Abstract

The molecular-level reinforcement mechanisms of high-loading SWCNTs in Aramid III fibers, critical for aerospace/defense applications, remain poorly understood. Here, we employ PCFF and GAFF all‑atom MD simulations coupled with bond dissociation energy analysis and Savitzky-Golay filtering to interrogate pristine and 3 wt% SWCNT‑doped Aramid III fibers. Tensile simulations at 10¹⁰s⁻¹ reveal a marked decrease in ultimate tensile stress from 0.80GPa to 0.08GPa upon CNT incorporation, indicating stress‑concentrating aggregates that embrittle the matrix. Bond dissociation energies quantify vulnerable amide linkages (86.0-86.6kcal/mol) versus robust aromatic C-C bonds (126.6kcal/mol). Temperature‑programming studies demonstrate that slow heating (0.15K/ps) stabilizes the interfacial binding energy at -200kcal/mol, ~30kcal/mol higher than rapid heating (-230kcal/mol). Integrating an 180ps NPT equilibration with accelerated heating reduces computational steps by 91.6% (from 1.8×10⁷ to 1.5×10⁶) without compromising stability. Collectively, these findings elucidate the dual stiffeningbrittleness transition induced by high CNT loadings and establish a multiscale MD workflow that balances accuracy and efficiency, offering actionable guidelines for designing advanced CNT‑reinforced polymer fibers.

Keywords:Aramid Ⅲ; SWNT; All-atom molecular dynamics; Tensile properties