Interfacial and mechanical properties of continuous ramie fiber reinforced biocomposites fabricated by in-situ impregnated 3D printing

Abstract Agricultural crops such as vegetal fiber are increasingly used for composite reinforcement, but additive manufacturing of biocomposite using vegetal fibers still needs to be developed. The present work aimed to study the mechanical properties and interfacial analysis of 3D printed continuous vegetal fiber reinforced biomass based composites. The biocomposites were obtained by in-situ impregnated fused deposition modeling (FDM) process where dry twisted continuous ramie fibers and polylactic acid (PLA) were utilized as reinforcing phase and matrix, respectively. The uniaxial tensile and peeling tests were conducted to evaluate the mechanical performance and interlayer strength of ramie fibers reinforced biocomposites printed with different processing parameters. The morphology and properties of the biocomposites were analyzed before and after the mechanical tests to reveal the multiscale interfaces. The results showed that the mechanical behaviors of the biocomposites depended on the interfacial properties between deposited layers, between ramie-yarn/matrix and between ramie-fiber/matrix. The increase of flowability of matrix, increase of forming pressure between the printing nozzle and bed, as well as increase of impregnation duration of ramie fibers, caused by the variation of printing parameters, led to significant microstructure changes of the studied biocomposites. A highest tensile strength of 86.4 MPa of the biocomposites with low porosity, good interaction between deposited lines as well as between PLA matrix and ramie fibers could be found, at a printing temperature of 220 C, a layer thickness of 0.3 mm, and a printing speed of 100 mm/min.