Preparation and Properties of Core–Sheath Structured Composite Fibers with Integrated Self-Healing and Self-Warning Functions

Abstract To overcome poor microcapsule dispersion and weak environmental stability of traditional self-healing materials, a core–sheath composite fiber integrating self-healing and self-warning dual functions was fabricated via wet spinning. The fiber core was a polyacrylonitrile (PAN) matrix embedded with SiO2 microcapsules loaded with epoxy resin, photo-initiator and carbon quantum dots (CQDs), and pure PAN formed the outer sheath layer. All resultant composite fibers had an average diameter of approximately 10 μm. The synthesized CQDs/SiO2 microcapsules possessed an average particle size of 2.3 μm, shell thickness of approximately 500 nm, and core material content of 82.6 wt %. The composite fibers exhibited outstanding repeatable self-healing capacity and superior resistance to photoaging. Upon scratch damage, the embedded microcapsules fractured and released healing agents and CQDs, accompanied by time-dependent intensified blue fluorescence at cracks, which realized visual damage self-warning. The fibers without photoaging achieved a healing efficiency of 96.6%, and maintained 93.4% efficiency after a second scratch on the pre-repaired fiber. Even after 72 h of photoaging, these fibers still maintained a healing efficiency of 94.7%, far exceeding two control samples: fiber with microcapsules aggregated in the sheath (70.6%) and fiber with microcapsules randomly dispersed throughout the matrix (77.0%). This study realizes a paradigm transition from coating-type smart materials to fiber-integrated smart systems, and provides a long-lived visual self-healing strategy for advanced functional applications.