Carbon nanotube-induced localized laser heating toward simultaneously enhanced laydown efficiency and fracture toughness of in-situ consolidated glass fiber thermoplastic composites

Thermoplastic composites suffer from weak inter-tape bonding during high-rate laser-assisted automated fiber placement (L-AFP). Here, we propose a strategy to simultaneously enhance the laser heating efficiency and fracture toughness of glass fiber-reinforced polypropylene prepreg tape for L-AFP process by depositing carbon nanotubes (CNTs) on the tape surface by a low-cost bath coating process. CNTs function as efficient light absorbing and photothermal coating to promote molecular inter-diffusion and interfacial healing between successive tapes, as well as toughen the weak interface by CNT pull-out and rupture. A 56% increase in the near-infrared laser absorption of tapes results in a 946% improvement in the laydown rate. CNTs also remarkably improve transverse temperature uniformity. Furthermore, double cantilever beam and pants tearing tests show that 0.5 wt.% CNTs improve the mode I interlaminar fracture toughness and mode III fracture strength by 17% and 52%, respectively, attributed to the enhanced molecular inter-diffusion and CNT bridging effect.