Interfacial modeling of flattened CNT composites with cyanate ester and PEEK polymers

Flattened carbon nanotubes (flCNTs) are a promising form of composite material reinforcement because of their capacity for self-assembly and packing efficiency, which could ultimately lead to improved thermo-mechanical properties relative to current state-of-the-art composite materials. An important material design parameter for composite materials is the choice of polymer matrix, as characteristics of the reinforcement/polymer interface can have a significant effect on the bulk-level properties. Because flCNT-based composites are too expensive to develop via experimental trail-and-error approaches, the goal of this research is to use computational methods to drive their design via efficient polymer selection. Molecular dynamics modeling is used to predict the flCNT/polymer interface properties for a thermoplastic resin (polyether ether ketone - PEEK), and two thermosetting resins (fluorinated and non-fluorinated cyanate esters). For each polymer system, the interfacial interaction energy, flCNT shearing friction, and the transverse tension strength is predicted. While the PEEK and non-fluorinated cyanate esters demonstrate superior interaction energies (23.1% and 11.4% higher, respectively) compared to the fluorinated cyanate ester, the fluorinated cyanate ester has a significantly higher resistance to shearing with the flCNT surface (125% higher than PEEK and non-fluorinated cyanate ester). In pull-apart transverse tension simulations, the non-fluorinated cyanate ester system demonstrates the highest peak strength (8.53% higher than PEEK and fluorinated cyanate ester), while the fluorinated cyanate ester exhibits the highest toughness and stiffness (12.8% and 4.89% higher, respectively, than PEEK and non-fluorinated cyanate ester). Given equal weight, these predictions show that the fluorinated cyanate ester demonstrates the best overall compatibility with flCNTs.