Mechanically robust carbon nanotube composite fibers via reinforced intertube interactions

Carbon nanotube fibers (CNTFs) offer exceptional intrinsic properties but are often limited by assembly defects and inefficient intertube load transfer. Here, we report a wet-spinning strategy enabled by poly(p-phenylene-2,6-benzobisoxazole nanofibers and chains (PBOs)-reinforced intertube interactions to fabricate mechanically robust PBO/CNT composite fibers (PCNTFs). By optimizing the PBOs content, highly aligned and densely packed CNT networks are formed and stabilized by a hydrogen-bonding interfacial architecture. Comprehensive structural characterization reveals maximized nanotube orientation, minimized void volume, and strengthened interfacial interactions at the optimal composition. As a result, the PCNTFs achieve a high tensile strength of 3.52 GPa, a Young’s modulus of 306 GPa, and a toughness of 71.5 MJ m⁻³, representing a 2.7-fold enhancement in toughness compared with pristine CNTFs. In situ Raman spectroscopy, stress-relaxation analysis, and fracture morphology observations further confirm the critical role of hydrogen-bonding-mediated interfacial interactions in governing efficient stress transfer and energy dissipation. Moreover, the optimized fibers exhibit a high specific penetration energy of 1.39 MJ kg⁻¹ under high-speed impact, exceeding that of conventional impact-resistant fibers. This work establishes a scalable interfacial design strategy for CNT-based fibers with simultaneously high strength and toughness and provides a feasible pathway toward next-generation fibers for structural and multifunctional applications.