Mechanical properties of aramid fibers modified with a polydopamine/carbon quantum dots bilayer coating

Aramid fibers (AFs) are widely used as high-performance reinforcements, yet their inert surfaces limit mechanical reliability. In this study, a facile and effective surface modification strategy is developed by constructing a polydopamine/carbon quantum dots (PDA/CDs) bilayer coating to enhance tensile performance. The PDA layer serves as an adhesive interface for uniform CDs deposition, while CDs concentration is identified as a key factor influencing the mechanical enhancement. The introduction of oxygen-containing functional groups is associated with improved surface condition and more uniform stress distribution. As a result, the tensile strength increases by 3.2–8.5%, accompanied by improved elongation at break, and the Weibull modulus rises from 29.09 to 48.36, indicating enhanced strength uniformity and reliability. In addition, Mori–Tanaka modeling predicts ∼15% increase in effective elastic modulus. Despite the relatively low thermal stability of PDA, the modified fibers retain superior mechanical performance after heat treatment at 120 °C, with tensile strength still ∼8.3% higher than that of untreated fibers. These results suggest that the enhancement is mainly related to interfacial regulation and defect-related effects induced by CDs. This work provides a low-damage strategy for improving the mechanical performance and reliability of AFs.