Photoacoustic effect on the electrical and mechanical properties of polymer-infiltrated carbon nanotube fiber/graphene oxide composites

Direct spinning of carbon nanotube (CNT) fibers is a facile method to produce CNT fibers because of its high productivity and the simplicity of the spinning process from CNT aerogels. Directly spun CNT fibers, however, generally include amorphous carbon and weak shear interaction between tubes or bundles, thereby causing insufficient load transfer. Here, we report newly designed polyimide/reduced graphene oxide (PI/RGO)/CNT fiber composites in combination with polymer infiltration followed by photonic flash sintering on a time scale of 0.5 ms to overcome the critical drawbacks in directly spun CNT fibers. The mechanical performances of the CNT fibers were closely related to the junction strength in CNT bundles. In addition, PI can be interlocked with CNT bundles and effectively serve as a binder to link the GO and CNT fibers with strong interfacial interactions. The PI infiltrated CNT fibers showed the highest load transfer, resulting in a significantly enhanced increase of 83% in specific strength (1.1 N/tex) and a 477% increase in tensile strength (800 MPa) compared to pristine CNT fibers. Furthermore, the photonic sintered PI/RGO/CNT fibers improved electrical conductivity by over 244% (5.5 × 10³ S cm⁻¹) over pristine CNT fibers without deteriorating mechanical properties. The results demonstrate that the mechanical strength, modulus and electrical conductivity can be enhanced simultaneously by molecular-level coupling of polymer/graphene with CNT fibers via photonic flash sintering.