Additive manufacture of programmable multi-matrix continuous carbon fiber reinforced gradient composites

Bio-inspired gradient materials and structures, including cartilage scaffolds, soft actuators, and sensors, demonstrate significant potential applications in the fields of biomedicine, robotics, and flexible electronics. This paper introduces a novel method for fabricating continuous fiber-reinforced gradient composites using additive manufacturing techniques. In-situ impregnation 3D printing of two distinct matrix materials and continuous fibers was realized utilizing a specially designed multi-channel nozzle. This allowed for the personalized distribution of matrix materials within the composite by controlling the extrusion rates. Employing polylactic acid (PLA) and thermoplastic polyurethane (TPU), which possess differing mechanical properties, as matrix materials, the study examined the tensile and three-point bending mechanical properties of continuous carbon fiber-reinforced PLA/TPU (CCFR-PLA/TPU) composites with varying ratios of the two matrix materials. Moreover, the ability to control the distribution of matrix materials enabled the tailoring of gradient composites. Additionally, this research investigated the fabrication and compression behavior of gradient thin-walled structures and lattice structures composed of CCFR-PLA/TPU composites. The findings suggest that this programmable, multi-material, continuous carbon fiber-reinforced composites additive manufacturing approach can fabricate composites with a broad spectrum of tunable mechanical properties.