Interface enhancement of 3D printed CF/PLA composites by introducing “rigid-flexible” structures through multi-bond synergies

The interfacial properties between the components of a composite material influence the overall material properties. Herein, we proposed a “rigid-flexible” approach to improve the relatively weak interlaminar characteristic of 3D printed CF/PLA composite. Graphene oxide (GO) and polyethyleneimine (PEI) were chosen as the “rigid” and “flexible” phases, respectively. A stepwise chemical grafting technique was used to introduce “rigid-flexible” structures to the continuous carbon fiber (CCF) surface. Subsequently, filaments were prepared using modified CF and polylactic acid (PLA) and samples were obtained by FDM process. The CF-PEI-GO/PLA composites exhibited remarkable enhancements in mechanical performance relative to neat CF/PLA. Specifically, their interfacial shear strength (IFSS) doubled (101.64% increase), while impact resistance surged by 74.50%. Additionally, tensile strength and flexural strength showed substantial improvements of 31.17% and 24.86%, respectively. The interfacial enhancement mechanism was analyzed through a variety of characterization techniques such as SEM, AFM, XPS and Raman. This research offered new insights and methods towards the development of engineering materials for high performance 3d printing.