Significantly enhanced laser trapping and heating of carbon nanotube/ carbon fibre hierarchical composites for efficient laser-assisted automated fibre placement

Laser-assisted automated fibre placement (LAFP) process is promising for manufacturing large-scale thermoplastic composite parts. However, its laydown speed suffers from the near-infrared (NIR) laser reflection from carbon fibres (CFs) and the high specific heat capacity of prepregs. Herein, the light-trapping carbon nanotube (CNT) forest was grown on CFs using a low-cost flame synthesis process, followed by its embedding in the polyether-ether-ketone (PEEK) matrix to produce CF/PEEK/CNTs prepregs with simultaneously enhanced laser absorption and reduced specific heat capacity. Spectroscopic analysis shows that CNTs reduce the NIR reflectance of prepregs due to enhanced light-trapping efficiency with hierarchical CNT/CF structures, further evidenced by a transition from diffuse reflection to specular reflection. Additionally, CNTs reduce 19 % of the specific heat capacity by restricting polymer chain movement. Therefore, the hierarchical structure increases the heating rate and maximum temperature of CF/PEEK prepregs by 18.5 % and 16.0 %, respectively, under 1080 nm laser radiation during the LAFP process.