Influence of printing-based factors on the mechanical properties of hexagonal lattice-structured 3D printed novel walnut shell/polylactic acid composite

Abstract

The incorporation of bio-based natural fillers and lattice structures in thermoplastic polymer has superior advantages such as a reduction in the usage of conventional polymers with improved damping and mechanical properties. The present work focuses on the development of Walnut Shell/PLA (WSP) lattice-structured composite by the Fused Filament Fabrication technique. The flexural strength, compression strength, and thickness error properties of the hexagon lattice-structured WSP composites are optimized by varying Printing-Based Factors (PBFs) which include infill density (60%, 80%, and 100%), nozzle temperature (190°C, 210°C, and 230°C), printing speed (10 mm/sec, 20 mm/sec, and 30 mm/sec), and layer height (0.1 mm, .2 mm, and .3 mm). The flexural and compression test experiments were conducted as per the ASTM D790 and ASTM D695 standards. The process optimization of the measured responses is made by using Taguchi grey relational grade optimization technique. The experimental outcomes such as compressive and flexural strength and minimal dimensional error are converted into the Grey Relational Grade (GRG) for the optimization process. The results show that the Signal-to-Noise ratio (S/N) from the measured GRG clearly shows that, the lower layer height of 0.1 mm, higher nozzle temperature of 230°C, higher infill density of 100%, and average printing speed of 20 mm/sec is an optimal experimental condition for attaining higher strengths and lower errors. From the Analysis of Variance (ANOVA) analysis, the printing temperature, and layer height are the most persuasive PBFs for the mechanical and physical characteristics with respect to the incorporated lattice structure. The optimized experimental conditions develop maximum flexural and compressive strengths of 4.98 MPa and 28.19 MPa, in addition to a lower thickness error of .186 mm obtained for hexagon lattice-structured WSP biopolymeric composites.