at 122.36 & PLUSMN; 16.48 GPa relative to experimental values of 146 - 256 GPa for nanoscale amorphous carbon samples.