Light-trapping carbon nanotube forests in glass fibre-reinforced thermoplastic prepregs for efficient laser-assisted automated fibre placement

Laser-assisted automated fibre placement (LATP) is an emerging technology for manufacturing thermoplastic composite components. However, major challenges are still encountered for the LAFP process for glass fibre (GF) reinforced composites due to the high near-infrared (NIR) laser reflectance and transmission as well as resulting poor absorption of prepreg constituents. Inspired by the efficient light-trapping and photothermal characteristics of carbon nanotube (CNT) forest, we fabricate CNT forest onto the GF surface by rapid and low-cost flame synthesis method, to enhance the photothermal conversion efficiency of poly-ether-ether-ketone (PEEK)/GF prepregs during LAFP process. CNT forests with different lengths, alignments and densities were produced by changing flame synthesis parameters. The spectroscopy results show that CNT forest suppresses transmission and reflection from GF and crystals in GF/PEEK prepreg within the NIR wavelength range at near normal incidence, decreasing transmission and reflectance to 0.3% and 7.9%, respectively, and increasing absorption to 91.8% at 1080 nm wavelength. Furthermore, CNTs forest improves the heating rate of GF/PEEK prepreg by more than 700% for a wide range of incident angles. Consequently, CNT forest enables a 400% increase in placement speed and a 79% reduction in energy consumption during LAFP process, while making negligible voids in the interlayer.