Corncob-inspired synthesis of carbon fiber/PO43− intercalated NiFe-LDH hybrid for simultaneously improving flame retardancy and mechanical properties of epoxy resin composites

The development of carbon fiber reinforced epoxy resin (EP/CF) composites with good balance on flame retardancy and mechanical properties remains a critical challenge. Inspired by the rod@sheets hierarchical structure of corncobs, herein a novel CF/PO 4 3− intercalated NiFe-LDH hybrid (CF@NiFe-LDH-P) was successfully fabricated via in-situ growth of NiFe-LDH nanosheets on CF surfaces, followed by PO 4 3− intercalation via an ion-exchange process. Subsequently, the as-synthesized CF@NiFe-LDH-P was incorporated with EP matrix. The resultant EP/CF@NiFe-LDH-P composites exhibited remarkable improvements in flame retardancy, including the limiting oxygen index (LOI) value of 36.8 %, UL-94 V0 rating, and a 66.8 % reduction in the peak of heat release rate (PHRR). According to the structure/composition analysis of residual char, the flame-retardant mechanism was mainly ascribed to the synergistic effect between NiFe-LDH and PO 4 3− , where NiFe-LDH catalyzed the carbonization of EP fragments into graphitized carbon, while PO 4 3− enhanced the cross-linking of char network through phosphate ester bonds. Meanwhile, the flame retarded EP/CF@NiFe-LDH-P composites displayed superior mechanical performances. Compared to the pristine EP/CF, EP/CF@NiFe-LDH-P displayed outstanding mechanical properties in Young's modulus (+26.9 %), tensile strength (+26.2 %) and impact strength (+39.4 %). These enhancements were attributed to the corncob-like structure of CF@NiFe-LDH-P, which established strong interfacial adhesion with EP via hydrogen bonding. This work presents an innovative bio-inspired strategy to achieve synergistic optimization of flame retardancy and mechanical performances in EP/CF composites, paving the way for their expanded applications in high-performance engineering and advanced technological fields.