Microstructure and thermal properties of nano-SiO₂ reinforced 3D printed multiscale PEEK composites

Additive manufacturing (AM) is growing as a resource-efficient and economical processing technique for polymer-based materials. In recent years, substantial advancements have been made in the fused filament fabrication (FFF) of high-performance polyether-ether-ketone (PEEK). However, there is a notable lack of information in the existing literature on the 3D printing of nanoparticle-filled PEEK composites. In this study, PEEK-based composite filaments filled with nanoscale silicon dioxide (SiO₂) and microscale short carbon fibers (SCF) were successfully fabricated using melt compounding and 3D printing using FFF. The addition of 2 wt% nano-SiO₂ significantly enhanced interfacial bonding, reduced internal porosity, and improved the microstructure of SCF-PEEK composites. Tomography and microstructure analysis revealed a uniform distribution of fibers. Thermal and structural analysis confirmed that the chemical integrity of the PEEK matrix remained intact during the filament processing and 3D printing. Nano-SiO₂ enhanced the thermal decomposition temperatures and improved the crystallization behavior of SCF-PEEK. Multiscale composites exhibited up to 40 % and 11 % increments in stiffness compared to neat PEEK and SCF-PEEK, respectively. Overall, SiO₂ improved the microstructure, thermal properties, and dynamic modulus of printed SCF-PEEK composites. The findings in this study demonstrate that nano-SiO₂ is a promising filament filler for 3D printing of PEEK composites.