Study on the mechanical properties of surface-modified CF/PEEK composite structures for potential implants fabricated by high-temperature air-assisted 3D printing

• The study employs a synergistic treatment method combining electrochemical oxidation and silane coupling agent to modify the CF to improve the bonding strength between CF and the PEEK matrix. • The high-temperature air-assisted 3D printing process is proposed and significantly improves the mechanical properties of 3D-printed CF/PEEK composite implants. Although PEEK material exhibits excellent mechanical properties, its performance still differs from that required for artificial bone implants. Therefore, additives such as carbon fiber (CF) are often incorporated to further enhance its mechanical properties. Additionally, the melting point of PEEK is approximately 343 °C, while the typical 3D printing environment temperature is approximately 25 °C. The significant temperature gradient between the extruded PEEK material and the ambient temperature restricts the alignment of molecular chains within the material, resulting in low crystallinity. To improve the bonding strength between CF and the PEEK matrix, this study employs a synergistic treatment method combining electrochemical oxidation and silane coupling agent to modify the CF surface, thereby enhancing the interfacial connection. Simultaneously, a high-temperature air-assisted printing process is introduced to precisely control the temperature field of the printing environment, suppress thermal stress, and promote molecular chain diffusion and crystallization, effectively strengthening the interlayer bonding. Experimental results demonstrate that the electrochemical oxidation-silane coupling agent modification improves the bonding strength approximately 14 % between CF and the PEEK matrix. The high-temperature air-assisted printing process enhances the interlayer adhesion between extruded layers. This study provides a practical technological approach and theoretical foundation for fabricating high-performance, customized CF/PEEK composite implants.