Effects of Air‐Sprayed Multiscale Carbon/Nano‐Silica Composite Coatings on the Performance of Carbon Fiber‐Reinforced Friction Composites

To address the challenges of insufficient thermal conductivity, unstable friction behavior, and interfacial wear of carbon fiber‐reinforced friction composites (CFRFCs), multiscale GNPs/nano‐SiO 2 and VGCFs/nano‐SiO 2 composite coatings were fabricated on preform surfaces by air spraying, followed by resin impregnation, hot pressing, and curing to obtain CFRFCs. The dimensional synergy between zero‐dimensional nano‐SiO 2 and carbon fillers with different geometries was systematically investigated. Results showed that nano‐SiO 2 played distinct roles in the two systems. In GNPs/nano‐SiO 2 , nano‐SiO 2 acted as point‐like spacers and defect fillers between two‐dimensional GNP sheets, forming a point–plane structure that promoted heat‐transfer pathways and lubricating film stability. In VGCFs/nano‐SiO 2 , nano‐SiO 2 was embedded in the one‐dimensional VGCF network, forming a line–point interlocking structure that enhanced interfacial anchoring and shear resistance. At a GNPs/nano‐SiO 2 mass ratio of 5:5, CFRFCs showed the best overall balance. Compared with the single GNPs‐reinforced composite, the GNPs/nano‐SiO 2 hybrid composite achieved a dynamic friction coefficient of 0.118, a dynamic/static friction coefficient ratio of 0.92, and a shear strength of 1.37 MPa at 2.96 MPa, representing increases of 9.3%, 24.32%, and 5.3%, respectively. The in‐plane thermal conductivity reached 0.51 W/(m·K), and the wear rate remained low at 0.92 × 10 −12 m 3 /(N·m). This work provides a multiscale dimensional‐synergy strategy for designing friction‐stable and wear‐resistant CFRFCs.