Flexible-rigid scalable structures for trans-scale interface reinforcement of carbon fiber/phenolic composites: Effect on properties

Light-weight and high-modulus carbon fiber/phenolic composites, were in large demand of heavy-loading engineering, vehicles and aerospace fields. However, the limitation in the weak interface would cause serious stress concentration and structural failure of materials. Herein, aramid nanofiber (ANF) and cellulose nanofiber (CNF) as flexible units, and zeolitic imidazolate frameworks-8 (ZIF-8) as a rigid unit, were employed to establish a trans-scale reinforced structure on the interphase for balancing the modulus of fibers/resin and improving interfacial properties of the composites. This flexible-rigid (ANF/CNF-ZIF-8) scalable structure, contributed to the integration of various components and forming effective bonds between fibers and the matrix, further promoting mechanical and tribological performances of the composites. Due to the trans-scale interface enhancement of this unique flexible-rigid structure, the flexural strength of 30%ANF-ZIF-8-composite (S_1-3) and 30%CNF-ZIF-8-composite (S_2-3) improved by 77.68% and 88.46%, respectively. Meanwhile, the elastic modulus of S_1-3 and S_2-3 reached 5.41 and 5.40 GPa, indicating a significant ascent of 137.28% and 136.84%, respectively. This work provides a promising and effective strategy of constructing a flexible-rigid scalable interfacial structure and opens an avenue toward the large-scale fabrication of new-generation advanced materials.