Super Tough High‐Flow Nylon Composites With Nylon Fiber‐Reinforcement

High‐melt‐flow nylon 6 (HMF‐PA6) offers excellent processability but suffers from poor interfacial bonding with reinforcements, reduced mechanical strength, and limited toughness, restricting its use in high‐performance composites. In this study, nylon 66 (PA66) fiber cloth was employed as a homologous reinforcing skeleton, and its surface was modified with polydopamine (PDA) to enhance interfacial compatibility. PDA was deposited via oxidative self‐polymerization, forming a thin coating that increased fiber surface roughness and introduced active functional groups capable of hydrogen bonding with the matrix. During hot pressing, the high fluidity of HMF‐PA6 enabled the PDA‐coated fibers to form a “mechanical interlocking” interface, thereby promoting efficient stress transfer and energy dissipation. As a result, the PDA‐PA66/PA6 composites exhibited remarkable improvements in mechanical performance: tensile strength increased by 96% compared with pure HMF‐PA6 and by 19% over unmodified PA66/PA6 composites, while elongation at break was enhanced by approximately 41%. Morphological observations confirmed that PDA improved fiber–matrix adhesion, and thermal analysis indicated enhanced stability despite partial PDA decomposition at high processing temperatures. These findings demonstrate a simple and scalable strategy to simultaneously reinforce and toughen HMF‐PA6, highlighting the potential of PDA‐modified homologous reinforcements for next‐generation high‐performance nylon‐based composites.