3D printing of vegetable yarn-reinforced polymer components

Abstract

Additive manufacturing has rapidly transformed over the years, moving from simply prototyping to producing objects and structures with advanced materials. The process, also known as 3D printing, enables complex shapes to be generated with great freedom of creation and low waste of resources. Although polymers have been widely used for the manufacture of small objects, the poorer mechanical properties and time required for 3D printing make the technique impractical for the production of real size structural components. This paper presents the development of a larger-diameter head nozzle for the manufacturing of a polymer-based material reinforced with continuous yarns. To address this issue, a continuous yarn reinforcing method was developed, utilizing a modified Fused Filament Fabrication (FFF) hotend adapted to the in-nozzle impregnation of vegetable fibers (i.e., a process by which the yarn and matrix are joined in a single nozzle), such as jute, ramie, and sisal, combined with polylactic acid (PLA) to produce bio-based printed filaments with diameters up to 3 mm. The combination of these materials aims to create printed composites with better mechanical properties and, above all, to meet the environmental need for low-energy biodegradable materials from natural sources that ultimately contribute to reduce the sector's ecological footprint. It was observed that the reinforced samples achieved gains of 28.6% in strength and 28.9% in stiffness in comparison to the unreinforced matrix, using fiber contents up to 48.2% that reduce the polymer utilization per printed volume. The feasibility of the production of multilayer components using the developed method was also confirmed for different types of reinforcement and printing paths.